Diastrophism refers to deformation of the Earth’s crust, and more especially to folding and mcknight physical geography pdf download. Diastrophism can be considered part of geotectonics. Diastrophism comes from the Greek word meaning a twisting.
All processes that move, elevate or build up portions of the earth’s crust come under diastrophism. Movement causes rock to be bent or broken. The most obvious evidence of disastrophic movement can be seen where sedimentary rocks have been bent, broken or tilted. Such non-horizontal strata provide visual proof of movement.
Diastrophic movement can be classified as two types, folding and faulting, tilted beds usually are part of a larger syncline or anticline. Diastrophic movement is often called orogenic as it is associated with mountain building. There are various theories of the cause of diastrophic movement such as being the result of pressures exerted by convection currents in the mantle or the rise of magma through the crust.
Other deformations are caused by meteorite impact and combinations of gravity and erosion such as landslides and slumping. The study of diastrophism encompasses the varying responses of the crust to tectonic stresses. Earth’s surface such as the weight of mountains, lakes, and glaciers.
Subsurface conditions also cause subsidence or uplift, known as epeirogeny, over large areas of Earth’s surface without deforming rock strata. By the end of the 19th Century it was generally accepted that the cause of folding and faults was lateral compression that resulted from a shrinking Earth caused by its gradual cooling. In the late 19th Century, Eduard Suess proposed his eustatic theory that provided the underpinnings for Chamberlin’s explanation of diastrophism.
In volume two of Das Antlitz der Erde Suess set out his belief that across geologic time, the rise and fall of sea levels were mappable across the earth, that is, that the periods of ocean transgression and regression were correlatable from one continent to another. Suess postulated that as sediments filled the ocean basins the sea levels gradually rose, and periodically there were events of rapid ocean bottom subsidence that increased the ocean’s capacity and caused the regressions.
Chamberlin proposed that instead of a thermal contraction, diastrophic movement was caused by gravitational contraction. In the United States, it was not until the late 1960s that thermal convection replaced the shrinking Earth theories. A Word A Day for 17 August 2009: diastrophism”. Deformation Style and Structural Relationships Associated with a Well-Exposed Slump Block within the Tongue River Formation of the Fort Union Group, Carter County, Southeastern Montana”.