Mid-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.[1] About 50 seamounts are distributed over the MPM.[2] 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.[3]

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.[4] In the Cretaceous, they formed large tropical islands located closer to the Equator that began to sink in the late Mesozoic.[5]

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.[6] 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[7] and Darwin Guyot.[8]

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.[9] 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.

Mid-Pacific Mountains is located in 100x100
Shatsky Rise
Hawaiian–Emperor seamount chain
Hess Rise
Mid-Pacific Mountains
Location

Sources

Notes

  1. ^ Thiede et al. 1981, Morphology, Age, Plate-Tectonic Setting, and Previous Studies, pp. 1073–1074
  2. ^ Menard 1959, p. 206
  3. ^ Wilde 2010, Abstract
  4. ^ Kroenke, Kellogg & Nemoto 1985, Abstract
  5. ^ Thiede et al. 1981, Abstract
  6. ^ Winterer & Metzler 1984, Abstract
  7. ^ Winterer et al. 1995, Origin and Formation of Igneous Basement, pp. 508–509
  8. ^ Ladd, H.S.; Newman, W.A.; Sohl, N.F. (1974). Cameron, A.M.; Cambell, B.M.; Cribb, A.B.; Endean, R.; Jell, J.S.; Jones, O.A.; Mather, P.; Talbot, F.H. (eds.). Darwin guyot, the Pacific's oldest atoll (PDF). Second International Coral Reef Symposium. 2. Brisbane, Australia: The Great Barrier Reef Committee. p. 513.
  9. ^ Clouard & Bonneville 2001, Easter, p. 696

Sources

2018 in arthropod paleontology

This list of fossil arthropods described in 2018 is a list of new taxa of trilobites, fossil insects, crustaceans, arachnids and other fossil arthropods of every kind that were described during the year 2018, as well as other significant discoveries and events related to arthropod paleontology that are scheduled to occur in the year 2018.

Alexa Bank

Alexa Bank is a seamount in Samoa, northwest of Rotuma. The seamount reaches a depth of 18–21 metres (59–69 ft) below sea level and has the appearance of an atoll with a flat top and steep slopes. Some active coral growth takes place at its top, but if it ever was an active atoll it has now drowned. It was probably formed by the Samoa hotspot 24 million years ago, although older volcanism about 40 million years ago has also been identified.

Allison Guyot

Allison Guyot (formerly known as Navoceano Guyot) is a tablemount (guyot) in the underwater Mid-Pacific Mountains of the Pacific Ocean. It is a trapezoidal flat mountain rising 1,500 metres above the seafloor to a depth of less than 1,500 m, with a summit platform 35 by 70 kilometres wide. The Mid-Pacific Mountains lie west of Hawaii and northeast of the Marshall Islands, but at the time of their formation were located in the Southern Hemisphere.

The tablemount was probably formed by a hotspot in the present-day Southern Pacific before plate tectonics moved it to its current location. Several hotspots, including the Easter, Marquesas and Society hotspots, may have been involved in the formation of the Mid-Pacific Mountains. Volcanic activity is dated to have occurred circa 111–85 million years ago and formed a volcanic island. Subsequently, carbonate deposition commenced as Allison Guyot subsided and eventually buried the island, forming an atoll-like structure and a carbonate platform. Among other animals, crocodilians lived on Allison Guyot.

The platform emerged above sea level during the Albian and Turonian ages. It drowned about 99 ± 2 million years ago for unknown reasons; possibly a phase of renewed emergence damaged the reefs, or it was located in unfavourable waters. Later, pelagic sedimentation commenced on the seamount and led to the deposition of sediments including limestone, ooze and sand, which bear traces of climatic events and ocean currents.

Cape Johnson Guyot

Cape Johnson Guyot is a guyot in the Pacific Ocean, more precisely in the Mid-Pacific Mountains, and the type locality of guyots. It is of middle Cretaceous age and a number of fossils have been dredged from it.

Darwin Guyot

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.

Darwin Rise

The Darwin Rise is broad triangular region in the north central Pacific Ocean where there is a concentration of atolls.

During his voyage across the globe Charles Darwin realised that vertical crustal motion must be responsible for the formation of continents and ocean basins, as well as isolated atolls in the Pacific. He deduced that the central basin of the Pacific had subsided while surrounding areas had risen. In 1964 U.S. geologist Henry Menard subsequently named the uplifted area in the Pacific after the English naturalist.

Horizon Guyot

Horizon Guyot is a presumably Cretaceous guyot (tablemount) in the Mid-Pacific Mountains, Pacific Ocean. It is an elongated ridge, over 300 kilometres (190 mi) long and 4.3 kilometres (2.7 mi) high, that stretches in a northeast-southwest direction and has two flat tops; it rises to a minimum depth of 1,443 metres (4,730 ft). The Mid-Pacific Mountains lie west of Hawaii and northeast of the Line Islands.

It was probably formed by a hotspot, but the evidence is conflicting. Volcanic activity occurred during the Turonian-Cenomanian eras 100.5–89.8 million years ago and another stage has been dated to have occurred 88–82 million years ago. Between these volcanic episodes, carbonate deposition from lagoonal and reefal environments set in and formed limestone. Volcanic islands developed on Horizon Guyot as well and were colonised by plants.

Horizon Guyot became a seamount during the Coniacian-Campanian period. Since then, pelagic ooze has accumulated on the seamount, forming a thick layer that is further modified by ocean currents and by various organisms that live on the seamount; sediments also underwent landsliding. Ferromanganese crusts were deposited on exposed rocks.

Magellan Rise (ocean plateau)

Magellan Rise is an oceanic plateau in the Pacific Ocean, which covers a surface area of 500,000 square kilometres (190,000 sq mi). There is another "Magellan Rise" west from the Marshall Islands as well.The Magellan Rise has been called a large igneous province by Coffin and Endholm 2001 and was emplaced 145 million or 135-128 million years ago, possibly as a consequence of intense volcanism at a former triple junction. Alternatively, the Rise was formed by a mantle plume. Candidate mantle plumes are the Easter hotspot and the Foundation hotspot.The volume of rocks in the Magellan Rise is about 1,800,000 cubic kilometres (430,000 cu mi)-19,740,000 cubic kilometres (4,740,000 cu mi). It apparently developed first on the Phoenix Plate before being transferred onto the Pacific Plate 125 million years ago. The Magellan Rise never rose to shallow depths at least since the Cretaceous, and the Rise is covered by sediments of Tithonian/Berriasian to Quaternary age.

Mid-Pacific Institute

Mid-Pacific Institute is a private, co-educational college preparatory school for grades preschool through twelve with an approximate enrollment of 1,550 students, the majority of whom are from Hawaii (although many also come from other states and other countries, such as Japan, Korea, China, Canada, Australia, Marshall Islands and countries in Europe and Africa). The school offers programs of study in the International Baccalaureate Diploma Programme and the Mid-Pacific School of the Arts (MPSA). Mid-Pacific Institute is located on 38 acres (150,000 m2) in Manoa, near the University of Hawaii, close to downtown Honolulu.

NOAAS Okeanos Explorer

NOAAS Okeanos Explorer (R 337) is a converted United States Navy ship (formerly USNS Capable (T-AGOS-16)), now an exploratory vessel for the National Oceanic and Atmospheric Administration (NOAA), officially launched in 2010. Starting in 2010, NOAA entered into a five-year partnership with the San Francisco Exploratorium. The focus is on gathering scientific information about oceans for the public as well as for scientific uses. As much as 95% of the ocean remains unexplored, NOAA officials said. The ship is equipped with cameras and will provide real-time viewing of the ocean floor for scientists and for the public.This is a pioneering use of what NOAA calls "telepresence technology". The Okeanos Explorer is the only vessel owned by the U.S. government that is dedicated to exploring the seabed and ocean crust. The ship is named after Okeanos, the Ancient Greek god of the sea, from which also comes the word "ocean".

Oceanic plateau

An oceanic or submarine plateau is a large, relatively flat elevation that is higher than the surrounding relief with one or more relatively steep sides.There are 184 oceanic plateaus covering an area of 18,486,600 km2 (7,137,700 sq mi), or about 5.11% of the oceans. The South Pacific region around Australia and New Zealand contains the greatest number of oceanic plateaus (see map).

Oceanic plateaus produced by large igneous provinces are often associated with hotspots, mantle plumes, and volcanic islands — such as Iceland, Hawaii, Cape Verde, and Kerguelen. The three largest plateaus, the Caribbean, Ontong Java, and Mid-Pacific Mountains, are located on thermal swells. Other oceanic plateaus, however, are made of rifted continental crust, for example Falkland Plateau, Lord Howe Rise, and parts of Kerguelen, Seychelles, and Arctic ridges.

Plateaus formed by large igneous provinces were formed by the equivalent of continental flood basalts such as the Deccan Traps in India and the Snake River Plain in the United States.

In contrast to continental flood basalts, most igneous oceanic plateaus erupt through young and thin (6–7 km (3.7–4.3 mi)) mafic or ultra-mafic crust and are therefore uncontaminated by felsic crust and representative for their mantle sources.

These plateaus often rise 2–3 km (1.2–1.9 mi) above the surrounding ocean floor and are more buoyant than oceanic crust. They therefore tend to withstand subduction, more-so when thick and when reaching subduction zones shortly after their formations. As a consequence, they tend to "dock" to continental margins and be preserved as accreted terranes. Such terranes are often better preserved than the exposed parts of continental flood basalts and are therefore a better record of large-scale volcanic eruptions throughout Earth's history. This "docking" also means that oceanic plateaus are important contributors to the growth of continental crust. Their formations often had a dramatic impact on global climate, such as the most recent plateaus formed, the three, large, Cretaceous oceanic plateaus in the Pacific and Indian Ocean: Ontong Java, Kerguelen, and Caribbean.

Outline of oceanography

The following outline is provided as an overview of and introduction to Oceanography.

Resolution Guyot

Resolution Guyot (formerly known as Huevo) is a guyot (tablemount) in the underwater Mid-Pacific Mountains in the Pacific Ocean. It is a circular flat mountain, rising 500 metres (1,600 ft) above the seafloor to a depth of about 1,320 metres (4,330 ft), with a 35 kilometres (22 mi) wide summit platform. The Mid-Pacific Mountains lie west of Hawaii and northeast of the Marshall Islands, but at the time of its formation the guyot was located in the Southern Hemisphere.

The guyot was probably formed by a hotspot in today's French Polynesia before plate tectonics shifted it to its present-day location. The Easter, Marquesas, Pitcairn and Society hotspots, among others, may have been involved in the formation of Resolution Guyot. Volcanic activity has been dated to have occurred 107–129 million years ago and formed a volcanic island that was subsequently flattened by erosion. Carbonate deposition commenced, forming an atoll-like structure and a carbonate platform.

The platform emerged above sea level at some time between the Albian and Turonian ages before eventually drowning for reasons unknown between the Albian and the Maastrichtian. Thermal subsidence lowered the drowned seamount to its present depth. After a hiatus, sedimentation commenced on the seamount and led to the deposition of manganese crusts and pelagic sediments, some of which were later modified by phosphate.

Shatsky Rise

The Shatsky Rise is Earth's third largest oceanic plateau, (after Ontong Java and Kerguelen) located in the north-west Pacific Ocean 1,500 km (930 mi) east of Japan. It is one of a series of Pacific Cretaceous large igneous provinces (LIPs) together with Hess Rise, Magellan Rise, and Ontong Java-Manihiki-Hikurangi.

It was named for Nikolay Shatsky (1895-1960), a Soviet geologist, expert in tectonics of ancient platforms.

The rise consists of three large volcanic massifs, Tamu, Ori, and Shirshov, but, in contrast, there are few traces of magmatism on the surrounding ocean floor. Tamu Massif is likely the largest volcano yet discovered on Earth. In 2016, a study found that Tamu Massif covered the entire Shatsky Rise, meaning that the volcano had a surface area of 533,000 square kilometres (206,000 sq mi), surpassing Olympus Mons in terms of surface area.

Takuyo-Daisan

Takuyo-Daisan is a guyot in the Western Pacific Ocean off Japan. It is 1,409 metres (4,623 ft) deep and has a square-shaped flat top surrounded by a perimeter ridge. Several other seamounts lie nearby.

The seamount formed as a volcanic island during the Cretaceous in the area currently occupied by French Polynesia. Subsequently reefs developed around the volcanic island and generated a carbonate platform which drowned during the Albian along with several other such platforms in the world.

Mid-Pacific Mountains
The main group
Individual guyots

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