Chapter 6 Major Landforms Of The Earth

The Earth's surface exhibits a vast variety of landforms, meaning the surface is not uniform everywhere. Some parts of the lithosphere are rugged and elevated, while others are flat and low-lying. These landforms are shaped by two primary processes:

1. Internal Process: Continuous movements within the Earth's interior lead to the upliftment (rising) and sinking of the Earth's surface in various places.
2. External Process: This involves the ongoing wearing down and rebuilding of the land surface. The wearing away of the Earth's surface by forces like water, ice, and wind is called erosion. The process by which eroded material is carried and deposited elsewhere, building up the land surface, is called deposition.

These two processes constantly shape the Earth's landforms.

Broadly, based on elevation and slope, we can group different landforms into three major categories: Mountains, Plateaus, and Plains (Figure 6.1).

Do you know? A hill is a land surface that rises higher than the surrounding area. Generally, a steep hill exceeding 600 metres in elevation is classified as a mountain. Some famous peaks over 8,000 metres include Mount Everest, K2, Kangchenjunga, Lhotse, Makalu, Cho Oyu, Dhaulagiri, Manaslu, Nanga Parbat, and Annapurna I.

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Mountains

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A mountain is a natural, significant elevation of the Earth's surface. Mountains typically have a small summit (peak) and a broad base. They are considerably higher than the surrounding land. Some mountains reach heights exceeding cloud levels, and as elevation increases, the climate becomes colder.

Some mountains feature permanently frozen rivers of ice called glaciers. There are also mountains located hidden beneath the sea.

Life is generally challenging in mountainous areas due to the harsh climate. The steep slopes also limit the availability of land suitable for farming, leading to less population density compared to flatter regions.

Mountains can be arranged in a series called a range. Many mountain systems consist of multiple parallel ranges extending over vast distances. Examples of major mountain ranges include the Himalayas (Asia), the Alps (Europe), and the Andes (South America).

Mountains vary in height and shape and are classified into three main types based on their formation:

1. Fold Mountains: Created when layers of the Earth's crust are folded and uplifted due to tectonic plate movements (Figure 6.2). Young fold mountains like the Himalayas and the Alps have rugged relief and high, conical peaks. Older fold mountains, such as the Aravalli range in India (one of the oldest in the world), the Appalachians in North America, and the Ural mountains in Russia, have been significantly worn down by erosion, resulting in rounded features and lower elevation.
2. Block Mountains: Formed when large blocks of the Earth's crust are broken along faults and are displaced vertically (Figure 6.3). The uplifted blocks are called horsts, and the lowered blocks are called grabens (or rift valleys). The Rhine valley and the Vosges mountain in Europe are examples of block mountain systems.
3. Volcanic Mountains: Created as a result of volcanic activity, where molten rock (lava) erupts and solidifies, building up a mountain over time (Figure 6.4). Famous examples include Mount Kilimanjaro in Africa and Mount Fujiyama in Japan.

Do you know? Mauna Kea in Hawaii (Pacific Ocean) is an undersea mountain. Measured from its base on the ocean floor, it is taller than Mount Everest, reaching 10,205 metres high.

Mountains are highly useful in several ways:

• They serve as storehouses of water, with many rivers originating from mountain glaciers. Water from mountains is harnessed for various purposes like irrigation and generating hydro-electricity.
• River valleys and terraces in mountainous regions can be suitable for cultivating crops.
• Mountains are rich in biodiversity (flora and fauna). Forests in mountains provide resources like fuel, fodder, shelter, gum, and raisins.
• Mountains offer scenic beauty and are popular destinations for tourism and adventure sports such as paragliding, hang gliding, river rafting, and skiing.

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Plateaus

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A plateau is an elevated flat land, resembling a flat-topped table standing above the surrounding area (Figure 6.5). Plateaus typically have one or more sides with steep slopes. Their height varies significantly, from a few hundred metres to several thousand metres.

Like mountains, plateaus can be young or old. The Deccan plateau in India is one of the oldest plateaus. Other examples include the East African Plateau and the Western plateau of Australia. The Tibet plateau is the world's highest plateau, with an average height of 4,000 to 6,000 metres above mean sea level.

Plateaus are very useful due to their richness in mineral deposits. Many significant mining areas globally are located in plateau regions. For instance, the African plateau is known for gold and diamond mining, while the Chhotanagpur plateau in India is rich in iron, coal, and manganese reserves.

Plateau areas often feature waterfalls where rivers plunge from the elevated land. Examples in India include the Hundru falls on the river Subarnarekha (Chhotanagpur plateau) and the Jog falls (Karnataka).

Lava plateaus are particularly fertile due to rich black soil, making them good for cultivation. Many plateaus also have scenic spots attractive to tourists.

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Plains

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Plains are extensive stretches of flat land, generally not exceeding 200 metres above mean sea level (Figure 6.6). While some plains are extremely level, others may have gentle slopes or undulations.

Most plains are formed by rivers and their tributaries. Rivers flowing down mountain slopes erode material and carry it downstream. This eroded material (stones, sand, silt) is deposited along the river courses and in valleys, gradually building up fertile plains.

Plains are generally very fertile, making them ideal for agriculture. The flat terrain also makes the construction of transport networks (roads, railways) easy. Consequently, plains are among the most densely populated regions in the world, as flat land is readily available for building houses and extensive cultivation. Major plains formed by rivers are found in Asia and North America, such as the Indo-Gangetic plains (Ganga and Brahmaputra) in India and the Yangtze plains in China. The Indo-Gangetic plains are one of the most densely populated areas in India.

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Landforms And The People

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Humans have adapted to living on different landforms in diverse ways. Life is generally more challenging in mountainous areas compared to plains, where growing crops, building houses, and constructing roads is easier due to the flat terrain.

Differences in landforms lead to variations in how people live, their occupations, and their ways of life. However, natural calamities like earthquakes, volcanic eruptions, storms, and floods can cause widespread destruction and loss of life and property, regardless of the landform.

Humans utilize both land and water resources in numerous ways from their surroundings. However, these resources are often used wastefully (e.g., building on fertile land, polluting land and water with garbage). It is essential to use these gifts of nature responsibly and avoid damaging them. Land is not solely for our use but must also be preserved for future generations. Government initiatives like the Swachh Bharat Mission aim to improve hygiene and cleanliness, recognizing that a healthy environment (clean water, air, surroundings) is essential for human health and well-being.