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Fracture (geology) A fractured rock in the Eastern Cape in South Africa, a mechanism of brittle deformation in response to stress. A fracture is any separation in a geologic formation, such as a joint or a fault that divides the rock into two or more pieces. A fracture will sometimes form a deep fissure or crevice in the rock.
Structural geology is the study of the three-dimensional distribution of rock units with respect to their deformational histories. The primary goal of structural geology is to use measurements of present-day rock geometries to uncover information about the history of deformation (strain) in the rocks, and ultimately, to understand the stress ...
Joint (geology) Horizontal joints in the sedimentary rocks of the foreground and a more varied set of joints in the granitic rocks in the background. Image from the Kazakh Uplands in Balkhash District, Kazakhstan. Orthogonal joint sets on a bedding plane in flagstones, Caithness, Scotland. Joints in the Almo Pluton, City of Rocks National ...
Thermal stress weathering is most effective when the heated portion of the rock is buttressed by surrounding rock, so that it is free to expand in only one direction. [12] Thermal stress weathering comprises two main types, thermal shock and thermal fatigue. Thermal shock takes place when the stresses are so great that the rock cracks ...
These folds were produced by Alpine deformation. In structural geology, a fold is a stack of originally planar surfaces, such as sedimentary strata, that are bent or curved ("folded") during permanent deformation. Folds in rocks vary in size from microscopic crinkles to mountain-sized folds. They occur as single isolated folds or in periodic ...
In geology, the term " tension " refers to a stress which stretches rocks in two opposite directions. The rocks become longer in a lateral direction and thinner in a vertical direction. One important result of tensile stress is jointing in rocks. However, tensile stress is rare because most subsurface stress is compressive, due to the weight of ...
Types of faulting. Anderson's theory of faulting, devised by Ernest Masson Anderson in 1905, is a way of classifying geological faults by use of principal stress. [1] [2] A fault is a fracture in the surface of the Earth that occurs when rocks break under extreme stress. [3] Movement of rock along the fracture occurs in faults.
(Left) Randomly-orientated grains in a rock before metamorphism. (Right) Grains align orthogonal to the applied stress if a rock is subjected to stress during metamorphism. Metamorphism is the set of processes by which existing rock is transformed physically or chemically at elevated temperature, without actually melting to any great degree.