Mid-Pacific Mountains

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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.

Oceanic plateau Relatively flat submarine region that rises well above the level of the ambient seabed

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.

Hawaiian–Emperor seamount chain A mostly undersea mountain range in the Pacific Ocean that reaches above sea level in Hawaii.

The Hawaiian–Emperor seamount chain is a mostly undersea mountain range in the Pacific Ocean that reaches above sea level in Hawaii. It is composed of the Hawaiian ridge, consisting of the islands of the Hawaiian chain northwest to Kure Atoll, and the Emperor Seamounts: together they form a vast underwater mountain region of islands and intervening seamounts, atolls, shallows, banks and reefs along a line trending southeast to northwest beneath the northern Pacific Ocean. The seamount chain, containing over 80 identified undersea volcanoes, stretches over 5,800 kilometres (3,600 mi) from the Aleutian Trench in the far northwest Pacific to the Loʻihi seamount, the youngest volcano in the chain, which lies about 35 kilometres (22 mi) southeast of the Island of Hawaiʻi.

Pacific Plate An oceanic tectonic plate under the Pacific Ocean

The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres (40,000,000 sq mi), it is the largest tectonic plate.


The ocean floor of the MPM dates back to the Jurassic-Cretaceous, some of the oldest oceanic crust on Earth. [3]

Oceanic crust The uppermost layer of the oceanic portion of a tectonic plate

Oceanic crust is the uppermost layer of the oceanic portion of a tectonic plate. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic cumulates. The crust overlies the solidified and uppermost layer of the mantle. The crust and the solid mantle layer together constitute oceanic lithosphere.

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]

Guyot An isolated, flat-topped underwater volcano mountain

In marine geology, a guyot, also known as a tablemount, is an isolated underwater volcanic mountain (seamount) with a flat top more than 200 m (660 ft) below the surface of the sea. The diameters of these flat summits can exceed 10 km (6.2 mi). Guyots are most commonly found in the Pacific Ocean, but they have been identified in all the oceans except the Arctic Ocean.

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]

Hotspot (geology) Volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle

In geology, the places known as hotspots or hot spots are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle. Their position on the Earth's surface is independent of tectonic plate boundaries. There are two hypotheses that attempt to explain their origins. One suggests that hotspots are due to mantle plumes that rise as thermal diapirs from the core–mantle boundary. The other hypothesis is that lithospheric extension permits the passive rising of melt from shallow depths. This hypothesis considers the term "hotspot" to be a misnomer, asserting that the mantle source beneath them is, in fact, not anomalously hot at all. Well-known examples include the Hawaii, Iceland and Yellowstone hotspots.

Superswell A large area of anomalously high topography and shallow ocean regions

A superswell is a large area of anomalously high topography and shallow ocean regions. These areas of anomalous topography are byproducts of large upwelling of mantle material from the core–mantle boundary, referred to as superplumes. Two present day superswells have been identified: the African superswell and the South Pacific superswell. In addition to these, the Darwin Rise in the south central Pacific Ocean is thought to be a paleosuperswell, showing evidence of being uplifted compared to surrounding ancient ocean topography.

Allison Guyot Seamount in the Pacific Ocean

Allison 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, 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 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.

Easter hotspot

The Easter hotspot is a volcanic hotspot located in the southeastern Pacific Ocean. The hotspot created the Sala y Gómez Ridge which includes Easter Island and the Pukao Seamount which is at the ridge's young western edge. Easter Island, because of its tectonomagmatic features, represents an end-member type of hotspot volcano in this chain.

Line Islands Chain of eleven atolls and low coral islands in the central Pacific Ocean

The Line Islands, Teraina Islands or Equatorial Islands, is a chain of atolls and coral islands. Kingman Reef is largely submerged and Filippo Reef is shown on some maps, although its existence is doubted. The islands were formed by volcanic activity and are located in the central Pacific Ocean, south of the Hawaiian Islands. The 11 islands stretch for 2,350 kilometres in a northwest–southeast direction, making it one of the longest island chains of the world. Eight of the islands form part of Kiribati, while the remaining three are United States territories grouped with the United States Minor Outlying Islands. Only Kiritimati and Tabuaeran atolls and Teraina Island have a permanent population.

Pacific-Farallon Ridge A spreading ridge during the late Cretaceous that separated the Pacific Plate to the west and the Farallon Plate to the east

The Pacific-Farallon Ridge was a spreading ridge during the late Cretaceous that extended 10,000 km in length and separated the Pacific Plate to the west and the Farallon Plate to the east. It ran south from the Pacific-Farallon-Kula triple junction at 51°N to the Pacific-Farallon-Antarctic triple junction at 43°S. As the Farallon Plate subducted obliquely under the North American Plate, the Pacific-Farallon Ridge approached and eventually made contact with the North American Plate about 30 million years ago. On average, this ridge had an equatorial spreading rate of 13.5 cm per year until its eventual collision with the North American Plate. In present day, the Pacific-Farallon Ridge no longer formally exists since the Farallon Plate has been broken up or subducted beneath the North American Plate, and the ridge has segmented, having been mostly subducted as well. The most notable remnant of the Pacific-Farallon Ridge is the 4000 km Pacific-Nazca segment of the East Pacific Rise.



  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. (Subscription required (help)).
  9. Clouard & Bonneville 2001 , Easter, p. 696


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Resolution Guyot

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Horizon Guyot

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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.


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Vlinder Guyot

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