Shimada Seamount is a

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 ...

located southwest of

Baja California Sur Baja California Sur (; 'South Lower California'), officially the Free and Sovereign State of Baja California Sur ( es, Estado Libre y Soberano de Baja California Sur), is the least populated state and the 31st admitted state of the 32 federal ent ...

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

. It is a shallow seamount, reaching a depth of below sea level and is a regular single-peaked mountain with a westerly spur and little relief otherwise. A platform lies at a depth of . Talus deposits surround the seamount at its base. The

seafloor The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

underneath Shimada is between 18 million and 21 million years old and lies at a depth of about ; other than

abyssal hill An abyssal hill is a small hill that rises from the floor of an abyssal plain. They are the most abundant geomorphic structures on the planet Earth, covering more than 30% of the ocean floors. Abyssal hills have relatively sharply defined edges and ...

s at a distance of up to from Shimada, Shimada is isolated. Volcanic rocks taken from Shimada are considered to be

icelandite Icelandite is a type of volcanic rock, an andesite that is enriched in iron but deficient in aluminium (< 16.5% ).Carmichael, Ian S. E., Francis J. Turner and John Verhoogen, 1974, ''Igneous Petrology,'' McGraw-Hill, p. 34

s. Most seamounts form at

mid-ocean ridge A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics. It typically has a depth of about and rises about above the deepest portion of an ocean basin. This feature is where seafloor spreading takes place along a diverge ...

s, but hotspots and

transform fault A transform fault or transform boundary, is a fault along a plate boundary where the motion is predominantly horizontal. It ends abruptly where it connects to another plate boundary, either another transform, a spreading ridge, or a subductio ...

s can also produce seamounts. These mechanisms cannot really explain the origin of Shimada Seamount, however; it may be part of a hotspot trace. Evidence from

core sample A core sample is a cylindrical section of (usually) a naturally-occurring substance. Most core samples are obtained by drilling with special drills into the substance, such as sediment or rock, with a hollow steel tube, called a core drill. The h ...

s around the seamount, the appearance of the summit area, and the presence of thin

manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...

crusts imply an age of about 10,000 years for some volcanic rocks at Shimada; the rocks are too young to be dated by potassium-argon dating, and all the evidence indicates that volcanic activity at Shimada is of late

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ...

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...

age. Possibly alive '' Lithothamnium''

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 have been

dredged Dredging is the excavation of material from a water environment. Possible reasons for dredging include improving existing water features; reshaping land and water features to alter drainage, navigability, and commercial use; constructing da ...

from a depth of at Shimada. Shimada Seamount is named for the American

fisheries scientist Fisheries science is the academic discipline of managing and understanding fisheries. It is a multidisciplinary science, which draws on the disciplines of limnology, oceanography, freshwater biology, marine biology, meteorology, conservation, ...

Bell M. Shimada Bell M. Shimada (January 17, 1922 - June 2, 1958) was an American fisheries scientist. He is noted for his study during the 1950s of tuna stocks in the tropical Pacific Ocean and its important effect on the development of the post-World War II tu ...

(1922–1958). It has been known under a variety of names throughout its history, including Shimada Bank, Shamada Seamount, Hurricane Bank and Allaire Bank.

References

Sources

External links

earthref.org Seamount Catalog: Shimada Seamount
{{Authority control Seamounts of the Pacific Ocean Quaternary volcanoes Undersea banks of the Pacific Ocean

See also

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External links