Topic 1: CONCEPT OF GEOGRAPHY
The word geography can be divided into two parts, ‘geo’ and ‘graphy’.
Geo comes from the Greek word ‘ge’ which means the earth and graphy
comes from ‘graphein’ which means to describe. Therefore geography
describes the earth.
Geography is the study of physical features of the earth and human
activities as it relates to these.
Or
Geography is the study of physical features of the earth and its
atmosphere, and of human activity as affected by these including social
and economic activities industries, land use, distribution of population
and resources.
Or
Is the science of distributions and is concerned with spatial variations
in any physical or cultural features.
BRANCHES OF GEOGRAPHY
There are three main branches of geography namely;
(a) Physical geography
(b) Practical geography
(c) Human and economic geography
A. Physical geography
Is concerned with land formation processes, and pattern in natural environment such as atmosphere. Also is the branch of geography that studies all physical features e.g mountains, rift valley
B. Practical geography
Is the branch of geography concerned with field study of photograph interpretation, map work, statistics and research.
C. Human and Economic geography or Regional geography.
It deals withal activities of human on the earth’s surface, which includes mining, agriculture, transportation, settlement etc.
Importance of studying geography
i. It helps u to understand basic physical system that affects everyday life e.g water cycles, wind and ocean current.
ii. To gain skills of observing, measuring, recording and interpreting phenomena
iii. To understand interaction between our country and other countries and share idea of solving problems.
iv. To acquire skills for combating environment problems in order to conserve and manage the environment in the sustainable way.
v. To develop awareness and knowledge about natural resources (Land, natural forests, mineral deposits, water etc) wild animals climatic regions and other natural resources.
vi. It provide base for specialization career for example cartographer, climatology, geologist etc.
vii. It helps to learn on how other countries in the world solve different problems like fire outbreak diseases, environmental problems etc.
viii. To gain the knowledge of employment opportunities.
BRANCHES OF GEOGRAPHY
There are three main branches of geography namely;
(a) Physical geography
(b) Practical geography
(c) Human and economic geography
A. Physical geography
Is concerned with land formation processes, and pattern in natural environment such as atmosphere. Also is the branch of geography that studies all physical features e.g mountains, rift valley
B. Practical geography
Is the branch of geography concerned with field study of photograph interpretation, map work, statistics and research.
C. Human and Economic geography or Regional geography.
It deals withal activities of human on the earth’s surface, which includes mining, agriculture, transportation, settlement etc.
Importance of studying geography
i. It helps u to understand basic physical system that affects everyday life e.g water cycles, wind and ocean current.
ii. To gain skills of observing, measuring, recording and interpreting phenomena
iii. To understand interaction between our country and other countries and share idea of solving problems.
iv. To acquire skills for combating environment problems in order to conserve and manage the environment in the sustainable way.
v. To develop awareness and knowledge about natural resources (Land, natural forests, mineral deposits, water etc) wild animals climatic regions and other natural resources.
vi. It provide base for specialization career for example cartographer, climatology, geologist etc.
vii. It helps to learn on how other countries in the world solve different problems like fire outbreak diseases, environmental problems etc.
viii. To gain the knowledge of employment opportunities.
Topic 2: THE SOLAR SYSTEM
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| The diagram showing solar system |
Components of the solar system includes the following:-
A STAR
Is a heavenly body that possesses and transmits its own light. A group of stars is known as galaxy. To the sky there are millions of stars.
SUN
Sun is the big star. It is one among the millions of stars that one sees at night except that it looks much bigger because it is closer to the earth than other distant stars. The sun is much larger than other distant stars from the earth, in fact much larger than all the planets put together. It forms about 91.8% of the mass of the solar system. The elements that form the material of the sun are different proportion from those of the earth. The sun is composed of approximately; 75% hydrogen, 23% helium, and 3% of other elements The earth is relatively cold body but the sun is so hot that nearly all molecules are broken into their separate atoms and all are mixed together into a single hot gas. Its average surface temperature is about 6000 0c, it is much hotter in the interior where it is about 14,000,000 0c. The sun is the main source of all light and heat that the planets receive.
SOLAR ENERGY
Solar energy is the energy produced by the sun. Solar energy has power that helps to perform an activity. This capacity exist in form of light and heat.
USES OF SOLAR ENERGY
Solar energy is used in many ways: -
1. In drying clothes, grains, fruits and meat.
2. Used by plants to sun to manufacture their food through the process known as photosynthesis.
3. Solar energy captured in solar panels and stored in batteries provides electricity used in generating industrial and home Appliances like television, refrigerator, Oven, electric iron and cooker.
4. Many everyday items such as calculators and other low power consuming devices can be powered by solar energy effectively
5. Is used as a source of vitamin D for human being
6. It is used for evaporation of water from water bodies which is necessary for rain formation
PLANETS
The planets are bodies that revolve around the sun. There are eight known planets in our solar system, these includes Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.. All planets revolve around the sun in the same orbit that are elliptical and nearly the same plane. A diagram of solar system The time taken to complete an orbit round the sun depends on the distance of the planet from the sun. All the light and heat of the planets come from the sun. Hence the temperatures on the planet depend on their relative distances from the sun. However, Pluto is not a planet because an object to be a planet, it needs to meet these requirements (criteria) defined by the International Astronomical Union (IAU) as follows:
i) It needs to be in orbit around the sun
ii) It needs to have enough to pull itself in a spherical shape
iii) It needs to have "Cleared neighborhood of its orbit"
Note: Any object that doesn't meet the 3rd criteria is considered a dwarf planet. And so, Pluto is a dwarf planet is not a planet.
PLANETS POSITION AND CHARACTERISTICS
COMETS
Sometimes at night one sees objects with leading heads and right tail at the sky. These are called comets. At present many scientists believe that comets are composed of ice crystals and fragment matters. Comets revolve around the sun far beyond the limits of Pluto. They can be seen from the earth only when they come close to the sun.
ASTEROIDS
Asteroids are solid heavenly bodies revolving around the sun mostly between the orbits of Mars and Jupiter. There are thousands of these, the largest having diameter of less than 800km. These bodies cannot be seen without a telescope because they are very far away.
METEORS
Meteors refers to the hard matter falling from outer space, they become visible between 110 and 145 km above the earth’s surface, where as a result of friction with the atmosphere become hot and usually disintegrate. When they do completely disintegrate as they pass through the atmosphere reach the earth’s surface and are known as meteorites. Meteorites are usually made of nickel, iron or silica fragments of disintegrated comets. There are two known meteorites in Tanzania one is found in Mbozi District and the other fell at Malampaka in Kwimba District in 1930.
SATELLITES
Natural satellite is anybody that moves around the planet or any other body larger than itself. There are 60 known satellite in the solar system. The largest know satellite is the earth’s moon.
THE EARTH
Is the third planet from the solar system that support life. The Earth is made of the Atmosphere (air), Hydrosphere (water bodies), The crust solid, Molten material, Biosphere (living things). About ¾ of the earth’s surface is covered by water. In fact no other planet in the solar system is known to have water bodies; the shape of the earth is a flattened sphere. This flattening is very slight as indicated by measurements in diameters through poles and at the equator. The diameter through the poles is 12,713 km while at the equator it is 12,757 km.
EVIDENCES OF THE EARTH’S SHAPE
There are some several evidences which are used to prove that the earth is sphere like structure, some of them are shown in the following: -
(i) SUNRISE AND SUNSET
The sunrise and sunset at different places of the earth, people in the east see the sun earlier than the people in the west due to earth’s rotation from west to east. If the earth was flat the whole world would have sunrise and sunset at the same time.
(ii) CIRCUMNAVIGATION OF THE EARTH
If traveling from a certain point of the earth and you go straight around the earth you will come to the point of origin. The first traveler around the world named Magellan in 1519-1522 proved this, image did not encounter abrupt edge over the world in his voyage.
(iii) AERIAL PHOTOGRAPHS
Photographs taken by satellites or aeroplane from the air show that the earth has a curved or round shape. (iv) SHIP’S VISIBILITY If you are in the coast viewing a ship which is very far you will see the soot, then the pipe and eventually
(v) LUNAR ECLIPSE
The shadow of the earth thrown to the moon during lunar eclipse is always round. Only a spherical object can give a circular shadow.
MOVEMENT OF THE EARTH.
The earth is in motion all the time. One does not feel this motion because one moves with it, like all other planets, the earth has two motions known as: -
(a) Rotation and
(b) Revolution
ROTATION
Rotation is the spinning of a body on its axis. Earth’s rotation – is a spinning of the earth on its axis. Axis – is an imaginary line joining the north and south poles through the center of the earth The earth rotates on its axis from west to east. It makes one complete rotation after every twenty four hours or one day, the following observations illustrates the earth’s rotation from west to east;
1. When traveling in a fast moving vehicle we notice trees and other objects on both sides of the road moving in the opposite direction. This observation is similar to the movement of the earth’s rotation to the sun.
2. In the morning the sun appears to rise over the eastern horizon but due to the fact that the sun is the center of the solar system we know that it does not move in relation to the solar system. This shows that the earth is moving from west to east.
3. At night most of the stars appear to move across the sky from east to west. This shows that the earth is moving from west to east.
THE CAUSE OF EARTHS ROTATION/EVIDENCE TO PROVE THAT THE EARTH ROTATES
(a) Day and night While the earth is rotating, the region of the earth facing the sun experience daylight. The region facing away from the sun experience darkness (night).
(b) Different hours As the earth rotate from west to east it takes 24 hours for the earth to make full rotation through 3600 . Therefore as the earth rotate it causes a difference of 4 minutes for every 10 in turn. This is in turn means that it causes a difference of 1 hour for every 150 it turns.
(c) Deflection of winds and ocean currents As the earth rotate from west to east winds are deflected because they are not flowing in their intended direction.
(d) Daily rising and falling of tides The rise and fall of tides are caused by gravitational forces of the moon and the sun acting on the earth.
REVOLUTION
Revolution is the movement of one body around another. Earth’s revolution: -
- Is the movement of the earth around the sun
- The earth takes 365 ¼ days for a complete revolution
- When the earth takes 366 days to accomplish one revolution is called a Leap year
- The earth revolution revolve around the sun in an elliptical
- Due to the shape of the earth’s orbit, the earth is very closer to the sun at one point of the year than at another.
APHELION AND PERIHELION
Aphelion is the furthest position of the earth’s orbit from the sun.
- The earth is at Aphelion each year on 4th July when it is in 152 million kilometers from the sun.
Perihelion is the nearest position of the earth from the sun.
- The earth is at perihelion each year on 3rd January when it is 147.3 million kilometers from the sun. Therefore the speed of revolution is about 29.66 km per second.
THE EFFECTS OF EARTH’S REVOLUTION
When the earth revolves around the sun it causes: -
(a) Seasons of the year
(b) Eclipse
(c) Difference in the length of day and night
(d) Change of midday sun in the latitudes.
SEASONS
Season is one of the four periods of the year separated from each other by different temperature conditions. The seasons are summer, autumn, winter and spring. They are more pronounced between 23 0 c and 66 0 c of latitudes. At the equator the year is divided between hot and wet seasons while at the poles is very cold all the year around and the season cannot be identified easily. The Northern hemisphere summer months are May, June and July. Autumn months are August, September and October, Winter Months are November, December and January while spring months are February, March and April. In the Southern Hemisphere summer months are November, December and January, Autumn months are February, March and April Winter has May, June and July while spring months are August , September and October.
CAUSE OF SEASONS
Seasons are caused by inclination of the earth’s axis and the earth’s revolution around the sun. The earth’s axis is tilted at an angle of 66 0 to the earth’s orbital plane and it is always pointing to the same direction in space. In its revolution around the sun one of the hemispheres is inclined towards the sun to one period of the year and away from it at another period of the year.
ECLIPSE
This is the movement of one heavily body between the two others, such that it casts shadow over the other. The eclipse involves three heavily bodies namely; the Sun, the Earth and the Moon. So long as the sun is the central body of the solar system, it never moves, only the earth and the moon are in the motion all the time. An eclipse is said to be total eclipse when the whole body is obscured i.e completely blocked from the sun light and it is described as a partial eclipse when the only part of the body becomes obscured. At any place an eclipse will last short time, hardly seven minutes because both the earth and the moon are in motion.
TYPES OF ECLIPSE
There are two types of eclipse i.e Lunar eclipse and solar eclipse
1. LUNAR ECLIPSE (ECLIPSE OF THE MOON)
This occurs when the earth moves between the sun and the moon, this casting its shadow over the moon. Image of the diagram showing lunar eclipse
2. THE SOLAR ECLIPSE
The solar eclipse also known as the sun eclipse This occurs when the moon passes between the earth and the sun casting casting its shadow over the earth. This can be partial solar eclipse or total solar eclipse depending on the position of the moon or the earth, in Tanzania 16th February 1980 was the a total solar eclipse and partial solar eclipse in Mbeya Tanzania at Wanging’ombe was 1st September 2016. Umbra or total eclipse it occurs when whole body obscured or completely blocked from the suns light, Penumbra or partial eclipse is when the only part of the body becomes obscured.
NB; At any place eclipse last for short time up to seven minutes
THE APPARENT MOVEMENT OF THE OVERHEAD SUN
The apparent movement of overhead sun is related to the different positions of the earth on its movements it revolve around the sun. The overhead sun appears to move northwards and southward in an osculating (swinging) manner. However the overhead suns northward limit is latitude 0 N People beyond this latitude never see the sun vertically above their head. The latitude of 230 N is known as Tropic of cancer. Similarly the overhead sun ends 230 N is apparent southward movement. This latitude is known as Tropic of Capricorn on 21st June the sun is vertically overhead on the tropical of cancer this known as summer solstice in the Northern hemisphere. On the 22nd December the sun is vertically overhead on the Tropic of Capricorn this is the winter solstice in the northern hemisphere. north ward and south ward journeys.
THE SOLSTICITES
The sun is overhead twice a year at the equators 21st march and 23rd September. 21st march is known as the spring equinox and 23rd September is known as autumn equinox in the northern hemisphere. Equinox means equal nights, at equinox the length of the day and night is equal over all places on the earth’s surface. Viewed from the southern hemisphere the solstices and equinoxes are reversed.
LENGTH OF DAY AND NIGHT
Places along the equator experience equal day and night all the year, but northwards or southwards towards the poles, the length of the day and night vary with latitudes for instance in northern summer when the northern hemisphere is inclined towards the sun, days are longer than nights. However at latitude 660 North known as the Arctic. Cycle and beyond the appears around the sky without setting in the North Pole day light is experienced for six months before the sun set. Then this region remains in darkness for the next six months, Latitude 660 south is known as Antarctic cycle. The polar regions south of the Antarctic cycle experience the long six months night from march to September and the six months day light from October to February.
PARALLEL AND MERIDIANS.
Parallels are more commonly known as Latitudes Latitude/Parallel Is an imaginary line drawn on map from west to east and forms a circle. It measured in degree minute and seconds of a point on the earth’s surface north or south of the earth from the equator. The equator is the latitude which divides the earth into two equal hemisphere, one in the north and other in the south. Meridians Are commonly known as longitude Longitude/Meridian, Is angular distance measured in degrees East or west of the prime meridian, they run from north to south.
IMPORTANCE OF PARALLEL AND MERIDIAN
a) Longitude (Meridian) enable us to calculate local and international times of different places on the earth’s surface.
b) Latitudes (Parallel) helps us to explain and understand the variation in climate on the surface of the earth. c) Parallel and meridian are used by pilots and sailors to guide their path.
d) They enables us to locate places on maps, for example Tanzania is found at the latitude of 6degre and 00 south of the equator and longitude 35degree and 00 east of Greenwich meridian.
LATITUDE AND LONGTUDE
Latitude: Is the angular distance north or south of the equator measured in degrees, minutes and seconds. OR Are lines drawn on map from east to west. The equator is latitude of zero (0) degree The equator divides the earth into equal parts (Hemisphere) The atmosphere north of the equator is called northern hemisphere and the hemisphere is known as southern hemisphere. Latitudes are also known as parallel lines because the equator never meet. The lines of latitude are measured from zero degree to 90 degree north and south.
LINES OF LATITUDE ARE
The equator 0 o The tropical of cancer 23 ½ 0N, The tropical of Capricorn 231/2 0s, The arctic cycle 661/2 0N, and Antarctic cycle 661/2 0s Longitude Is an angular distance measured in degrees east or west of the prime meridian, they run from north to south. Greenwich is the longitude of zero (0) degree, it’s also known as prime meridian. The prime meridian the line running through the poles (North and South) and is known as Greenwich 0 Longitude are measured from 0 to 180 degree East or West of the Greenwich, all meridians are passing through the north and south poles.
LONGITUDE AND TIME:
The earth rotates on its own axis from west to east once on every twenty four hours (one day). This means that the earth turns through 360 degree in twenty four hours. All place along the given meridian will experience midday along the same meridian, it is known as Local mean, on the Greenwich meridian is known as Local Mean Time (LMT) When it is 12:00 noon, on the Greenwich meridian it will be 1:00 at a place of 15 degree E or 11:00 at a place of 15 degree W. Find time for example for Musoma in Tanzania 34 degree when it is 12:00 in Kinshasa Zaire. 1. Note the longitude position of Kinshasa 15 30 degree E and Musoma 34 degree 2. Find the difference in degree of longitude between Kinshasa and Zaire
GREAT CIRCLE
The intersection of the surface of the sphere and a plane through its center for example meridian of longitude and equator are great circle in the earth’s surface. There for is no limit to the number of great circle that can be drawn. The great circle is drawn on a globe (or other sphere) with a center that includes the center of the globe. Thus a great circle divides the globe into two equal halves.
IMPORTANCE OF GREAT CIRCLE
1. The great circles are important for aero planes which use them as route ways to guide their path.
2. Great circle are important for ship to follow routes along great circles.
TIME
Refers to a period that is used for event or activity. It is measured in seconds, hours, days, months or years.
TIME ZONES
Is the region having the same standard time. Standard time is common on time for all countries belonging to the same time zone for example Tanzania, Kenya, Uganda, Ethiopia, Djibouti and Somalia use the same standard time. This commonly referred to the East African Standard time. There would be problems of telling time if every place had its own time set according to local mean time. For example, there would be great confusion in railway airway time table or in radio programs if they had to show difference time each one place within a small area. To avoid this problem difference stretches on earth takes their time from great meridian. The time adopted is known as STANDARD TIME.
In East Africa Standard time is taken from meridian of 45 degree E when a whole stretch of land keeps to the same standard time that stretches from a time zone. There for time zone refers to a stretch of land where standard time is accepted through out a longitudinal zone 15 degree width. Countries with large stretches of land have several standard zones. There are 24 time zones in the World. The Greenwich meridian is the starting point for dividing the globe into 24 time zones, The standard time for Greenwich is known as Greenwich Mean Time (GMT). Essence of Time zone. In a certain place there could be a place on the surface using its own local time. This would bring a lot of confusion example every radio station would have to announce different times for every region within the same country; Local time of Bukoba would be different from that of Dodoma. The above confusion was avoid when it was internationally agreed to split the World into 24 time zone according to longitudes The longitudinal division across the earth with an approximates with of 15 degree of longitude which is regular across the oceans. Each time zone has standard time which is the time of longitude (Meridian near the center of time zone. In the same way, all countries belonging to the same way, all countries belonging to the same time zone have common time. Note: Large countries like Canada, USA and Russia have different standards for different regions within them because they are crossed by many time zone.
Question: 1. If it is 9:30 am at Kasse 15 degree what time is in Zanzibar 45 degree? 2. Find the time for the youncle 30 degree W if it is 12:00 noon London 3. When it is 3:30 pm at Nairobi 25 degree E what is the time for Comoro 120 E?
INTERNATIONAL DATE LINE.
Is the line where date changed or where the calendar day begins. The one travel eastward across the date line will gain a day, if one travel westwards and cross the date line will lose a day, if Greenwich it is noon at Tuesday a place 90 degree W would be 10 am on Tuesday, at a place 180 degree it would be midnight midnight Monday .On other hand a place 90 degree E would be 6:00 pm on Tuesday and at a place 180 degree E would be midnight on Tuesday
Topic 3: MAJOR FEATURES OF THE EARTH’S SURFACE
Earth is the fifth largest planet in the solar system. Its surface is
approximately 510 millions square kilometers. This means that earth is
very large. The surface of the earth is made up of two main features
LAND and WATER BODIES The land's surface area is estimated at 29.2% of
the total area of the earth's surface, while water covers the remaining
70.8%. Most of the land exists in large blocks called Continents.
Likewise, most of the water is contained in large water bodies called
seas and oceans.CONTINENT
Continent is a major landmass rising from the ocean floor. Formerly the continents were big landmass known as Pangaea. Due to the forces operating continuously, the landmass was separated into two parts namely Laurasia to the northern hemisphere and Gondwanaland to the Southern hemisphere. Further separation or drifting led to the formation of the present continents which include Africa, Antarctica, Asia, Australia, Europe, North America and Southern America. The boundaries of the continents with the exception of Asia and Europe were filled with water. Ural Mountains separated Europe and Asia. While other continents are separated by water bodies called seas and oceans. For instance African continent and Asia to the north are separated by Mediterranean sea and Red sea. Africa and South America are separated by Atlantic ocean, etc. The land surface occupies 29% of the surface of the earth, it forms seven continents. It includes Islands adjacent to the continents. The seven continents are Asia, Africa, South America, North America, Australia, Europe and Antarctica. Oceans surround these continents. There is more land surfaces in the Northern Hemisphere than in the southern hemisphere. The table below shows Size of continents. Continents Area (km2) Asia 43 608 000 Africa 30 335 000 North America 25 349 000 South America 17 611 000 Antarctica 13 340 000 Europe 10 498 000 Australia 7 682 000
MAJOR RELIEF FEATURES OF CONTINENTS
The surface of any continent is not smooth. It has mountains, hills, plain and plateaus, river valleys, lakes, basins and rift valleys. Altitude and slope give rise to the different relief features. Plain, plateaus and mountains form the major relief features of continent.
PLAINS
Plains are large and continuous stretches of comparatively flat land and not rising much above the sea level. Many extensive plains are a result of down warping of the earth’s crust for example, Siberia in Asia, North European plains, Indo- getic plain and the Great central plains of North America.
PLATEAUS
Extensive high altitude areas with more or less uniform summit levels are known as plateaus. They are formed when forces formed within the earth uplift a plain region. Major plateaus regions include the central plateau of Africa, the Brazilian Highlands and the Arabian plateau. The African plateau is higher in the South and East of the continent than it is in the north and west. In some areas, the outflow and spread of lava have formed plateaus over an extensive area, for instance the Deccan plateau in the India sub-continent and Colombia plateaus in the United states.
MOUNTAIN
Is a large and elevated part of the earth’s surface rising to greater height than ordinary hills. There are three major types of Mountains depending on how they are, These are;
a] Fold mountains
b] Block mountain
c] Volcanic mountain
a] FOLD MOUNTAIN
The wrinkling of the earth’s crust forms fold mountains, folding once occurs where rocks are laid in layers, fold mountains usually consist of high ranges that extend for hundreds of kilometers across the continent. Thus fold mountains form the most extensive ranges in the world. For example the Rock mountains in North America vary in width from 640 to 1,600 kilometers and are about 5,000 kilometers in length. These types of mountains have some of the highest peaks of the world. Mountain Everest is 8,848 meters above sea level and the Andes is 7,003m above sea level. Apart from the Himalayas in Asia and the Andes in South America, this group of mountains includes the Andes-in South America, the Alps in Europe, the Atlas in North Africa, the Cap Rangers in South Africa, the Appalachians in U.S.A and the Great Divide Range in Australia.
b] BLOCK MOUNTAINS
Block Mountains are formed when a movement in the earth’s crust forces the rocks to break. As a result, enormous cracks or faults are formed when sets of faults run parallel to each other and the ground between is forced up, a block mountain (horst) is formed. Usually Block Mountains do not extend over wide areas as Fold Mountains do. Example of block mountains are the Sambara, Uruguru and Ruwenzori mountains in East Africa, the Vosges and Black forest mountains in Europe and mount Sinai in Asia. Other features associated with faulting and Block Mountains are rift valleys or grabens. Rift valleys are formed when the land is between two sets of faults sink down. The Great East African Rift valley is the longest in the world. It stretches from the Baka’s valley east of the Lebanon mountains, through the Red sea, Ethiopia, East Africa to the lower Zambezi Area. A branch of the valley runs along Lake Tanganyika in Tanzania to Lake Albert in Uganda. Another less extensive rift valley is the middle Rhine Rift valley between the Vosges and black forest mountains. The walls of a rift valley form fault lines or escarpments. Trenches formed by rift valley are sometimes filled with water to form Lakes like Lake Nyasa, Lake Albert, Lake Eyas, and Lake Turkana all of which are in East Africa and the Dead Sea in Jordan.
c] VOLCANIC MOUNTAIN
Volcanic mountains are formed from the pouring up and cooling of hot molten lava and ashes that are thrown out from the earth’s interior after a volcanic eruption. Among the existing volcanic mountains some still experience a periodic eruptions for example the mountain Italy, the Krakatoa in Indonesia, the Mufumbiro in Uganda, the Oldonyo Lengai in Tanzania and the Cameroons in Equatorial Africa. These are said to be active volcanic. The volcanic mountains, which erupted only once in historical time and are no longer active, are said to be dormant. Good examples are the Kilimanjaro and Meru mountains both of which are in Tanzania. That volcanic mountain which have not erupted for a very long time and have not shown any signs of erupting again are said to be extinct (dead). Good examples are the Kenya, Elgon and Rungwe Mountains, all of which are in East Africa.
TYPES OF VOLCANIC MOUNTAIN
i) Active volcanic mountain
ii) Dormant volcanic mountain
iii) Extinct ( dead) volcanic mountain
Volcanic Mountains are usually conical in shape and mostly contain craters at their summits, for example, Fujiama and Kilimanjaro Mountains. Sometimes craters are filled with water to form crater lake for example, Lake Duluti and Ngorongoro both of which are in Arusha Region in Tanzania. Also Lake Ngozi found at Rungwe district in Mbeya.
RESIDUAL MOUNTAINS
Apart from the three types of mountains, there are Residual Mountains which are formed by a prolonged denudation. Denudation involves removing weaker rocks from the land the result of which landforms are lowered leaving behind resistant rock. The remaining resistant rock is known as residual mountains. Examples of residual mountains include the Haggard Mountains of central Sahara, the Sekenke hills of Singida in Tanzania, the Adamawa mountains of Eastern Niger, the Highlands of Scotland. The sierras of central Spain, and the Mess and Butlers of the western plateau of the United States.
BASINS
A basin is a form of natural or artificial depression (hollow) varying in size in the earth’s surface.
WATER BODIES
Water bodies includes the folowing;
RIVERS
When rain falls or snows melt, water flows in small channels which finally join together and form large streams or river.
Is the natural out floor of water from different sources can be from Lakes, Spring, melted ice etc. to the mouth which can be ocean, lake or sea.
TRIBUTARIES
These are the streams that join together to form main streams or parent
DISTRIBUTARIES
These are the small streams which are formed when the main river branches off before it enters the sea or lake. The area from which the river system collect its rain water known as RIVER BASIN or DRAINAGE BASIN or CATCHMENT AREA. The boundary between one drainage basin to the next is known as WATER DIVIDE or WATER SHED or BASIN PERIMETER.
RIVER SYSTEM (THE WATER) DIVIDE ENCLOSING A DRAINAGE BASIN
Water flows down a slope by the help of force of gravity, While flowing it carries minerals in solution, rock fragments and organic matters from high land area to low land area. The end of running water (run-off) is to the sea/ocean.
THE MAIN RIVERS IN AFRICA
These are : The Congo River, The Niger river, The Orange river, The Nile river, The Zambezi river and the Limpopo river. The Congo, Niger and Orange rivers flows and pour their water into Atlantic Ocean. Zambezi and Limpopo flows into Indian Ocean. River Nile flows into Mediterranean Sea
THE VOLUME OF WATER IN THE RIVERS
The volume of water in the river varies seasonally. During the rainy season or when ice melts, streams channels carry more water than in dry season. When it rains heavily the stream channel fail to hold all of it so the water- over flows the river banks and floods the river valley. Flood causes destruction to crops, building, animals and human.
LAKES
Is a hollow in the earth's surface in which water collects. Lakes are formed when some run-offs (running and being holded by depressions or hollows on the continent) have their outlets to the sea. Example of Lakes is Nyasa, Victoria and Kyoga in Africa.
OCEANS
Ocean is a large body of salt water. that occupies about 75 percent of the earth’s surface. There is more water surface in the Southern hemisphere than in the North Hemisphere. Ocean include the Indian, the pacific, the Atlantic, the Arctic and the Southern Ocean. Ocean water contains a number of dissolved mineral salts. They include sodium Chloride (common salts) which makes up about 78 percent of all salt in the ocean water. Ocean water also contain compounds of magnesium, potassium, and calcium, Most of these minerals are in the ocean as a result of constant accumulation. Since the formation of the oceans Most minerals come from the land have been dissolved by water and brought into the ocean by rivers, wind and ice. Another source has been volcanic activity that takes place in the oceans. Saltiness of the ocean water is not the same everywhere in the ocean. Saltiness of ocean water depends mainly on temperature which affects capacity of water to dissolve salt, the amount of fresh water brought into the ocean by rivers and rainfall and the amount of evaporation taking place from surface. Generally temperature of ocean water decreases from the equator where surface temperature is about 250C, to the Polar Regions where water is very cold temperature drops to 2.20 C.
The table below shows the oceans and their size.
Ocean Area (km2) Average depth (m) Pacific 155557000 4028 Atlantic 76762000 3926 Indian 68556000 3936 Southern 20327000 [4000-5000] Arctic 14056000 1205 Ocean water is constantly in motion. There are two types of movement .One is horizontal movement, which is in the form of current and the other is a vertical movement which is the rising of sub- surface water and the sinking of surface water.
Ocean Current
An ocean current is the movement of surface water in the ocean. These are warm and cold currents. Currents of the oceans are set in motion by prevailing winds; differences of density and temperature of the ocean water, the rotation of the earth and the shape of continent influence the flow of the major ocean current of the world.
Tides
Tides are the rising and falling in the level of water in the ocean. The tides occur twice in 24 hours. The level of which tides rise and fall varies slightly. On the days when it rises to its highest level it also falls to its lowest level. This rising and falling is caused by the pull of gravity of the moon and the sun.
Waves
Waves are the up and down movement of the surface of water. The highest part of the waves is called the crest and the lowest is called the trough. The distance from one crest to the next or from trough to trough called the wave length. Upper waves travel in a definite direction, while the lower waves are the up and down movement. For example a cork thrown into the water does not travel with the waves. It moves up and down but not forward. Waves are driven to the shore by wind. The higher of the wave and the force with which it is driven are determined by the strength of the wind and the distance of open water which it has blown.
The ocean floor
Is the bottom of the surface of the ocean. The floor of the ocean is irregular. The diagram below shows the ocean floor. The major relief features of the ocean floor are;
The continental shelf
The continental shelf is a gently sloping margin of a continent. Continental shelf are occupied by shallow water that extends from the coast to the depth of about 200 meters towards the ocean basin.
The continental Slope
The continental slope is found at the point where the continental shelf forms a steep slope towards the ocean floor.
Oceanic Deep or Trenches
Ocean Deep or trenches are long narrow depressions or trough found on the ocean floor.
Deep sea plains or abyssal plain;
Deep sea planes are the most extensive area of the ocean floor. They are monotonous undulating areas. Large parts of these plains are covered with time mode.
Topic 4: WEATHER
The weather should not be equated with climate, though they are very
closely related to each other in the study of meteorology and
climatology.
Weather: The conditions of the atmosphere which occur at a place at
specific time period from hour to hour or day to day.
There for when we say it is hot, or wet, or cloudy we are saying
something about weather, which is the condition of the atmosphere at a
place at a specific time periods (from hour to hour or day to day). It
is never be static, and thus cannot be generalized. In the same country,
even over a small area weather can vary tremendously. It may be sunny
in one part of district but raining heavily in few kilometers.
Climate: Is the average weather condition of an area recorded over a
long period of time ( over 30 or 35 years). This involves systematic
observation, recording and processing of the various elements of climate
such as rainfall, temperature, humidity, air pressure, winds, clouds
and sunshine before any standardization of the climatic means or average
can be arrived at.
For example when we say climate of Norway is hot wet equatorial climate
that is the summing up of the average everyday weather conditions of the
country throughout the year.
Importance of weather:
a) Good weather improves people's lives
b) Weather determines the kind of clothing to be worn by people in an area.
c) Knowledge of the weather of a place enables people to carry out economic activities which can be sustained by the weather in that place. e.g. dairy cattle do well in a cool and wet place.
d) By studying the weather of a place over a long time, we can establish its climate.
Weather and Human activities
Most human activities affected by weather that is experienced at a place. For example, When the rains are heavy, flooding occurs and causes damage to crops, animals and infrastructure like roads. This means that few economic activities can take place. When there is no rain, plants and animals die, rivers and streams dry up, and irrigation and other economic activities like fishing cannot be carried out. Therefore weather affects the social economic activities of a place.
Elements of Weather
Are the basic atmospheric condition of a place at a given time.
There are 7 element of weather
i) Sunshine
ii) Temperature
iii) Humidity
iv) Cloud cover
v) Precipitation
vi) Wind
vii) Atmospheric pressure
IMPORTANCE OF EACH ELEMENT OF WEATHER
i. Sunshine refers to the sun's rays that reach the surface of the earth. Importance of Sunshine: The sun's energy enables plants to manufacture food through the process of photosynthesis People need sunshine to dry their crops, food like cassava, millet, maize and fish They also use sunshine to warm themselves Dries clothes after washing them
ii. Temperature Refers to how hot or cold an object or place is. The heat in the atmosphere is supplied by the sun. Importance of Temperature: Warm is essential for plant and animal survival Plants need warm in order to manufacture their fool Facilitates formation of clouds
iii. Humidity Is the amount of water vapor(moisture) in the atmosphere There are two types of humidity:
a) Absolute humidity and
b) Relative humidity
a) Absolute humidity: Is the actual amount of water vapor or moisture in a given volume of air at a particular temperature.
b) Relative humidity: Is the ratio of the actual amount of water vapor or moisture in a given volume of air (i.e. absolute humidity) to the maximum amount of water vapor that the same volume of air can hold at the same temperature
iv. Cloud cover Clouds are masses of tiny droplets of water or ice particles or both which are suspended in the atmosphere. They are formed when water vapor or moisture in the atmosphere cools and condenses. Importance of cloud cover: Are important because they condense to form rain and other forms of precipitation.
v. Precipitation This refers as the fall or deposition of moisture water vapor or frozen water from the atmosphere onto the earth’s surface. Importance of Precipitation: All life on the earth is purely dependent on moisture provided through precipitation The importance of rain is that, rain provides water for plants to grow (i.e. water for irrigation, growth of grass and pasture depend on rain) Also animals too need water to drink and human needs for domestic and industrial uses. Note: Excess rain and rainstorms result in disasters due to flooding
vi. Wind
Wind is air in motion. It is made up of variety of gases, such as oxygen and carbon dioxide. Wind move horizontally from areas of high pressure to areas of low pressure. Importance of wind: They are important in many aspects of weather for instance they cause flow of heat and moisture and their transfer from one point to another and are also responsible for the movement of clouds. Wind direction and wind speed or velocity is two important aspects in geography. Wind direction is important because it help us to understand characteristics of the particular winds in terms of temperature and moisture content. Wind speed or velocity determines wind strength or force and therefore determines weather conditions of a place. Example, When strong winds blow over a place, little or no rainfall will be experienced.
vii. Atmospheric Pressure
This is the force at a point on the earth's surface due to the weight of air above that point. The atmosphere is the air surrounding earth's surface and it has weight, which is force with which it presses down on a unit area. The weight of atmosphere on the earth's surface and at sea level at 1033.3g/cm2 -Areas of very low pressure cause feeling of weightlessness and that is the feeling one gets when he or she is on top of a very high mountain like Mt Kilimanjaro. -Areas under very low pressure may experience very strong winds periodically as air flows into such areas from high pressure regions.
WEATHER STATION
Is a place where the elements of weather are measured and recorded. Or A station for taking meteorological observations, making weather forecasts, and disseminating such information. Examples of the elements are temperature, humidity, pressure, rainfall, wind direction and speed, cloud cover, and sunshine.
STEVENSON SCREEN
Is the white wooden box, which is mounted on four legs with louver sides in order to allow free air to enter inside. In order to prevent sun’s heat to reach inside, the roof is double bodied. The screen is painted white to improve insulation. The screen is then placed on a stand which is about 121 centimeters above the ground. Instruments used to measure elements of weather. Instruments used for measuring elements of weather include rain gauge, wind vane, anemometer, barometer, hygrometer, and the camp-bell stokes sunshine recorder.
1. Temperature:
Temperature is the degree of hotness or coldness of a body, an instrument used to measure temperature is thermometer and expressed in degrees of centigrade or Fahrenheit scales. There are three main types of thermometer inside the Stevenson screen, these includes minimum thermometer, the maximum thermometer, and six’s thermometer.
Maximum thermometer
Is the thermometer made of glass and uses mercury to measure and record the highest temperature reached in a day. The maximum temperature is read from the side of the metal index nearest to the mercury. When the temperature falls the mercury falls, leaving behind the metal index still indicating the maximum temperature reached. A magnet is used to bring back the metal index into contact with the mercury.
Minimum thermometer
Is the thermometer used to measure and record the lowest temperature reached in a day. Alcohol is used because it has lower freezing point than mercury. Any fall in temperature will cause the alcohol column to contract and the meniscus (the curved upper surface of the alcohol column) will pull the index back along the tube whenever temperature rises, the alcohol will expand and flow freely past the metal index without pushing it up. Therefore the metal index is always left as a record of the lowest temperature reached between the readings. The part of the metal index away from the bulb will indicate the lowest temperature reached.
Six’s thermometer
This thermometer used for measuring and recording maximum and minimum temperature reached in a day. The thermometer consists of a “U” shaped glass tube. When temperature rises, the alcohol on the left hand side expands, pushing the mercury underneath downward and up the right hand side. While the mercury on the right hand side rises, it pushes the metal index upwards, until the highest temperature is reached for the day. This temperature is read from the scale on the right hand side, when temperature falls the alcohol on the left hand side contracts. This pushes the mercury downward and up by the mercury. Reading and Recording Temperature are taken every day in the morning at regular fixed times but not later than 9:00 a.m. In well-equipped meteorological station, temperature are measured and recorded continuously by self-recording instrument called thermograph.
What does the following mean?
(a)The mean dairy temperature Is the average of the maximum and minimum temperature. The monthly range of temperature is the difference between the highest mean daily temperature and the lowest mean daily temperature in a month.
(b) The dairy range of temperature Daily range of temperature is the different between the maximum and the minimum temperatures.
(c) The annual range of temperature The annual range of temperature in a year which is the difference between the highest mean monthly temperature and the lowest mean monthly temperature. The temperature are represented by using a graph. Lines are drawn to connect places with the same mean monthly temperature. These lines are known as isotherms.
EXERCISE
Study the table below of Monthly temperature data for Inyala-Mbeya then calculate. Month J F M A M J J A S O N D Temperature 0C 15 12 17 16 10 9 8 10 20 21 20 19 (a)The mean monthly temperature
(b) The annual range of temperature
(c) Draw a graph to represent the above table and show the hottest month?
Factors affecting temperature
Factors that affect temperature include: altitude, ocean currents, and distance from the sea, latitude and prevailing winds.
Altitude
Temperature decreases with an increase in altitude at the rate of 0.6 0 c for every 100 meters. That is why the summit of Mount Kilimanjaro with 5895 meters above sea level permanently covered with ice.
Ocean currents
Ocean currents are either warm or cold. Warm currents raise the temperature of wind blowing across them while cold currents lower temperature of such winds. Some winds blowing on shore will influence the temperature of such winds in some of coastal areas with the temperature of the ocean currents.
Distance from the sea
Distance from the sea affects temperature. This is because large areas of land masses lying at great distance from the sea do not get the moderating influence of the oceans. Lack of these moderating effects makes the land masses experience very low temperature in winter and very high temperature in summer. This extremely results in high annual range of temperature. The interior of the continent of Asia is a typical example.
Latitude
The amount of heat received at any place depends on the angle at which the sun’s rays strike the surface of the earth and the duration of sunshine. At the equator the sun’s rays reached the earth’s surface at almost right angles. Throughout the year but the angle decreases as one move towards the pole. Therefore temperature decreases with increase in latitude because the sun rays spread over a larger area and its heating effect decreases.
Prevailing wind.
2. Humidity
The sun’s heat causes water to evaporate from the surface of the ocean and other water bodies. to form water vapor in the atmosphere. Humidity is the amount of water vapor in air. Or Humidity is the state of the atmosphere in relation to the amount of water vapour it contains. Humidity indicates the degree of dampness of the air and it is one of the main influences on weather. It is expressed in either absolute or relative terms. Absolute humidity, expressed in grams per cubic meter, is the actual amount of water vapour present in a certain volume of air at a given temperature. Relative humidity is the amount of water vapour present in a mass of air expressed as a percentage of the total amount of water vapour that would be present when that air is saturated at the temperature. Air is saturated when the atmosphere cannot hold any more water vapour. This condition depends on the temperature and pressure of the air. Humidity is measured by a hygrometer which consists of wet and dry bulb thermometers. The wet bulb thermometer is kept moist (wet) by wrapping it in a Muslin which is then dipped in a container of distilled water. When the air is not saturated water evaporates from the muslin and cools the wet bulb. The cooling effect causes the mercury to contract. The dry bulb is not affected in the same way as wet bulb because it does have a Muslin wrapping. It is affected by the surrounding air. So when the air is not saturated the two thermometers show different readings, when the air is saturated the two thermometers show the same readings. Therefore when there is a big difference in reading between the two thermometers humidity is low and when there is small difference humidity is high.
Exercise 1.
Define the following terms: a) Climate b)Weather station c) Temperature d) Maximum thermometer e) Minimum thermometer f) Humidity g) Absolute humidity h) Relative humidity i) Weather
2.Mention seven elements of weather and their instruments
3.How can you obtain the following; a) Daily range temperature b) Mean daily temperature
4. List down five factors affecting temperature
3. Precipitation:
Precipitation refers to the deposition of moisture from the atmosphere on the earth’s surface. It includes dew, frost, snow, mist and hail, sleet and rain.
Dew: Is the water vapor that condenses on solid objects when the dew is reached. The droplets formed after condensation of water vapor which is then deposited on the cool surface such as building, leaves, grass and stones.
Frost: Frost is a tiny ice crystals deposited on objects on the ground, frost is formed when temperature falls below freezing point.
Snow: snow is the frozen droplets of water; snow formed when water vapor in the atmosphere turns into crystals of ice and reaches the ground before melting.
Mist: mist refers to tiny water droplets suspended immediately above the ground. Frost is similar to mist but it is denser with less visibility.
Hail: Hail is the form of precipitation falling with small ice blocks Sleet: is a mixture of snow and rain. It forms when the temperature of the ground is lower than the temperature above.
Rain: Rain is the droplets of water falling from the atmosphere after condensation. When water vapor rises, It cools at high altitude until dew point is reached. Dew point is the temperature rate at which the atmosphere is saturated with water vapors. Condensation takes place after dew point has been reached to form water droplets. These droplets combine to form larger drops which fall as rain.
TYPES OF RAINFALL
a) Convectional rainfall When rain is formed through vertical rising of moist air currents it is called convectional rain Convectional currents arise due to differential heating of the earth’s surface. Convectional rains are common in the tropical areas.
b) Relief rain Sometimes moist winds are forced by a high mountain to rise and when they reach high altitude the moisture in them condenses to form droplets, which fall as rain. Rain formed in this way is called relief or orthographical rain. The sides of the mountain facing the direction of the winds is known as the wind ward side while that which faces away from the direction of the wind is known as the lee wards side or the rain shadow, the lee ward side gets very little rain . A typical example of rain shadow in Tanzania is found in the western side of mountain Kilimanjaro, winds blow from the Indian Ocean in the east and are forced by this mountain to rise and drop most of their moisture on the eastern and south eastern slopes. When these winds blow to the western side of the mountain they already relatively dry.
c) Cyclonic rain When large masses of air with different characteristics of temperature and moisture, cyclonic rain may occur. As the warm and moist air is forced up over the cool and dry air, it expands. At higher altitude the warm air cools and water vapor condenses to form clouds and rain. On the other hand tropical cyclones are formed over oceans is the tropical between latitude 8 0 N and 8 0 S. They usually bring very heavy rainfall and are associated with thunderstorms and very fast moving wind, which often causes destruction along coastal settlements. In the Caribbean and U.S.A tropical cyclones are called hurricanes in Africa they are known as cyclones and in China and Japan they are called typhoons. Rainfall is measured by using a rain gauge. The rain gauge consist of an outer case , a copper-receiving vessel, a funnel whose diameter is normally 13 centimeters, a clear glass jar or bottle and a graduated measuring cylinder.
Rainfall Variation
Rainfall variation is a normal phenomenon on the earth which is caused by a number of factors. Some of them include Ocean currents, distance from the equator, prevailing winds, water bodies, nature and shape of the coast, distance from the sea, altitude and human activities.
Ocean Currents.
There are two types of Ocean Currents. The warms and the cold currents. The warm Ocean Currents yield rainfall over the adjustment land. This is because the winds cross over them do carry large amounts of moisture for example Mozambique current. Much rainfall is experienced along the East Coast of Africa. Cold ocean currents are crossed by wind which have no moisture, hence brings very little or no rain in the adjacent land. For example banguera currents in south-west Africa coast and the canary current in the north-west coast of Africa.
Distance from the equator.
Areas along the equator receive more rain than areas away from it. This is because of high amount of solar radiation, which result into evaporation and raising of air moisture hence condensation takes place resulting into convectional rainfall. Congo basin and Brazil are few examples which receive much rainfall due to their position. Prevailing winds. Winds blowing from the land towards the sea (off-shore) are carrying moist air from the land and yield no rainfall except in the sea. These winds usually lead to dryness of the land with very low rains in the coast. Effects of these winds are development of deserts. Eg, the Sahara Dessert in the North of Africa. Lack of water bodies. Areas with large water bodies such as areas around lake Victoria receive much rain than areas without water bodies like central Tanzania and North Eastern Kenya. Water bodies increase much rain to adjacent areas. Nature and shape of the coast. The coastal areas, which align parallel to the prevailing wind such as the N.E trade winds move parallel with the North Eastern Coast of Kenya, yield no rainfall. As result a dry climate is experienced along the coast.
Distance from the sea.
The areas near the sea or ocean experience high rainfall due to winds blowing moisture from the sea which would cause rainfall to the coastal areas. Areas that are very far from the sea receive very little or no rainfall for example, Dar es Salaam in Tanzania and Mombasa in Kenya receive heavier rains than Dodoma, Singida and Tabora, which have long distance from the Indian Ocean.
Altitude
Altitude is also a factor for uneven distribution of rainfall, highlands force the warm air to rise over them. When they condense, they cause rain to fall on the wind ward side. The other side of the highland (leeward) may receive very little or no rainfall at all. People of such areas includes the eastern part of South Africa receives heavy rain (orographic) while the Western part experiences prolonged droughts due to effects of Drankensburg mountains. The eastern part of East Africa also receives heavier rainfall than the western side due to warm moist winds blowing from the Indian Ocean.
Human activity.
Besides other environmental benefit plants or trees intercept precipitation and return moisture to the air through transpiration and evaporation. This process becomes balanced when there is no destruction of the vegetation. Human activity such as settlement, animal rearing, farming and transportation however can cause rainfall variations on the earth’s surface through land degradation. When people cut trees or clear the bushes, land is naturally destroyed. The destruction of vegetation disturbs evaporation, condensation and precipitation process, which are necessary elements of rainfall. In turn the amount of precipitation in the air is interrupted either by causing floods or droughts. The California desert in U.S.A and the Sahel in Africa are the results of droughts caused by human activities, which have led to the expansion of the deserts in the 1980s.
RAINFALL EFFECTS
Too much rainfall for example, the case of Elnino (1998) results into negative impacts on life and properties. Heavy rainfall may cause destruction of houses, roads and bridges, crop and loss of life for both human and animals. In addition to the loss of life and property, floods, which are the results of heavy rainfall results into eruption of diseases such as malaria, cholera, and dysentery. On the other hand, too little rainfall leads to little yield of food and cash crops. Famine and hunger in the parts of the world is a result of lack of rainfall. Prolonged dry seasons in some parts of the world have resulted into the loss of lives of both animals and the people. North Eastern Kenya, Somalia, Sudan, and Ethiopia are some of the areas where people and animals have lost their lives because of long droughts. Rainfall reliability leads to continuous crops production and animal keeping hence improves standard of living and the industrial development of a nation may be realized. Sustainable agriculture is made possible and people are assured of enough food and cash crops.
4, Pressure
The air surrounding the earth’s surface from the atmosphere. The atmosphere has weight. The force with which it presses down on a unit area is called atmospheric pressure. The pressure is exerted equally in all directions. To demonstrate that atmospheric pressure is exerted equally in all directions one can do the following experiment. Take a glass with full of water. Cover the top of the glass with a piece of thin paper Hold the glass upside down. Atmospheric pressure is measured by an instrument called a barometer.
There are two types of barometer, mercury barometer and aneroid barometer.
A mercury barometer is a simple apparatus consisting of a glass of about 9.2 centimeters long and bowl filled with mercury. The glass tube is filled with mercury and being put upside down in the bowl of mercury. At sea level the mercury will fall until the column is about 76 centimeters above the surface of the mercury in the bowl. A vacuum is left at the top of the tube. To read the pressure centimeter rule is placed besides the glass tube and the change in height of the mercury column gives the reading of the atmospheric pressure. Mercury barometers are not portable. Barometer Another instrument commonly used is the aneroid barometer. It consists of an air fight box of thin metal containing very little air. The top of this box moves inwards and outwards with changes in atmospheric pressure. This movement is transmitted by a system of levers to a circular seal with a pointer which shows the reading of atmospheric pressure. Pressure is expressed in millimeters with reference to the height of mercury column or in millibars. A bar is the standard unit of pressure measurement. It is divided into one thousand units called millibars. At sea level pressure is one thousand millimeters of mercury or 1.5 kilograms of force per square centimeters. This is equivalent to 1013.2 millibars approximately one bar. Lines joining places with the same pressure are called isobars Lines joining places with the same pressure are called and the pressure is greater at sea level where the whole thickness of the atmosphere exert its weight.
Pressure decreases at the rate of 10 millibars for every 100 meters increase in height because the thickness of the atmosphere decreases. Pressure
1. What is pressure? Pressure is the air surrounding the earth’s surface forms the atmosphere.
2. Define atmospheric pressure – Is the force with which atmosphere presses down on a unit area 3. Atmospheric pressure is measured by a barometer
4. Two types of barometers are; a) A mercury barometer. b) Aneroid barometer.
5. Pressure is expressed in millimeter.
6. A bar is the standard unit of pressure measurement
7. It is divided into one thousand units called millibars.
8. Lines joining places with the same pressure is called isobars.
9. Mention three roles of pressure in human life.
a) Partial filling of tires hinders proper movement of the vehicle.
b) Pressure is also helpful to the patients whose parts of body fail and pump blood to other parts of the body.
c) Other pressured things include the decoration balloons and playing.
10.Pressure decreases at the rate of 10 millibars for every 100 meters
5. Winds
Wind is air in motion from high pressure to low pressure area.
SEA BREEZE (DAY) Is when winds blow from sea to land during a day.
LAND BREEZE (NIGHT)
This occurs during night when winds blow from land to sea.
During the day the land is usually warmer than the sea, and the air pressure on the land is lower than that over the sea. Therefore winds blow from sea to land. These winds are known as sea breezes. During the night the land is cooler than the sea and there is low pressure on the sea. Therefore winds blow from land to sea, these are called land breezes.
There are great variations in the general patterns of wind systems in areas of the earth’s surface where there are large land masses adjacent to large water bodies. During summer, intense low pressure develops in central Asia in the Northern hemisphere and winds blow inform of high pressure over the Indian and pacific oceans. Wind belts of the world Occasionally in the westerly wind system depressions and anticyclones develop. A depression is an area of low pressure in which winds blow a circular motion. This motion is anti-clockwise in the Northern hemisphere but clockwise in the southern hemisphere. A depression develops when cold heavy air comes into contact with warm moisture. A depression is usually associated with cyclonic rains. Anticyclones are areas of high pressure in which winds blow in a clockwise circular motion in the Northern hemisphere. They normally follow a depression and are associated with cool fine weather with no rain.
Wind direction is measured by a wind-vane.
A wind-vane consists of a freely rotating arrow fitted to a central rod. The arrow of the wind-vane always points to the direction from which winds blows, and the wind is named after this direction. Four arms marking the directions of the cardinal points are fixed to the stationary central rod.
Wind speed is measured by an instrument called an anemometer. This instrument consists of three or four horizontal arms that when there is wind the arms rotate. This movement operates a meter which records the speed of the wind in kilometers per hour.
Weather forecasting
Weather forecasting is defined as a prediction of weather condition of a place at a given time approximately 24 to 48hrs. Weather forecasting is obtained through two methods namely, traditional and modern methods. The traditional method predicts weather through observation of types of birds voices, crocking of frogs, rainbow, migration of birds, changes of wind direction, position of the moon and general body feeling. The method is still widely used in predicting weather by the indigenous communities. Modern method involves the use of modern equipment such as satellites, electronic computers, radar, and aircraft, balloons, ships, submarines, rockets and daily records from weather stations. This method of predicting weather is more reliable and accurate.
METHODS AND INSTRUMENTS USED FOR WEATHER FORECASTING (MODERN METHODS)
1. Radiosonde This is an instrument used to register pressure and temperature from the ground to roughly 12km above the ground. The instruments are fixed to balloons filled with helium gas and are released into the atmosphere every day at a particular time from different weather stations. The radiosonde transmits radio signals to computers on the ground station where they are analyzed. The signal transmitted give pressure, temperature and humidity readings at different altitude. These balloons are made in such a way that they burst when they reach a certain altitude.
2. Satellite The satellite used for predicting weather are human made space. They move around the earth so that they can provide various types of information. They are also used in radio, television and telephone communication. Satellite transmits photographs on weather conditions on a daily basis. The movement of clouds can be predicted from an analysis of the movement of winds force period of 24hours.
3. Persistence method This is simpler way of making a weather forecast. It assumes that the atmosphere conditions of a place at the time of forecast will not change. For example, if it is 28°C in Dodoma today the persistence method predicts that it will still be 28°C in Dodoma tomorrow. If two inches of rain fell in Arusha yesterday, this method predicts that two inches of rain will fall in Arusha today.
4. Statistical forecasting In this method, meteorologists ask themselves how is the weather usually like at this time of the year?. They then collect records of average temperatures and rainfall over the last five years. This give forecasters an idea of what the weather is "supposed to be like" at the certain time of year.
Weather forecasting is useful to people in the following ways;
a) Farmers planning their work for a year. This is because weather broad casting helps farmers to adjust their farming activities to suit the expected weather conditions.
b) Weather broadcasting greatly influence transport since it helps sailors and air travelers to know condition of the winds.
c) Helps in planning sport activities.
d) Helps in selecting suitable clothes.
e) Helps fishermen to plan their fishing activities.
f) Helps contractors to plan for suitable houses.
g) Helps in geographical expeditions like tours and military.
h) Military personnel benefit from weather broadcasting as they can plan their military activities depending on weather conditions
Importance of weather:
a) Good weather improves people's lives
b) Weather determines the kind of clothing to be worn by people in an area.
c) Knowledge of the weather of a place enables people to carry out economic activities which can be sustained by the weather in that place. e.g. dairy cattle do well in a cool and wet place.
d) By studying the weather of a place over a long time, we can establish its climate.
Weather and Human activities
Most human activities affected by weather that is experienced at a place. For example, When the rains are heavy, flooding occurs and causes damage to crops, animals and infrastructure like roads. This means that few economic activities can take place. When there is no rain, plants and animals die, rivers and streams dry up, and irrigation and other economic activities like fishing cannot be carried out. Therefore weather affects the social economic activities of a place.
Elements of Weather
Are the basic atmospheric condition of a place at a given time.
There are 7 element of weather
i) Sunshine
ii) Temperature
iii) Humidity
iv) Cloud cover
v) Precipitation
vi) Wind
vii) Atmospheric pressure
IMPORTANCE OF EACH ELEMENT OF WEATHER
i. Sunshine refers to the sun's rays that reach the surface of the earth. Importance of Sunshine: The sun's energy enables plants to manufacture food through the process of photosynthesis People need sunshine to dry their crops, food like cassava, millet, maize and fish They also use sunshine to warm themselves Dries clothes after washing them
ii. Temperature Refers to how hot or cold an object or place is. The heat in the atmosphere is supplied by the sun. Importance of Temperature: Warm is essential for plant and animal survival Plants need warm in order to manufacture their fool Facilitates formation of clouds
iii. Humidity Is the amount of water vapor(moisture) in the atmosphere There are two types of humidity:
a) Absolute humidity and
b) Relative humidity
a) Absolute humidity: Is the actual amount of water vapor or moisture in a given volume of air at a particular temperature.
b) Relative humidity: Is the ratio of the actual amount of water vapor or moisture in a given volume of air (i.e. absolute humidity) to the maximum amount of water vapor that the same volume of air can hold at the same temperature
iv. Cloud cover Clouds are masses of tiny droplets of water or ice particles or both which are suspended in the atmosphere. They are formed when water vapor or moisture in the atmosphere cools and condenses. Importance of cloud cover: Are important because they condense to form rain and other forms of precipitation.
v. Precipitation This refers as the fall or deposition of moisture water vapor or frozen water from the atmosphere onto the earth’s surface. Importance of Precipitation: All life on the earth is purely dependent on moisture provided through precipitation The importance of rain is that, rain provides water for plants to grow (i.e. water for irrigation, growth of grass and pasture depend on rain) Also animals too need water to drink and human needs for domestic and industrial uses. Note: Excess rain and rainstorms result in disasters due to flooding
vi. Wind
Wind is air in motion. It is made up of variety of gases, such as oxygen and carbon dioxide. Wind move horizontally from areas of high pressure to areas of low pressure. Importance of wind: They are important in many aspects of weather for instance they cause flow of heat and moisture and their transfer from one point to another and are also responsible for the movement of clouds. Wind direction and wind speed or velocity is two important aspects in geography. Wind direction is important because it help us to understand characteristics of the particular winds in terms of temperature and moisture content. Wind speed or velocity determines wind strength or force and therefore determines weather conditions of a place. Example, When strong winds blow over a place, little or no rainfall will be experienced.
vii. Atmospheric Pressure
This is the force at a point on the earth's surface due to the weight of air above that point. The atmosphere is the air surrounding earth's surface and it has weight, which is force with which it presses down on a unit area. The weight of atmosphere on the earth's surface and at sea level at 1033.3g/cm2 -Areas of very low pressure cause feeling of weightlessness and that is the feeling one gets when he or she is on top of a very high mountain like Mt Kilimanjaro. -Areas under very low pressure may experience very strong winds periodically as air flows into such areas from high pressure regions.
WEATHER STATION
Is a place where the elements of weather are measured and recorded. Or A station for taking meteorological observations, making weather forecasts, and disseminating such information. Examples of the elements are temperature, humidity, pressure, rainfall, wind direction and speed, cloud cover, and sunshine.
STEVENSON SCREEN
Is the white wooden box, which is mounted on four legs with louver sides in order to allow free air to enter inside. In order to prevent sun’s heat to reach inside, the roof is double bodied. The screen is painted white to improve insulation. The screen is then placed on a stand which is about 121 centimeters above the ground. Instruments used to measure elements of weather. Instruments used for measuring elements of weather include rain gauge, wind vane, anemometer, barometer, hygrometer, and the camp-bell stokes sunshine recorder.
1. Temperature:
Temperature is the degree of hotness or coldness of a body, an instrument used to measure temperature is thermometer and expressed in degrees of centigrade or Fahrenheit scales. There are three main types of thermometer inside the Stevenson screen, these includes minimum thermometer, the maximum thermometer, and six’s thermometer.
Maximum thermometer
Is the thermometer made of glass and uses mercury to measure and record the highest temperature reached in a day. The maximum temperature is read from the side of the metal index nearest to the mercury. When the temperature falls the mercury falls, leaving behind the metal index still indicating the maximum temperature reached. A magnet is used to bring back the metal index into contact with the mercury.
Minimum thermometer
Is the thermometer used to measure and record the lowest temperature reached in a day. Alcohol is used because it has lower freezing point than mercury. Any fall in temperature will cause the alcohol column to contract and the meniscus (the curved upper surface of the alcohol column) will pull the index back along the tube whenever temperature rises, the alcohol will expand and flow freely past the metal index without pushing it up. Therefore the metal index is always left as a record of the lowest temperature reached between the readings. The part of the metal index away from the bulb will indicate the lowest temperature reached.
Six’s thermometer
This thermometer used for measuring and recording maximum and minimum temperature reached in a day. The thermometer consists of a “U” shaped glass tube. When temperature rises, the alcohol on the left hand side expands, pushing the mercury underneath downward and up the right hand side. While the mercury on the right hand side rises, it pushes the metal index upwards, until the highest temperature is reached for the day. This temperature is read from the scale on the right hand side, when temperature falls the alcohol on the left hand side contracts. This pushes the mercury downward and up by the mercury. Reading and Recording Temperature are taken every day in the morning at regular fixed times but not later than 9:00 a.m. In well-equipped meteorological station, temperature are measured and recorded continuously by self-recording instrument called thermograph.
What does the following mean?
(a)The mean dairy temperature Is the average of the maximum and minimum temperature. The monthly range of temperature is the difference between the highest mean daily temperature and the lowest mean daily temperature in a month.
(b) The dairy range of temperature Daily range of temperature is the different between the maximum and the minimum temperatures.
(c) The annual range of temperature The annual range of temperature in a year which is the difference between the highest mean monthly temperature and the lowest mean monthly temperature. The temperature are represented by using a graph. Lines are drawn to connect places with the same mean monthly temperature. These lines are known as isotherms.
EXERCISE
Study the table below of Monthly temperature data for Inyala-Mbeya then calculate. Month J F M A M J J A S O N D Temperature 0C 15 12 17 16 10 9 8 10 20 21 20 19 (a)The mean monthly temperature
(b) The annual range of temperature
(c) Draw a graph to represent the above table and show the hottest month?
Factors affecting temperature
Factors that affect temperature include: altitude, ocean currents, and distance from the sea, latitude and prevailing winds.
Altitude
Temperature decreases with an increase in altitude at the rate of 0.6 0 c for every 100 meters. That is why the summit of Mount Kilimanjaro with 5895 meters above sea level permanently covered with ice.
Ocean currents
Ocean currents are either warm or cold. Warm currents raise the temperature of wind blowing across them while cold currents lower temperature of such winds. Some winds blowing on shore will influence the temperature of such winds in some of coastal areas with the temperature of the ocean currents.
Distance from the sea
Distance from the sea affects temperature. This is because large areas of land masses lying at great distance from the sea do not get the moderating influence of the oceans. Lack of these moderating effects makes the land masses experience very low temperature in winter and very high temperature in summer. This extremely results in high annual range of temperature. The interior of the continent of Asia is a typical example.
Latitude
The amount of heat received at any place depends on the angle at which the sun’s rays strike the surface of the earth and the duration of sunshine. At the equator the sun’s rays reached the earth’s surface at almost right angles. Throughout the year but the angle decreases as one move towards the pole. Therefore temperature decreases with increase in latitude because the sun rays spread over a larger area and its heating effect decreases.
Prevailing wind.
2. Humidity
The sun’s heat causes water to evaporate from the surface of the ocean and other water bodies. to form water vapor in the atmosphere. Humidity is the amount of water vapor in air. Or Humidity is the state of the atmosphere in relation to the amount of water vapour it contains. Humidity indicates the degree of dampness of the air and it is one of the main influences on weather. It is expressed in either absolute or relative terms. Absolute humidity, expressed in grams per cubic meter, is the actual amount of water vapour present in a certain volume of air at a given temperature. Relative humidity is the amount of water vapour present in a mass of air expressed as a percentage of the total amount of water vapour that would be present when that air is saturated at the temperature. Air is saturated when the atmosphere cannot hold any more water vapour. This condition depends on the temperature and pressure of the air. Humidity is measured by a hygrometer which consists of wet and dry bulb thermometers. The wet bulb thermometer is kept moist (wet) by wrapping it in a Muslin which is then dipped in a container of distilled water. When the air is not saturated water evaporates from the muslin and cools the wet bulb. The cooling effect causes the mercury to contract. The dry bulb is not affected in the same way as wet bulb because it does have a Muslin wrapping. It is affected by the surrounding air. So when the air is not saturated the two thermometers show different readings, when the air is saturated the two thermometers show the same readings. Therefore when there is a big difference in reading between the two thermometers humidity is low and when there is small difference humidity is high.
Exercise 1.
Define the following terms: a) Climate b)Weather station c) Temperature d) Maximum thermometer e) Minimum thermometer f) Humidity g) Absolute humidity h) Relative humidity i) Weather
2.Mention seven elements of weather and their instruments
3.How can you obtain the following; a) Daily range temperature b) Mean daily temperature
4. List down five factors affecting temperature
3. Precipitation:
Precipitation refers to the deposition of moisture from the atmosphere on the earth’s surface. It includes dew, frost, snow, mist and hail, sleet and rain.
Dew: Is the water vapor that condenses on solid objects when the dew is reached. The droplets formed after condensation of water vapor which is then deposited on the cool surface such as building, leaves, grass and stones.
Frost: Frost is a tiny ice crystals deposited on objects on the ground, frost is formed when temperature falls below freezing point.
Snow: snow is the frozen droplets of water; snow formed when water vapor in the atmosphere turns into crystals of ice and reaches the ground before melting.
Mist: mist refers to tiny water droplets suspended immediately above the ground. Frost is similar to mist but it is denser with less visibility.
Hail: Hail is the form of precipitation falling with small ice blocks Sleet: is a mixture of snow and rain. It forms when the temperature of the ground is lower than the temperature above.
Rain: Rain is the droplets of water falling from the atmosphere after condensation. When water vapor rises, It cools at high altitude until dew point is reached. Dew point is the temperature rate at which the atmosphere is saturated with water vapors. Condensation takes place after dew point has been reached to form water droplets. These droplets combine to form larger drops which fall as rain.
TYPES OF RAINFALL
a) Convectional rainfall When rain is formed through vertical rising of moist air currents it is called convectional rain Convectional currents arise due to differential heating of the earth’s surface. Convectional rains are common in the tropical areas.
b) Relief rain Sometimes moist winds are forced by a high mountain to rise and when they reach high altitude the moisture in them condenses to form droplets, which fall as rain. Rain formed in this way is called relief or orthographical rain. The sides of the mountain facing the direction of the winds is known as the wind ward side while that which faces away from the direction of the wind is known as the lee wards side or the rain shadow, the lee ward side gets very little rain . A typical example of rain shadow in Tanzania is found in the western side of mountain Kilimanjaro, winds blow from the Indian Ocean in the east and are forced by this mountain to rise and drop most of their moisture on the eastern and south eastern slopes. When these winds blow to the western side of the mountain they already relatively dry.
c) Cyclonic rain When large masses of air with different characteristics of temperature and moisture, cyclonic rain may occur. As the warm and moist air is forced up over the cool and dry air, it expands. At higher altitude the warm air cools and water vapor condenses to form clouds and rain. On the other hand tropical cyclones are formed over oceans is the tropical between latitude 8 0 N and 8 0 S. They usually bring very heavy rainfall and are associated with thunderstorms and very fast moving wind, which often causes destruction along coastal settlements. In the Caribbean and U.S.A tropical cyclones are called hurricanes in Africa they are known as cyclones and in China and Japan they are called typhoons. Rainfall is measured by using a rain gauge. The rain gauge consist of an outer case , a copper-receiving vessel, a funnel whose diameter is normally 13 centimeters, a clear glass jar or bottle and a graduated measuring cylinder.
Rainfall Variation
Rainfall variation is a normal phenomenon on the earth which is caused by a number of factors. Some of them include Ocean currents, distance from the equator, prevailing winds, water bodies, nature and shape of the coast, distance from the sea, altitude and human activities.
Ocean Currents.
There are two types of Ocean Currents. The warms and the cold currents. The warm Ocean Currents yield rainfall over the adjustment land. This is because the winds cross over them do carry large amounts of moisture for example Mozambique current. Much rainfall is experienced along the East Coast of Africa. Cold ocean currents are crossed by wind which have no moisture, hence brings very little or no rain in the adjacent land. For example banguera currents in south-west Africa coast and the canary current in the north-west coast of Africa.
Distance from the equator.
Areas along the equator receive more rain than areas away from it. This is because of high amount of solar radiation, which result into evaporation and raising of air moisture hence condensation takes place resulting into convectional rainfall. Congo basin and Brazil are few examples which receive much rainfall due to their position. Prevailing winds. Winds blowing from the land towards the sea (off-shore) are carrying moist air from the land and yield no rainfall except in the sea. These winds usually lead to dryness of the land with very low rains in the coast. Effects of these winds are development of deserts. Eg, the Sahara Dessert in the North of Africa. Lack of water bodies. Areas with large water bodies such as areas around lake Victoria receive much rain than areas without water bodies like central Tanzania and North Eastern Kenya. Water bodies increase much rain to adjacent areas. Nature and shape of the coast. The coastal areas, which align parallel to the prevailing wind such as the N.E trade winds move parallel with the North Eastern Coast of Kenya, yield no rainfall. As result a dry climate is experienced along the coast.
Distance from the sea.
The areas near the sea or ocean experience high rainfall due to winds blowing moisture from the sea which would cause rainfall to the coastal areas. Areas that are very far from the sea receive very little or no rainfall for example, Dar es Salaam in Tanzania and Mombasa in Kenya receive heavier rains than Dodoma, Singida and Tabora, which have long distance from the Indian Ocean.
Altitude
Altitude is also a factor for uneven distribution of rainfall, highlands force the warm air to rise over them. When they condense, they cause rain to fall on the wind ward side. The other side of the highland (leeward) may receive very little or no rainfall at all. People of such areas includes the eastern part of South Africa receives heavy rain (orographic) while the Western part experiences prolonged droughts due to effects of Drankensburg mountains. The eastern part of East Africa also receives heavier rainfall than the western side due to warm moist winds blowing from the Indian Ocean.
Human activity.
Besides other environmental benefit plants or trees intercept precipitation and return moisture to the air through transpiration and evaporation. This process becomes balanced when there is no destruction of the vegetation. Human activity such as settlement, animal rearing, farming and transportation however can cause rainfall variations on the earth’s surface through land degradation. When people cut trees or clear the bushes, land is naturally destroyed. The destruction of vegetation disturbs evaporation, condensation and precipitation process, which are necessary elements of rainfall. In turn the amount of precipitation in the air is interrupted either by causing floods or droughts. The California desert in U.S.A and the Sahel in Africa are the results of droughts caused by human activities, which have led to the expansion of the deserts in the 1980s.
RAINFALL EFFECTS
Too much rainfall for example, the case of Elnino (1998) results into negative impacts on life and properties. Heavy rainfall may cause destruction of houses, roads and bridges, crop and loss of life for both human and animals. In addition to the loss of life and property, floods, which are the results of heavy rainfall results into eruption of diseases such as malaria, cholera, and dysentery. On the other hand, too little rainfall leads to little yield of food and cash crops. Famine and hunger in the parts of the world is a result of lack of rainfall. Prolonged dry seasons in some parts of the world have resulted into the loss of lives of both animals and the people. North Eastern Kenya, Somalia, Sudan, and Ethiopia are some of the areas where people and animals have lost their lives because of long droughts. Rainfall reliability leads to continuous crops production and animal keeping hence improves standard of living and the industrial development of a nation may be realized. Sustainable agriculture is made possible and people are assured of enough food and cash crops.
4, Pressure
The air surrounding the earth’s surface from the atmosphere. The atmosphere has weight. The force with which it presses down on a unit area is called atmospheric pressure. The pressure is exerted equally in all directions. To demonstrate that atmospheric pressure is exerted equally in all directions one can do the following experiment. Take a glass with full of water. Cover the top of the glass with a piece of thin paper Hold the glass upside down. Atmospheric pressure is measured by an instrument called a barometer.
There are two types of barometer, mercury barometer and aneroid barometer.
A mercury barometer is a simple apparatus consisting of a glass of about 9.2 centimeters long and bowl filled with mercury. The glass tube is filled with mercury and being put upside down in the bowl of mercury. At sea level the mercury will fall until the column is about 76 centimeters above the surface of the mercury in the bowl. A vacuum is left at the top of the tube. To read the pressure centimeter rule is placed besides the glass tube and the change in height of the mercury column gives the reading of the atmospheric pressure. Mercury barometers are not portable. Barometer Another instrument commonly used is the aneroid barometer. It consists of an air fight box of thin metal containing very little air. The top of this box moves inwards and outwards with changes in atmospheric pressure. This movement is transmitted by a system of levers to a circular seal with a pointer which shows the reading of atmospheric pressure. Pressure is expressed in millimeters with reference to the height of mercury column or in millibars. A bar is the standard unit of pressure measurement. It is divided into one thousand units called millibars. At sea level pressure is one thousand millimeters of mercury or 1.5 kilograms of force per square centimeters. This is equivalent to 1013.2 millibars approximately one bar. Lines joining places with the same pressure are called isobars Lines joining places with the same pressure are called and the pressure is greater at sea level where the whole thickness of the atmosphere exert its weight.
Pressure decreases at the rate of 10 millibars for every 100 meters increase in height because the thickness of the atmosphere decreases. Pressure
1. What is pressure? Pressure is the air surrounding the earth’s surface forms the atmosphere.
2. Define atmospheric pressure – Is the force with which atmosphere presses down on a unit area 3. Atmospheric pressure is measured by a barometer
4. Two types of barometers are; a) A mercury barometer. b) Aneroid barometer.
5. Pressure is expressed in millimeter.
6. A bar is the standard unit of pressure measurement
7. It is divided into one thousand units called millibars.
8. Lines joining places with the same pressure is called isobars.
9. Mention three roles of pressure in human life.
a) Partial filling of tires hinders proper movement of the vehicle.
b) Pressure is also helpful to the patients whose parts of body fail and pump blood to other parts of the body.
c) Other pressured things include the decoration balloons and playing.
10.Pressure decreases at the rate of 10 millibars for every 100 meters
5. Winds
Wind is air in motion from high pressure to low pressure area.
SEA BREEZE (DAY) Is when winds blow from sea to land during a day.
LAND BREEZE (NIGHT)
This occurs during night when winds blow from land to sea.
During the day the land is usually warmer than the sea, and the air pressure on the land is lower than that over the sea. Therefore winds blow from sea to land. These winds are known as sea breezes. During the night the land is cooler than the sea and there is low pressure on the sea. Therefore winds blow from land to sea, these are called land breezes.
There are great variations in the general patterns of wind systems in areas of the earth’s surface where there are large land masses adjacent to large water bodies. During summer, intense low pressure develops in central Asia in the Northern hemisphere and winds blow inform of high pressure over the Indian and pacific oceans. Wind belts of the world Occasionally in the westerly wind system depressions and anticyclones develop. A depression is an area of low pressure in which winds blow a circular motion. This motion is anti-clockwise in the Northern hemisphere but clockwise in the southern hemisphere. A depression develops when cold heavy air comes into contact with warm moisture. A depression is usually associated with cyclonic rains. Anticyclones are areas of high pressure in which winds blow in a clockwise circular motion in the Northern hemisphere. They normally follow a depression and are associated with cool fine weather with no rain.
Wind direction is measured by a wind-vane.
A wind-vane consists of a freely rotating arrow fitted to a central rod. The arrow of the wind-vane always points to the direction from which winds blows, and the wind is named after this direction. Four arms marking the directions of the cardinal points are fixed to the stationary central rod.
Wind speed is measured by an instrument called an anemometer. This instrument consists of three or four horizontal arms that when there is wind the arms rotate. This movement operates a meter which records the speed of the wind in kilometers per hour.
Weather forecasting
Weather forecasting is defined as a prediction of weather condition of a place at a given time approximately 24 to 48hrs. Weather forecasting is obtained through two methods namely, traditional and modern methods. The traditional method predicts weather through observation of types of birds voices, crocking of frogs, rainbow, migration of birds, changes of wind direction, position of the moon and general body feeling. The method is still widely used in predicting weather by the indigenous communities. Modern method involves the use of modern equipment such as satellites, electronic computers, radar, and aircraft, balloons, ships, submarines, rockets and daily records from weather stations. This method of predicting weather is more reliable and accurate.
METHODS AND INSTRUMENTS USED FOR WEATHER FORECASTING (MODERN METHODS)
1. Radiosonde This is an instrument used to register pressure and temperature from the ground to roughly 12km above the ground. The instruments are fixed to balloons filled with helium gas and are released into the atmosphere every day at a particular time from different weather stations. The radiosonde transmits radio signals to computers on the ground station where they are analyzed. The signal transmitted give pressure, temperature and humidity readings at different altitude. These balloons are made in such a way that they burst when they reach a certain altitude.
2. Satellite The satellite used for predicting weather are human made space. They move around the earth so that they can provide various types of information. They are also used in radio, television and telephone communication. Satellite transmits photographs on weather conditions on a daily basis. The movement of clouds can be predicted from an analysis of the movement of winds force period of 24hours.
3. Persistence method This is simpler way of making a weather forecast. It assumes that the atmosphere conditions of a place at the time of forecast will not change. For example, if it is 28°C in Dodoma today the persistence method predicts that it will still be 28°C in Dodoma tomorrow. If two inches of rain fell in Arusha yesterday, this method predicts that two inches of rain will fall in Arusha today.
4. Statistical forecasting In this method, meteorologists ask themselves how is the weather usually like at this time of the year?. They then collect records of average temperatures and rainfall over the last five years. This give forecasters an idea of what the weather is "supposed to be like" at the certain time of year.
Weather forecasting is useful to people in the following ways;
a) Farmers planning their work for a year. This is because weather broad casting helps farmers to adjust their farming activities to suit the expected weather conditions.
b) Weather broadcasting greatly influence transport since it helps sailors and air travelers to know condition of the winds.
c) Helps in planning sport activities.
d) Helps in selecting suitable clothes.
e) Helps fishermen to plan their fishing activities.
f) Helps contractors to plan for suitable houses.
g) Helps in geographical expeditions like tours and military.
h) Military personnel benefit from weather broadcasting as they can plan their military activities depending on weather conditions
Topic 5: MAP WORK
A map is a scaled representation the earth’s surface on a flat material.
For example a piece of paper, wall, clothes and a piece of wood.
Map reading is the process of examining the given topographical map,
conventional symbols and signs
Map interpretation is the process of examining a given topographical map
of an area represented for the purpose of identifying the geographical
information of an area.
TYPES OF MAPS
The classification of maps is based on the purpose for which each map is drawn. Therefore map can be categorized into three types as follows:
i) Sketch map
ii) Atlas map/ wall maps
iii) Topographical maps
i) Sketch maps; A map drawn from observation (rather than from exact measurements) and representing the main features of an area.
ii) Atlas map/ wall map; A collection of different maps that have been bound together in one volume to form a book. These maps are usually drawn to scales example shows town and cities, hills, mountains, valleys, forests, countries, etc.
iii) Topographical maps; Shows selected physical and human features in an area and their positions on the ground for example hills, village, mountains, lakes, ponds, rivers
COMPONENTS/ESSENTIALS OF A GOOD MAP
A map is good if it contains all the essentials of maps, therefore the essentials are good qualities of maps. The essentials of a good map are:
1) Key. Used to interpret symbols and signs found on a map. They appear in a box at one of the bottom corner of the map. 2) Title; Used to show what’s map is all about. This is the heading of the map. It can appear on top of the map or anywhere else
3) North direction; This is an indication of the north direction. It shows where north is and by knowing north one can know the direction and bearing of the place.
4) Margin; This is a boundary or limit around the map. It gives or shows the reader and interpreter the end of the map.
5) Publisher and date publication; This shows when the map was produced and a publisher.
6) Latitude and Longitude / Grid reference. It used to locate the place on the map. For example the map of Tanzania is located at latitude 6°00' south of the equator and longitude 35°00' east of Greenwich meridian.
7) A scale; It shows the relationship between map distance and the actual ground distance for example 1cm to 10km means one centimeter on the map represents ten kilometers on the ground MAP SCALE Is the relationship or ratio between map distance and actual ground distance. Scale = Map distance Ground (actual) distance.
TYPES OF SCALE.
We can classify the scale according to the size in our criteria. There are three types of scales;
a) Large scale.
They are used to present information on small areas for example a map of village buildings and farms. The map size involves all numbers less than 1:25000 I.e. 1:10000 and 1:5000 Characteristics of large scale.
i) It has smaller numbers in the denominator.
ii) It shows features clearly
iii) It contains geographical details.
b) Medium scale.
They are used to represent medium details shown on the map. i.e. 1:50,000 and 1:100,000. Example of a map that can be drawn using medium scale is a map of a district, region, city etc. c) Small scale. They are used to present information that is long. This type of scale covers a big area with less detail. For example a map of a country, continent or world. May involve numbers between 1 : 500,000 to 1 : 1000,000
Characteristics of small scale.
i) It has the largest denominator.
ii) Contains a lot of geographical information.
iii) It does not show geographical features clearly.
WAYS USED TO EXPRESS MAP SCALE.
i) Statement scale. Refers to the scale which is expressed in terms of words or explanation. For example one centimeter on a map is equivalent to 10 centimeters on the ground.
ii) Linear scale Also is called plain or graphic scale. This is a line which is divided into two parts. The primary division and secondary division. The secondary are expressed in meters and placed on the left side from zero and primaries are expressed in kilometers and placed on the right side from zero.
iii) Representative fraction (RF) scale
Is written as a fraction or ratio eg. 1:50,000 50,000 The distance on a map is expressed as fraction of the actual distance on the ground. Therefore, RF scale = map distance Ground distance. The top number (numerator) represents the map distance on the ground and is usually more than 1. Scale conversion a) To change statement to R.F scale. 1cm represents 60km
Soln
1km=100000cm 60km= x 1:6000000 Therefore R.F scale = 1:6000000 b) One centimeter represents 0.75km b) 1:250000 To convert into statement scale If 1km = 100000 cm ? = 250000 cm 100000cm. x = 250000 cm x 1km 100000 cm 100000 cm X = 1 4 Thus, 1 cm represents 0.25
IMPORTANCE OF SCALE ON THE MAP
a) Scale help to calculate area of a map
b) It enable us to calculate distance on a map
c) Scale shows the relationship between map distance and the actual ground distance d) Scale help us to enlarge and reduce the area on a map or the whole map
e) Scale can be used to calculate the vertical exaggeration on a map f) Scale is used to calculate the gradient on a map Question: Distinguish signs from symbols
QUANTITATIVE INFORMATION ON MAPS
A) MEASURING DISTANCE ON THE MAP
Distance is the length of elongated features on the earth’s surface such as road, railway, river etc. How to measure distance. In order to obtain distance of any feature on the map, consideration should be made on whether the distance to be measured is straight or curved. Straight distance For all straight distances a ruler is used to obtain the distance directly from the topographical map given. Curved distance. It becomes difficult to obtain curved distance of the features by the use of a ruler directly from the topographical map when the area is inclined. In this case the following devices can be used:-
A. A pair of divider. A pair of divider is commonly used to measure the distance. You should start by breaking the length by using a pair of dividers then transfer some of the already drawn straight lines. Then transfer the measured line to the linear scale or ruler for calculation to get the actual distance.
B. A piece of a string. Slowly measures the distances by a piece of string along a given length then transfer it to a linear scale or ruler for actual calculation of the distance.
C. A piece of strip paper Slowly lay a piece of paper along a given length then break your lengths into short segments then transfer to the linear scale for measuring and calculation. For example: The railway distance from station A to B was 20 cm, find ground distance in km if the scale used to construct a map is 1:50000 20 cm map distance Scale distance= map distance Actual distance Scale: 1:50000 If 1km = 100000 cm ? = 50,000 cm 100000 cm = 1km x 50,000 cm 100000 cm 100000 cm = ½ km = ½ km x 20cm =10km. The ground distance of railway from station A to B is 10 km
MEASURING AREAS ON A MAP/CALCULATE AREA OF REGULAR IRREGULAR
Area size refers to the bigness or smallness of an area on the earth’s surface i.e. the bigness or smallness of earth’s surface from topographical map consideration should be made whether the area is regular or not.
E x e r c i s e 1)
To state the following.
a) map
b) map reading
c) Scale
d) Contour
2) Why do we study maps?
3) State the ways of expressing scale.
4) What is the importance of a scale?
5) List at least 3 methods of calculating the linear distance of an object
6) The distance of the road is 16cm from Igurusi to Chimala, convert the distance in kilometers if the scale used is 1:100000 b) From the above convert the same distance in km if the scale is changed to 1:50000
REGULAR SHAPE These are areas with definite shapes such as squares, triangles etc. Their total perimeters or areas are obtained by mathematical formula i.e. length x width, side x side etc.
IRREGULAR SHAPE These are areas with indefinite shapes such as lakes, farms, ponds etc where these areas can be obtained by any of the following three methods; a) Square method b) Strip method c) Geometrical method
SQUARE METHOD
This is the most accurate and most widely method used. Square methods are normally used as follows;
a) Count all full squares that are complete
b) Count incomplete squares and divide them by 2 c) Add them with the full squares to obtain the total area in km2
METHODS USED TO SHOW OR LOCATE POSITIONS OF A PLACE ON A MAP.
The following are major methods used to show positions of a place on a map.
i) Grid reference.
ii) Place name
iii) Bearing and compass direction.
iv) Latitude and longitude. Place name. You can locate the position of a place by where the features are found i.e. Kigoma, Mbeya, Dodoma, Lindi etc. Grid reference. Grid reference is a network of vertical lines and horizontal lines on a map. Vertical lines whose numbers increases towards the east are called easting. Horizontal lines whose numbers increase towards the north is known as Northings. Where horizontal lines and vertical lines meet or cross each other they form a square known as grid square. (G.S). A grid reference point is written inform of six digits starting with three digits of Eastings then three digits of nothings. ·A ·C D· ·B 31 32 33 34 35 36 37 38 39 40 41 42 09 08 07 06 05 04 03 02 01 To write down the grid reference of point A, B, C, and D. A = 343086 B = 333036 C = 383077 D = 397046 NB: To write numbers of grid reference starts with easting then northing.
LOCATION AND POSITION: COMPASS BEARING AND DIRECTION
How to find direction of a place on map. Identify them due to points on the given map. Points may be given by using grid reference points, place name or letter. Draw a straight line connecting the two points Mark the major four cardinal points at the starting point with the word from. Now look at the question asked then provide your answer.
COMPASS BEARING.
Bearing are directions which measure degrees clockwise from north. They are written in three figures i.e. 0900 , 0450
HOW TO FIND BEARING ON THE MAP.
Identify the grid reference points given on the maps. Draw a straight line connecting the two points Draw the major four cardinal lines at the starting Now look at the question asked use a protector to measure degree clockwise from north up to the line joining the two points. Then Provide your answer in degrees BEARING. In bearing there is;
a) Forward bearing
b) Backward bearing
a) Forward bearing Is a bearing into a subject. Procedures to calculate forward bearing
i. Identify the two points.
ii. Join them with a straight lines
iii. Draw north direction on a second point.
iv. Measure the angle by using a protector.
v. State the bearing in terms of degrees of the direction.
b) Backward bearing. Is the opposite of forward bearing, it’s taken from the object to the observer while forward bearing is taken from observer to the object.
How to determine the back bearing.
i) Find forward bearing.
ii) Mark the cardinal point north direction of the opposite point
iii) Find the bearing of the observer along the straight line principally to determine the back bearing = FB + OR – 1800 BB= FB +1800 if FB < 1800 BB= FB -1800 if FB >1800 For example: The forward bearing (FB) of Tukuyu from Kyela is 0450 , Back bearing (BB) will be; BB = FB + or – 180. BB = 45 + 180 (FB added because it’s not greater than 180) Therefore Back bearing is 2250
IMPORTANCE OF THE USE OF MAPS
a) People use them to reach their directions
b) Maps are used to describe the features of the earth
c) Builders are maps to plan the best use of the land
d) Road constructors use maps to construct new roads
e) Maps are useful in military activities f)Maps are used in conducting various geographical researches
TYPES OF MAPS
The classification of maps is based on the purpose for which each map is drawn. Therefore map can be categorized into three types as follows:
i) Sketch map
ii) Atlas map/ wall maps
iii) Topographical maps
i) Sketch maps; A map drawn from observation (rather than from exact measurements) and representing the main features of an area.
ii) Atlas map/ wall map; A collection of different maps that have been bound together in one volume to form a book. These maps are usually drawn to scales example shows town and cities, hills, mountains, valleys, forests, countries, etc.
iii) Topographical maps; Shows selected physical and human features in an area and their positions on the ground for example hills, village, mountains, lakes, ponds, rivers
COMPONENTS/ESSENTIALS OF A GOOD MAP
A map is good if it contains all the essentials of maps, therefore the essentials are good qualities of maps. The essentials of a good map are:
1) Key. Used to interpret symbols and signs found on a map. They appear in a box at one of the bottom corner of the map. 2) Title; Used to show what’s map is all about. This is the heading of the map. It can appear on top of the map or anywhere else
3) North direction; This is an indication of the north direction. It shows where north is and by knowing north one can know the direction and bearing of the place.
4) Margin; This is a boundary or limit around the map. It gives or shows the reader and interpreter the end of the map.
5) Publisher and date publication; This shows when the map was produced and a publisher.
6) Latitude and Longitude / Grid reference. It used to locate the place on the map. For example the map of Tanzania is located at latitude 6°00' south of the equator and longitude 35°00' east of Greenwich meridian.
7) A scale; It shows the relationship between map distance and the actual ground distance for example 1cm to 10km means one centimeter on the map represents ten kilometers on the ground MAP SCALE Is the relationship or ratio between map distance and actual ground distance. Scale = Map distance Ground (actual) distance.
TYPES OF SCALE.
We can classify the scale according to the size in our criteria. There are three types of scales;
a) Large scale.
They are used to present information on small areas for example a map of village buildings and farms. The map size involves all numbers less than 1:25000 I.e. 1:10000 and 1:5000 Characteristics of large scale.
i) It has smaller numbers in the denominator.
ii) It shows features clearly
iii) It contains geographical details.
b) Medium scale.
They are used to represent medium details shown on the map. i.e. 1:50,000 and 1:100,000. Example of a map that can be drawn using medium scale is a map of a district, region, city etc. c) Small scale. They are used to present information that is long. This type of scale covers a big area with less detail. For example a map of a country, continent or world. May involve numbers between 1 : 500,000 to 1 : 1000,000
Characteristics of small scale.
i) It has the largest denominator.
ii) Contains a lot of geographical information.
iii) It does not show geographical features clearly.
WAYS USED TO EXPRESS MAP SCALE.
i) Statement scale. Refers to the scale which is expressed in terms of words or explanation. For example one centimeter on a map is equivalent to 10 centimeters on the ground.
ii) Linear scale Also is called plain or graphic scale. This is a line which is divided into two parts. The primary division and secondary division. The secondary are expressed in meters and placed on the left side from zero and primaries are expressed in kilometers and placed on the right side from zero.
iii) Representative fraction (RF) scale
Is written as a fraction or ratio eg. 1:50,000 50,000 The distance on a map is expressed as fraction of the actual distance on the ground. Therefore, RF scale = map distance Ground distance. The top number (numerator) represents the map distance on the ground and is usually more than 1. Scale conversion a) To change statement to R.F scale. 1cm represents 60km
Soln
1km=100000cm 60km= x 1:6000000 Therefore R.F scale = 1:6000000 b) One centimeter represents 0.75km b) 1:250000 To convert into statement scale If 1km = 100000 cm ? = 250000 cm 100000cm. x = 250000 cm x 1km 100000 cm 100000 cm X = 1 4 Thus, 1 cm represents 0.25
IMPORTANCE OF SCALE ON THE MAP
a) Scale help to calculate area of a map
b) It enable us to calculate distance on a map
c) Scale shows the relationship between map distance and the actual ground distance d) Scale help us to enlarge and reduce the area on a map or the whole map
e) Scale can be used to calculate the vertical exaggeration on a map f) Scale is used to calculate the gradient on a map Question: Distinguish signs from symbols
QUANTITATIVE INFORMATION ON MAPS
A) MEASURING DISTANCE ON THE MAP
Distance is the length of elongated features on the earth’s surface such as road, railway, river etc. How to measure distance. In order to obtain distance of any feature on the map, consideration should be made on whether the distance to be measured is straight or curved. Straight distance For all straight distances a ruler is used to obtain the distance directly from the topographical map given. Curved distance. It becomes difficult to obtain curved distance of the features by the use of a ruler directly from the topographical map when the area is inclined. In this case the following devices can be used:-
A. A pair of divider. A pair of divider is commonly used to measure the distance. You should start by breaking the length by using a pair of dividers then transfer some of the already drawn straight lines. Then transfer the measured line to the linear scale or ruler for calculation to get the actual distance.
B. A piece of a string. Slowly measures the distances by a piece of string along a given length then transfer it to a linear scale or ruler for actual calculation of the distance.
C. A piece of strip paper Slowly lay a piece of paper along a given length then break your lengths into short segments then transfer to the linear scale for measuring and calculation. For example: The railway distance from station A to B was 20 cm, find ground distance in km if the scale used to construct a map is 1:50000 20 cm map distance Scale distance= map distance Actual distance Scale: 1:50000 If 1km = 100000 cm ? = 50,000 cm 100000 cm = 1km x 50,000 cm 100000 cm 100000 cm = ½ km = ½ km x 20cm =10km. The ground distance of railway from station A to B is 10 km
MEASURING AREAS ON A MAP/CALCULATE AREA OF REGULAR IRREGULAR
Area size refers to the bigness or smallness of an area on the earth’s surface i.e. the bigness or smallness of earth’s surface from topographical map consideration should be made whether the area is regular or not.
E x e r c i s e 1)
To state the following.
a) map
b) map reading
c) Scale
d) Contour
2) Why do we study maps?
3) State the ways of expressing scale.
4) What is the importance of a scale?
5) List at least 3 methods of calculating the linear distance of an object
6) The distance of the road is 16cm from Igurusi to Chimala, convert the distance in kilometers if the scale used is 1:100000 b) From the above convert the same distance in km if the scale is changed to 1:50000
REGULAR SHAPE These are areas with definite shapes such as squares, triangles etc. Their total perimeters or areas are obtained by mathematical formula i.e. length x width, side x side etc.
IRREGULAR SHAPE These are areas with indefinite shapes such as lakes, farms, ponds etc where these areas can be obtained by any of the following three methods; a) Square method b) Strip method c) Geometrical method
SQUARE METHOD
This is the most accurate and most widely method used. Square methods are normally used as follows;
a) Count all full squares that are complete
b) Count incomplete squares and divide them by 2 c) Add them with the full squares to obtain the total area in km2
METHODS USED TO SHOW OR LOCATE POSITIONS OF A PLACE ON A MAP.
The following are major methods used to show positions of a place on a map.
i) Grid reference.
ii) Place name
iii) Bearing and compass direction.
iv) Latitude and longitude. Place name. You can locate the position of a place by where the features are found i.e. Kigoma, Mbeya, Dodoma, Lindi etc. Grid reference. Grid reference is a network of vertical lines and horizontal lines on a map. Vertical lines whose numbers increases towards the east are called easting. Horizontal lines whose numbers increase towards the north is known as Northings. Where horizontal lines and vertical lines meet or cross each other they form a square known as grid square. (G.S). A grid reference point is written inform of six digits starting with three digits of Eastings then three digits of nothings. ·A ·C D· ·B 31 32 33 34 35 36 37 38 39 40 41 42 09 08 07 06 05 04 03 02 01 To write down the grid reference of point A, B, C, and D. A = 343086 B = 333036 C = 383077 D = 397046 NB: To write numbers of grid reference starts with easting then northing.
LOCATION AND POSITION: COMPASS BEARING AND DIRECTION
How to find direction of a place on map. Identify them due to points on the given map. Points may be given by using grid reference points, place name or letter. Draw a straight line connecting the two points Mark the major four cardinal points at the starting point with the word from. Now look at the question asked then provide your answer.
COMPASS BEARING.
Bearing are directions which measure degrees clockwise from north. They are written in three figures i.e. 0900 , 0450
HOW TO FIND BEARING ON THE MAP.
Identify the grid reference points given on the maps. Draw a straight line connecting the two points Draw the major four cardinal lines at the starting Now look at the question asked use a protector to measure degree clockwise from north up to the line joining the two points. Then Provide your answer in degrees BEARING. In bearing there is;
a) Forward bearing
b) Backward bearing
a) Forward bearing Is a bearing into a subject. Procedures to calculate forward bearing
i. Identify the two points.
ii. Join them with a straight lines
iii. Draw north direction on a second point.
iv. Measure the angle by using a protector.
v. State the bearing in terms of degrees of the direction.
b) Backward bearing. Is the opposite of forward bearing, it’s taken from the object to the observer while forward bearing is taken from observer to the object.
How to determine the back bearing.
i) Find forward bearing.
ii) Mark the cardinal point north direction of the opposite point
iii) Find the bearing of the observer along the straight line principally to determine the back bearing = FB + OR – 1800 BB= FB +1800 if FB < 1800 BB= FB -1800 if FB >1800 For example: The forward bearing (FB) of Tukuyu from Kyela is 0450 , Back bearing (BB) will be; BB = FB + or – 180. BB = 45 + 180 (FB added because it’s not greater than 180) Therefore Back bearing is 2250
IMPORTANCE OF THE USE OF MAPS
a) People use them to reach their directions
b) Maps are used to describe the features of the earth
c) Builders are maps to plan the best use of the land
d) Road constructors use maps to construct new roads
e) Maps are useful in military activities f)Maps are used in conducting various geographical researches
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