Mountains

A mountain is any landform that rises sharply above the land around it, usually higher than 600 metres. Most of the world's tallest mountains were built when two giant pieces of Earth's surface (called tectonic plates) crashed slowly into each other and pushed the rock skyward. The same process is still going on today, and the Himalayas grow a few millimetres taller every year.

• Tallest on LandEverest8,849 m, in Nepal & Tibet
• Tallest from BaseMauna Kea10,000+ m, mostly underwater
• Longest RangeAndes7,000+ km, South America
• How They FormTectonic Platescrashing slowly for millions of years
• Oldest Mountainsapprox. 4 billion yearsin the Barberton Range, South Africa
• Climbed Everestapprox. 6,000 peoplesince 1953

How tall are the famous mountains?

All in metres above sea level:

Height (metres)

Everest8,849

K28,611

Aconc.6,961

Denali6,190

Kilim.5,895

M. Blanc4,808

Everest only just beats K2, which is widely considered a harder climb because of its steeper slopes and worse weather.

What is a mountain?

Most geographers say a mountain is any landform that rises at least 300 metres above the land around it, with a fairly small summit area. Anything shorter is usually called a hill. Mountains can stand alone (like Mount Fuji in Japan) or join up into a long line called a range (like the Alps or the Himalayas).

How mountains form

The Earth's outer shell is broken into a few dozen big pieces called tectonic plates. These plates drift around slowly on the hot rock beneath, and when two of them push into each other the rock at the edges has nowhere to go but up. The Himalayas began rising when India crashed into Asia approx. 50 million years ago, and the crash is still going on. Other mountains form when one plate slides under another (the Andes) or when hot rock pushes up through the surface as a volcano (Mount Fuji, Kilimanjaro).

FactMount Everest is still growing. India is still pushing into Asia at approx. 5 centimetres a year, which lifts Everest roughly 4 millimetres taller every year.

Life on a mountain

As you climb a mountain, the air gets thinner and colder. Plants and animals change with the height. Lower slopes have thick forest, the middle has tougher trees and grass, and high above the tree line you find rocks, ice, and only the hardiest species (like the snow leopard of Asia or the mountain goat of North America).

Climbing the great peaks

People started climbing mountains for fun in the 1700s. The first ascent of Mont Blanc came in 1786, the first of the Matterhorn in 1865. The 14 mountains over 8,000 metres (all in Asia) became targets in the 20th century. Everest was first reached by Edmund Hillary and Tenzing Norgay in 1953.

Did you know?If you measure from base to summit instead of from sea level, the tallest mountain on Earth is Mauna Kea in Hawaii. Most of it sits under the ocean, so only the top 4,200 metres show above the water, but the whole thing is over 10,000 metres tall, taller than Everest.

Deeper dive: the four ways mountains are built

• Fold mountains form when two plates push into each other and the rock crumples up like a rug pushed against a wall. The Himalayas, the Alps, and the Andes are all fold mountains.
• Block mountains form when blocks of rock get pushed up while neighbouring blocks drop down along giant cracks called faults. The Sierra Nevada in California is a block mountain range.
• Volcanic mountains grow when hot rock pushes up through the crust and piles up around the vent. Mount Fuji, Kilimanjaro, and Mount Etna are all volcanoes.
• Dome mountains bulge upward when hot rock pushes the surface up without breaking through. The Black Hills of South Dakota and Ayers Rock (Uluru) are dome features.

Pick a mountain or range below to see its fact file.