Mountains
What is a mountain?
A mountain is a landform that extends above the surrounding terrain in a limited area. A mountain is generally higher and steeper than a hill, but there is considerable overlap, and usage often depends on local custom. Some authorities define a mountain as a peak with a topographic prominence.
24% of the Earth's land mass is mountainous; 1 in 10 people live in mountainous regions. All the world's major rivers are fed from mountain sources, and more than half of humanity depends on mountains for water.
Heights of mountains are generally given as heights above mean sea level. The Himalayas average 5 km (3 miles) above sea level, whilst the Andes average 4 km (2.4 miles). Most other mountain ranges average 2-2.5 km.
Mountain are formed through the movement of Plate Tectonics.
The highest mountain
The tip of Mount Everest is the highest point on the entire planet, soaring 8,848 m (29,029 ft) above the border of Nepal and Tibet in China. That height is enough to thrust the mountain up into the powerful winds of the jet stream. At the peak, wind speeds sometimes exceed 400 km/h.
In Nepal, Everest is called Sagarmatha, 'goddess of the sky', while in Tibet, its known as Chomolungma, 'goddess mother of the world'. Westerners, however, originally gave Everest the rather uninspired name Peak XV. It was only after a carefully undertaken 1852 survey established it as the highest mountain on Earth, that it was renamed in honor of British surveyor Sir George Everest.
Since then Everest has become a Mecca for mountaineers of all stripes and nationalities. Sir Edmond Hillary and Sherpa Tenzing Norgay were the first to reach the top in 1953. Now, more than fourteen hundred people from sixty-three nations have reached the summit.
Besides the weather and the constant walking and hauling gear, one of the most difficult aspects of the trek to Everest is the altitude. It affects the length of the trip and climbers even have to respond physiologically or behaviorally to the increase in elevation.
At the peak of Mount Everest, the air is very thin, there's only one third as much oxygen as there is at sea level. This simple fact, more than any other, explains why climbing Mt. Everest is such a challenge, because without air, the human body begins to shut down. The higher a person climbs, the slightest physical exertion takes enormous effort.