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Joints arise from brittle fracture of a rock or layer due to tensile stress.This stress may be imposed from outside; for example, by the stretching of layers, the rise of pore fluid pressure, or shrinkage caused by the cooling or desiccation of a rock body or layer whose outside boundaries remained fixed.
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.
Exfoliation joints following the topography of inclined valley walls, bedrock hill slopes, and cliffs can create rock blocks that are particularly prone to sliding. Especially when the toe of the slope is undercut (naturally or by human activity), sliding along exfoliation joint planes is likely if the joint dip exceeds the joint's frictional ...
In geotechnical engineering, a discontinuity (often referred to as a joint) is a plane or surface that marks a change in physical or chemical characteristics in a soil or rock mass. A discontinuity can be, for example, a bedding , schistosity , foliation , joint , cleavage , fracture , fissure , crack, or fault plane.
Structural geology is a critical part of engineering geology, which is concerned with the physical and mechanical properties of natural rocks. Structural fabrics and defects such as faults, folds, foliations and joints are internal weaknesses of rocks which may affect the stability of human engineered structures such as dams , road cuts, open ...
In geology and geophysics, thermal subsidence is a mechanism of subsidence in which conductive cooling of the mantle thickens the lithosphere and causes it to decrease in elevation. This is because of thermal expansion : as mantle material cools and becomes part of the mechanically rigid lithosphere, it becomes denser than the surrounding material.
One way in particular that joints can be formed is due to fluid pressure, as well as at the crest of folds in rocks. This occurs at the peak of the fold or due to the fluid pressure because a localized tensile stress forms, eventually leading to jointing. [2] Another way in which joints form is due to the change in the weight of the overburden ...
Basalt columns seen on Porto Santo Island, Portugal. Columnar jointing of volcanic rocks exists in many places on Earth. Perhaps the most famous basalt lava flow in the world is the Giant's Causeway in Northern Ireland, in which the vertical joints form polygonal columns and give the impression of having been artificially constructed.