Major landforms of the earth
The surface of the earth is uneven. It is not same everywhere. The earth has an infinite variety of landforms. Some parts of the lithosphere may be rugged and some flat. These landforms are a result of two processes.
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Within the earth, a continuous movement is taking place. The first or the internal process leads to the upliftment and sinking of the earth’s surface at several places.
The 2nd or
the external process is the continuous wearing down and rebuilding
of the land surface. The wearing away of the earth’s surface is called erosion.
The surface is being lowered by the process of erosion and rebuilt by the
process of deposition. These two processes are carried out by running
water, ice and wind. Broadly, we can group different landforms depending on
elevation and slope as mountains, plateaus and plains.
Mountains
A mountain is any natural elevation of the earth surface. The
mountains may have a small summit and a broad base. It is considerably higher
than the surrounding area. Some mountains are even higher than the clouds. As
we go higher, the climate becomes colder.
In some mountains, there are permanently
frozen rivers of ice. They are called glaciers. There are some mountains we
cannot see as they are under the sea. Because of harsh climate, less people
live in the mountain areas. Since the slopes are steep, less land is available
for farming.
Mountains may be
arranged in a line known as range. Many mountain systems consist of a series of
parallel ranges extending over hundreds of kilometers. The Himalayas,
the Alps and the Andes are mountain ranges of Asia, Europe
and South America, respectively. Mountains vary in their heights and shape.
There are three types
of mountains – 1.
Fold Mountains,
2. Block Mountains and
3. Volcanic Mountains.
Fold Mountains
The Himalayan Mountains and the Alps are young fold mountains with
rugged relief and high conical peaks. The Aravali range in India is one of the
oldest fold mountain systems in the world. The range has considerably worn down
due to the processes of erosion. The Appalachians in North America and the Ural
mountains in Russia have rounded features and low elevation. They are very old
fold mountains.
Block Mountains
Block Mountains are created when large areas are broken and
displaced vertically. The uplifted blocks are termed as horst and the
lower blocks are called graben. The Rhine valley and the Vosges
mountains in Europe are examples of such mountain systems.
Volcanic Mountains
Volcanic mountains are formed due to volcanic activity.
Mt. Kilimanjaro in Africa and Mt. Fujiyama in Japan are examples of such
mountains.
Plateaus
A plateau is an elevated flat land. It is a flat-toped table land
standing above the surrounding area. A plateau may have one or more sides
with steep slopes. The height of plateaus often varies from few hundred meters
to several thousand meters. Plateaus, like mountains may be young or old. The
Deccan plateau in India is one of the oldest plateaus. The East African plateau
in Kenya, Tanzania and Uganda and the Western plateau of Australia are other
examples. The Tibet plateau is the highest plateau in the world with a height
of 4,000 to 6,000 meters above the mean sea level. Plateaus are very useful
because they are rich in mineral deposits. As a result, many of the mining
areas in the world are located in the plateau areas. The African plateau is
famous for gold and diamond mining. In India huge reserves of iron, coal and
manganese are found in the Chotanagpur plateau. In the plateau areas, there may
be several waterfalls as the river falls from a great height. In India, the
Hundru falls in the Chotanagpur plateau on the river Subarnarekha and the Jog
fals in Karnataka are examples of such waterfalls. The lava plateaus are rich
in black soil that are fertile and good for cultivation. Many plateaus have
scenic spots and are of great attraction to tourists.
Plains
Plains are large stretches of flat land. They are, generally, not
more than 200 meters above mean sea level. Some plains are extremely level. Others
may be slightly rolling and undulating. Most of the plains are formed by rivers
and their tributaries. The rivers flow down the slopes of mountains and erode
them. They carry forward the eroded materials. Then they deposit their load
consisting of stones, sand and silt along their courses and in their valleys.
It is from these deposits that plains are formed. Generally, plains are very
fertile. Construction of transport network is easy. Thus, these plains are very
thickly-populated regions of the world. Some of the largest plains made by the
rivers are found in Asia and North America. For example, in Asia, these plains
are formed by the Ganga and the Brahmaputra in India and the Yangtze in China.
Plains are the most useful areas for human habitation. There is great
concentration of people as more flat land is available for building houses, as
well as for cultivation. Because of fertile soils, the land is highly
productive for cultivation. In India too, the Indo-Gangetic plains are the most
densely populated regions of the country.
