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Plate tectonics is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large tectonic plates which have been slowly moving since about 3.4 billion years ago. The model builds on the concept of continental drift, an idea developed during the first decades of the 20th century. Plate tectonics came to be generally accepted by geoscientists after seafloor spreading was validated in the mid to late 1960s.
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, the growth and behavior of the strong, old cores of continents known as cratons, and the ways in which the relatively rigid plates that constitute the Earth's outer shell interact with each other. Tectonics also provide a framework for understanding the earthquake and volcanic belts that directly affect much of the global population.
A mantle plume is a proposed mechanism of convection within the Earth's mantle, hypothesized to explain anomalous volcanism. Because the plume head partially melts on reaching shallow depths, a plume is often invoked as the cause of volcanic hotspots, such as Hawaii or Iceland, and large igneous provinces such as the Deccan and Siberian Traps. Some such volcanic regions lie far from tectonic plate boundaries, while others represent unusually large-volume volcanism near plate boundaries.
Seismic tomography or seismotomography is a technique for imaging the subsurface of the Earth with seismic waves produced by earthquakes or explosions. P-, S-, and surface waves can be used for tomographic models of different resolutions based on seismic wavelength, wave source distance, and the seismograph array coverage. The data received at seismometers are used to solve an inverse problem, wherein the locations of reflection and refraction of the wave paths are determined. This solution can be used to create 3D images of velocity anomalies which may be interpreted as structural, thermal, or compositional variations. Geoscientists use these images to better understand core, mantle, and plate tectonic processes.
Earth's mantle is a layer of silicate rock between the crust and the outer core. It has a mass of 4.01 × 1024 kg and thus makes up 67% of the mass of Earth. It has a thickness of 2,900 kilometers (1,800 mi) making up about 84% of Earth's volume. It is predominantly solid but, on geologic time scales, it behaves as a viscous fluid, sometimes described as having the consistency of caramel. Partial melting of the mantle at mid-ocean ridges produces oceanic crust, and partial melting of the mantle at subduction zones produces continental crust.
Mountain formation refers to the geological processes that underlie the formation of mountains. These processes are associated with large-scale movements of the Earth's crust. Folding, faulting, volcanic activity, igneous intrusion and metamorphism can all be parts of the orogenic process of mountain building. The formation of mountains is not necessarily related to the geological structures found on it.
A large igneous province (LIP) is an extremely large accumulation of igneous rocks, including intrusive and extrusive, arising when magma travels through the crust towards the surface. The formation of LIPs is variously attributed to mantle plumes or to processes associated with divergent plate tectonics. The formation of some of the LIPs in the past 500 million years coincide in time with mass extinctions and rapid climatic changes, which has led to numerous hypotheses about causal relationships. LIPs are fundamentally different from any other currently active volcanoes or volcanic systems.
The Iceland hotspot is a hotspot which is partly responsible for the high volcanic activity which has formed the Iceland Plateau and the island of Iceland.
The East African Rift (EAR) or East African Rift System (EARS) is an active continental rift zone in East Africa. The EAR began developing around the onset of the Miocene, 22–25 million years ago. In the past it was considered to be part of a larger Great Rift Valley that extended north to Asia Minor.
A geosyncline is an obsolete geological concept to explain orogens, which was developed in the late 19th and early 20th centuries, before the theory of plate tectonics was envisaged. A geosyncline was described as a giant downward fold in the Earth's crust, with associated upward folds called geanticlines, that preceded the climax phase of orogenic deformation.
William Jason Morgan is an American geophysicist who has made seminal contributions to the theory of plate tectonics and geodynamics. He retired as the Knox Taylor Professor emeritus of geology and professor of geosciences at Princeton University. He currently serves as a visiting scholar in the Department of Earth and Planetary Sciences at Harvard University.
The Anahim hotspot is a hypothesized hotspot in the Central Interior of British Columbia, Canada. It has been proposed as the candidate source for volcanism in the Anahim Volcanic Belt, a 300 kilometres long chain of volcanoes and other magmatic features that have undergone erosion. This chain extends from the community of Bella Bella in the west to near the small city of Quesnel in the east. While most volcanoes are created by geological activity at tectonic plate boundaries, the Anahim hotspot is located hundreds of kilometres away from the nearest plate boundary.
In geodynamics, delamination refers to the loss and sinking (foundering) of the portion of the lowermost lithosphere from the tectonic plate to which it was attached.
The Afar Triple Junction is located along a divergent plate boundary dividing the Nubian, Somali, and Arabian plates. This area is considered a present-day example of continental rifting leading to seafloor spreading and producing an oceanic basin. Here, the Red Sea Rift meets the Aden Ridge and the East African Rift. The latter extends a total of 6,500 kilometers (4,000 mi) from the Afar Triangle to Mozambique.
This is a list of articles related to plate tectonics and tectonic plates.
The opening of the North Atlantic Ocean is a geological event that has occurred over millions of years, during which the supercontinent Pangea broke up. As modern-day Europe and North America separated during the final breakup of Pangea in the early Cenozoic Era, they formed the North Atlantic Ocean. Geologists believe the breakup occurred either due to primary processes of the Iceland plume or secondary processes of lithospheric extension from plate tectonics.
Warren B. Hamilton was an American geologist known for integrating observed geology and geophysics into planetary-scale syntheses describing the dynamic and petrologic evolution of Earth's crust and mantle. His primary career (1952–1995) was as a research scientist with the US Geological Survey (USGS) in geologic, then geophysical, branches. After retirement, he became a Distinguished Senior Scientist in the Department of Geophysics, Colorado School of Mines (CSM). He was a member of the National Academy of Sciences, and a holder of the Penrose Medal, highest honor of the Geological Society of America (GSA). Hamilton served in the US Navy from 1943 to 1946, completed a bachelor's degree at the University of California, Los Angeles (UCLA) in a Navy training program in 1945, and was a commissioned officer on the aircraft carrier USS Tarawa. After returning to civilian life, he earned an MSc in geology from the University of Southern California in 1949, and a PhD in geology from UCLA in 1951. He married Alicita V. Koenig (1926–2015) in 1947. Hamilton died in October 2018 at the age of 93; until the last few weeks he was working on new research. His final paper, "Toward a myth-free geodynamic history of Earth and its neighbors," was published posthumously (2019) in Earth-Science Reviews. In 2022 the Geological Society of America published an edited volume in his honor, with 33 papers: In the Footsteps of Warren B. Hamilton: New Ideas in Earth Science. The first chapter of this book describes how Hamilton's last paper was written; the second applies Thomas Kuhn's model of scientific change to interpreting Hamilton's career.
Earth's crustal evolution involves the formation, destruction and renewal of the rocky outer shell at that planet's surface.
The plate theory is a model of volcanism that attributes all volcanic activity on Earth, even that which appears superficially to be anomalous, to the operation of plate tectonics. According to the plate theory, the principal cause of volcanism is extension of the lithosphere. Extension of the lithosphere is a function of the lithospheric stress field. The global distribution of volcanic activity at a given time reflects the contemporaneous lithospheric stress field, and changes in the spatial and temporal distribution of volcanoes reflect changes in the stress field. The main factors governing the evolution of the stress field are:
- Changes in the configuration of plate boundaries.
- Vertical motions.
- Thermal contraction.
Intraplate volcanism is volcanism that takes place away from the margins of tectonic plates. Most volcanic activity takes place on plate margins, and there is broad consensus among geologists that this activity is explained well by the theory of plate tectonics. However, the origins of volcanic activity within plates remains controversial.
References
- Maruyama, Shigenori (1994). "Plume tectonics". Journal of the Geological Society of Japan. 100: 24–49. doi: 10.5575/geosoc.100.24 .
- Yuen, DA; Maruyama, S; Karato, SJ; et al., eds. (2007). Superplumes: beyond plate tectonics. AA Dordrecht, NL: Springer. ISBN 978-1-4020-5749-6.
- Segev, A (2002). "Flood basalts, continental breakup and the dispersal of Gondwana: evidence for periodic migration of upwelling mantle flows (plumes)". EGU Stephan Mueller Special Publication Series. 2: 171–91. doi: 10.5194/smsps-2-171-2002 .
