The Samoa hotspot is a volcanic

Volcano

2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

 hotspot

Hotspot (geology)

The places known as hotspots or hot spots in geology are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the mantle elsewhere. They may be on, near to, or far from tectonic plate boundaries. There are two hypotheses to explain them...

 located in the south Pacific Ocean

Pacific Ocean

The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

.
In geology

Geology

Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...

 the Hotspot model describes a hot upwelling plume of molten magma through the Earth's crust as an explanation of how volcanic islands are formed. The hotspot idea came from J. Tuzo Wilson in 1963 based on the Hawai'i volcanic island chain.

In theory, the Samoa hotspot is based on the Pacific Tectonic Plate

Pacific Plate

The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres, it is the largest tectonic plate....

 traveling over a fixed hotspot located deep underneath the Samoa islands.
The Samoa hotspot includes the Samoan Islands

Samoan Islands

The Samoan Islands or Samoa Islands is an archipelago covering in the central South Pacific, forming part of Polynesia and the wider region of Oceania...

 (American Samoa

American Samoa

American Samoa is an unincorporated territory of the United States located in the South Pacific Ocean, southeast of the sovereign state of Samoa...

 and Samoa

Samoa

Samoa , officially the Independent State of Samoa, formerly known as Western Samoa is a country encompassing the western part of the Samoan Islands in the South Pacific Ocean. It became independent from New Zealand in 1962. The two main islands of Samoa are Upolu and one of the biggest islands in...

), and extends to the islands of Uvea or Wallis Island

Wallis Island

Wallis is an island in the Pacific Ocean belonging to the French overseas collectivity of Wallis and Futuna....

 (Wallis and Futuna) and Niulakita

Niulakita

Niulakita is the southernmost reef island, which is a district of Tuvalu, and the name of the only village on this island. The junior school is Lotoalofa Primary School.-Geographical features:...

 (Tuvalu

Tuvalu

Tuvalu , formerly known as the Ellice Islands, is a Polynesian island nation located in the Pacific Ocean, midway between Hawaii and Australia. Its nearest neighbours are Kiribati, Nauru, Samoa and Fiji. It comprises four reef islands and five true atolls...

).

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 Hawaii hotspot

Hawaii hotspot

The Hawaii hotspot is the volcanic hotspot that created the Hawaiian Islands in the central Pacific Ocean, and is one of Earth's best-known and most heavily-studied hotspots....

, results in islands located further from the hotspot being progressively older with newer and younger islands closest to the fixed hotspot, like the Loihi Seamount

Loihi Seamount

Lōihi Seamount is an active undersea volcano located around off the southeast coast of the island of Hawaii about below sea level. It lies on the flank of Mauna Loa, the largest shield volcano on Earth...

, the only submarine volcano which has been studied in detail by scientists. The scientific research from Loihi has resulted in a 'Hawai'i' model for hotspots primarily limited to the information gathered from the Hawai'i islands.

However, the Samoa hotspot is currently an enigma for scientists. In the Samoa Islands, the eastern most island of Ta'u

Tau, American Samoa

Ta‘ū is the largest island in the Manu‘a Group and the easternmost volcanic island of the Samoan Islands. Ta‘ū is part of American Samoa. In the early 19th century, the island was sometimes called Opoun....

 and the western most island of Savai'i

Savai'i

Savaii is the largest and highest island in Samoa and the Samoa Islands chain. It is also the biggest landmass in Polynesia outside Hawaii and New Zealand. The island of Savai'i is also referred to by Samoans as Salafai, a classical Samoan term used in oratory and prose...

 have both erupted in the past 150 years. The most recent eruption on Sava'i occurred with Mount Matavanu (1905–1911) and on Ta'u in 1866.

Vailulu'u

In 1975, geophysicist Rockne Johnson discovered the Vailulu'u Seamount

Vailulu'u

Vailulu'u is a volcanic seamount discovered by geophysicist Rockne Johnson in the Samoa Islands on October 18, 1975. The finding of an active, undersea, hotspot volcano is significant for scientists studying the Earth's fundamental processess...

, 45km east of Ta'u island in American Samoa which has since been studied by an international team of scientists. Growing inside the summit crater of Vailulu'u is an active underwater volcanic cone

Volcanic cone

Volcanic cones are among the simplest volcanic formations. 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 size of the fragments ejected during the eruption...

 called Nafanua, named after a war goddess in Samoan mythology

Samoan mythology

Samoan mythology tell stories of many different gods. There were gods of the forest, the seas, rain, harvest, villages and war. There were two types of gods, atua who had non-human origins and aitu who were of human origin. Tagaloa was a supreme god who made the islands and the people. Mafui'e was...

. The study of Vailulu'u provides scientists with another possible model for hotspots as an alternative to the Hawai'i hotspot model.

An important difference between Vailulu'u and Loihi in Hawai'i, is a total lack of tholeiitic basalt compositions at Vailulu'u although both are located at the eastern most point of their respective island chains. It must be stated that the hotspot is special in many ways. The northern Tonga Islands (Vava'u

Vava'u

Vavau is an island chain of one large island and 40 smaller ones in Tonga. According to tradition Maui fished both Tongatapu and Vavau but put a little more effort into the former. Vavau rises 204 meters above sea level...

 and Niuatoputapu

Niuatoputapu

For the 2009 tsunami, see the main article: 2009 Samoa tsunami.Niuatoputapu is an island in the island nation of Tonga, Pacific Ocean. Its name means sacred island. Older European names for the island are Traitors island or Keppel island.Niuatoputapu is located in the north of the country,...

) are moving away from the Australian plate (Fiji

Fiji

Fiji , officially the Republic of Fiji , is an island nation in Melanesia in the South Pacific Ocean about northeast of New Zealand's North Island...

) at rates of c. 130 mm/yr and c. 160 mm/yr, respectively, while the Pacific plate (Niue

Niue

Niue , is an island country in the South Pacific Ocean. It is commonly known as the "Rock of Polynesia", and inhabitants of the island call it "the Rock" for short. Niue is northeast of New Zealand in a triangle between Tonga to the southwest, the Samoas to the northwest, and the Cook Islands to...

 and Rarotonga

Rarotonga

Rarotonga is the most populous island of the Cook Islands, with a population of 14,153 , out of the country's total population of 19,569.The Cook Islands' Parliament buildings and international airport are on Rarotonga...

) is approaching the Australian plate at c. 80 mm/yr. This implies that Pacific plate is tearing at the corner of the trench-transform boundary at a rate that is the sum of these two (160 + 80) c. 240 mm/yr.