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Information on Mountains
Some people therefore enjoy the sport of mountaineering. Mountains are also the site for

the sport of downhill skiing. People engaging in these activities often stay at mountain
resorts built for the purpose.

Geology

The Himalayan mountain range with Mount Everest.

A mountain is usually produced by the movement of lithospheric

plates, either orogenic movement or epeirogenic movement. The compressional forces,
isostatic uplift and intrusion of igneous matter forces surface rock upwards, creating a
landform higher than the surrounding features. The height of the feature makes it either a
hill or, if higher and steeper, a mountain. The absolute heights of features termed mountains
and hills vary greatly according to an area's terrain. The major mountains tend to occur in

long linear arcs, indicating tectonic plate boundaries and activity. Mountain creation tends to
occur in discrete periods, each referred to as an orogeny. The orogeny may last millions of
years, and the uplifted region is being eroded away, producing valley-and-peak terrain, even

while the uplift is taking place. Two types of mountain are formed depending on how the rock
reacts to the tectonic forces – block mountains or fold mountains.

The compressional forces in continental collisions may cause the compressed region to
thicken, so the upper surface is forced upwards. In order to balance the weight, much of the
compressed rock is forced downwards, producing deep "mountain roots". Mountains
therefore form downwards as well as upwards (see isostasy). However, in some continental

collisions part of one continent may simply override part of the others, crumpling in the
process.

Some isolated mountains were produced by volcanoes, including many apparently small
islands that reach a great height above the ocean floor.

Block mountains are created when large areas are widely broken up by faults creating large
vertical displacements. This occurrence is fairly common. The uplifted blocks are block

mountains or horsts. The intervening dropped blocks are termed graben: these can be small
or form extensive rift valley systems. This form of landscape can be seen in East Africa, the
Vosges, the Basin and Range province of Western North America and the Rhine valley.

Where rock does not fault it folds, either symmetrically or asymmetrically. The upfolds are
anticlines and the downfolds are synclines; in asymmetric folding there may also be
recumbent and overturned folds. The Jura mountains are an example of folding. Over time,

(God's Amazing Landscapes) 9