Mountain, Hill, and Plateau Landforms

A mountain is a large natural elevation of the land that rises steeply to a peak or ridge, a hill is a lower and more rounded rise, and a plateau is an elevated area of relatively flat land bordered by steep slopes on at least one side. In brief: there is no universal height that separates a hill from a mountain (some countries use about 600 m as a rule of thumb). Mountains are formed mainly by plate tectonics as fold, fault-block, dome or volcanic mountains. Plateaus are formed by uplift, lava flows or erosion of surrounding land, and are often dissected by deep river valleys.

High ground shapes climate, rivers, ecosystems and human activity. This guide describes mountains, hills and plateaus, how each type forms, compares them in a table, works through calculations of slope and temperature, outlines how these landforms have influenced history and corrects common mistakes.

What are landforms?

A landform is a natural feature of Earth’s surface with a recognizable shape, such as a mountain, valley, plain or beach. Landforms are created by endogenic (internal) processes, such as tectonic uplift and volcanism, and are modified by exogenic (surface) processes: weathering, erosion by water, ice, wind and gravity, and deposition. Relief is the difference in height between the highest and lowest points in an area, and it is used to describe the roughness of the land.

How do mountains form?

• Fold mountains: formed when two plates collide and the crust is compressed and folded, such as the Himalayas, the Alps and the Andes.
• Fault-block mountains: formed when large blocks of crust are lifted or tilted along faults, with steep faces on one side, such as the Sierra Nevada in California or the Black Forest and the Vosges.
• Volcanic mountains: formed by the accumulation of lava and ash: stratovolcanoes (Mount Fuji, Mount Kilimanjaro) and shield volcanoes (Mauna Kea and Mauna Loa in Hawaii).
• Dome mountains: formed when magma pushes up the crust without breaking through, and erosion exposes the dome, such as the Black Hills in South Dakota.
• Residual (erosional) mountains: hard rock left standing after the surrounding land has eroded.

Mountain building (orogeny) takes millions of years, and erosion starts as soon as the land rises. Mountain environments have steep slopes, thin soils, cold temperatures that fall with altitude, and zones of vegetation at different heights (altitudinal zonation).

What are hills and plateaus?

Hills have gentler slopes and rounded tops, and less relief than mountains; they are often the remains of older mountains worn down by erosion, or of glacial deposits (drumlins). In Britain, a rise of less than about 600 m has traditionally been called a hill, but this is a convention that is not universal. Plateaus are high, large, flat-topped areas; they can be formed by tectonic uplift (the Tibetan Plateau, with an average height of about 4,500 m and an area of about 2.5 million km²), by thick layers of lava (the Deccan Plateau, the Columbia Plateau) or by the erosion of surrounding areas (the Colorado Plateau, cut by the Grand Canyon). Plateaus often have a dry climate and are cut by canyons, with steep edges called escarpments. Related forms are the mesa (a flat-topped hill with steep sides) and the butte (a smaller, isolated remnant).

Mountains, hills and plateaus compared

Worked example: slope and temperature

1. Relief: a hiker climbs from a valley floor at 1,200 m to a summit at 3,200 m; the relief is 3,200 − 1,200 = 2,000 m.
2. Slope: the horizontal distance on the map is 10 km. The gradient is 2,000 ÷ 10,000 = 0.20, or 1 in 5; the angle is arctan(0.20) = 11.3°.
3. Temperature: the air cools by about 6.5 °C per 1,000 m. For 2,000 m: 2 × 6.5 = 13 °C. If the valley is at 14 °C, the summit is at about 14 − 13 = 1 °C.
4. Mountain height measurements: Mauna Kea rises about 4,207 m above sea level, but its base is on the sea floor about 6,000 m deep, so its total height from base to summit is roughly 10,200 m, more than Everest (8,849 m above sea level), which shows the difference between height above sea level and base-to-peak height.
5. Plateau elevation: the Tibetan Plateau at an average of 4,500 m is higher than almost all mountain summits outside Asia; with a lapse rate of 6.5 °C per 1,000 m, an average sea-level temperature of 25 °C would fall to about 25 − 4.5 × 6.5 = −4 °C, a reason why its climate is cold.

How have these landforms influenced people?

Mountains have been barriers to movement, refuges for peoples and sources of minerals, timber and water. Passes such as the Brenner in the Alps and the Khyber in Afghanistan and Pakistan formed trade and military routes. Plateaus, such as the Ethiopian Highlands and the Andean Altiplano, supported farming and large civilizations (the Inca) at altitudes where lowland climates are hot. Hills provided defensive sites for forts and towns. In recent times, mountains have become a center for tourism, skiing and hydroelectric power.

Which mistakes are common?

Mistake 1: Assuming a fixed height separates hills and mountains

There is no worldwide definition. The distinction depends on relief, steepness and local conventions.

Mistake 2: Thinking all mountains are formed by plate collisions

Some are volcanic, fault-block, dome or erosional.

Mistake 3: Confusing a plateau with a plain

Both are flat, but a plateau is elevated and has steep edges, while a plain is low.

Mistake 4: Equating the tallest mountain above sea level with the tallest from base to summit

Everest has the highest summit above sea level, but Mauna Kea is taller from its base on the sea floor.