thumb|upright=1.35|Diagram showing a [[Cross section (geology)|cross section through Earth at the Hawaii hotspot. Magma originating in the mantle rises into the asthenosphere and lithosphere. A chain of volcanoes is created as the lithosphere moves over the source of magma. ("Ma" means millions of years old/ago).]]
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. 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. 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
thumb|right|Schematic diagram showing the physical processes inside the Earth that lead to the generation of magma. Partial melting begins above the fusion point.
thumb|upright=1.35|right|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 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 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 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. 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.<!---unverifable reference as of 2023 ---->
The hotspot hypothesis is now closely linked to the mantle plume hypothesis. and its seismic imaging developments. 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.
Postulated hotspot volcano chains
[[File:CourtHotspots.png|thumb|right|An example of mantle plume locations suggested by one recent group. Figure from Foulger (2010).
- Tuamotu–Line Island chain (Easter hotspot)
- Cape Verde (Cape Verde hotspot)
- Iceland hotspot (14)
- Azores hotspot (1)
- , w= 0.8 az= 079° ±5° rate= 18 ±3 mm/yr
- Raton hotspot (32)
- , w= 1 az= 240°±4° rate= 30 ±20 mm/yr
Australian plate
- Lord Howe hotspot (22)
- , w= 0.8 az= 351° ±10°