Hotspot (geology) explained

In geology, hotspots (or hot spots) are volcanic locales thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle.[1] Examples include the Hawaii, Iceland, and Yellowstone hotspots. A hotspot's position on the Earth's surface is independent of tectonic plate boundaries, and so hotspots may create a chain of volcanoes as the plates move above them.

There are two hypotheses that attempt to explain their origins. One suggests that hotspots are due to mantle plumes that rise as thermal diapirs from the core–mantle boundary.[2] The alternative plate theory is that the mantle source beneath a hotspot is not anomalously hot, rather the crust above is unusually weak or thin, so that lithospheric extension permits the passive rising of melt from shallow depths.[3] [4]

Origin

The origins of the concept of hotspots lie in the work of J. Tuzo Wilson, who postulated in 1963 that the formation of the Hawaiian Islands resulted from the slow movement of a tectonic plate across a hot region beneath the surface.[5] It was later postulated that hotspots are fed by streams of hot mantle rising from the Earth's core–mantle boundary in a structure called a mantle plume.[6] Whether or not such mantle plumes exist has been the subject of a major controversy in Earth science,[7] but seismic images consistent with evolving theory now exist.[8]

At any place where volcanism is not linked to a constructive or destructive plate margin, the concept of a hotspot has been used to explain its origin. A review article by Courtillot et al. listing possible hotspots makes a distinction between primary hotspots coming from deep within the mantle and secondary hotspots derived from mantle plumes. The primary hotspots originate from the core/mantle boundary and create large volcanic provinces with linear tracks (Easter Island, Iceland, Hawaii, Afar, Louisville, Reunion, and Tristan confirmed; Galapagos, Kerguelen and Marquersas likely). The secondary hotspots originate at the upper/lower mantle boundary, and do not form large volcanic provinces, but island chains (Samoa, Tahiti, Cook, Pitcairn, Caroline, MacDonald confirmed, with up to 20 or so more possible). Other potential hotspots are the result of shallow mantle material surfacing in areas of lithospheric break-up caused by tension and are thus a very different type of volcanism. Estimates for the number of hotspots postulated to be fed by mantle plumes have ranged from about 20 to several thousand, with most geologists considering a few tens to exist.[8] Hawaii, Réunion, Yellowstone, Galápagos, and Iceland are some of the most active volcanic regions to which the hypothesis is applied. The plumes imaged to date vary widely in width and other characteristics, and are tilted, being not the simple, relatively narrow and purely thermal plumes many expected.[8] Only one, (Yellowstone) has as yet been consistently modelled and imaged from deep mantle to surface.[8]

Composition

Most hotspot volcanoes are basaltic (e.g., Hawaii, Tahiti). As a result, they are less explosive than subduction zone volcanoes, in which water is trapped under the overriding plate. Where hotspots occur in continental regions, basaltic magma rises through the continental crust, which melts to form rhyolites. These rhyolites can form violent eruptions.[9] [10] For example, the Yellowstone Caldera was formed by some of the most powerful volcanic explosions in geologic history. However, when the rhyolite is completely erupted, it may be followed by eruptions of basaltic magma rising through the same lithospheric fissures (cracks in the lithosphere). An example of this activity is the Ilgachuz Range in British Columbia, which was created by an early complex series of trachyte and rhyolite eruptions, and late extrusion of a sequence of basaltic lava flows.[11]

The hotspot hypothesis is now closely linked to the mantle plume hypothesis.[12] [8] The detailed compositional studies now possible on hotspot basalts have allowed linkage of samples over the wider areas often implicate in the later hypothesis,[13] and it's seismic imaging developments.[8]

Contrast with subduction zone island arcs

Hotspot volcanoes are considered to have a fundamentally different origin from island arc volcanoes. The latter form over subduction zones, at converging plate boundaries. When one oceanic plate meets another, the denser plate is forced downward into a deep ocean trench. This plate, as it is subducted, releases water into the base of the over-riding plate, and this water mixes with the rock, thus changing its composition causing some rock to melt and rise. It is this that fuels a chain of volcanoes, such as the Aleutian Islands, near Alaska.

Hotspot volcanic chains

The joint mantle plume/hotspot hypothesis originally envisaged the feeder structures to be fixed relative to one another, with the continents and seafloor drifting overhead. The hypothesis thus predicts that time-progressive chains of volcanoes are developed on the surface. Examples are Yellowstone, which lies at the end of a chain of extinct calderas, which become progressively older to the west. Another example is the Hawaiian archipelago, where islands become progressively older and more deeply eroded to the northwest.

Geologists have tried to use hotspot volcanic chains to track the movement of the Earth's tectonic plates. This effort has been vexed by the lack of very long chains, by the fact that many are not time-progressive (e.g. the Galápagos) and by the fact that hotspots do not appear to be fixed relative to one another (e.g. Hawaii and Iceland).[14] That mantle plumes are much more complex than originally hypothesised and move independently of each other and plates is now used to explain such observations.[8]

In 2020, Wei et al. used seismic tomography to detect the oceanic plateau, formed about 100 million years ago by the hypothesized mantle plume head of the Hawaii-Emperor seamount chain, now subducted to a depth of 800 km under eastern Siberia.[15]

Postulated hotspot volcano chains

List of volcanic regions postulated to be hotspots

Eurasian Plate

African Plate

Antarctic Plate

South American Plate

North American Plate

Australian Plate

Nazca Plate

Pacific Plate

Former hotspots

See also


Further reading

External links

Notes and References

  1. Web site: The source of Yellowstone's heat . . 16 April 2018 . 14 June 2021.
  2. Convection Plumes in the Lower Mantle. W. J. Morgan. Nature . 230 . 42–43 . 5 March 1971 . 10.1038/230042a0 . 1971Natur.230...42M . 5288. 4145715.
  3. Web site: Do plumes exist? . 2010-04-25.
  4. Book: Plates vs. Plumes: A Geological Controversy . Foulger, G.R. . 2010 . 978-1-4051-6148-0 . Wiley-Blackwell.
  5. A possible origin of the Hawaiian Islands . J. Tuzo . Wilson . Canadian Journal of Physics . 1963 . 41 . 863–870 . 10.1139/p63-094. 6 . 1963CaJPh..41..863W.
  6. Web site: Hotspots: Mantle thermal plumes . . 5 May 1999 . 2008-05-15.
  7. Web site: Wright . Laura . Earth's interior: Raising hot spots . Geotimes . . November 2000 . 15 June 2008.
  8. Koppers. A.A.. Becker. T.W.. Jackson . M.G.. Konrad. K.. Müller. R.D.. Romanowicz. B.. Steinberger. B.. Whittaker . J.M.. Mantle plumes and their role in Earth processes. Nature Reviews Earth & Environment. 2021. 2. 6. 382–401. 10.1038/s43017-021-00168-6. 2021NRvEE...2..382K. 21 November 2023.
  9. Donald Hyndman; David Hyndman (1 January 2016). Natural Hazards and Disasters. Cengage Learning. pp. 44–. .
  10. Wolfgang Frisch; Martin Meschede; Ronald C. Blakey (2 November 2010). Plate Tectonics: Continental Drift and Mountain Building. Springer Science & Business Media. pp. 87–. .
  11. Holbek, Peter . Report on Preliminary Geology and Geochemistry of the Ilga Claim Group . November 1983 . 15 June 2008 . 12 January 2014 . https://web.archive.org/web/20140112031459/http://aris.empr.gov.bc.ca/ArisReports/12214.PDF . dead .
  12. Mainak Choudhuri; Michal Nemčok (22 August 2016). Mantle Plumes and Their Effects. Springer. pp. 18–. .
  13. Bredow. E. Steinberger. B. Variable melt production rate of the Kerguelen hotspot due to long-term plume-ridge interaction. Geophysical Research Letters. 16 January 2018. 45. 1. 126–36. 10.1002/2017GL075822. free. 2018GeoRL..45..126B. 10852/70913. free.
  14. Web site: Insight into Motion of the Hawaiian Hotspot from Paleomagnetism. www.MantlePlumes.org. William W. . Sager. 4 June 2007.
  15. Wei. Songqiao Shawn. Shearer. Peter M.. Lithgow-Bertelloni. Carolina. Carolina Lithgow-Bertelloni. Stixrude. Lars. Tian. Dongdong. 2020-11-20. Oceanic plateau of the Hawaiian mantle plume head subducted to the uppermost lower mantle. Science. en. 370. 6519. 983–987. 10.1126/science.abd0312. 33214281. 2020Sci...370..983W. 227059993. 0036-8075.
  16. E. V. Verzhbitsky. Geothermal regime and genesis of the Ninety-East and Chagos-Laccadive ridges. Journal of Geodynamics . 35 . 2003. 10.1016/S0264-3707(02)00068-6. 3. 289. 2003JGeo...35..289V .
  17. Book: 2021-01-01. North-East Atlantic Islands: The Macaronesian Archipelagos. https://www.sciencedirect.com/science/article/pii/B9780081029084000278. en. 674–699. 10.1016/B978-0-08-102908-4.00027-8. Encyclopedia of Geology. Carracedo. Juan Carlos. Troll. Valentin R.. 9780081029091. 226588940.
  18. Web site: W. J. Morgan and J. P. Morgan. Plate velocities in hotspot reference frame: electronic supplement. 2011-11-06.
  19. Søren B. . Nielsen . Randell . Stephenson . Erik . Thomsen . Nature . 450 . Letter:Dynamics of Mid-Palaeocene North Atlantic rifting linked with European intra-plate deformations . 7172 . 1071–1074 . 13 December 2007 . 18075591 . 10.1038/nature06379 . 2007Natur.450.1071N . 4428980 .
  20. O'Neill . C. . Müller . R. D. . Steinberger . B. . Revised Indian plate rotations based on the motion of Indian Ocean hotspots . Earth and Planetary Science Letters . 215 . 1–2 . 151–168 . 2003 . 2003E&PSL.215..151O . 10.1016/S0012-821X(03)00368-6 . dead . https://web.archive.org/web/20110726011820/http://www.earthbyte.org/people/dietmar/Pdf/Muller-etal-hotspots-Geology1993.pdf . 26 July 2011 . 10.1.1.716.4910 .
  21. 10.1016/0012-821X(92)90138-L . O'Connor . J. M. . le Roex . A. P. . 1992 . South Atlantic hot spot-plume systems. 1: Distribution of volcanism in time and space . Earth and Planetary Science Letters . 113 . 343–364 . 1992E&PSL.113..343O. 3.
  22. Smith . Robert B.. Jordan, Michael. Steinberger, Bernhard. Puskas, Christine M.. Farrell, Jamie. Waite, Gregory P.. Husen, Stephan. Chang, Wu-Lung. O'Connell, Richard . 20 November 2009 . Geodynamics of the Yellowstone hotspot and mantle plume: Seismic and GPS imaging, kinematics and mantle flow . Journal of Volcanology and Geothermal Research . 188 . 1–3 . 26–56 . 10.1016/j.jvolgeores.2009.08.020 . 2009JVGR..188...26S.
  23. Web site: Catalogue of Canadian volcanoes- Anahim volcanic belt . Natural Resources Canada . . https://web.archive.org/web/20110716135149/http://gsc.nrcan.gc.ca/volcanoes/cat/belt_anahim_e.php . 16 July 2011 . 2008-06-14.

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Hotspot (geology)".

Except where otherwise indicated, Everything.Explained.Today is © Copyright 2009-2024, A B Cryer, All Rights Reserved. Cookie policy.