Large-scale deformation of the Earth's crust by natural processes, which leads to the formation of continents and ocean basins, mountain systems and rift valleys, and other features by mechanisms such as lithospheric plate movement (see plate tectonics), volcanic loading, or folding. The study of diastrophism, or tectonic processes, is the central unifying principle in modern geology and geophysics.
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The term covers movement of solid crust material (as opposed to molten material which is volcanism). The movements cause rock to be bent or broken as a result of pressures exterted by plate tectonics or the rise of magma from below.
The most obvious evidence of disastrophic movement can be seen in sedimentary rock where bent, broken or non-horizontal strata provide visual proof of movement. Diastrophic movement can be classified as two types, folding and faulting.
See Structural geology for more information.