Geology
A mountain is usually produced by the movement of lithospheric plates, either orogenic movement or epeirogenic movement. Compressional forces, isostatic uplift and intrusion of igneous matter forces surface rock upward, 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. Two types of mountain are formed in this way depending on how the rock reacts to the tectonic forces, — fold mountains or fault-block mountains. Other mountain building processes include volcanoes and sea floor spreading.
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