Rock Deformation
Rock deformation is the process by which rock structure is altered due to external forces such as pressure, temperature and shear. It occurs when rocks are subjected to conditions that cause them to deform, or to change shape, volume and stress in response to the forces around them. As rocks deform different types of texture, fractures, and strain may form. Rock deformation plays an important role in the formation and evolution of the Earth’s crust and is a basic component of geologic processes such as metamorphism, tectonics, and sedimentation.
Rock deformation can occur in a variety of ways. Basal and internal deformation result from an external force that pushes the rock down in a vertical direction. Horizontal or folding deformation results when the external force pushes it in a horizontal direction. Twisting deformation, which occurs when an external force applies a rotational torque to the rock, is another type of deformation. All of these types of deformation can cause the rock to move out of its original shape and create fractures and other features.
Increases in pressure and temperature can also cause rocks to deform. The increased pressure and temperature can cause frictional heating, which reduces the friction of the rock along its boundaries. Pressure may also cause plastic deformation as rock grains adjust to the increased pressure by pushing and pulling against one another. The resulting changes in grain size and shape can cause the rock to become mmaller and thicker, with a greater strength and compression. In addition to pressure, temperature is an important factor in controlling rock deformation. Temperature changes can cause rocks to expand or contract. The greater the temperature change, the more intense the deformation.
Over extended periods of time, rock deformation can be seen in the shaping of Earth’s landforms. The process through which rocks are folded or bent is known as folding. Pressure and temperature also play a role in mountain building as subduction of plates causes intense deformation in the Earth’s crust. Rocks in the lower layers of the crust may be subjected to high temperatures and pressure, resulting in metamorphism. Igneous and sedimentary rocks may also undergo metamorphosis as a result of extreme stress due to plate tectonic movement.
The study of rock deformation is important for understanding the formation and evolution of Earth and its surface features, as well as its tectonic and geologic history. In addition to its importance for geology, rock deformation can also be used to study the physical and chemical properties of rocks and their response to a variety of conditions, including changes in pressure and temperature.
