Shatsky Rise

The Shatsky Rise is Earth's third largest oceanic plateau,[1] (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.[2] 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.[3] Tamu Massif is likely the largest volcano yet discovered on Earth.[4] 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.[5]

Location of Shatsky Rise
Shatsky Rise
Hess Rise
Emperor Seamounts Chain
Hawaiian Ridge
Mid-Pacific Mts
Japan
Kamchatka
Shatsky Rise
Hess Rise
Emperor Seamounts Chain
Hawaiian Ridge
Mid-Pacific Mts
Japan
Kamchatka
EmperorSeamounts
Location of Shatsky Rise
EmperorSeamounts

Extent and volume

It covers an area that has been estimated to c. 480,000 km2 (190,000 sq mi) (roughly the size of California or Sumatra) and a volume of c. 4,300,000 km3 (1,000,000 cu mi).[6] Beneath Shatsky rise, however, the Mohorovičić discontinuity (Moho, the mantle-crust boundary) disappears at a depth of 20 km (12 mi) whereas it is normally observed at a depth of 17 km (11 mi). Furthermore, the crustal thickness between the massifs of the Shatsky Rise is almost twice that of normal crust thickness. This considered, the area covered by the rise, assuming the crust was also formed by the Shatsky Rise volcanism, has been estimated to 533,000 km2 (206,000 sq mi) and the volume to 6,900,000 km3 (1,700,000 cu mi).[7]

Subsidence

After its formation Shatsky Rise was uplifted 2,500–3,500 m (8,200–11,500 ft) and it then subsided 2,600–3,400 m (8,500–11,200 ft), which, in both cases, is considerably more than in the case the Ontong-Java Plateau. There was least subsidence at the centre of the Tamu Massif (c. 2,600 m (8,500 ft)), subsidence increased at the northern flank of the Tamu Massif and at the Ori Massif (c. 3,300 m (10,800 ft)), and it becomes greatest at the flank of Ori Massif. The cause of this gradual increase in subsidence can be underplating beneath Tamu Massif. There was much less subsidence at Shirshov Massif farther north (c. 2,900 m (9,500 ft)) which probably represents a later, different phase of volcanism.[8]

Origin controversy

Scientific studies of the size, shape, and eruption rate of the Shatsky Rise have concluded that the rise originated from a mantle plume, whereas studies of magnetic lineations and plate tectonic reconstructions have shown that it must have originated near a triple junction and drifted up to 2,000 km (1,200 mi) during the Early Cretaceous (140–100 Ma). A 2016 study concluded that the Tamu Massif formed at a mid-ocean ridge that interacted with a plume head and that the Ori Massif formed off-axis probably from a plume tail.[9]

Shatsky Rise formed at a triple junction, but the thickness of the plateau coupled with the depth and intensity of melting is different from those of MORB (mid-ocean ridge basalt), making a recycled mantle slab a more likely source. A decrease in magma volume with time is more consistent with the involvement of a mantle plume.[10]

Tectonic history

It formed during the Late Jurassic and Early Cretaceous at the PacificFarallonIzanagi triple junction, probably making it the oldest unaltered ocean plateau. Because this occurred before the so-called Cretaceous silent period, a long period without magnetic reversals, its formation can be precisely dated.[6] Magnetic lineations on and surrounding Shatsky Rise range from M21 (147 Ma) at the south-western edge to M1 (124 Ma) at the northern tip.[3]

The Shatsky Rise LIP erupted at the location of the Pacific–Farallon–Izanagi triple junction c. 147–143 Ma either because a mantle plume reached the surface or because of decompression melting at a mid-ocean ridge. The eruption coincided with a 800 km (500 mi), nine-stage jump in the location of the triple junction and a configuration change from ridge-ridge-ridge to ridge-ridge-transform.[11]

A set of magnetic lineations, called the Hawaiian lineations, between Shatsky Rise, Hess Rise, and the Mid-Pacific Mountains, formed during the spreading between the Pacific and Farallon plates 156–120 Ma. North of Shatsky Rise the so-called Japanese lineations are oriented in another direction and the differences in orientations trace the path of the Pacific–Farallon–Izanagi triple junction.[11]

The triple junction moved north-west before M22 (150 Ma) after-which it started to reorganise, a microplate formed and the triple junction made an 800 km (500 mi) eastward jump to the oldest part of the rise, the TAMU Massif. The remainder of Shatsky Rise formed before M3 (126 Ma) along the trace of the triple junction. Shaktsky volcanism was episodic and tied to at least nine ridge jumps from this episode.[3]

The volume of the rise decreases along the trace of the triple junction. The TAMU Massif at the southern end has an estimated volume of 2,500,000 km3 (600,000 cu mi) whereas both ORI and Shirshov (136 Ma) attained 700,000 km3 (170,000 cu mi). Papanin Ridge, the north end of the rise, has a volume of 400,000 km3 (96,000 cu mi) but was probably emplaced over a longer period (131–124 Ma).[3]

The conjugates of the Shatsky and Hess rises on the Farallon Plate were most likely involved in the Laramide orogeny; the former subducted beneath North America and the latter below northern Mexico.[12]

References

Notes

  1. ^ Geldmacher et al. 2014, Geological background and Exp. 324 drilling results, p. 1
  2. ^ Ingle et al. 2007, Fig. 1a, p. 595
  3. ^ a b c d Sager 2005, Tectonic History, pp. 725–726
  4. ^ Sager et al. 2013, Abstract
  5. ^ Stephen Chen (24 March 2016). "Tamu Massif even more massive: world's largest volcano almost same size as Japan, widest in solar system". South China Morning Post. Retrieved 2 July 2019.
  6. ^ a b Sager 2005, Introduction, pp. 720–721
  7. ^ Zhang, Sager & Korenaga 2016, Abstract; Conclusions, p. 152
  8. ^ Shimizu et al. 2013, Subsidence of Shatsky Rise, pp. 42–43; Conclusions, pp. 43–44
  9. ^ Li et al. 2016, Discussion and conclusions, pp. 575–576; Fig. 11, p. 577
  10. ^ Heydolph et al. 2014, Conclusions, pp. 58–59; Geldmacher et al. 2014, Abstract
  11. ^ a b Seton et al. 2012, p. 228; Fig. 6, p. 227
  12. ^ Liu et al. 2010, Abstract

Sources

Coordinates: 32°02′00″N 158°04′00″E / 32.0333°N 158.0667°E

Anoxic event

Oceanic anoxic events or anoxic events (anoxia conditions) were intervals in the Earth's past where portions of oceans became depleted in oxygen (O2) at depths over a large geographic area. During some of these events, euxinia, waters that contained hydrogen sulfide, H2S, developed. Although anoxic events have not happened for millions of years, the geological record shows that they happened many times in the past. Anoxic events coincided with several mass extinctions and may have contributed to them. These mass extinctions include some that geobiologists use as time markers in biostratigraphic dating. Many geologists believe oceanic anoxic events are strongly linked to slowing of ocean circulation, climatic warming, and elevated levels of greenhouse gases. Researchers have proposed enhanced volcanism (the release of CO2) as the "central external trigger for euxinia".

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.

Farallon Plate

The Farallon Plate was an ancient oceanic plate that began subducting under the west coast of the North American Plate—then located in modern Utah—as Pangaea broke apart during the Jurassic period. It is named for the Farallon Islands, which are located just west of San Francisco, California.

Over time, the central part of the Farallon Plate was completely subducted under the southwestern part of the North American Plate. The remains of the Farallon Plate are the Juan de Fuca, Explorer and Gorda Plates, subducting under the northern part of the North American Plate; the Cocos Plate subducting under Central America; and the Nazca Plate subducting under the South American Plate.The Farallon Plate is also responsible for transporting old island arcs and various fragments of continental crustal material rifted off from other distant plates and accreting them to the North American Plate.

These fragments from elsewhere are called terranes (sometimes, "exotic" terranes). Much of western North America is composed of these accreted terranes.

Glacial period

A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate between glacial periods. The last glacial period ended about 15,000 years ago. The Holocene epoch is the current interglacial. A time with no glaciers on Earth is considered a greenhouse climate state.

Integrated Ocean Drilling Program

The Integrated Ocean Drilling Program (IODP) was an international marine research program. The program used heavy drilling equipment mounted aboard ships to monitor and sample sub-seafloor environments. With this research, the IODP documented environmental change, Earth processes and effects, the biosphere, solid earth cycles, and geodynamics.The program began a new 10-year phase with the International Ocean Discovery Program, from the end of 2013.

List of shield volcanoes

This list of shield volcanoes includes active, dormant and extinct shield volcanoes.

Shield Volcanoes are one of the three types of volcanoes. They have a short cone shape, and have basaltic lava which means the lava has low viscosity (viscosity is a measure of the ability for a liquid to flow)

List of submarine topographical features

This is a list of submarine topographical features, oceanic landforms and topographic elements.

List of volcanoes in the Pacific Ocean

A list of active and extinct volcanoes in the Pacific Ocean.

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.

Mauna Loa

Mauna Loa ( or ; Hawaiian: [ˈmɐwnə ˈlowə]; English: Long Mountain) is one of five volcanoes that form the Island of Hawaii in the U.S. state of Hawaiʻi in the Pacific Ocean. The largest subaerial volcano in both mass and volume, Mauna Loa has historically been considered the largest volcano on Earth, dwarfed only by Tamu Massif. It is an active shield volcano with relatively gentle slopes, with a volume estimated at approximately 18,000 cubic miles (75,000 km3), although its peak is about 125 feet (38 m) lower than that of its neighbor, Mauna Kea. Lava eruptions from Mauna Loa are silica-poor and very fluid, and they tend to be non-explosive.

Mauna Loa has probably been erupting for at least 700,000 years, and may have emerged above sea level about 400,000 years ago. The oldest-known dated rocks are not older than 200,000 years. The volcano's magma comes from the Hawaii hotspot, which has been responsible for the creation of the Hawaiian island chain over tens of millions of years. The slow drift of the Pacific Plate will eventually carry Mauna Loa away from the hotspot within 500,000 to one million years from now, at which point it will become extinct.

Mauna Loa's most recent eruption occurred from March 24 to April 15, 1984. No recent eruptions of the volcano have caused fatalities, but eruptions in 1926 and 1950 destroyed villages, and the city of Hilo is partly built on lava flows from the late 19th century. Because of the potential hazards it poses to population centers, Mauna Loa is part of the Decade Volcanoes program, which encourages studies of the world's most dangerous volcanoes. Mauna Loa has been monitored intensively by the Hawaiian Volcano Observatory since 1912. Observations of the atmosphere are undertaken at the Mauna Loa Observatory, and of the Sun at the Mauna Loa Solar Observatory, both located near the mountain's summit. Hawaii Volcanoes National Park covers the summit and the southeastern flank of the volcano, and also incorporates Kīlauea, a separate volcano.

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. 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.

Nikolay Shatsky

Nikolay Sergeyevich Shatsky (Nicholas Shatski, Russian: Николай Серге́евич Шатский) (August 28 [O.S. August 16] 1895 in Moscow – August 1, 1960 in Moscow) was a Soviet geologist, an expert in tectonics of ancient platforms.Shatsky Rise, an oceanic plateau in North Pacific is named after him.

Since 1982 the USSR Academy of Sciences/Russian Academy of Sciences has awarded the annual Shatsky Prize (ru:Премия имени Н. С. Шатского) for achievements in tectonics.

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.

Orstenoloricus

Orstenoloricus is a loriciferan larva, presumably from the stem group, preserved by early three-dimensional mineralization in an orsten-type setting in the mid-Cambrian of Australia. It somewhat resembles the larva of the unusual loriciferan Tenuiloricus.

Paleocene

The Paleocene, ( PAL-ee-ə-seen, -⁠ee-oh-, PAY-lee-, -⁠lee-oh-) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name derives from the combining of the Ancient Greek palæo- meaning "old" and the Eocene Epoch (which succeeds the Paleocene), translating to "the old part of the Eocene".

The epoch is bracketed by two major events in Earth's history: the K-Pg extinction event and the Paleocene–Eocene thermal maximum. The K-Pg extinction event, brought on by an asteroid impact and an ensuing impact winter, marked the beginning of the Paleocene and killed off 75% of life on Earth, most famously the non-avian dinosaurs. The end of the epoch was marked by the Paleocene–Eocene thermal maximum, which was a major climatic event wherein about 2,500–4,500 gigatons of carbon was released into the atmosphere and ocean systems en masse, causing a spike in global temperatures and ocean acidification.

The Paleocene continued many geological processes initiated in Mesozoic, and the continents continued moving towards their present positions. The Northern Hemisphere continents were still connected via some land bridges as well as the Southern Hemisphere continents, the Rocky Mountains were being uplifted, the Americas had not yet joined, and the Indian Plate had begun its collision with Asia. In the oceans, the thermohaline circulation probably was much different than it is today, with downwellings occurring in the North Pacific rather than the North Atlantic, and water density was mainly controlled by salinity rather than temperature.

The extinction event caused a floral and faunal turnover of species, with previously abundant species being replaced by previously uncommon ones. With a global average temperature of about 24–25 °C (75–77 °F), compared to 14 °C (57 °F) in more recent times, the Earth had a greenhouse climate without permanent ice sheets at the poles. As such, there were forests worldwide–including at the poles–with low species richness in regards to plant life, populated by mainly small creatures which were rapidly evolving to take advantage of the recently-emptied Earth. Though some animals attained enormous size, most remained rather small. The forests grew quite dense in the general absence of large herbivores. Mammals proliferated in the Paleocene, and the earliest placentals and marsupials are recorded from this time, but most Paleocene taxa have ambiguous affinities. In the seas, ray-finned fish rose to dominate open ocean and reef ecosystems.

Phantom island

A phantom island is a purported island which appeared on maps for a period of time (sometimes centuries) during recorded history, but was removed from later maps after it was proven not to exist.

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.

Tamu Massif

Tamu Massif is an extinct submarine shield volcano in the northwest Pacific Ocean, with the characteristics of a hybrid between a mid-ocean ridge and a shield volcano. On 5 September 2013, researchers announced that it could be a single volcano, which if corroborated, would make Tamu Massif the largest known volcano on Earth. Tamu Massif is located in the Shatsky Rise about 1,600 km (990 mi) east of Japan. The volcano, which comprises the entire Skatsky Rise, covers an area of about 553,000 square kilometres (214,000 sq mi), making Tamu Massif the largest known volcano in the solar system, in terms of surface area. Its summit is about 1,980 m (6,500 ft) below the surface of the ocean, and its base extends to about 6.4 km (4.0 mi) deep. The volcano is about 4,460 metres (14,620 ft) tall.

William Sager, a marine geophysicist from the Department of Earth and Atmospheric Sciences at the University of Houston, began studying the volcano in about 1993 at the Texas A&M College of Geosciences. According to Sager and his team, Tamu Massif is "the biggest single shield volcano ever discovered on Earth". Other igneous features on the planet are larger, such as the Ontong Java Plateau, but it has not yet been determined if they are indeed just one volcano or rather complexes of several volcanoes.

Tenuiloricus

Tenuiloricus is a genus of loriciferans known from its larval form, and occupying an uncertain taxonomic position.

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