Diastrophism
Encyclopedia
Diastrophism refers to deformation of the Earth's crust
, and more especially to folding
and faulting
. 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. They include: (i) orogenic processes involving mountain building through severe folding and affecting long and narrow belts of the earth’s crust; (ii) epeirogenic processes involving uplift or warping of large parts of the earth’s crust; (iii) earthquakes involving local relatively minor movements; (iv) plate tectonics involving horizontal movements of crustal plates.
Diastrophism covers movement of solid (plastic) crust material, as opposed to movement of molten material which is covered by volcanism
. Movement causes rock to be bent or broken. The most obvious evidence of disastrophic movement can be seen where sedimentary rock
s 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 landslide
s and slumping.
The study of diastrophism encompasses the varying responses of the crust to tectonic stresses. These responses include linear or torsional horizontal movements (such as continental drift) and vertical subsidence and uplift of the lithosphere (strain) in response to natural stresses on 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. Such changes include the thickening of the lithosphere by overthrusting, changes in rock density of the lithosphere caused by metamorphism or thermal expansion and contraction, increases in the volume of the asthenosphere (part of the upper mantle supporting the lithosphere) caused by hydration of olivine, and orogenic, or mountain-building, movements.
proposed his eustatic theory that provided the underpinnings for Chamberlin's explanation of disastrophism.
In volume two of Das Amlicz 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.
Crust (geology)
In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle...
, and more especially to folding
Fold (geology)
The term fold is used in geology when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of permanent deformation. Synsedimentary folds are those due to slumping of sedimentary material before it is lithified. Folds in rocks vary in...
and faulting
Geologic fault
In geology, a fault is a planar fracture or discontinuity in a volume of rock, across which there has been significant displacement along the fractures as a result of earth movement. Large faults within the Earth's crust result from the action of tectonic forces...
. Diastrophism can be considered part of geotectonics. Diastrophism comes from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
word meaning a twisting.
All processes that move, elevate or build up portions of the earth’s crust come under diastrophism. They include: (i) orogenic processes involving mountain building through severe folding and affecting long and narrow belts of the earth’s crust; (ii) epeirogenic processes involving uplift or warping of large parts of the earth’s crust; (iii) earthquakes involving local relatively minor movements; (iv) plate tectonics involving horizontal movements of crustal plates.
Diastrophism covers movement of solid (plastic) crust material, as opposed to movement of molten material which is covered by volcanism
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...
. Movement causes rock to be bent or broken. The most obvious evidence of disastrophic movement can be seen where sedimentary rock
Sedimentary rock
Sedimentary rock are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution....
s have been bent, broken or tilted. Such non-horizontal strata
Stratum
In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...
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
Syncline
In structural geology, a syncline is a fold, with younger layers closer to the center of the structure. A synclinorium is a large syncline with superimposed smaller folds. Synclines are typically a downward fold, termed a synformal syncline In structural geology, a syncline is a fold, with younger...
or anticline
Anticline
In structural geology, an anticline is a fold that is convex up and has its oldest beds at its core. The term is not to be confused with antiform, which is a purely descriptive term for any fold that is convex up. Therefore if age relationships In structural geology, an anticline is a fold that is...
. Diastrophic movement is often called orogenic
Orogeny
Orogeny refers to forces and events leading to a severe structural deformation of the Earth's crust due to the engagement of tectonic plates. Response to such engagement results in the formation of long tracts of highly deformed rock called orogens or orogenic belts...
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
Plate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...
or the rise of magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
through the crust. Other deformations are caused by meteorite impact
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...
and combinations of gravity and erosion such as landslide
Landslide
A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...
s and slumping.
The study of diastrophism encompasses the varying responses of the crust to tectonic stresses. These responses include linear or torsional horizontal movements (such as continental drift) and vertical subsidence and uplift of the lithosphere (strain) in response to natural stresses on 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. Such changes include the thickening of the lithosphere by overthrusting, changes in rock density of the lithosphere caused by metamorphism or thermal expansion and contraction, increases in the volume of the asthenosphere (part of the upper mantle supporting the lithosphere) caused by hydration of olivine, and orogenic, or mountain-building, movements.
Historical development of the concept
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 SuessEduard Suess
Eduard Suess was a geologist who was an expert on the geography of the Alps. He is responsible for hypothesising two major former geographical features, the supercontinent Gondwana and the Tethys Ocean.Born in London to a Jewish Saxon merchant, when he was three his family relocated toPrague,...
proposed his eustatic theory that provided the underpinnings for Chamberlin's explanation of disastrophism.
In volume two of Das Amlicz 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
Transgression (geology)
A marine transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, resulting in flooding. Transgressions can be caused either by the land sinking or the ocean basins filling with water...
and regression
Marine regression
Marine regression is a geological process occurring when areas of submerged seafloor are exposed above the sea level. The opposite event, marine transgression, occurs when flooding from the sea covers previously exposed land....
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.
Further reading
- Chorley, Richard J. (1963). "Diastrophic Background to Twentieth-Century Geomorphological Thought". Geological Society of America Bulletin 74(8): pp. 953–970.