Major Mountain Ranges, Plains, and Deserts

Mountain ranges, plains and deserts are three of the main types of landscape on the continents: mountain ranges are chains of high, steep land, plains are large areas of flat or gently rolling land, and deserts are regions that receive very little precipitation, usually less than about 250 mm a year. In brief: the longest mountain range on land is the Andes (about 7,000 km), the highest is the Himalayas, which contain Mount Everest (about 8,849 m), and the largest hot desert is the Sahara (about 9 million km²). Plains, such as the Great Plains of North America and the North European Plain, are often fertile and densely settled.

These large landforms influence climate, rivers, farming and where people live. This guide describes the world’s major mountain ranges, deserts and plains, compares examples in a table, works through length, area and rainfall calculations, outlines their history and corrects common mistakes.

What are the major mountain ranges?

• Himalayas (Asia): about 2,400 km long, formed by the collision of the Indian and Eurasian plates; they contain Everest (about 8,849 m) and many of the other highest peaks, and are the source of great rivers.
• Andes (South America): about 7,000 km, the longest continental range, running along the west coast; Aconcagua is about 6,960 m.
• Rocky Mountains (North America): about 4,800 km from Canada to the southwestern United States; they include the Continental Divide.
• Alps (Europe): about 1,200 km, with Mont Blanc (about 4,806 m); an important source of water and a center for tourism.
• Urals: about 2,500 km, traditionally part of the boundary between Europe and Asia.
• Others: the Great Dividing Range in Australia, the Atlas Mountains in North Africa, the Appalachians in eastern North America, the Caucasus, and the Tian Shan.

Most of the highest ranges are young fold mountains made by plate collisions, while older ranges, such as the Appalachians and the Urals, have been worn down by long erosion.

What are the major deserts?

A desert is defined mainly by dryness: less than about 250 mm of precipitation a year, or evaporation exceeding rainfall. Deserts can be hot or cold. Hot deserts include the Sahara in North Africa (about 9 million km², the largest hot desert), the Arabian Desert (about 2.3 million km²), the Australian deserts, the Kalahari and Namib in southern Africa, the Thar in India and Pakistan, the Sonoran and Chihuahuan in North America, and the Atacama in Chile, one of the driest places on Earth. Cold deserts include the Gobi in Mongolia and China (about 1.3 million km²), the Taklamakan, and the polar regions: Antarctica is the largest desert in the world by area because of its very low precipitation. Deserts are not all sand; they can be rocky (hamada), gravel plains (reg) or sand seas (erg). Many lie near 30° latitude, where dry air sinks, or in the rain shadow of mountains or far from the sea.

What are the major plains?

Plains are extensive flat or gently undulating lands with low relief, usually formed by deposition of sediment by rivers, glaciers or wind, or by uplift of the sea floor. Examples: the Great Plains and Central Lowlands of North America (a grain-growing region), the North European Plain from France to Russia, the West Siberian Plain, the Indo-Gangetic Plain (one of the most densely populated areas in the world), the North China Plain, the Amazon basin lowlands and the Pampas of Argentina. Plains offer easy farming and transport, so many cities and populations are found on them. Plateaus are different: they are high, flat-topped lands bordered by steep slopes.

Examples compared

Worked example: length, area and rainfall

1. Length: the Andes (about 7,000 km) are 7,000 ÷ 2,400 = 2.9 times as long as the Himalayas, but the Himalayas are higher: 8,849 − 6,960 = 1,889 m higher at their highest peaks.
2. Sahara compared with a country: the Sahara (about 9.2 million km²) is about as large as the United States (about 9.8 million km²); 9.2 ÷ 9.8 = 94 percent.
3. Sahara and Africa: 9.2 ÷ 30.4 = 30 percent, so about three-tenths of Africa is covered by the Sahara.
4. Desert threshold: 250 mm a year is 250 ÷ 365 = 0.68 mm a day on average. A place with 120 mm a year receives 120 ÷ 250 = 48 percent of the desert threshold, and so is clearly arid.
5. Antarctica as a desert: at 14.2 million km², Antarctica is 14.2 ÷ 9.2 = 1.5 times the area of the Sahara.
6. Temperature with height: the air temperature falls by about 6.5 °C per 1,000 m. Between sea level at 25 °C and a pass at 4,000 m, the temperature is about 25 − 4 × 6.5 = −1 °C, so high mountains are cold even near the equator.

How have these landforms shaped human history?

Mountains have been barriers and refuges: the Alps and the Himalayas limited movement and shaped borders, and peoples such as the Incas built empires in the Andes. Mountain passes, such as the Khyber Pass, were important trade and invasion routes. Deserts were crossed by caravans along trade routes, such as the trans-Saharan trade in salt and gold, and oases formed the centers of settlement. Fertile plains supported early agriculture and the growth of cities and states, such as in the Indo-Gangetic Plain and the North China Plain, and today they hold much of the world’s food production.

Which mistakes are common?

Mistake 1: Thinking all deserts are hot and sandy

Many are cold or rocky, and the largest are polar (Antarctica and the Arctic).

Mistake 2: Confusing the highest range with the longest

The Himalayas are the highest, but the Andes are the longest.

Mistake 3: Mixing up plains and plateaus

Both are flat, but plateaus are elevated and have at least one steep side, while plains are low.

Mistake 4: Assuming mountain ranges are permanent

They rise through tectonic uplift and are worn down by erosion over millions of years.