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
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
The concept of a solarsystem
(Note that Pluto is no longer considered a planet)
Order of the planets -
1. Mercury
2. Venus
3. Earth
4. Mars
5. Jupiter
6. Saturn
7. Uranus
8. Neptune
The four inner planets from the sun namely Mercury, Venus, Earth and Mars are referred to as “terrestrial planets” because - They are all relatively small, rocky in composition and clustered together close to the sun and they are visible to the naked eyes, which means they resemble Earth
Examples of celestial bodies - Asteroids, moons, planets and stars Aphelion - The position of the Earth when it is furthest from the Sun Asteroids - Rocky planetary bodies which orbit the sun
Eclipse - Occurs when three heavenly bodies (e.g. planets/stars) are in one line and one of them is a source of light such as when the moon comes between the Sun andEarth
Equinox - Occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the centre of the Sun being in the same plane as the Earth'sequator
Meteorites - Pieces of hard matter such as rocks falling from outer space
The Milky Way - The galaxy which contains our solar system and the planet Earth, it is our galaxy
Tides are highest during an eclipse
The sun is the main source of light, heat and energy for Earth
The lunar eclipseis evidence which proves that the Earth is spherical
TheEarth
The rotation of the Earth causes - Day and night, difference of one hour between two meridians of 15°, the deflation of winds and ocean currents, the daily rising and falling of ocean tides
Earths movements are caused by isostatic adjustmentDay and night are caused by the rotation of the Earth
The Earth shape is a flattened sphere called a geoid or oblate spheroidThe rotation of the Earth causes the deflection of winds and ocean currentsPangea was divided into two parts called Laurasia andGondwana
The four seasons which occur on the earth’s surface are result of the revolution of the earth
Deflection - Due to spinning effect of the earth, water and air currents do not travel in straight lines
Coriolis Effect (Ferrel’s Law) - Is an apparent deflection of moving objects when they are viewed from a rotating reference frame
The Earth has an angle of inclination of 66½ degrees which causes the variation in the length of day andnight
The importance of parallels and meridians
Chronometer - Is a clock which is precise enough to be used as a portable time standard; it can therefore be used to determine longitude by means of celestial navigation
Latitude - Angular distance east or west of the prime meridian, used for north-south measurement
Longitude - Is the geographic coordinate used for east-west measurement
Meridian (Line of Longitude) - Is an imaginary arc on the Earth's surface from the North Pole to the South Pole that connects all locations running along it with a given longitude
Prime Meridian - Is the meridian (line of longitude) at which the longitude is defined to be 0° which runs through Greenwhich UK
Summer Solstice - Occurs exactly when the Earth’s axial tilt is most inclined towards the sun at its maximum of 23° 26’. In the Southern Hemisphere it occurs on December 22, in the Northern Hemisphere it occurs June 22
Great Circle - A circle in the surface whose plane passes through the centre of the globe, used to plot routes for ships and planes across great distances
Horse Latitudes - Sub-tropic latitudes between 30º and 35º in both the North and South Hemispheres Circle of Latitude - An imaginary east-west circle connecting all locations that share the same latitude Tropic of Capricorn (Southern Tropic) - Marks the southerly latitude at which the sun can appear directly
overhead at noon, occurs during the December solstice
Tropic of Cancer (Northern Tropic) - Marks the northerly latitude at which the sun can appear directly overhead at noon, occurs during the June solstice
Winter Solstice - Occurs exactly when the Earth's axial tilt is farthest away from the sun at its maximum of 23° 26'. In the Northern Hemisphere, the Winter Solstice occurs on December 21, in the Southern Hemisphere it occurs June 22
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.
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.
Water bodies
(Not present in exams)
Weather
The concept of weather
Atmosphere - A blanket of air or other gasses which surrounds planets including Earth
Mesosphere - The middle layer of the Earth’s atmosphere
Tropopause - Is the atmospheric boundary between the troposphere and the stratosphere
Troposphere - The lowest portion of the Earth’s atmosphere
Order of layers of the Atmosphere from lowest to highest -
Troposphere - Ends atthetropopause - Lowest
Stratosphere Mesosphere Thermosphere
Exosphere -Highest
Elements of weather
How to calculate Fahrenheit and Celsius -
[°C] = ([°F] − 32) × 5⁄9
[°F] = [°C] × 9⁄5 + 32
Types of rainfall - Convectional rainfall, cyclonic rainfall, orographic rainfall
Convectional Rainfall - Occurs when the atmosphere becomes heated more than its surroundings leading to upward motion, rain falls from convective clouds like cumulonimbus clouds
Cyclonic Rainfall - Occurs who masses of air with different density (moisture and temperature) meet, warmer air rises over cold air which produces precipitation (rain)
Orographic Rainfall - Is caused when masses of air pushed by wind are forced up the side of elevated land formations like mountains
Weatherstations
The suitable area to set up a weather station is on fairly level ground in an open space
Climate
Concept ofclimate
Climate - Is the temperature, humidity, atmospheric pressure, wind, rainfall, and other meteorological elements in a given region over long periods of time
Clouds - Small particles of condensed water at the lower part of the atmosphere
Constant Volume Gas Thermometer - Measures temperature by the variation in volume/pressure of a gas
Desertification - Is the process of forming desert by increased heat on the Earths surface causing evaporation or by the destruction of forests
Dew - Is water in the form of droplets that appears on thin, exposed objects in the morning or evening
Doldrums - It is an area with low pressure in the tropics
Drought - A prolonged lack of moisture in an area as a result of a long period without rainfall
Fog - Is a cloud that is in contact with the ground
Front - The zone separating two air masses
Hail - Is a form of solid precipitation which consists of balls or irregular lumps of ice
Humidity - Is the amount of water vapor in the air
Hygrometers - Are instruments used for measuring relative humidity
Inter-Tropical Convergence Zone (ITCZ) - The zone between the maritime and continental air masses
Land Breezes - Occur at night due to the fact that land temperatures drop faster than water (because of different specific heat values), so it is cooler on the land than water
Macroclimate - Refers to the regional climate of a broad area
Maximum Temperature Thermometer - Used to measure the highest temperature reached in a day
Microclimate - A detailed small scale study of weather elements within a natural environment
Mist - Is a phenomenon of small droplets suspended in air
Polar Front - Where cold air from the Polar Regions meets warmer air from lower latitudes
Relative Humidity - Is the amount of water vapor that exists in a gaseous mixture of air and water vapor
Sea Breezes - During the day the breeze comes from the sea because the land is warmer and air travels from areas of high pressure to areas of low pressure
Sleet - A mixture of snow and rain
Trade Winds - Winds blowing from horse latitudes to the equatorial belts. Found in the tropics in the lower troposphere. Used in the past for trade and conquest by Europeans
Tropical Cyclone - A low pressure center with develops in low altitudes
Tsunami - A strong wave in the ocean caused by an earthquake or by a volcanic eruption
Weather - The state of the atmosphere measured by hot or cold, wet or dry, calm or storm, clear or cloudy Hurricanes and typhoons are tropical cyclones
Salinity of ocean water increases with an increased rate of evaporation of ocean waterWind blows from areas of high pressure to areas of low pressure
Weather andclimate
(Not present in exams)
Impact ofclimate
(Not present in exams)
Mapwork
Concept of amap
Choropleth Map - Is a thematic map in which areas are shaded or patterned in proportion to the measurement of the statistical variable being displayed on the map, such as population density or per- capita income
Atlas - Is a collection of maps; it is typically a map of the Earth or a region of the Earth
Components of amap
Contours - Lines that are drawn on the map joining different places with the same height above sea level
Isobar - Is a line connecting points of equal atmospheric pressure Isobeth - Is a line joining all place with equal depth in the ocean Isohel - Is a line of equal or constant solar radiation
Isohyet - Is a line joining points of equal precipitation on a map
Isoneph - Is a line indicating equal cloud cover
Time Zone - Is a region on Earth, more or less bounded by lines of longitude, that has a uniform, legally mandated standard time, usually referred to as the local time
Quantitative information aboutmaps
Essentials of a map - Key (legend or reference), scale, margin (frame), title, indication of north direction
Ways of showing topographical features on a map - Using contours, hill shading, layer colouring, form lines, hachure, benchmarks, spot height, trigonometrical stations (points)
Techniques of expressing scale of a map - Linear scale, statement (verbal) scale, representative fractional scale (RF scale)
Uses ofmaps
(Not present in study guide)
Humanactivities
Concept of humanactivities
(Not present in exams)
No comments:
Post a Comment