Pioneer Seamount is an undersea

mountain A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited Summit (topography), summit area, and ...

, or

seamount A seamount is a large geologic landform that rises from the ocean floor that does not reach to the water's surface (sea level), and thus is not an island, islet or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise abru ...

, in the

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 continen ...

off the coast of central

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

Location

Pioneer Seamount is located at 37° 21.1' North

Latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north pol ...

, 123° 26.1' West

Longitude Longitude (, ) is a geographic coordinate that specifies the east–west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek letter l ...

,NOAA Vents Program Acoustic Monitoring; Acousting Monitoring Program Pioneer Seamount
/ref> at the base of the

continental slope A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental margin ...

United States Geological Survey Monthly Newsletter ''Sound Waves'': Fieldwork: Geologists and Biologists Endeavor to Understand Seamount Environments Off California
/ref> of

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

about off the coast just southwest of

San Francisco San Francisco (; Spanish language, Spanish for "Francis of Assisi, Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California. The city proper is the List of Ca ...

, California.

Physical characteristics

The seamount is a

volcano 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 are ...

between 10.9 and 11.1 million years old. It is about long as well as about wide, and has a volume of about . It rises about above the surrounding ocean floor, and its peak is a minimum of below the oceans surface. Samples from the seamount consist of highly vesicular alkalic

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 ...

hawaiite Hawaiite is an olivine basalt with a composition between alkali basalt and mugearite. It was first used as a name for some lavas found on the island of Hawaii. It occurs during the later stages of volcanic activity on oceanic islands such as Haw ...

, and

mugearite Mugearite () is a type of oligoclase-bearing basalt, comprising olivine, apatite, and opaque oxides. The main feldspar in mugearite is oligoclase. Mugearite is a sodium-rich member of the alkaline magma series. In the TAS classification of volc ...

. The seamount and its volcano once extended above the sea surface, but eroded and sank as the seamount and the seabed at its base were carried further away from the spreading center from which it presumably originated.

Biological environment

A wide variety of sealife lives on the seamount.

Coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and sec ...

s dominate in deeper areas and

sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through t ...

s in its shallower parts.

Naming

Pioneer Seamount was named for USC&GS ''Pioneer'', the first of three

survey ship A survey vessel is any type of ship or boat that is used for underwater surveys, usually to collect data for mapping or planning underwater construction or mineral extraction. It is a type of research vessel, and may be designed for the purpo ...

s of the

United States Coast and Geodetic Survey The United States Coast and Geodetic Survey (abbreviated USC&GS), known from 1807 to 1836 as the Survey of the Coast and from 1836 until 1878 as the United States Coast Survey, was the first scientific agency of the United States Government. It ...

to bear the name. ''Pioneer'' operated along the

United States West Coast The West Coast of the United States, also known as the Pacific Coast, Pacific states, and the western seaboard, is the coastline along which the Western United States meets the North Pacific Ocean. The term typically refers to the contiguous U.S ...

and in the then-

Territory of Alaska The Territory of Alaska or Alaska Territory was an organized incorporated territory of the United States from August 24, 1912, until Alaska was granted statehood on January 3, 1959. The territory was previously Russian America, 1784–1867; the ...

during her Coast and Geodetic Survey career, which lasted from 1922 to 1941.NOAA History: Tools of the Trade: Coast and Geodetic Survey Ships: Pioneer
/ref>

Notes

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References

* ttp://www.history.noaa.gov/ships/pioneer1.html NOAA History: Tools of the Trade: Coast and Geodetic Survey Ships: Pioneer Seamounts of the Pacific Ocean