The Erebus hotspot is a

volcanic A volcano is a rupture 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 found where tectonic plates a ...

hotspot responsible for the high volcanic activity on Ross Island in the western

Ross Sea The Ross Sea is a deep bay of the Southern Ocean in Antarctica, between Victoria Land and Marie Byrd Land and within the Ross Embayment, and is the southernmost sea on Earth. It derives its name from the British explorer James Clark Ross who ...

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...

. Its current eruptive zone,

Mount Erebus Mount Erebus () is the second-highest volcano in Antarctica (after Mount Sidley), the highest active volcano in Antarctica, and the southernmost active volcano on Earth. It is the sixth-highest ultra mountain on the continent. With a summ ...

, has erupted continuously since its discovery in 1841.

Magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...

s of the Erebus hotspot are similar to those erupted from hotspots at the active East African Rift in eastern

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

Mount Bird Mount Bird is a high shield volcano standing about south of Cape Bird, the northern extremity of Ross Island. It was mapped by the British National Antarctic Expedition, 1901–04, under Robert Falcon Scott, and apparently named by them aft ...

at the northernmost end of Ross Island and Mount Terror at its eastern end are large

basalt 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 ...

ic shield volcanoes that have been potassium-argon dated 3.8–4.8 and 0.8–1.8 million years old.Morgan, W.J.; Phipps Morgan, J. (2007
"Plate velocities in hotspot reference frame: electronic supplement"

About

There is currently disagreement over the cause of volcanic activity on Ross Island. The traditional view is that the area is underlain by a

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 hot ...

which has given rise to volcanism and, in conjunction with a second plume thought to be under Marie Byrd Land on the mainland to the east, a system of

rift In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-grabe ...

s known as the

West Antarctic Rift System The West Antarctic Rift System is a series of rift valleys between East and West Antarctica. It encompasses the Ross Embayment, the Ross Sea, the area under the Ross Ice Shelf and a part of Marie Byrd Land in West Antarctica, reaching to the ...

. Support for a plume origin includes

petrological Petrology () is the branch of geology that studies rocks and the conditions under which they form. Petrology has three subdivisions: igneous, metamorphic, and sedimentary petrology. Igneous and metamorphic petrology are commonly taught together ...

, geochemical, and isotopic evidence for a deep-mantle source, high heat flow in the area, high volcanic output, domal uplift, and

seismic Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other ...

anomalies in the upper mantle consistent with a plume approximately in diameter extending below the surface where it changes into a narrow column that extends at least a further and according to some studies as deep as . The area lacks the time-progressive volcanism typically associated with mantle plumes. This has been explained by the

Antarctic Plate The Antarctic Plate is a tectonic plate containing the continent of Antarctica, the Kerguelen Plateau, and some remote islands in the Southern Ocean and other surrounding oceans. After breakup from Gondwana (the southern part of the superconti ...

being stationary since the late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

. Other observations appear to be inconsistent with the plume model. Uplift in the region lacks the circular symmetry typically associated with mantle plumes. Rifting occurred mainly in the late Cretaceous, whereas uplift occurred mainly in the middle

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

, so uplift followed extension rather than preceding it as would be expected with a mantle plume. The volume of

magmatism Magmatism is the emplacement of magma within and at the surface of the outer layers of a terrestrial planet, which solidifies as igneous rocks. It does so through magmatic activity or igneous activity, the production, intrusion and extrusion of ...

, when the long duration of volcanic activity is taken into account, appears lower than would be expected to result from a mantle plume. Seismic imaging does not show the circular symmetry expected for a mantle plume but indicates rather a linear, tectonic feature extending from

Tasmania ) , nickname = , image_map = Tasmania in Australia.svg , map_caption = Location of Tasmania in AustraliaCoordinates: , subdivision_type = Country , subdi ...

to the Ross Sea. Owing to these issues, some scientists have questioned the plume model and propose instead a shallow, tectonic mechanism. In this view, lithospheric extension and rifting during the late Cretaceous stretched the lithosphere, giving rise to partial melts. Though insufficient to break the surface, fertile, low- liquidus material was distributed throughout the lithospheric mantle. During the middle Eocene, tectonic changes in the

Southern Ocean The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the World Ocean, generally taken to be south of 60° S latitude and encircling Antarctica. With a size of , it is regarded as the second-small ...

gave rise to further lithospheric deformation, causing strike-slip faulting which enabled

decompression melting Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or ...

and

extrusion Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section. Its two main advantages over other manufacturing processes are its ability to create very complex ...

of the fertile material emplaced during the late Cretaceous.

References

Hotspots of the Southern Ocean Geology of Antarctica Ross Island {{Hotspots