The Samoa 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 located in the south

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contin ...

. The hotspot model describes a hot upwelling plume of

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 ...

through the Earth's crust as an explanation of how

volcanic island Geologically, a high island or volcanic island is an island of volcanic origin. The term can be used to distinguish such islands from low islands, which are formed from sedimentation or the uplifting of coral reefs (which have often formed ...

s are formed. The hotspot idea came from J. Tuzo Wilson in 1963 based on the Hawaiian Islands volcanic chain. In theory, the Samoa hotspot is based on the Pacific Tectonic Plate traveling over a fixed hotspot located deep underneath the

Samoan Islands The Samoan Islands ( sm, Motu o Sāmoa) are an archipelago covering in the central South Pacific, forming part of Polynesia and of the wider region of Oceania. Administratively, the archipelago comprises all of the Independent State of Samoa an ...

. The Samoa hotspot includes the Samoan Islands (

American Samoa American Samoa ( sm, Amerika Sāmoa, ; also ' or ') is an unincorporated territory of the United States located in the South Pacific Ocean, southeast of the island country of Samoa. Its location is centered on . It is east of the Internationa ...

and

Samoa Samoa, officially the Independent State of Samoa; sm, Sāmoa, and until 1997 known as Western Samoa, is a Polynesian island country consisting of two main islands ( Savai'i and Upolu); two smaller, inhabited islands ( Manono and Apolima); ...

), and extends to the islands of Uvea or

Wallis Island Wallis ( Wallisian: ''Uvea'') is a Polynesian atoll/island in the Pacific Ocean belonging to the French overseas collectivity (''collectivité d'outre-mer'', or ''COM'') of Wallis and Futuna. It lies north of Tonga, northeast of Fiji, east-n ...

(Wallis and Futuna) and Niulakita (

Tuvalu Tuvalu ( or ; formerly known as the Ellice Islands) is an island country and microstate in the Polynesian subregion of Oceania in the Pacific Ocean. Its islands are situated about midway between Hawaii and Australia. They lie east-nor ...

), as well as the submerged Pasco banks and Alexa Bank. As the Pacific Plate moves slowly over the hotspot, thermal activity builds up and is released in magma plume spewing through the Earth's crust, forming each island in a chain. The Samoa islands generally lie in a straight line, east to west, in the same direction of the tectonic plate 'drifting' over the hotspot. A characteristic of a “classic” hotspot, like the Hawaiʻi hotspot, results in islands located further from the hotspot being progressively older with newer and younger islands closest to the fixed hotspot, like the

Kamaʻehuakanaloa Seamount Kamaʻehuakanaloa Seamount (previously known as Lōʻihi) is an active submarine volcano about off the southeast coast of the island of Hawaii. The top of the seamount is about below sea level. This seamount is on the flank of Mauna Loa, the la ...

(formerly Lōʻihi), the only submarine volcano which has been studied in detail by scientists. The scientific research from Kamaʻehuakanaloa has resulted in a 'Hawaiʻi' model for hotspots primarily limited to the information gathered from the Hawaiian Islands. However, the Samoa hotspot is currently an enigma for scientists. In the Samoa Islands, the easternmost island of

Taʻū Taʻū is the largest island in the Manuʻa Islands and the easternmost volcanic island of the Samoan Islands. Taū is part of American Samoa. In the early 19th century, the island was sometimes called ''Opoun''. Taū is well known as the site ...

and the westernmost island of

Savaiʻi Savaii is the largest (area 1,694 km2) and highest ( Mt Silisili at 1,858 m) island both in Samoa and in the Samoan Islands chain. The island is also the sixth largest in Polynesia, behind the three main islands of New Zealand and ...

have both erupted in the past 150 years. The most recent eruption on Savaiʻi occurred with Mount Matavanu (1905–1911) and on Taʻū in 1866.

Vailulu'u

In 1975, geophysicist Rockne Johnson discovered the Vailuluʻu Seamount, 45 km east of Taʻū island in American Samoa which has since been studied by an international team of scientists. Within the summit crater of Vailuluʻu is an active underwater

volcanic cone Volcanic cones are among the simplest volcanic landforms. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and ...

called Nafanua, named after a war goddess in

Samoan mythology Samoan culture tells stories of many different deities. There were deities of the forest, the seas, rain, harvest, villages, and war. There were two types of deities, ''atua'', who had non-human origins, and ''aitu'', who were of human origin. Taga ...

. The study of Vailuluʻu provides scientists with another possible model for hotspots as an alternative to the Hawaiʻi hotspot model. An important difference between Vailuluʻu and Kamaʻehuakanaloa in Hawaiʻi, is a total lack of

tholeiitic basalt The tholeiitic magma series is one of two main magma series in subalkaline igneous rocks, the other being the calc-alkaline series. A magma series is a chemically distinct range of magma compositions that describes the evolution of a mafic magma ...

compositions at Vailuluʻu although both are located at the easternmost point of their respective island chains. The northern Tonga Islands ( Vavaʻu and

Niuatoputapu Niuatoputapu is a high island in the island nation of Tonga, Pacific Ocean. Its highest point is , and its area is . Its name means ''sacred island''. Older European names for the island are Traitors Island or Keppel Island. Niuatoputapu is ...

) are moving away from Fiji on the

Australian plate The Australian Plate is a major tectonic plate in the eastern and, largely, southern hemispheres. Originally a part of the ancient continent of Gondwana, Australia remained connected to India and Antarctica until approximately when India broke ...

at rates of about 130 mm/yr and 160 mm/yr, respectively, while

Niue Niue (, ; niu, Niuē) is an island country in the South Pacific Ocean, northeast of New Zealand. Niue's land area is about and its population, predominantly Polynesian, was about 1,600 in 2016. Niue is located in a triangle between Tong ...

and Rarotonga on the Pacific plate are approaching the Australian plate at about 80 mm/yr. This implies that Pacific plate is tearing at the corner of the trench-

transform boundary A transform fault or transform boundary, is a fault along a plate boundary where the motion is predominantly horizontal. It ends abruptly where it connects to another plate boundary, either another transform, a spreading ridge, or a subductio ...

at a rate that is the sum of these two (160 + 80) 240 mm/yr.

References

{{Samoa topics, state=collapsed Hotspots of the Pacific Ocean Geology of Oceania Geography of Samoa Geography of American Samoa Geography of Oceania

Vailulu'u

See also

References