geology Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth ...

, hotspots (or hot spots) are

volcanic A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often fo ...

locales thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle. Examples include the

Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...

Iceland Iceland is a Nordic countries, Nordic island country between the Atlantic Ocean, North Atlantic and Arctic Oceans, on the Mid-Atlantic Ridge between North America and Europe. It is culturally and politically linked with Europe and is the regi ...

, 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 A hypothesis (: hypotheses) is a proposed explanation for a phenomenon. A scientific method, scientific hypothesis must be based on observations and make a testable and reproducible prediction about reality, in a process beginning with an educ ...

that attempt to explain their origins. One suggests that hotspots are due to

mantle plume 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 ho ...

s that rise as thermal diapirs from the core–mantle boundary. 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.

Origin

Tectonic plates boundaries physical World map Wt 180degE centered-en

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 The Hawaiian Islands () are an archipelago of eight major volcanic islands, several atolls, and numerous smaller islets in the Pacific Ocean, North Pacific Ocean, extending some from the Hawaii (island), island of Hawaii in the south to nort ...

resulted from the slow movement of a

tectonic plate Plate tectonics (, ) is the scientific theory that the Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago. The model builds on the concept of , an idea developed durin ...

across a hot region beneath the surface. 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

. Whether or not such mantle plumes exist has been the subject of a major controversy in Earth science, but seismic images consistent with evolving theory now exist. 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.

Réunion Réunion (; ; ; known as before 1848) is an island in the Indian Ocean that is an overseas departments and regions of France, overseas department and region of France. Part of the Mascarene Islands, it is located approximately east of the isl ...

Yellowstone Yellowstone National Park is a List of national parks of the United States, national park of the United States located in the northwest corner of Wyoming, with small portions extending into Montana and Idaho. It was established by the 42nd U ...

, Galápagos, and

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. Only one, Yellowstone, has as yet been consistently modelled and imaged from deep mantle to surface.

Composition

Most hotspot volcanoes are

basaltic Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron ( mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% ...

(e.g.,

Tahiti Tahiti (; Tahitian language, Tahitian , ; ) is the largest island of the Windward Islands (Society Islands), Windward group of the Society Islands in French Polynesia, an overseas collectivity of France. It is located in the central part of t ...

). 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,

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

rises through the continental crust, which melts to form

rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture (geology), texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained matri ...

s. These

s can form violent eruptions. 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 Trachyte () is an extrusive igneous rock composed mostly of alkali feldspar. It is usually light-colored and aphanite, aphanitic (fine-grained), with minor amounts of mafic minerals, and is formed by the rapid cooling of lava (or shallow intrus ...

and

eruptions, and late extrusion of a sequence of basaltic lava flows. The hotspot hypothesis is now closely linked to the

hypothesis. The detailed compositional studies now possible on hotspot basalts have allowed linkage of samples over the wider areas often implicate in the later hypothesis, and its seismic imaging developments.

Contrast with subduction zone island arcs

Hotspot volcanoes are considered to have a fundamentally different origin from

island arc Island arcs are long archipelago, chains of active volcanoes with intense earthquake, seismic activity found along convergent boundary, convergent plate tectonics, tectonic plate boundaries. Most island arcs originate on oceanic crust and have re ...

volcanoes. The latter form over

subduction Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second p ...

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 The Aleutian Islands ( ; ; , "land of the Aleuts"; possibly from the Chukchi language, Chukchi ''aliat'', or "island")—also called the Aleut Islands, Aleutic Islands, or, before Alaska Purchase, 1867, the Catherine Archipelago—are a chain ...

, near

Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...

Hotspot volcanic chains

The joint

/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 include

, 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.

and

). 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. 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.

Postulated hotspot volcano chains

* Hawaiian–Emperor seamount chain ( Hawaii hotspot) * Louisville Ridge ( Louisville hotspot) * Walvis Ridge (Gough and Tristan hotspot) * Kodiak–Bowie Seamount chain ( Bowie hotspot) * Cobb–Eickelberg Seamount chain (

Cobb hotspot The Cobb hotspot is a marine volcanic Hotspot (geology), hotspot at , which is west of Oregon and Washington (state), Washington, United States, in the Pacific Ocean. Over geologic time, the Earth's surface has migrated with respect to the hotsp ...

) * New England Seamounts ( New England hotspot) * Anahim Volcanic Belt ( Anahim hotspot) * Mackenzie dike swarm ( Mackenzie hotspot) * Great Meteor hotspot track ( New England hotspot) * St. Helena Seamount Chain– Cameroon Volcanic Line ( Saint Helena hotspot) * Southern Mascarene Plateau– Chagos-Maldives-Laccadive Ridge ( Réunion hotspot) * Ninety East Ridge ( Kerguelen hotspot) * Tuamotu– Line Island chain ( Easter hotspot) * Austral– Gilbert– Marshall chain ( Macdonald hotspot) * Juan Fernández Ridge ( Juan Fernández hotspot) * Tasmantid Seamount Chain ( Tasmantid hotspot) *

Canary Islands The Canary Islands (; ) or Canaries are an archipelago in the Atlantic Ocean and the southernmost Autonomous communities of Spain, Autonomous Community of Spain. They are located in the northwest of Africa, with the closest point to the cont ...

( Canary hotspot) *

Cape Verde Cape Verde or Cabo Verde, officially the Republic of Cabo Verde, is an island country and archipelagic state of West Africa in the central Atlantic Ocean, consisting of ten volcanic islands with a combined land area of about . These islands ...

( Cape Verde hotspot)

List of volcanic regions postulated to be hotspots

In the following list of hotspots, "az" is the

azimuth An azimuth (; from ) is the horizontal angle from a cardinal direction, most commonly north, in a local or observer-centric spherical coordinate system. Mathematically, the relative position vector from an observer ( origin) to a point ...

of the hotspot track; "w" is the "weight", or estimated accuracy, of the azimuth (1 is most accurate, 0.2 is least accurate).

Eurasian plate

* Eifel hotspot (8) ** , w= 1 az= 082° ±8° rate= 12 ±2 mm/yr * Iceland hotspot (14) ** *** Eurasian Plate, w= 0.8 az= 075° ±10° rate= 5 ±3 mm/yr *** North American Plate, w= 0.8 az= 287° ±10° rate= 15 ±5 mm/yr ** Possibly related to the North Atlantic continental rifting (62 Ma),

Greenland Greenland is an autonomous territory in the Danish Realm, Kingdom of Denmark. It is by far the largest geographically of three constituent parts of the kingdom; the other two are metropolitan Denmark and the Faroe Islands. Citizens of Greenlan ...

. * Azores hotspot (1) ** *** Eurasian Plate, w= 0.5 az= 110° ±12° *** North American Plate, w= 0.3 az= 280° ±15° * Jan Mayen hotspot (15) ** * Hainan hotspot (46) ** , az= 000° ±15°

African plate

Mount Etna Mount Etna, or simply Etna ( or ; , or ; ; or ), is an active stratovolcano on the east coast of Sicily, Italy, in the Metropolitan City of Catania, between the cities of Messina, Italy, Messina and Catania. It is located above the Conve ...

(47) ** * Hoggar hotspot (13) ** , w= 0.3 az= 046° ±12° * Tibesti hotspot (40) ** , w= 0.2 az= 030° ±15° * Jebel Marra/Darfur hotspot (6) ** , w= 0.5 az= 045° ±8° * Afar hotspot (29, misplaced in map) ** , w= 0.2 az= 030° ±15° rate= 16 ±8 mm/yr ** Possibly related to the Afar triple junction, 30 Ma. *

Cameroon Cameroon, officially the Republic of Cameroon, is a country in Central Africa. It shares boundaries with Nigeria to the west and north, Chad to the northeast, the Central African Republic to the east, and Equatorial Guinea, Gabon, and the R ...

hotspot (17) ** , w= 0.3 az= 032° ±3° rate= 15 ±5 mm/yr *

Madeira Madeira ( ; ), officially the Autonomous Region of Madeira (), is an autonomous Regions of Portugal, autonomous region of Portugal. It is an archipelago situated in the North Atlantic Ocean, in the region of Macaronesia, just under north of ...

hotspot (48) ** , w= 0.3 az= 055° ±15° rate= 8 ±3 mm/yr * Canary hotspot (18) ** , w= 1 az= 094° ±8° rate= 20 ±4 mm/yr * New England/Great Meteor hotspot (28) ** , w= 0.8 az= 040° ±10° *

hotspot (19) ** , w= 0.2 az= 060° ±30° * Sierra Leone hotspot * St. Helena hotspot (34) ** , w= 1 az= 078° ±5° rate= 20 ±3 mm/yr * Gough hotspot (49), at 40°19' S 9°56' W. ** , w= 0.8 az= 079° ±5° rate= 18 ±3 mm/yr * Tristan hotspot (42), at 37°07′ S 12°17′ W. ** * Vema hotspot (Vema Seamount, 43), at 31°38' S 8°20' E. ** ** Related maybe to the Paraná and Etendeka traps (c. 132 Ma) through the Walvis Ridge. * Discovery hotspot (50) ( Discovery Seamounts) ** , w= 1 az= 068° ±3° * Bouvet hotspot (51) ** * Shona/Meteor hotspot (27) ** , w= 0.3 az= 074° ±6° * Réunion hotspot (33) ** , w= 0.8 az= 047° ±10° rate= 40 ±10 mm/yr ** Possibly related to the Deccan Traps (main events: 68.5–66 Ma) *

Comoros The Comoros, officially the Union of the Comoros, is an archipelagic country made up of three islands in Southeastern Africa, located at the northern end of the Mozambique Channel in the Indian Ocean. Its capital and largest city is Moroni, ...

hotspot (21) ** , w= 0.5 az=118 ±10° rate=35 ±10 mm/yr

Antarctic plate

* Marion hotspot (25) ** , w= 0.5 az= 080° ±12° * Crozet hotspot (52) ** , w= 0.8 az= 109° ±10° rate= 25 ±13 mm/yr ** Possibly related to the Karoo-Ferrar geologic province (183 Ma) * Kerguelen hotspot (20) ** , w= 0.2 az= 050° ±30° rate= 3 ±1 mm/yr ** Related to the Kerguelen Plateau (130 Ma) *** Heard hotspot (53), possibly part of Kerguelen hotspot *** , w= 0.2 az= 030° ±20° **

Île Saint-Paul is an island forming part of the French Southern and Antarctic Lands (, TAAF) in the Indian Ocean, with an area of . The island is located about south of the larger Île Amsterdam , northeast of the Kerguelen Islands, and southeast of Réuni ...

and Île Amsterdam could be part of the Kerguelen hotspot trail (St. Paul is possibly not another hotspot) * Balleny hotspot (2) ** , w= 0.2 az= 325° ±7° * Erebus hotspot (54) **

South American plate

* Trindade/Martin Vaz hotspot (41) ** , w= 1 az= 264° ±5° * Fernando hotspot (9) ** , w= 1 az= 266° ±7° ** Possibly related to the Central Atlantic Magmatic Province (c. 200 Ma) * Ascension hotspot (55) **

North American plate

* Bermuda hotspot (56) ** , w= 0.3 az= 260° ±15° * Yellowstone hotspot (44) ** , w= 0.8 az= 235° ±5° rate= 26 ±5 mm/yr ** Possibly related to the Columbia River Basalt Group (17–14 Ma). * Raton hotspot (32) ** , w= 1 az= 240°±4° rate= 30 ±20 mm/yr * Anahim hotspot (45) ** ( Nazko Cone)

Australian plate

* Lord Howe hotspot (22) ** , w= 0.8 az= 351° ±10° * Tasmantid hotspot (39) ** , w= 0.8 az= 007° ±5° rate= 63 ±5 mm/yr * East Australia hotspot (30) ** , w= 0.3 az= 000° ±15° rate= 65 ±3 mm/yr

Nazca plate

* Juan Fernández hotspot (16) ** , w= 1 az= 084° ±3° rate= 80 ±20 mm/yr * San Felix hotspot (36) ** , w= 0.3 az= 083° ±8° * Easter hotspot (7) ** , w= 1 az= 087° ±3° rate= 95 ±5 mm/yr * Galápagos hotspot (10) ** *** Nazca Plate, w= 1 az= 096° ±5° rate= 55 ±8 mm/yr *** Cocos Plate, w= 0.5 az= 045° ±6° ** Possibly related to the Caribbean large igneous province (main events: 95–88 Ma).

Pacific plate

* Louisville hotspot (23) ** , w= 1 az= 316° ±5° rate= 67 ±5 mm/yr ** Possibly related to the Ontong Java Plateau (125–120 Ma). * Foundation hotspot/ Ngatemato seamounts (57) ** , w= 1 az= 292° ±3° rate= 80 ±6 mm/yr * Macdonald hotspot (24) ** , w= 1 az= 289° ±6° rate= 105 ±10 mm/yr * North Austral/President Thiers ( President Thiers Bank, 58) ** , w= (1.0) az= 293° ± 3° rate= 75 ±15 mm/yr * Arago hotspot (Arago Seamount, 59) ** , w= 1 az= 296° ±4° rate= 120 ±20 mm/yr * Maria/Southern Cook hotspot ( Îles Maria, 60) ** , w= 0.8 az= 300° ±4° * Samoa hotspot (35) ** , w= 0.8 az= 285°±5° rate= 95 ±20 mm/yr * Crough hotspot ( Crough Seamount, 61) ** , w= 0.8 az= 284° ± 2° * Pitcairn hotspot (31) ** , w= 1 az= 293° ±3° rate= 90 ±15 mm/yr * Society/Tahiti hotspot (38) ** , w= 0.8 az= 295°±5° rate= 109 ±10 mm/yr * Marquesas hotspot (26) ** , w= 0.5 az= 319° ±8° rate= 93 ±7 mm/yr * Caroline hotspot (4) ** , w= 1 az= 289° ±4° rate= 135 ±20 mm/yr * Hawaii hotspot (12) ** , w= 1 az= 304° ±3° rate= 92 ±3 mm/yr * Socorro/Revillagigedos hotspot (37) ** * Guadalupe hotspot (11) ** , w= 0.8 az= 292° ±5° rate= 80 ±10 mm/yr *

(5) ** , w= 1 az= 321° ±5° rate= 43 ±3 mm/yr * Bowie/Pratt-Welker hotspot (3) ** , w= 0.8 az= 306° ±4° rate= 40 ±20 mm/yr

Former hotspots

* Euterpe/Musicians hotspot ( Musicians Seamounts) * Mackenzie hotspot * Matachewan hotspot

References

External links

Formation of Hotspots

Large Igneous Provinces (LIPs)

Maria Antretter, PhD Thesis (2001): ''Moving hotspots – Evidence from paleomagnetism and modeling''

Do Plumes Exist?
{{DEFAULTSORT:Hotspot (Geology) Plate tectonics Volcanology * Structure of the Earth