![East Asia topographic map](https://upload.wikimedia.org/wikipedia/commons/2/26/East_Asia_topographic_map.png)
Intraplate deformation is the folding, breaking, or flow of the
Earth's crust
Earth's crust is Earth's thin outer shell of rock, referring to less than 1% of Earth's radius and volume. It is the top component of the lithosphere, a division of Earth's layers that includes the crust and the upper part of the mantle. The ...
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 (at about under the oceans and about under the continents) and ends at the top of the lower mantle at . Temperatures range from appro ...
, such as the
Tibetan Plateau
The Tibetan Plateau (, also known as the Qinghai–Tibet Plateau or the Qing–Zang Plateau () or as the Himalayan Plateau in India, is a vast elevated plateau located at the intersection of Central, South and East Asia covering most of the Ti ...
(Figure 1). Intraplate deformation brings another aspect to
plate tectonic
Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large te ...
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 is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stres ...
. 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 ...
s,
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 ...
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
![India-Asia collision with no intraplate deformation](https://upload.wikimedia.org/wikipedia/commons/b/b5/India-Asia_collision_with_no_intraplate_deformation.jpg)
Central/East Asia is possibly the best example of large-scale intraplate deformation. The formation and
uplift
Uplift may refer to: Science
* Geologic uplift, a geological process
** Tectonic uplift, a geological process
* Stellar uplift, the theoretical prospect of moving a stellar mass
* Uplift mountains
* Llano Uplift
* Nemaha Uplift
Business
* Uplif ...
of the Tibetan plateau and the
Himalayan mountain range started in the
Cenozoic era
The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configura ...
around 50 million years ago when the
Indian plate
The Indian Plate (or India Plate) is 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 , began mov ...
collided with the
Eurasian plate
The Eurasian Plate is a tectonic plate that includes most of the continent of Eurasia (a landmass consisting of the traditional continents of Europe and Asia), with the notable exceptions of the Indian subcontinent, the Arabian subcontinent and ...
.
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 (geology), crust and the portion of the upper mantle (geology), mantle that behaves elastically on time sca ...
, adding to increased crustal thickness and high stress in the Himalaya/Tibet region.
Many geophysical observations in
Tibet
Tibet (; ''Böd''; ) is a region in East Asia, covering much of the Tibetan Plateau and spanning about . It is the traditional homeland of the Tibetan people. Also resident on the plateau are some other ethnic groups such as Monpa people, ...
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-sectional profile by pushing material through a die of the desired cross-section. Its two main advantages over other manufacturing processes are its ability to create very complex c ...
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; Mongolian script: , , ; lit. "Mongol Nation" or "State of Mongolia" () is a landlocked country in East Asia, bordered by Russia to the north and China to the south. It covers an area of , with a population of just 3.3 million, ...
or the
Tian Shan mountains
The Tian Shan,, , otk, 𐰴𐰣 𐱅𐰭𐰼𐰃, , tr, Tanrı Dağı, mn, Тэнгэр уул, , ug, تەڭرىتاغ, , , kk, Тәңіртауы / Алатау, , , ky, Теңир-Тоо / Ала-Тоо, , , uz, Tyan-Shan / Tangritog‘ ...
. 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.
See also
*
Alice Springs Orogeny
The Alice Springs Orogeny was a major intraplate tectonic (mountain building) episode in central Australia responsible for the formation of a series of large mountain ranges. The deformation associated with the Alice Spring Orogeny caused the ve ...
*
Intraplate earthquake
The term intraplate earthquake refers to a variety of earthquake that occurs ''within the interior'' of a tectonic plate; this stands in contrast to an interplate earthquake, which occurs ''at the boundary'' of a tectonic plate. Intraplate earth ...
*
Lower crustal flow
*
North Atlantic breakup
References
{{reflist
Plate tectonics