Mountains Wallpaper, #12645

A mountain is a landform that extends above the surrounding terrain in a limited area, with a peak. A mountain is generally steeper than a hill, but there is no universally accepted standard definition for the height of a mountain or a hill although a mountain usually has an identifiable summit. Mountains cover 64% of Asia, 36% of North America, 25% of Europe, 22% of South America, 17% of Australia, and 3% of Africa. As a whole, 24% of the Earth's land mass is mountainous. 10% of people live in mountainous regions. Most of the world's rivers are fed from mountain sources, and more than half of humanity depends on Mountains for water.Even though Everest is the highest mountain on Earth today, there have been much taller Mountains in the past. During the Precambrian era, the Canadian Shield once had Mountains 12,000 m (39,370 ft) in height that are now eroded down into rolling hills. These formed by the collision of tectonic plates much like the Himalaya and the Rocky Mountains.Some isolated Mountains were produced by volcanoes, including many apparently small islands that reach a great height above the ocean floor.