Intraplate deformation is the folding, breaking, or flow of the

Earth's crust Earth's crust is its thick outer shell of rock, referring to less than one percent of the planet's radius and volume. It is the top component of the lithosphere, a solidified division of Earth's layers that includes the crust and the upper ...

within plates instead of at their margins. This process usually occurs in areas with especially weak crust and

upper mantle The upper mantle of Earth is a very thick layer of rock inside the planet, which begins just beneath the crust (geology), crust (at about under the oceans and about under the continents) and ends at the top of the lower mantle (Earth), lower man ...

, such as the

Tibetan Plateau The Tibetan Plateau, also known as the Qinghai–Tibet Plateau or Qingzang Plateau, is a vast elevated plateau located at the intersection of Central Asia, Central, South Asia, South, and East Asia. Geographically, it is located to the north of H ...

(Figure 1). Intraplate deformation brings another aspect to

plate tectonic Plate may refer to: Cooking * Plate (dishware), broad, mainly flat vessel commonly used to serve food * Plates, tableware, dishes or dishware used for setting a table, serving food and dining * Plate, the content of such a plate (for example: r ...

theory.

Crustal deformation processes

The theory of plate tectonics states that the Earth's lithosphere (crust and upper mantle) is made up of rigid plates that "float" on top of the asthenosphere (lower mantle) and move relative to one another. As the plates move, the crust deforms dominantly along the plate margins. Intraplate deformation differs from that respect by the observation that deformation can occur anywhere the crust is weak and not just at plate margins. Deformation is the folding, breaking, or flow of rocks. There are many different types of crustal deformation depending on whether the rocks are brittle or

ductile Ductility refers to the ability of a material to sustain significant plastic deformation before fracture. Plastic deformation is the permanent distortion of a material under applied stress, as opposed to elastic deformation, which is reversi ...

. The aspects that determine these properties are due to certain temperatures and pressures that rocks experience within the Earth. Therefore, temperature and pressure control deformation processes. Ductile rocks tend to bend, fold, stretch, or flow due to compressional or extensional forces. Brittle rocks, on the other hand, tend to break. The zone where the crust breaks is termed a fault. There are three main types of faults:

normal fault In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

reverse fault In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic f ...

s and strike slip (transform) faults. All of these are ways the crust can deform is due to the different types of plate margins, which are: divergent boundaries,

convergent boundaries A convergent boundary (also known as a destructive boundary) is an area on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction. The subduction zone can be defined by a ...

, and transform boundaries. These three boundaries do not always form perfectly and this can lead to a mixed boundary. Mixed boundaries can be a combination of a transform with convergence or a transform with divergence.

Intraplate deformation examples

Asia

Central/East Asia is possibly the best example of large-scale intraplate deformation. The formation and uplift of the Tibetan plateau and the

Himalayan mountain range The Himalayas, or Himalaya ( ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the Earth's highest peaks, including the highest, Mount Everest. More than 100 peak ...

started in the

Cenozoic era The Cenozoic Era ( ; ) is Earth's current geological Era (geology), era, representing the last 66million years of Earth's history. It is characterized by the dominance of mammals, Insect, insects, birds and flowering plant, angiosperms (floweri ...

around 50 million years ago when the

Indian plate The Indian plate (or India plate) is or was a minor tectonic plate straddling the equator in the Eastern Hemisphere. Originally a part of the ancient continent of Gondwana, the Indian plate broke away from the other fragments of Gondwana an ...

collided with the Eurasian plate. The collision caused much shortening of the

lithosphere A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the lithospheric mantle, the topmost portion of the upper mantle that behaves elastically on time ...

, adding to increased crustal thickness and high stress in the Himalaya/Tibet region. Many geophysical observations in

Tibet Tibet (; ''Böd''; ), or Greater Tibet, is a region in the western part of East Asia, covering much of the Tibetan Plateau and spanning about . It is the homeland of the Tibetan people. Also resident on the plateau are other ethnic groups s ...

show a weak crustal zone and suggest that the middle to lower crust may contain fluids and be partially melted. As the Himalayan-Tibet region began to rise, lateral

extrusion Extrusion is a process used to create objects of a fixed cross section (geometry), cross-sectional profile by pushing material through a Die (manufacturing), die of the desired cross-section. Its two main advantages over other manufacturing pro ...

of the crust in the Tibetan plateau gradually became the dominant mechanism for accommodating the collision and crustal shortening. The lateral extrusion is sliding dominantly to the east and out of India's path. Eastern Tibet is traditionally interpreted as being part of a broad accommodation zone. Much of the eastern movement is due to major strike-slip faults. These strike-slip faults, along with the other faults in Tibet could still be interpreted as on a plate margin though. True intraplate deformation occurs farther north in areas such as

Mongolia Mongolia is a landlocked country in East Asia, bordered by Russia to the north and China to the south and southeast. It covers an area of , with a population of 3.5 million, making it the world's List of countries and dependencies by po ...

or the

Tian Shan mountains The Tian Shan, also known as the Tengri Tagh or Tengir-Too, meaning the "Mountains of God/Heaven", is a large system of mountain ranges in Central Asia. The highest peak is Jengish Chokusu at high and located in Kyrgyzstan. Its lowest point is ...

. These areas display true intraplate deformation because there is still much faulting and folding to accommodate some of the crustal shortening from the India/Eurasia collision hundreds of kilometers away from the plate margin.

References

{{reflist Plate tectonics

Crustal deformation processes

Intraplate deformation examples

Asia

See also

References