Wikipedia

Hotspot (geology)

Ingeology,hotspots(orhot spots) arevolcaniclocales thought to be fed by underlyingmantlethat is anomalously hot compared with the surrounding mantle.[1]Examples include theHawaii,Iceland,andYellowstone hotspots.A hotspot's position on the Earth's surface is independent oftectonic plate boundaries,and so hotspots may create a chain of volcanoes as the plates move above them.

Diagram showing across sectionthrough Earth at the Hawaii hotspot.Magmaoriginating in themantlerises into theasthenosphereandlithosphere.A chain of volcanoes is created as the lithosphere moves over the source of magma.

There are twohypothesesthat attempt to explain their origins. One suggests that hotspots are due tomantle plumesthat rise as thermaldiapirsfrom the core–mantle boundary.[2]The alternativeplate theoryis 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

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Schematic diagram showing the physical processes inside the Earth that lead to the generation of magma. Partial melting begins above the fusion point.
Map showing approximate location of many current hotspots and the relationship to current tectonic plates and their boundaries and movement vectors

The origins of the concept of hotspots lie in the work ofJ. Tuzo Wilson,who postulated in 1963 that the formation of theHawaiian Islandsresulted from the slow movement of atectonic plateacross a hot region beneath the surface.[5]It was later postulated that hotspots are fed by streams of hotmantlerising from the Earth'score–mantle boundaryin a structure called amantle plume.[6]Whether or not such mantle plumes exist has been the subject of a major controversy in Earth science,[4][7]but seismic images consistent with evolving theory now exist.[8]

At any place wherevolcanismis 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.[9]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,andIcelandare 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

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Most hotspot volcanoes arebasaltic(e.g.,Hawaii,Tahiti). As a result, they are less explosive thansubduction zonevolcanoes, in which water is trapped under the overriding plate. Where hotspots occur incontinental regions,basalticmagmarises through the continental crust, which melts to formrhyolites.Theserhyolitescan form violent eruptions.[10][11]For example, theYellowstone Calderawas 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 theIlgachuz Rangein British Columbia, which was created by an early complex series oftrachyteandrhyoliteeruptions, and late extrusion of a sequence of basaltic lava flows.[12]

The hotspot hypothesis is now closely linked to themantle plumehypothesis.[13][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,[14]and it's seismic imaging developments.[8]

Contrast with subduction zone island arcs

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Hotspot volcanoes are considered to have a fundamentally different origin fromisland arcvolcanoes. The latter form oversubductionzones, 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 theAleutian Islands,nearAlaska.

Hotspot volcanic chains

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Over millions of years, thePacific platehas moved over theHawaii hotspot,creatinga trail of underwater mountainsthat stretches across the Pacific.
Kilaueais the most active shield volcano in the world. The volcano erupted from 1983 to 2018 and is part of theHawaiian–Emperor seamount chain.
Mauna Loais a large shield volcano. Itslast eruption was in 2022and it is part of theHawaiian–Emperor seamount chain.
Bowie Seamountis a dormant submarine volcano and part of theKodiak-Bowie Seamount chain.
Axial Seamountis the youngest seamount of theCobb–Eickelberg Seamount chain.Its last eruption was in 2015.
Mauna Keais the tallest volcano in theHawaiian–Emperor seamount chain.Manycinder coneshave been emplaced around its summit.
Hualalaiis a massive shield volcano in theHawaiian–Emperor seamount chain.Its last eruption was in 1801.

The jointmantle plume/hotspot hypothesis originally envisaged the feeder structures to be fixed relative to one another, with the continents andseafloordrifting overhead. The hypothesis thus predicts that time-progressive chains of volcanoes are developed on the surface. Examples areYellowstone,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. theGalápagos) and by the fact that hotspots do not appear to be fixed relative to one another (e.g.HawaiiandIceland).[15]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. usedseismic tomographyto detect the oceanic plateau, formed about 100 million years ago by the hypothesized mantle plume head of the Hawaii-Emperor seamount chain, nowsubductedto a depth of 800 km under eastern Siberia.[16]

Postulated hotspot volcano chains

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An example of mantle plume locations suggested by one recent group.[9]Figure from Foulger (2010).[4]

List of volcanic regions postulated to be hotspots

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Distribution of hotspots in the list to the left, with the numbers corresponding to those in the list. The Afar hotspot (29) is misplaced.
Map all coordinates usingOpenStreetMap

Download coordinates as:

Eurasian plate

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African plate

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Antarctic plate

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South American plate

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North American plate

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Australian plate

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Nazca plate

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Pacific plate

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Over millions of years, the Pacific Plate has moved over theBowie hotspot,creating theKodiak–Bowie Seamount chainin theGulf of Alaska.
TheHotspot highwayin the south Pacific Ocean

Former hotspots

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See also

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References

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  1. ^"The source of Yellowstone's heat".USGS.16 April 2018.Retrieved14 June2021.
  2. ^abW. J. Morgan (5 March 1971)."Convection Plumes in the Lower Mantle".Nature.230(5288):42–43.Bibcode:1971Natur.230...42M.doi:10.1038/230042a0.S2CID4145715.
  3. ^"Do plumes exist?".Retrieved25 April2010.
  4. ^abcFoulger, G.R. (2010).Plates vs. Plumes: A Geological Controversy.Wiley-Blackwell.ISBN978-1-4051-6148-0.
  5. ^Wilson, J. Tuzo (1963)."A possible origin of the Hawaiian Islands"(PDF).Canadian Journal of Physics.41(6):863–870.Bibcode:1963CaJPh..41..863W.doi:10.1139/p63-094.
  6. ^"Hotspots: Mantle thermal plumes".United States Geological Survey.5 May 1999.Retrieved15 May2008.
  7. ^Wright, Laura (November 2000)."Earth's interior: Raising hot spots".Geotimes.American Geological Institute.Retrieved15 June2008.
  8. ^abcdefgKoppers, A.A.; Becker, T.W.; Jackson, M.G.; Konrad, K.; Müller, R.D.; Romanowicz, B.; Steinberger, B.; Whittaker, J.M. (2021)."Mantle plumes and their role in Earth processes"(PDF).Nature Reviews Earth & Environment.2(6):382–401.Bibcode:2021NRvEE...2..382K.doi:10.1038/s43017-021-00168-6.Retrieved21 November2023.
  9. ^abCourtillot, V.; Davaillie, A.; Besse, J.; Stock, J. (2003). "Three distinct types of hotspots in the Earth's mantle".Earth Planet. Sci. Lett.205(3–4):295–308.Bibcode:2003E&PSL.205..295C.CiteSeerX10.1.1.693.6042.doi:10.1016/S0012-821X(02)01048-8.
  10. ^Donald Hyndman; David Hyndman (1 January 2016). Natural Hazards and Disasters. Cengage Learning. pp. 44–.ISBN978-1-305-88818-0.
  11. ^Wolfgang Frisch; Martin Meschede; Ronald C. Blakey (2 November 2010). Plate Tectonics: Continental Drift and Mountain Building. Springer Science & Business Media. pp. 87–.ISBN978-3-540-76504-2.
  12. ^Holbek, Peter (November 1983)."Report on Preliminary Geology and Geochemistry of the Ilga Claim Group"(PDF).Archived fromthe original(PDF)on 12 January 2014.Retrieved15 June2008.{{cite journal}}:Cite journal requires|journal=(help)
  13. ^Mainak Choudhuri; Michal Nemčok (22 August 2016). Mantle Plumes and Their Effects. Springer. pp. 18–.ISBN978-3-319-44239-6.
  14. ^abcBredow, E; Steinberger, B (16 January 2018)."Variable melt production rate of the Kerguelen hotspot due to long-term plume-ridge interaction".Geophysical Research Letters.45(1):126–36.Bibcode:2018GeoRL..45..126B.doi:10.1002/2017GL075822.hdl:10852/70913.
  15. ^Sager, William W. (4 June 2007)."Insight into Motion of the Hawaiian Hotspot from Paleomagnetism".MantlePlumes.org.
  16. ^Wei, Songqiao Shawn; Shearer, Peter M.;Lithgow-Bertelloni, Carolina;Stixrude, Lars; Tian, Dongdong (20 November 2020)."Oceanic plateau of the Hawaiian mantle plume head subducted to the uppermost lower mantle".Science.370(6519):983–987.Bibcode:2020Sci...370..983W.doi:10.1126/science.abd0312.ISSN0036-8075.PMID33214281.S2CID227059993.
  17. ^E. V. Verzhbitsky (2003). "Geothermal regime and genesis of the Ninety-East and Chagos-Laccadive ridges".Journal of Geodynamics.35(3): 289.Bibcode:2003JGeo...35..289V.doi:10.1016/S0264-3707(02)00068-6.
  18. ^abCarracedo, Juan Carlos; Troll, Valentin R. (1 January 2021)."North-East Atlantic Islands: The Macaronesian Archipelagos".Encyclopedia of Geology.pp.674–699.doi:10.1016/B978-0-08-102908-4.00027-8.ISBN9780081029091.S2CID226588940.
  19. ^abcdefghijklmnopqrstuvwxyzaaabacadaeafagahaiajakalamanaoapaqarasatauavawaxayazbabbbcbdbebfbgbhbiW. J. Morgan and J. P. Morgan."Plate velocities in hotspot reference frame: electronic supplement"(PDF).Retrieved6 November2011.
  20. ^Nielsen, Søren B.; Stephenson, Randell; Thomsen, Erik (13 December 2007). "Letter:Dynamics of Mid-Palaeocene North Atlantic rifting linked with European intra-plate deformations".Nature.450(7172):1071–1074.Bibcode:2007Natur.450.1071N.doi:10.1038/nature06379.PMID18075591.S2CID4428980.
  21. ^O'Neill, C.; Müller, R. D.; Steinberger, B. (2003)."Revised Indian plate rotations based on the motion of Indian Ocean hotspots"(PDF).Earth and Planetary Science Letters.215(1–2):151–168.Bibcode:2003E&PSL.215..151O.CiteSeerX10.1.1.716.4910.doi:10.1016/S0012-821X(03)00368-6.Archived fromthe original(PDF)on 26 July 2011.
  22. ^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(3):343–364.Bibcode:1992E&PSL.113..343O.doi:10.1016/0012-821X(92)90138-L.
  23. ^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"(PDF).Journal of Volcanology and Geothermal Research.188(1–3):26–56.Bibcode:2009JVGR..188...26S.doi:10.1016/j.jvolgeores.2009.08.020.
  24. ^"Catalogue of Canadian volcanoes- Anahim volcanic belt".Natural Resources Canada.Geological Survey of Canada.Archived fromthe originalon 16 July 2011.Retrieved14 June2008.

Further reading

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Wikimedia Commons has media related toHot spots (volcanism).
The WikibookHistorical Geologyhas a page on the topic of:Hotspots

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