mountain

Mountains are created when two continental plates collide and no subduction takes place, resulting in the land at the collision zone being squeezed together and thrust upwards.

Compassberg Mountains in South Africa. Many geological processes are at work here, particularly freeze-thaw action in which rocks are broken apart by the expansion of frozen water and repeated heating and cooling.

A mountain landscape near Compassberg, South Africa.

Pen y Fan, one of the major peaks or beacons that give the South Wales National Park its name, the Brecon Beacons. The mountain rises to a height of 886 m/2,907 ft above sea level and towers over Neuadd reservoir. It is a popular challenge for climbers from all over the UK.

Natural upward projection of the Earth's surface, higher and steeper than a hill. Mountains are at least 330 m/1,000 ft above the surrounding topography. The existing rock below a high mountain may be subjected to high temperatures and pressures, causing metamorphism. Plutonic activity also can accompany mountain building.

Mountain

Province of northern Luzon Island in the Philippines; area 2,098 sq km/810 sq mi; population (1995) 131,000. The capital is Bontoc. The terrain is rugged, mountainous, and heavily forested. Rice, corn, and root crops are grown.