Adams Seamount (also known as Forty Mile Reef) is a submarine volcano above the Pitcairn hotspot in the central Pacific Ocean about 100 kilometres (62 mi) southwest of Pitcairn Island.Allison Guyot
Allison Guyot (formerly known as Navoceano Guyot) is a tablemount (guyot) in the underwater Mid-Pacific Mountains of the Pacific Ocean. It is a trapezoidal flat mountain rising 1,500 metres above the seafloor to a depth of less than 1,500 m, with a summit platform 35 by 70 kilometres wide. The Mid-Pacific Mountains lie west of Hawaii and northeast of the Marshall Islands, but at the time of their formation were located in the Southern Hemisphere.
The tablemount was probably formed by a hotspot in the present-day Southern Pacific before plate tectonics moved it to its current location. Several hotspots, including the Easter, Marquesas and Society hotspots, may have been involved in the formation of the Mid-Pacific Mountains. Volcanic activity is dated to have occurred circa 111–85 million years ago and formed a volcanic island. Subsequently, carbonate deposition commenced as Allison Guyot subsided and eventually buried the island, forming an atoll-like structure and a carbonate platform. Among other animals, crocodilians lived on Allison Guyot.
The platform emerged above sea level during the Albian and Turonian ages. It drowned about 99 ± 2 million years ago for unknown reasons; possibly a phase of renewed emergence damaged the reefs, or it was located in unfavourable waters. Later, pelagic sedimentation commenced on the seamount and led to the deposition of sediments including limestone, ooze and sand, which bear traces of climatic events and ocean currents.Arago hotspot
Arago hotspot is a hotspot in the Pacific Ocean, presently located below the Arago seamount close to the island of Rurutu, French Polynesia.
Arago is part of a family of hotspots in the southern Pacific, which include the Society hotspot and the Macdonald hotspot among others. These are structures beneath Earth's crust which generate volcanoes and which are in part formed by mantle plumes, although Arago itself might have a shallower origin. As the Pacific plate moves over the hotspots, new volcanoes form and old volcanoes are carried away; sometimes an older volcano is carried over the hotspot and is then uplifted as happened with Rurutu.
The Arago hotspot is responsible for the formation of Arago seamount and uplift on Rurutu; however reconstructions of the past positions of tectonic plates and geochemistry suggest that other islands and seamounts were constructed by the Arago hotspot during the past 120 million years. These potentially include Tuvalu, Gilbert Islands, the Ratak Chain of the Marshall Islands as well as part of the Austral Islands and Cook Islands.Foundation Seamounts
Foundation Seamounts are a series of seamounts in the southern Pacific Ocean. Discovered in 1992, these seamounts form a 1,350 kilometres (840 mi) long chain which starts from the Pacific-Antarctic Ridge. Some of these seamounts may have once emerged from the ocean.
The Foundation Seamounts were probably formed by a now-weakening mantle plume called the Foundation hotspot that is located close to the Pacific-Antarctic Ridge. It is possible that this hotspot generated additional volcanoes, such as the Ngatemato and Taukina seamounts farther west. The oldest volcanism on the Foundation Seamounts occurred 21 million years ago, while the youngest volcanism appears to be hydrothermal venting and the eruption of a lava flow between 1997-2001 where the Foundation Seamounts intersect the Pacific-Antarctic Ridge.Hotspot (geology)
In geology, the places known as hotspots or hot spots are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle. Their position on the Earth's surface is independent of tectonic plate boundaries. 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 other hypothesis is that lithospheric extension permits the passive rising of melt from shallow depths. This hypothesis considers the term "hotspot" to be a misnomer, asserting that the mantle source beneath them is, in fact, not anomalously hot at all. Well-known examples include the Hawaii, Iceland and Yellowstone hotspots.Ioah Guyot
Ioah Guyot is a seamount in the Pacific Ocean, close to the Marshall Islands. Part of the Magellan Seamounts, it is a shield volcano that has erupted alkali basalt and hawaiite 87 million years ago, but may have continued erupting into the Miocene. During the Cretaceous, reefs developed on the guyot.Ita Mai Tai
Ita Mai Tai is a Cretaceous-early Cenozoic seamount northwest of the Marshall Islands and north of Micronesia. One among a number of seamounts in the Pacific Ocean, it is part of the Magellan Seamounts which may have a hotspot origin although Ita Mai Tai itself may not have formed on a hotspot.
The seamount is formed by volcanic rocks which form two adjacent volcanic centres that erupted between the Aptian-Albian and possibly as late as the Pliocene. Reef systems developed on the seamount after its formation and led to the deposition of limestones. Especially during the Oligocene the seamount subsided and lies now at 1,402 metres (4,600 ft) depth below sea level. Ferromanganese crusts as well as pelagic oozes were deposited on the submerged rocks.Limalok
Limalok (formerly known as Harrie or Harriet) is a Cretaceous-Paleocene guyot/tablemount in the southeastern Marshall Islands, one of a number of seamounts (a type of underwater volcanic mountain) in the Pacific Ocean. It was probably formed by a volcanic hotspot in present-day French Polynesia. Limalok lies southeast of Mili Atoll and Knox Atoll, which rise above sea level, and is joined to each of them through a volcanic ridge. It is located at a depth of 1,255 metres (4,117 ft) and has a summit platform with an area of 636 square kilometres (246 sq mi).
Limalok is formed by basaltic rocks and was probably a shield volcano at first; the Macdonald, Rarotonga, Rurutu and Society hotspots may have been involved in its formation. After volcanic activity ceased, the volcano was eroded and thereby flattened, and a carbonate platform formed on it during the Paleocene and Eocene. These carbonates were chiefly produced by red algae, forming an atoll or atoll-like structure with reefs.
The platform sank below sea level 48 ± 2 million years ago during the Eocene, perhaps because it moved through the equatorial area, which was too hot or nutrient-rich to support the growth of a coral reef. Thermal subsidence lowered the drowned seamount to its present depth. After a hiatus lasting into the Miocene, sedimentation commenced on the seamount leading to the deposition of manganese crusts and pelagic sediments; phosphate accumulated in some sediments over time.List of seamounts in the Marshall Islands
The Marshall Islands are the site of a number of seamounts. These volcanoes form several groups, including the Ralik Chain, the Ratak Chain and some seamounts around Anewetak. These seamounts are in turn part of a larger province that extends from the South Pacific to the Mariana Trench and is characterized by unusually shallow ocean ground.These seamounts and volcanoes do not have simple hotspot-like age progressions, with some volcanoes being younger than one would expect from age progression and having more than one active episode. In some places, a middle Cretaceous and a late Cretaceous episode of volcanic activity have been determined by radiometric dating. Despite this, some hotspot-based genesis models have been formulated, often implying that French Polynesian hotspots are responsible for the formation of seamounts, with the Society hotspot, Rurutu hotspot, Rarotonga hotspot and the Macdonald hotspot being candidate hotspots responsible for the development of the Marshall Islands seamounts. Such linkages are in part supported by geochemical data. Some discrepancies between the age and position of such seamounts and the predictions of the hotspot model may reflect the activity of short-lived hotspots linked to large mantle plumes that produce more than one hotspot.Macdonald hotspot
The Macdonald hotspot is a volcanic hotspot in the southern Pacific Ocean. The hotspot was responsible for the formation of the Macdonald Seamount, and possibly the Austral-Cook Islands chain. It probably did not generate all of the volcanism in the Austral and Cook Islands as age data imply that several additional hotspots were needed to generate some volcanoes.
In addition to the volcanoes in the Austral Islands and Cook Islands, Tokelau, the Gilbert Islands, the Phoenix Islands and several of the Marshall Islands as well as several seamounts in the Marshall Islands may have been formed by the Macdonald hotspot.Mo'orea
Mo'orea (English: or ; Tahitian: /moʔore(ʔ)a/), also spelled Moorea, is a high island in French Polynesia, one of the Windward Islands, part of the Society Islands, 17 kilometres (11 mi) northwest of Tahiti. The name comes from the Tahitian Mo'ore'a, meaning "yellow lizard": Mo'o = lizard ; Re'a (from re'are'a) = yellow. An older name for the island is 'Aimeho, sometimes spelled 'Aimeo or 'Eimeo (among other spellings given by early visitors before Tahitian spelling was standardized). Early Western colonists and voyagers also referred to Mo'orea as York Island.Mount Tohivea
Mount Tohivea (or Tohiea) is a volcanic peak and the highest point on the island of Moorea in French Polynesia at 3,960 feet (1,207 m). On its slopes are many streams and fertile soils. There are hiking trails along the summit close to Belvedere Point where people can view Mont Routui and the two bays and three peninsulas of Moorea. Mount Tohivea is a dormant volcano that is easily visible from Papeete, the capital of French Polynesia. The surrounding peaks are almost as tall as Mount Tohivea.Rarotonga hotspot
The Rarotonga hotspot is a volcanic hotspot in the southern Pacific Ocean. The hotspot was responsible for the formation of Rarotonga and some volcanics of Aitutaki.
In addition to these volcanoes in the Cook Islands, the composition of volcanic rocks in Samoa and in the Lau Basin may have been influenced by the Rarotonga hotspot, and some atolls and seamounts in the Marshall Islands may have formed on the hotspot as well.Tahiti
Tahiti (; French pronunciation: [ta.iti]; previously also known as Otaheite) is the largest island of the Windward group of the Society Islands in French Polynesia, located in the central part of the Pacific Ocean. Divided into two parts, Tahiti Nui (bigger, northwestern part) and Tahiti Iti (smaller, southeastern part), the island was formed from volcanic activity; it is high and mountainous with surrounding coral reefs. Its population is 189,517 inhabitants (2017), making it the most populous island of French Polynesia and accounting for 68.7% of its total population.
Tahiti is the economic, cultural, and political centre of French Polynesia, an overseas collectivity (and the sole overseas country) of the French Republic. The capital of French Polynesia, Papeete, is located on the northwest coast of Tahiti. The only international airport in the region, Faa'a International Airport, is on Tahiti near Papeete. Tahiti was originally settled by Polynesians between 300 and 800 CE. They represent about 70% of the island's population, with the rest made up of Europeans, Chinese people, and those of mixed heritage. The island was part of the Kingdom of Tahiti until its annexation by France in 1880, when it was proclaimed a colony of France, and the inhabitants became French citizens. French is the only official language, although the Tahitian language (Reo Tahiti) is widely spoken.Takuyo-Daisan
Takuyo-Daisan is a guyot in the Western Pacific Ocean off Japan. It is 1,409 metres (4,623 ft) deep and has a square-shaped flat top surrounded by a perimeter ridge. Several other seamounts lie nearby.
The seamount formed as a volcanic island during the Cretaceous in the area currently occupied by French Polynesia. Subsequently reefs developed around the volcanic island and generated a carbonate platform which drowned during the Albian along with several other such platforms in the world.Teahitia
Teahitia is a submarine volcano, located 40 km (25 mi) northeast of the southeast tip of Tahiti of the Society Islands in the Pacific Ocean, with its peak 1600 meters below the water surface. It belongs to the Society hotspot.
Teahitia's last eruption occurred in 1985.Wōdejebato
Wōdejebato (formerly known as Sylvania) is a Cretaceous guyot or tablemount in the northern Marshall Islands, Pacific Ocean. Wōdejebato is probably a shield volcano and is connected through a submarine ridge to the smaller Pikinni Atoll 74 kilometres (46 mi) southeast of the guyot; unlike Wōdejebato, Pikinni rises above sea level. The seamount rises for 4,420 metres (14,500 ft) to 1,335 metres (4,380 ft) depth and is formed by basaltic rocks. The name Wōdejebato refers to a sea god of Pikinni.
It was probably formed by a hotspot in what is present-day French Polynesia before plate tectonics moved it to its present-day location. The Macdonald, Rarotonga, Rurutu and Society hotspots may have been involved in its formation. The first volcanic phase took place in the Cenomanian and was followed by the formation of a carbonate platform that quickly disappeared below the sea. A second volcanic episode between 85 and 78.4 million years ago (in the Campanian) led to the formation of an island. This island was eventually eroded and rudist reefs generated an atoll or atoll-like structure, covering the former island with carbonates and thus a second carbonate platform.
The second carbonate platform drowned about 68 million years ago (in the Maastrichtian), perhaps because at that time it was moving through the equatorial area which may have been too hot or too nutrient-rich to support the growth of a coral reef. Thermal subsidence lowered the drowned seamount to its present depth. After a hiatus, sedimentation commenced on the seamount and led to the deposition of manganese crusts and pelagic sediments, some of which were later modified by phosphate.