Types of Mountains, Plateaus and Plains: Notes for Exams

Mountains, plateaus and plains are the three major relief features, or first-order landforms, of the earth. Questions on them come up in almost every General Awareness paper, usually as a type matched with an example: the Himalayas with fold mountains, the Vosges with block mountains, Tibet with intermontane plateaus, Khadar with the newer alluvium. These notes set out how each landform is formed, the names examiners expect with each type, and the divisions of the northern plains of India.

Mountains and their four types

A mountain is a natural elevation of the earth surface that rises well above its surroundings, has a restricted summit area and steep slopes; in Indian textbooks an elevation above about six hundred metres is treated as a mountain and anything lower as a hill. Mountains are classified by the way they were formed.

Fold mountains are the youngest and the highest, and they carry the world highest peaks: Mount Everest in the Himalayas, whose height was announced jointly by Nepal and China in December 2020 as 8,848.86 metres, and Kanchenjunga, 8,586 metres, the highest peak within India. The Andes of South America is the longest mountain range on land, about seven thousand kilometres long, while the longest ranges on earth are the mid-oceanic ridges, which are submarine mountains. Mountains are also grouped by position as coastal, such as the Western Ghats, inland, such as the Aravalli and the Urals, and oceanic. Among the peninsular ranges, Dhupgarh in the Pachmarhi hills is the highest peak of the Satpura, Kalsubai of the Sahyadri and Doddabetta of the Nilgiri.

Plateaus and their types

A plateau is an elevated tableland with a flat or gently undulating top that rises abruptly above the land around it. It is usually wider than it is high. Plateaus too are named after the way they came up.

• Intermontane plateaus lie enclosed by mountain ranges and are the highest and the largest. The Plateau of Tibet, called the Roof of the World, is the highest and the most extensive; the Bolivian and the Anatolian plateaus belong to the same class.
• Piedmont plateaus stand at the foot of mountains, with the sea or a plain on the other side, such as the Piedmont plateau of the eastern United States and the Patagonian plateau of Argentina.
• Continental or tableland plateaus rise sharply from the coastal plain or the sea, such as the plateaus of peninsular India, Africa, Western Australia and Antarctica.
• Volcanic or lava plateaus are built by sheets of fluid basalt lava. The Deccan Trap of Maharashtra, the Columbia and Snake plateau of the United States, the Antrim plateau of Northern Ireland and the Ethiopian plateau are the standard examples, and the black regur soil of the Deccan comes from this basalt.
• Dissected plateaus have been cut up by streams, such as the Chotanagpur plateau, and loess plateaus, such as the Loess plateau of China, are built of wind-blown silt.

The peninsular plateau of India is the oldest landmass of the country, a part of the ancient Gondwana land. Its main units are the Deccan plateau between the Western and the Eastern Ghats, the Malwa plateau and the Bundelkhand and Baghelkhand uplands in the north, the Chotanagpur plateau in the east, the Telangana and Karnataka plateaus in the south, and the Meghalaya or Shillong plateau, which is separated from the main block by the Garo-Rajmahal gap. Anamudi in Kerala, about 2,695 metres, is the highest peak of the Western Ghats and of the whole peninsular plateau. Plateaus matter in the economy because minerals lie close to the surface in them, which is why the Chotanagpur plateau is called the storehouse of minerals, and because rivers plunge over their edges and give waterfalls and hydel power, as the Sharavati does at Jog Falls.

Plains and their types

A plain is a stretch of low, nearly level land, generally below two hundred metres above sea level, with a very gentle slope. Plains are classified by the process that made them.

• Structural plains are made by the uplift of a part of the sea floor or by the subsidence of land, like the coastal plains of India and the Russian platform.
• Depositional plains are laid down by rivers, glaciers, wind or waves. Alluvial plains such as the Indo-Gangetic plain, the Hwang Ho plain and the Mississippi plain, flood plains, deltaic plains such as the Sundarbans, piedmont alluvial plains, lacustrine plains such as the Karewa flats of the Kashmir valley, glacial drift plains, loess plains and coastal plains all belong here.
• Erosional plains are worn down rather than built up. A peneplain is the almost level surface left by long river erosion, a pediplain is the corresponding surface in a desert, worn by sheet wash, and a karst plain is formed by solution in limestone country.

The Northern Plain of India is the classic depositional plain, built by the alluvium of the Indus, the Ganga and the Brahmaputra and their tributaries over a foredeep between the Himalayas and the peninsular block. It runs for about two thousand four hundred kilometres from west to east and is divided from the hills southwards into four belts.

The Northern Plain is itself divided into the Punjab plain, with its doabs between the tributaries of the Indus, the Ganga plain, and the Brahmaputra plain of Assam, which holds Majuli, the largest river island in the world. Plains carry the densest populations and the best farmland, which is why the northern plains of India support a far larger share of the population than the plateaus do.

How examiners mix the three

A single question often puts all three landforms together: the Satpura is a block mountain but it also bounds a plateau, the Western Ghats are a coastal range and also the western edge of the Deccan tableland, and the Karewa of Kashmir is a lacustrine plain lying inside a mountain valley. Keep one example ready for every type and the matching questions become easy marks.