Geologists Seamounts (alternatively were named South West Hawaii Group) are a cluster of

seamount A seamount is a large submarine landform that rises from the ocean floor without reaching the water surface (sea level), and thus is not an island, islet, or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise abruptly a ...

s in the

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

, located mainly south of

Oahu Oahu (, , sometimes written Oahu) is the third-largest and most populated island of the Hawaiian Islands and of the U.S. state of Hawaii. The state capital, Honolulu, is on Oahu's southeast coast. The island of Oahu and the uninhabited Northwe ...

Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...

and south-west from

Big Island (Hawaii) Hawaii is the largest island in the United States, located in the state of Hawaii, the southernmost state in the union. It is the southeasternmost of the Hawaiian Islands, a chain of volcanic islands in the North Pacific Ocean. With an area of ...

. Clockwise from north they are named Perret, Jaggar, McCall, Pensacola, Daly, Swordfish, Cross, Washington and Ellis. The Kauluakalana seamount to the north of

on the far side of the Hawaiian chain to the other seamounts of the cluster, and south-east of the Musicians Seamounts has reason to be regarded as part of the Geologists Seamounts, but would not so be grouped logically by the former name for the cluster.

Geology

The seamounts developed during the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

, about 80 million years ago, and there is no geological relationship to the neighbouring

Hawaiian Islands The Hawaiian Islands () are an archipelago of eight major volcanic islands, several atolls, and numerous smaller islets in the Pacific Ocean, North Pacific Ocean, extending some from the Hawaii (island), island of Hawaii in the south to nort ...

. There is about contemporaneous timing with the formation of the Musicians Seamounts to the north-west of Oahu and Hawaii, from the limited sampling and analysis to date. Ages that have been obtained include 80.5 for Kauluakalana, 84.5 Ma for Cross and 82.7 Ma for McCall. Rocks dredged from the seamounts include

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

manganese Manganese is a chemical element; it has Symbol (chemistry), symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese was first isolated in the 1770s. It is a transition m ...

crusts,

carbonate A carbonate is a salt of carbonic acid, (), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word "carbonate" may also refer to a carbonate ester, an organic compound containing the carbonate group ...

s and

basalt Basalt (; ) is an aphanite, 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 planetary surface, surface of a terrestrial ...

Ecology

Coral Corals are colonial marine invertebrates within the subphylum Anthozoa of the phylum Cnidaria. They typically form compact Colony (biology), colonies of many identical individual polyp (zoology), polyps. Coral species include the important Coral ...

s and

sponge Sponges or sea sponges are primarily marine invertebrates of the animal phylum Porifera (; meaning 'pore bearer'), a basal clade and a sister taxon of the diploblasts. They are sessile filter feeders that are bound to the seabed, and a ...

s have been recorded at the south-western Swordfish Seamount at a depth of with

plexauridae Plexauridae is a Family (biology), family of marine Colony (biology), colonial Octocorallia, octocorals in the phylum Cnidaria. Members of this family are found in shallow tropical and subtropical seas. Many species contain Symbiosis, symbiotic P ...

alcyonacea Alcyonacea is the old scientific order name for the informal group known as "soft corals". It is now an unaccepted name for class Octocorallia. It became deprecated . The following text should be considered a historical, outdated way of treatin ...

, and

coralliidae Coralliidae, also known as precious corals, is a taxonomic Family (biology), family of soft Coral, corals belonging to the suborder Scleraxonia of the phylum Cnidaria. These sessile corals are one of the most dominant members of hard-bottomed Ben ...

corals. The deeper coral community on Ellis Seamount at a depth of was less diverse with

bamboo coral Bamboo coral, family Keratoisididae (formerly Isididae) is a family of coral of the phylum Cnidaria. It is a commonly recognized inhabitant of the deep sea, due to the clearly articulated skeletons of the species. Deep water coral species suc ...

s dominant.

References

Sources

* * Cretaceous volcanism Seamounts of the Pacific Ocean {{Ocean-stub