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Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of
mountain building A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. A mountain differs from a plateau in having a limited summit area, and is larger than a hill, typically rising at lea ...
, the growth and behavior of the strong, old cores of continents known as
craton A craton (, , or ; from el, κράτος ''kratos'' "strength") is an old and stable part of the continental lithosphere A lithosphere ( grc, λίθος [] for "rocky", and [] for "sphere") is the rigid, outermost shell of a terrestrial p ...
s, and the ways in which the relatively rigid tectonic plate, plates that constitute the Earth's outer shell interact with each other. Tectonics also provide a framework for understanding the
earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth Earth is the third planet from the Sun and the only astronomical object known ...

earthquake
and
volcanic belt in Mexico A volcanic belt is a large volcano, volcanically active region. Other terms are used for smaller areas of activity, such as volcanic fields. Volcanic belts are found above zones of unusually high temperature (700-1400 °C) where m ...
s that directly affect much of the global population. Tectonic studies are important as guides for economic geologists searching for
fossil fuel A fossil fuel is a hydrocarbon In , a hydrocarbon is an consisting entirely of and . Hydrocarbons are examples of s. Hydrocarbons are generally colourless and hydrophobic with only weak odours. Because of their diverse molecular structure ...
s and
ore deposit Ore is natural rock Rock most often refers to: * Rock (geology) A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its Chemical compound, chemica ...
s of metallic and nonmetallic resources. An understanding of tectonic principles is essential to
geomorphologists
geomorphologists
to explain erosion patterns and other Earth surface features.


Main types of tectonic regime


Extensional tectonics

Extensional tectonics is associated with the stretching and thinning of the crust or the
lithosphere A lithosphere ( grc, λίθος [] for "rocky", and [] for "sphere") is the rigid, outermost shell of a terrestrial planet, terrestrial-type planet or natural satellite. On Earth, it is composed of the crust (geology), crust and the portion o ...
. This type of tectonics is found at divergent plate boundaries, in continental
rift In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear Fault (geology), downfaulted depression, called a graben, or more commonly ...

rift
s, during and after a period of
continental collision Continental collision is a phenomenon A phenomenon (; plural phenomena) is an observable fact or event. The term came into its modern philosophical usage through Immanuel Kant Immanuel Kant (, ; ; 22 April 1724 – 12 February 1804) ...

continental collision
caused by the lateral spreading of the thickened crust formed, at releasing bends in
strike-slip faults In geology, a fault is a Plane (geometry), planar fracture or discontinuity in a volume of Rock (geology), rock across which there has been significant displacement as a result of rock-mass movements. Large faults within the Earth's Crust (geolo ...
, in
back-arc basin Back-arc basins are geologic Structural basin, basins, submarine features associated with island arcs and subduction zones. They are found at some convergent boundary, convergent plate boundaries, presently concentrated in the western Pacific Ocean ...
s, and on the continental end of
passive margin A passive margin is the transition between oceanic and continental lithosphere that is not an active plate Continental margin, margin. A passive margin forms by sedimentation above an ancient rift, now marked by transitional lithosphere. Contin ...

passive margin
sequences where a detachment layer is present.


Thrust (contractional) tectonics

Thrust tectonics is associated with the shortening and thickening of the crust, or the lithosphere. This type of tectonics is found at zones of
continental collision Continental collision is a phenomenon A phenomenon (; plural phenomena) is an observable fact or event. The term came into its modern philosophical usage through Immanuel Kant Immanuel Kant (, ; ; 22 April 1724 – 12 February 1804) ...

continental collision
, at restraining bends in strike-slip faults, and at the oceanward part of passive margin sequences where a detachment layer is present.


Strike-slip tectonics

Strike-slip tectonics is associated with the relative lateral movement of parts of the crust or the lithosphere. This type of tectonics is found along oceanic and continental
transform fault A transform fault or transform boundary, sometimes called a strike-slip boundary, is a fault Fault commonly refers to: *Fault (geology), planar rock fractures showing evidence of relative movement *Fault (law), blameworthiness or responsibility ...

transform fault
s which connect offset segments of
mid-ocean ridge A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics File:Earth cutaway schematic-en.svg, upright=1.35, Diagram of the internal layering of Earth showing the lithosphere above the asthenosphere (not to scale) Plate ...
s. Strike-slip tectonics also occurs at lateral offsets in extensional and
thrust fault A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault Reverse or reversing may refer to: Arts ...

thrust fault
systems. In areas involved with
plate collisions
plate collisions
strike-slip deformation occurs in the over-riding plate in zones of oblique collision and accommodates deformation in the foreland to a collisional belt.


Plate tectonics

In plate tectonics the outermost part of the Earththe crust and uppermost
mantle Mantle may refer to: *Mantle (geology) A mantle is a layer inside a planetary body A planet is an astronomical body Astronomy (from el, ἀστρονομία, literally meaning the science that studies the laws of the stars) is a n ...
are viewed as acting as a single mechanical layer, the
lithosphere A lithosphere ( grc, λίθος [] for "rocky", and [] for "sphere") is the rigid, outermost shell of a terrestrial planet, terrestrial-type planet or natural satellite. On Earth, it is composed of the crust (geology), crust and the portion o ...
. The lithosphere is divided into separate "plates" that move relative to each other on the underlying, relatively weak
asthenosphere The asthenosphere ( grc, ἀσθενός 'asthenos''meaning "without strength", and thus "weak", and 'sphaira''meaning "sphere") is the highly viscous The viscosity of a fluid In physics, a fluid is a substance that continually Defor ...
in a process ultimately driven by the continuous loss of heat from the Earth's interior. There are three main types of plate boundaries: divergent, where plates move apart from each other and new lithosphere is formed in the process of
sea-floor spreading Seafloor spreading is a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcano, volcanic activity and then gradually moves away from the ridge. History of study Earlier theories by Alfred Wegener and Alexander ...
;
transform Transform may refer to: Arts and entertainment *Transform (Powerman 5000 album), ''Transform'' (Powerman 5000 album), 2003 *Transform (Rebecca St. James album), ''Transform'' (Rebecca St. James album), 2000 *Transform (scratch), a type of scratc ...

transform
, where plates slide past each other, and
convergent Convergent is an adjective for things that wikt:converge, converge. It is commonly used in mathematics and may refer to: *Convergent boundary, a type of plate tectonic boundary * Convergent (continued fraction) * Convergent evolution * Convergent s ...
, where plates converge and lithosphere is "consumed" by the process of
subduction Subduction is a geological process in which the oceanic lithosphere A lithosphere ( grc, λίθος [] for "rocky", and [] for "sphere") is the rigid, outermost shell of a terrestrial planet, terrestrial-type planet or natural satellite. O ...

subduction
. Convergent and transform boundaries form the largest structural discontinuities in the lithosphere and are responsible for most of the world's major ( Mw > 7)
earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth Earth is the third planet from the Sun and the only astronomical object known ...

earthquake
s. Convergent and divergent boundaries are also the site of most of the world's
volcano A volcano is a rupture in the crust of a planetary-mass object A planet is an astronomical body orbit In physics, an orbit is the gravitationally curved trajectory of an physical body, object, such as the trajectory of a planet a ...

volcano
es, such as around the
Pacific Ring of Fire The Ring of Fire (also known as the Pacific Ring of Fire, the Rim of Fire, the Girdle of Fire or the Circum-Pacific belt) is a region around much of the rim of the Pacific Ocean The Pacific Ocean is the largest and deepest of Earth ...

Pacific Ring of Fire
. Most of the deformation in the lithosphere is related to the interaction between plates, either directly or indirectly.


Other fields of tectonic studies


Salt tectonics

Salt tectonics is concerned with the structural geometries and deformation processes associated with the presence of significant thicknesses of
rock salt Halite ( or ), commonly known as rock salt, is a type of salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a cry ...

rock salt
within a sequence of rocks. This is due both to the low density of salt, which does not increase with burial, and its low strength.


Neotectonics

Neotectonics is the study of the motions and deformations of the
Earth's crust 350px, Plates in the crust of Earth Earth's crust is a thin shell on the outside of Earth, accounting for less than 1% of Earth's volume. It is the top component of the lithosphere, a division of Earth's layers that includes the Crust (geology), ...
(
geological Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which it is composed, and the processes by which th ...

geological
and
geomorphological incised into shale at the foot of the North Caineville Plateau, Utah, within the pass carved by the Fremont River (Utah), Fremont River and known as the Blue Gate. Grove Karl Gilbert, GK Gilbert studied the landscapes of this area in great detail, ...

geomorphological
processes) that are current or recent in
geological time The geologic time scale (GTS) is a system of chronological datingChronological dating, or simply dating, is the process of attributing to an object or event a date in the past, allowing such object or event to be located in a previously establish ...

geological time
."Encyclopedia of Coastal Science" (2005), Springer, , Chapter 1: "Tectonics and Neotectonics" The term may also refer to the motions and deformations themselves. The corresponding time frame is referred to as the ''neotectonic period''. Accordingly, the preceding time is referred to as ''palaeotectonic period''.


Tectonophysics

Tectonophysics is the study of the physical processes associated with deformation of the crust and mantle from the scale of individual mineral grains up to that of tectonic plates.


Seismotectonics

Seismotectonics is the study of the relationship between earthquakes, active tectonics, and individual faults in a region. It seeks to understand which faults are responsible for seismic activity in an area by analysing a combination of regional tectonics, recent instrumentally recorded events, accounts of historical earthquakes, and geomorphological evidence. This information can then be used to quantify the
seismic hazardA seismic hazard is the probability that an earthquake will occur in a given geographic area, within a given window of time, and with ground motion intensity exceeding a given threshold. With a hazard thus estimated, risk can be assessed and includ ...
of an area.


Planetary tectonics

Techniques used in the analysis of tectonics on Earth have also been applied to the study of the
planets A planet is an astronomical body orbit In physics, an orbit is the gravitationally curved trajectory of an physical body, object, such as the trajectory of a planet around a star or a natural satellite around a planet. Normally, orbit r ...
and their moons.


See also

*
Tectonophysics Tectonophysics, a branch of geophysics, is the study of the physical processes that underlie tectonic deformation. The field encompasses the spatial patterns of stress, strain, and differing rheologies in the lithosphere and asthenosphere of ...
*
Seismology Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "Earthquake, earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes and the propagation of Linear elasticity#Elastic wave, elast ...
* UNESCO world heritage site Glarus Thrust *
Volcanology Volcanology (also spelled vulcanology) is the study of volcanoes, lava, magma and related geology, geological, geophysical and geochemistry, geochemical phenomena (volcanism). The term ''volcanology'' is derived from the Latin language, Latin ...

Volcanology
*
Mohorovičić discontinuity The Mohorovičić discontinuity ( , ), usually referred to as the Moho discontinuity or the Moho, is the boundary between the Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. About 29% of ...


References


Further reading

* Edward A. Keller (2001
''Active Tectonics: Earthquakes, Uplift, and Landscape''
Prentice Hall; 2nd edition, * Stanley A. Schumm, Jean F. Dumont and John M. Holbrook (2002) ''Active Tectonics and Alluvial Rivers'', Cambridge University Press; Reprint edition, *


External links


The Origin and the Mechanics of the Forces Responsible for Tectonic Plate Movements

The Paleomap Project
{{Structural geology