Geologists Seamounts

Geologists Seamounts
Bathymetric map of the south-west Geologists Seamounts
Location within Pacific Ocean
Location
Location	North Pacific Ocean
Coordinates	18°40′N 157°40′W / 18.667°N 157.667°W / 18.667; -157.6671
Geology
Age of rock	Cretaceous

Geologists Seamounts (alternatively were named South West Hawaii Group²) are a cluster of seamounts in the Pacific Ocean, located mainly 100 miles (160 km) south of Oahu, Hawaii³ and 100–200 kilometres (62–124 mi)⁴ south-west from Big Island (Hawaiʻi).⁵ Clockwise from north they are named Perret, Jaggar, McCall, Pensacola, Daly, Swordfish, Cross, Washington and Ellis.⁶ The Kauluakalana seamount to the north of Oahu 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,⁷ but would not so be grouped logically by the former name for the cluster.

The mountains have a height above seafloor of about 5 kilometres (3.1 mi). They developed on a mid-ocean ridge⁸ during the Cretaceous,⁹ about 80 million years ago, and there is no geological relationship to the neighbouring Hawaiian Islands.⁴ There is about contemporaneous timing with the formation of the Musicians Seamounts to the north-west of Oahu and Hawaiʻi, from the limited sampling and analysis to date.¹⁰ Ages that have been obtained include 80.5 Ma for Kauluakalana, 84.5 Ma for Cross and 82.7 Ma for McCall.⁷ Rocks dredged from the seamounts include iron-manganese crusts, carbonates and basalts.¹¹¹²

Corals and sponges have been recorded at the south-western Swordfish Seamount at a depth of 1,071 m (3,514 ft) with plexauridae, alcyonacea, and coralliidae corals.¹³ The deeper coral community on Ellis Seamount at a depth of 2,135 m (7,005 ft) was less diverse with bamboo corals dominant,¹³ but coverage is still widespread.¹⁴