Darwin Guyot is a volcanic underwater mountain top, or guyot, in the Mid-Pacific Mountains between the Marshall Islands and Hawaii. Named after Charles Darwin, it rose above sea level more than 118 million years ago during the early Cretaceous period to become an atoll, developed rudist reefs, and then drowned, perhaps as a consequence of sea level rise. The flat top of Darwin Guyot now rests 1,266 metres (4,154 ft) below sea level.
|Summit depth||1,266 metres (4,154 ft)|
The name Darwin Guyot was proposed in 1970 and accepted by the Board on Geographic Names shortly thereafter; it refers to Charles Darwin and the fact that unlike other guyots in the region it resembles an atoll. On the second voyage of the Beagle, in the 1830s, Darwin had theorised that as land rose, oceanic islands sank, and coral reefs round them grew to form atolls. It was dredged and surveyed in 1968 by the ship R/V Alexander Agassiz; previously in the same year the R/V Argo had crossed over the guyot.
Darwin Guyot lies between Hawaii and the Marshall Islands, within the submerged Mid-Pacific Mountains. Agassiz Guyot and Allison Guyot lie to its east-southeast. These underwater mountains as well as abovewater atolls concentrate in the Western Pacific Ocean. Darwin Guyot may be part of a hotspot trail.
It lies at a depth of 1,285 metres (4,216 ft)-1,266 metres (4,154 ft) and has an elongated, northwest-southeast trending shape; an older survey had indicated a more rounded shape. The summit features an elevated rim which is probably a former fringing reef surrounding an internal lagoon like a bucket; this resembles the structure of present-day atolls and it is the first guyot in the Pacific Ocean that was discovered to have this atoll-like structure. This 18 metres (59 ft) deep depression may be a volcanic crater but the more likely explanation is that the rim was formed by living organisms. The whole summit plateau covers an area of 5 by 8 kilometres (3.1 mi × 5.0 mi) and the total volume of the seamount is about 2,287 cubic kilometres (549 cu mi).
Dredging has yielded no volcanic material, but chert, limestones (in the form of grainstone, packstone and wackestone) encrusted with ferromanganese as well as living animals were pulled up. The seafloor underneath the guyot lies at a depth of 5,250 metres (17,220 ft) and has an age of 157 million years.
Darwin Guyot is considered to be of Cretaceous origin; its age exceeds 118 million years and its history might go back to the Cretaceous subdivision "Barremian". It probably started as an emergent volcanic island that was then levelled by erosion. On the resulting platform molluscs such as rudists became established. They formed the rim as well as the irregular mounds on the summit plateau. Darwin Guyot is considered to be the oldest known atoll.
Dredging has produced fossils of animals, chiefly gastropods and rudists. Fish remnants, coral debris, and foraminifera of Albian to Turonian age have also been found. Rudists formed organic frameworks resembling coral reefs on Darwin Guyot and elsewhere in Tethyan seas during the Albian-Aptian eras. Other environments such as seagrass flats and lagoons have been inferred from the fossils.
The resulting carbonate platform drowned about 100 million years ago, or at the time of the Cenomanian-Turonian boundary event (94 million years ago). It is not clear why the reefs on Darwin Guyot eventually ceased growing; one possibility is that sea levels rose quickly enough to overwhelm the ability of the reef forming organisms to keep up. Unlike other guyots, Darwin Guyot did not accumulate a substantial cap of pelagic sediments after drowning; perhaps it is too small to accumulate a substantial sediment layer or sedimentation took place but ocean currents swept the sediment off the platform. Presently, fish such as snubnosed eels occur at Darwin Guyot.
The Pacific Ocean evolved in the Mesozoic from the Panthalassic Ocean, which had formed when Rodinia rifted apart around 750 Ma. The first ocean floor which is part of the current Pacific Plate began 160 Ma to the west of the central Pacific and subsequently developed into the largest oceanic plate on Earth.The tectonic plates continue to move today. The slowest spreading ridge is the Gakkel Ridge on the Arctic Ocean floor, which spreads at less than 2.5 cm/year (1 in/year), while the fastest, the East Pacific Rise near Easter Island, has a spreading rate of over 15 cm/year (6 in/year).List of things named after Charles Darwin
Several places, concepts, institutions, and things are namesakes of the English biologist Charles Darwin:
PlacesCharles Darwin National Park
Charles Darwin Foundation
Charles Darwin Research Station
Charles Darwin University
Darwin College, Cambridge
Darwin, Falkland Islands
Darwin, Northern Territory
Darwin Glacier (California)
Darwin Guyot, a seamount in the Pacific Ocean
Darwin Island, Galapagos Islands
Darwin Island (Antarctica)
Darwin Sound (Canada)
Mount Darwin (California)
Mount Darwin (Tasmania)Things named after Darwin in relation to his Beagle voyageCordillera Darwin
Mount Darwin (Andes)Scientific names of organismsSome 250 species and several higher groups bear Darwin's name; most are insects.
Darwinilus, a rove beetle
Darwinius, an extinct primate
Darwinopterus, a genus of pterosaur
Darwinula, a genus of seed shrimp
Darwinivelia, a water treader genus
Darwinysius, a seed bug
Darwinomya, a genus of flies
Darwinella, a sponge genus
Darwinsaurus, a dinosaur
Darwinhydrus, a diving beetle
darwini (multiple species)
darwinii (multiple species)
Ingerana charlesdarwini, a frogPhilosophiesDarwinism
Social DarwinismOtherDarwin, a unit of evolutionary change
Darwin, an operating system
Darwin (ESA) (a proposed satellite system)
Division of Darwin, a former electoral division in Australia
1991 Darwin, a stony Florian asteroid
Darwin (lunar crater) a lunar crater
Darwin (Martian crater) a martian craterMid-Pacific Mountains
The Mid-Pacific Mountains (MPM) is a large oceanic plateau located in the central North Pacific Ocean or south of the Hawaiian–Emperor seamount chain. Of volcanic origin and Mesozoic in age, it is located on the oldest part of the Pacific Plate and rises up to 2 km (1.2 mi) (Darwin Rise) above the surrounding ocean floor and is covered with several layers of thick sedimentary sequences that differ from those of other plateaux in the North Pacific. About 50 seamounts are distributed over the MPM. Some of the highest points in the range are above sea level which include Wake Island and Marcus Island.
The ocean floor of the MPM dates back to the Jurassic-Cretaceous, some of the oldest oceanic crust on Earth.The MPM is a range of guyots with a lava composition similar to those found in Iceland and the Galapagos Islands, and they probably formed similarly at or near a rift system.
In the Cretaceous, they formed large tropical islands located closer to the Equator that began to sink in the late Mesozoic.The MPM formed in the Early Cretaceous (at c. 110 Ma) over a hotspot that uplifted the ocean floor of the still young Pacific Plate. Reefs developed on the subsiding islands and renewed volcanism in the Late Cretaceous helped maintain some of eastern islands but inevitably the guyots sank to their present depth.
It has been proposed that the MPM has crossed over several hotspots, and the MPM guyots are indeed older on the western MPM than the eastern part, but the guyots do not form chains that can be traced to any known hotspots. The MPM, nevertheless, must have originated over the South Pacific Superswell. Among the guyots in the Mid-Pacific Mountains are Allison Guyot, Horizon Guyot, Resolution Guyot and Darwin Guyot.The western half of the Easter hotspot chain, a lineament that includes the Line Islands and Tuamotu archipelago, begins near the eastern part of the MPM. The formation of the MPM thus probably occurred at the Pacific-Farallon Ridge and the Easter hotspot, or where the Easter Microplate is now located.Outline of oceanography
The following outline is provided as an overview of and introduction to Oceanography.
|The main group|