Mountains make up a quarter of the world’s landscape. They are found on every continent and in three- quarters of all the world’s countries. Only 46 countries have no mountains or high plateaus, and most of these are small island nations. Some of the highest mountains are found beneath the sea. Some islands are actually mountain peaks emerging out of the water. Even though the world’s highest peak (from sea level) is Mount Everest in the Himalayas (at 8850 metres high), Mauna Loa in Hawaii is actually higher when measured from its base on the ocean floor. 14.4.1 Mountain climate and weather It is usually colder at the top of a mountain than at the bottom, because air gets colder with altitude . Air becomes thinner and is less able to hold heat. For every 1000 metres you climb, the temperature drops by 6 ° C. FIGURE2 Ecosystems change with altitude on mountains.
High alpine environment. Snow and ice all year. Shallowest soils and high wind exposure. Average temperatures can drop to −15°C (to −40°C at 8000 metres). Air lacks oxygen —‘thin air’.
Tundra environment. Shallow soils and wind exposure. Average temperatures are between 3 and −3°C.
Coniferous forest environment. Shallow, slightly acidic soils. Average temperatures are around 5–9°C.
Cool temperature deciduous forest environment. Soils with moderate humus. Average temperatures are around 10–15°C.
Rainforest — evergreen forests with deep,
relatively poor, leached soils. Base average temperature of around 20–25°C.
SkillBuilder discussion Geographical inquiry 1. Explain why there are no trees in the tundra and high alpine environments. 2. Research why coniferous trees would be found at the highest elevation of all the tree types. 3. What is the difference between deciduous trees and evergreen trees? Explain why they would be found at their respective elevations.
TOPIC14 Geomorphological processes and hazards
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