Diagram showing a cross section through the Earth's lithosphere
(in yellow) with magma
rising from the mantle
(in red). Lower diagram illustrates a hotspot track caused by their relative movement.
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.
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.
Schematic diagram showing the physical processes inside the Earth that lead to the generation of magma. Partial melting begins above the fusion point.
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.
It was later postulated that hotspots are fed by narrow streams of hot mantle
rising from the Earth's core–mantle boundary
in a structure called a mantle plume
Whether or not such mantle plumes exist is the subject of a major controversy in Earth science.
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. In a review article by Courtillot et al.
listing possible hotspots, distinction is made between primary hotspots coming from deep within the mantle (possibly originating from the core/mantle boundary), creating large volcanic provinces with linear tracks (Easter Island, Iceland, Hawaii, Afar, Louisville, Reunion, Tristan confirmed, Galapagos, Kerguelen and Marquersas likely) and secondary hotspots derived from mantle plumes (Samoa, Tahiti, Cook, Pitcairn, Caroline, MacDonald confirmed, up to about 20 possible) at the upper/lower mantle boundary that do not form large volcanic provinces but form island chains. 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. Hawaii
, and Iceland
are some of the most active volcanic regions to which the hypothesis is applied.
Most hotspot volcanoes are basaltic
). 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.
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
eruptions, and late extrusion of a sequence of basaltic lava flows.
The hotspot hypothesis is now closely linked to the mantle plume
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 envisages 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
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
An example of mantle plume locations suggested by one recent group.
Figure from Foulger (2010).
List of volcanic regions postulated to be hotspots
Distribution of hotspots in the list to the left, with the numbers corresponding to those in the list. The Afar hotspot (29) is misplaced.
Download coordinates as: KML
- Mount Etna (47)
- Hoggar hotspot (13)
- Tibesti hotspot (40)
- Jebel Marra/Darfur hotspot (6)
- Afar hotspot (29, misplaced in map)
- Cameroon hotspot (17)
- Madeira hotspot (48)
- Canary hotspot (18)
- New England/Great Meteor hotspot (28)
- Cape Verde hotspot (19)
- Sierra Leone hotspot
- St. Helena hotspot (34)
- Gough hotspot (49), at 40°19' S 9°56' W.
- Tristan hotspot (42), at 37°07′ S 12°17′ W.
- Vema hotspot (Vema Seamount, 43), at 31°38' S 8°20' E.
- Discovery hotspot (50) (Discovery Seamounts)
- Bouvet hotspot (51)
- Shona/Meteor hotspot (27)
- Réunion hotspot (33)
- Comoros hotspot (21)
South American Plate
North American Plate
- Louisville hotspot (23)
- Foundation hotspot/Ngatemato seamounts (57)
- Macdonald hotspot (24)
- North Austral/President Thiers (President Thiers Bank, 58)
- Arago hotspot (Arago Seamount, 59)
- Maria/Southern Cook hotspot (Îles Maria, 60)
- Samoa hotspot (35)
- Crough hotspot (Crough Seamount, 61)
- Pitcairn hotspot (31)
- Society/Tahiti hotspot (38)
- Marquesas hotspot (26)
- Caroline hotspot (4)
- Hawaii hotspot (12)
- Socorro/Revillagigedos hotspot (37)
- Guadalupe hotspot (11)
- Cobb hotspot (5)
- Bowie/Pratt-Welker hotspot (3)
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Last edited on 22 May 2021, at 19:10
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