Geography Form One Notes – Major Features of the Earth's Surface
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MAJOR FEATURES OF THE EARTH’S
SURFACE
Continents
Meaning of a Continent
Explain the meaning of a continent
‘The land surface occupies 29% ofthe surface of the globe, and the remaining 71% is covered by
water. The land surface forms seven continents. A continent is a major landmass rising fom the
‘ocean floor. It includes islands adjacent to the continent. There are seven continents namely,
Aftica, Asia, South America, North America, Furope, Australia and Antarctica, These continents
are surrounded by the following oceans: The Indian Ocean, the Atlantic Ovean, the Pacific
Ocean, the Arctic Ocean and the Souther ocean
There is more land surface in the northern hemisphere than inthe southern hemisphere but there
is more water surface in the southem hemisphere than in the northern hemisphere. The
continents are broader in the northern hemisphere. The seven continents that make up the globe
are explained below:
1. Australia: Australia is the smallest continent and it is about a quarter of the size of
Alta. Is size i about 8.5 million square kilometres. Australia is approximately 10°S and 40°S
and between 115°E and 150°E, The islands of New Zealand to the south east of Australia are
part of this continent. The continent is bordered to the west and north by the Indian Ocean, to the
«east by the Pacific Ocean, and tothe south by the Southem Ocean.
2. Europe: Europe is the sixth continent in size and itis about two-fifth the size of Africa
‘The size of Europe is 9.8 million square kilometres. Most of Europe lies between 40°N and the 1
Arctic cirle, and between 10°W and 60°E. It lies to the west of Asia, separated by the Ural
Mountains. Europe is bordered to the north by the Arctic Ocean, to the west by the Atlantic
(Ocean, and tothe south by the Mediterranean Sea,
3. Antareticn: Antarctica is the fih continent in size and itis about one-thitd the size of
Affica. Its area is about 11.4 million square kilometres. This is the southemmost continent,
{Forming a circle atthe South Pole and extends south of 661/2°S. It is surrounded by the southern
‘ocean, The continent is mostly uninhabited.
4. North America: North America is the fourth continent in size and iti slightly more than
half the size of Attica. Its size is about 17.9 million square kilometres, If extends from 10°N to
(65°N and from 60°W to 160°W. Its bordered to the west by the Pacific Ocean, to the East by
the Atlantic Ocean, and the North by the Arctic Ocean
5. South America: South America is the third largest continent and it is about two-thirds
the size of Africa. Its size is about 24.3 million square kilometres. It lies between 10°N and S0°S
and between 35°W and 80°W. This continent is bordered to the east by the Atlantic Ocean, to the
‘West by the Pacific Ocean, and itis joined to North America by the Isthmus of Panama,
6. Africa: Africa isthe second largest continent with an area of about 3.6 square kilometres.
Atica extends from 37°N to 35°S and from SO°W to 50°E and itis crossed by Tropics of Cancer
and Capricorn. Thus the greater part, about three quarters of the whole area les in the topics.
Atica is bordered to the north by the Mediterranean Sea, to the west by the Atlantic Ocean, and
to the East by the Indian Ocean,
7. Asia: Asia is the largest of all continents. It covers more than one thied of the land
surface of the earth. It is approximately one and a half times the size of Aftica. Its total area is
about 45.6 million square kilometres, Asia stretches from 0° to 67°N and from 30°E to about
18°E, The Ural Mountains form the boundary between Asia and Europe. This continent is
attached to Affica by the narrow Isthmus of Suez which has been dug to form the Suez Canal.
‘The continent is bordered to the North by the Arctic Ocean, tothe East by the Pacifie Ocean, and
to the South by the Indian Ocean
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The following table summarizes the locaton and area ofall seven continents discussed above
Continent Geograph cation Aree (Mition Kim)
Asia © -67N, 30° 180°E 486
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South America WON 50°8;38″ W- 80° W m3
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Major Features of the Continent
deny the major features ofthe continent
‘The surface ofthe continents is not smooth. It has mountains, hills, rivers and valleys, plateaus,
and plains. Mountains are landforms which have high relief generally over 300 metres above the
surrounding area. Hills are landforms that have moderate relief generally between 150 and 300
metres above the surrounding area. Plateaus are extensivehighland areas with more of less
uniform summit level, bounded by one or more slopes fallin steeply away, sometimes rising on
‘one or more sides by steep slopes to mountain ridges. Plains are continuous sketches of
comparatively lat land not much above sea level, sometimes gently rolling or undulating
Mountains
‘There are four types of mountains These are the Fold Mountains, Block Mountains, Residual
Mountains, and Volcanic Mountains. These mountains are all named according to the way they
were formed
+ Fold Mountains:Fold Mountains are formed by wrinkling or (Folding) of the Earth’s
crust. Fold Mountains usually form parallel ranges which extend for hundreds of miles across a
continent. Thus, Fold Mountains are the most extensive ranges in the world, For example, the
Rocky Mountains in North America vary in width from 640 to 1,600 kilometres and are about
5,000 kilometres in length. These types of mountains have some of the highest peaks in the
‘world, Mount Everest in the Himalayas is 8,848 metres above sea level and the Aconcagua in the
‘Andes is 7,003 metres above sea level. Examples of Fold Mountains include the Himalayas in
‘Asia; the Rockies in North America; the Andes in South America; the Alps in Europe; the Atlas
in North Africa; the Cape ranges in South Africa; the Appalachians in the USA; and the Great
Dividing Ranges in Australia
+ Block Mountains:Block Mountains are formed when a movement in the earth’s crust
forces the rocks to break instead of folding, As a result enormous cracks or faults are formed.
‘When two sets of faults run parallel to each other and the ground between is forced to rise up, a
block (fault) mountain is formed. Usually Block Mountains do not extend over wide areas as
Fold Mountains do, Examples of Block Mountains are the Usambara, Uluguru and Ruwenzori
Mountains in Africa; the Vosges and Black Forest Mountains in Europe; and Mount Sinai in
Asia
+ Residual Mountains:Residual mountains are formed when an area of highland remains
standing above the general level of land afte the rivers and other natural agents have lowered the
surface ofthe surrounding area. Sometimes such highlands are called mountains of denudation.
“These mountains may in some cases appear as isolated hills but in other cases they appear as
long ridges, generally steep on one side (the scarp slope) and gentle on the other side (dip slope).
[Examples of residual mountains are the Ahaggar Mountains of central Sahara; the Sekenke hills
of Singida in Tanzania; the Admawa mountains of eastern Nigeria; the Highlands of Scotland,
the Sierras of central Spain; and the Mesas and Buttes of the western plateau of the United
States.
+ Volcanic Mountains: Voleanic mountains are formed from the piling up and cooling of
hhot molten lava and ashes that are thrown out from the earth’s interior after a volcanic eruption.
Some of the volcanic mountains existing today were built up by a single eruption, but others
‘were built by several eruptions. Volcanic eruptions are still taking place in some parts of the
earth, Among the existing voleanic mountains, some still experience periodic eruptions, for
example, the Vesuvius in Italy; the Krakatoa in Indonesia; the Mufimbiro in Uganda; and the
Oldoinyo-Lengai in Tanzania. The Volcanic Mountains that stil experience periodic eruptions
are called active volcanic mountains.The Voleanic Mountains which erupted once in historical
times and are no longer active are said to be dormant, In this group are included the Kilimanjaro
and Meru mountains in Tanzania. Those volcanic mountains which have never experienced
ruption and have shown no signs of erupting again are said to be extinet (dead). Included inthis
group are mountains Kenya, Elgon, Ngorongoro and Rungwe in East Africa; and Demavend in
Iran Voleanic mountains are usually conical in shape and mostly contain crates or depressions at
their summits, for example, mountains Fujiyama and Kilimanjaro. Sometimes the eraters are
filled with wate to form crater lakes.
Plateaus
In geology and earth science, a plateau (plural: plateaus or plateaux), also called a high plain or
fableland, is an area of highland, usually consisting of relatively flat terrain that is raised
significantly above the surrounding area, often with one or more sides with step slopes.
“The largest and highest plateau in the world isthe Tibetan Plateau, called the “oof ofthe world”
‘The Tibetan plateau covers approximately 250,000 km2 at about 5,000 m above se level
‘The second-highest plateau is Deosai National Park (also known as Deoasai Plains) at an average
elevation of 4,114 m and is located in the Skardu District of Gilgi-Balistan, in northern
Pakistan
“The third-largest plateau isthe Antarctic Plateau, which covers most of central Antarctica, where
there are no known mountains, but rather 3,000 m or more fie.
Other plateaus in the world include the Colorado Plateau (North America); the Great Central
Plateau, Ahagger Plateau and FoutaDallon Plateau (Aftica); Bravlian Plateau (South America),
Mexican Plateau and Laurentian Plateau (North America); Arabian Plateau, Deccan Plateau and
Tibet Plateau (Asia).
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Plains
{A plain is abroad area of relatively at land. Plains are one ofthe major landforms, oF types of
land, on Earth, They cover more than one-third ofthe word’s land aca. Pains exist on every
continent except Antarctica. Plains occur as lowlands and at the bottoms of valleys but also on
plateaus or uplands at high elevations
Plains in many areas are important for agriculture because where the soils were deposited as
sediments they may be decp and fertile, and the fatness facilitates mechanization of erop
production; or because they support grasslands which provide good pasture for livestock.
Plains vary widely in size. The smallest occupy only a few hectares, whereas the largest cover
hhundreds of thousands of square kilometres. For example, the Great Plains of North America
extends from Pyrenees Range on the French-Spanish border across northerm Europe and Asia,
almost halfway around the world.
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The Yellow River winds through the plains of Sichuan, China. Many rivers are surrounded by
plains, or broad areas of fla land.
Water Bodies
Meaning of a Water Body
Define a water body
‘A water body is any significant accumulation of water, generally on a planets surface. The term
‘most often refers to oceans, seas, and lakes, but it includes smaller pools of water such as ponds,
wwellands, or more rarely, puddles. A body of water does not have to be still or contained. Rivers,
streams, canals, and other geographical features where water moves from one place to another
are also considered water bodies,
Oceans and Other Water Bodies
‘demfy the oceans and other water bodies
‘An ocean is defined as a body of saline water covering much of the earth. The largest ocean is
the Pacific. Is area is about 165.3 million square kilometres. The second largest ocean is the
Allantic, which covers about 82.2 million square kilometres. The IndianOcean, covering about
TBA square kilometres is the third largest, followed by the Arctic Ocean, covering about 14.0
million square kilometres,
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Composition of ocean water
Ccean water contains a numberof dissolved mineral salts. These mineral sls include sodium
chloride (common sal) which makes up 78% of all salt in the ocean wate; and compounds of
magnesium, potassium and calciom, Most ofthe minerals in te ocean area esl of constant
accumulation since the formation ofthe oceans However, a small amount ofthe minerals come
from the land, having been dissolved by water and brought into the ocean by rivers. But the
tier salts ves are only in very small quantities.
‘The siess of the ocean water is not the same everywhere. Sains of the ooean water
depends mainly on temperature which affects the amount of salt that can dissolve in the water,
the amount of fresh water brought ino the ocean by rivers and sani, and the amount of
evaporation taking place fom the surface
Water temperature
Waters heated bythe sun’s ays much mor slowly than Landis. Water also loses het tothe ir
arvund it more slowly than the Ind does. This causes the temperature ofthe sa wart vary
only slightly from season to season. In general, the temperature of the ocean water decreases
fom the eat, where the surface temperate is 25°C othe polar regions whee the wae is
very cold (22°C), But the decrease in temperature poleward isnot uniform because ofthe
cecurrence of warm and cold ocean cues. Onthe other hand, water temperature decreases
wit depth inthe tropics up tothe depth where the temperature i 11°C
Water movements
Ocean water is constantly ia mation, There are two types of movement, Ooe is horactal
movement, which sin the form of ocean ues an tides, and he thes veri which is the
rising of subeatie water andthe sinking ofthe surfice wate. The moved of ccc water
are a result of density variations inthe water which & particularly import in vertal
movements and winds which re partcuatly important in borzona movements
‘Am oven current isthe permanent o eaonal movement of srfice water in the ocean, Tete
are ware and ol cure, the oan creas re set in mio by combination of pevaing
winds, dfrences in density and temperature of the ocean wales, the oation ofthe earth, and
the shape of dass
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Lakes
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inflowing sas. Te Caspian Sx, Dad Se, and Gre Sa Lak among te pratt te
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area of 82,414 sq km. The Caspian Sea isthe largest lake inthe world, with an area of 372,960
sq km, Lake Titicaca in the AndesMountains of South America is the world’s highest lake at
3,800 m above sea level; while the Dead Sea is the lowest at 425 m below sea level
Rivers
A tiver is natural water flowing in a definite channel towards an ocean, sea, lake, desert basin,
‘marsh or another river. In some cases, river flows into the ground and become dry a the end of|
its course without reaching another body of water. Small rivers can be refered to using names
such as stream, creek, brook, rivulet, and rill
Rivers are part ofthe hydrological cycle. Water generally collects in a river from precipitation
through a drainage basin from surface runoff and other sources such as groundwater, springs, and
the release of stored water in natural ice and snowpacks (eg. from glaciers).
Examples of rivers in Africa include the Nile, Congo, Niger, Zambezi and Orange. In Tanzania
wwe have rivers lke Rufij, Ruvuma, Ruaha, Pangani, Wami and Malagalasi
Features of the Ocean Floor
Describe the features of the ocean floor
The floor of the ocean is irregular. The major relief features of the ocean floor are explained
below
1, Continental shelf:This is a gentle-slope margin of a continent that forms the shallow
areas of oceans. These shallow areas extend from the coast to a depth of about 200 metres
towards the ocean, and usually end suddenly.
2 Continental slope:The continental slope is found at the point where the continental shelf
{forms a steep slope with the lower slope of the ocean floor towards the sea
3. Ridge:A ridge is the raised part of the ocean floor. Some ofthese rides appear above the
surface ofthe oceans as oceanic islands.
4. Ocean deep or trench:An ocean deep isa long, narrow depression (or trough) found on
the ocean Moor.
5. Deep sea plain (ocean plain):An ocean plain is the most extensive, flat area ofthe ocean
floor. It is a monotonous and undulating area. A large part of the plain is covered by mud.
ean plain Continent
Oceanic ge
Oceanic island Continental slope
(ean deep otreach | |
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‘The Map Showing the Distribution of Continents and Water Bodies
Draw he map o show the dsribution of coninens and water bodes
The Map showing distribution of water bodies
