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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 Reserve, Idaho.
Columnar jointing is a geological structure where sets of intersecting closely spaced fractures, referred to as joints, result in the formation of a regular array of polygonal prisms (basalt prisms), or columns. Columnar jointing occurs in many types of igneous rocks and forms as the rock cools and contracts.
One possible extension of this theory to match with the compressive stress theory (outlined below) is as follows [3] (Goodman, 1989): The exhumation of deeply buried rocks relieves vertical stress, but horizontal stresses can remain in a competent rock mass since the medium is laterally confined. Horizontal stresses become aligned with the ...
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.
Various geological processes create discontinuities at a broadly regular spacing. For example, bedding planes are the result of a repeated sedimentation cycle with a change of sedimentation material or change in structure and texture of the sediment at regular intervals, folding creates joints at regular separations to allow for shrinkage or expansion of the rock material, etc. Normally ...
The degree of deformation and metamorphism along with rock type determines the kind of cleavage feature that develops. Generally, these structures are formed in fine grained rocks composed of minerals affected by pressure solution. [1] Cleavage is a type of rock foliation, a fabric element that describes the way planar features develop in a ...
Horizontal stylolites This is the most commonly observed stylolite type. They occur parallel or nearly parallel to the bedding of rocks. This type is most frequently found in layered sedimentary rocks, mostly in carbonate rocks, which have not been affected by intensive tectonic structural activity or metamorphism. Inclined stylolites or ...
Sand dune cross-beds can be large, such as in the Jurassic-age erg deposits of Navajo Sandstone in Canyonlands National Park. Aztec Butte shown here Formation of cross-stratification Schematic of eolian cross-bedding Close up of cross-bedding and scour, Logan Formation, Ohio Tabular cross-bedding in the Navajo Sandstone in Zion National Park Tabular cross-bedding in the South Bar Formation in ...