MAIN: ROCKS AND MINING: ROCKS DEFORM
Rocks Deform
Rocks can be pushed, pulled, squeezed, and sheared. Their folds and fractures show that rocks deform under stress. Rock can become deformed during earthquakes, mountain-building, and other events caused by movements of Earth's huge tectonic plates.
How Do Rocks Deform?
Rocks That Break
Rocks That Flow
How Do Rocks Deform?
How a particular rock deforms depends on: its temperature and depth; the amount, rate, and direction of the stress; the rock's inherent strength; and the quantity of water in the rock.
Rocks That Break
Like a pane of glass dropped on the floor, some rocks are brittle: They break, or fracture, in response to stress. Rocks tend to fracture when stress is applied rapidly, at shallow depths, or at low temperatures. If rocks on each side of a fracture are displaced, the fracture becomes a fault. Earthquakes result from the brittle deformation that also creates faults.
Rocks That Flow
Like a caramel bar on a hot day, some rocks are ductile: They flow, or change their shape, in response to stress. If stress is applied over millions of years to hot, layered rocks within the Earth, the layers may flow into folds. Flowing rocks can also be stretched into elongated forms.
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