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 (low eruptive rate, scattered rift zones, and scarce lateral collapses), represents an end-member type of hotspot volcano in this chain.[1]

The hotspot may also be responsible for the formation of the Tuamotu Archipelago, Line Islands, and the chain of seamounts lying in between.[2]

Hotspots
The Easter hotspot is marked 7 on map.

See also

References

  1. ^ Vezzoli, Luigina; Acocella, Valerio (2009-05-01). "Easter Island, SE Pacific: An end-member type of hotspot volcanism". GSA Bulletin. 121 (5–6): 869–886. Bibcode:2009GSAB..121..869V. doi:10.1130/B26470.1. ISSN 0016-7606.
  2. ^ W. J. Morgan (1971). "Convection Plumes in the Lower Mantle". Nature. 230 (5288): 42. Bibcode:1971Natur.230...42M. doi:10.1038/230042a0.

External links

  • Haase, Karsten M.; Peter Stoffers; C. Dieter Garbe-Schönberg (October 1997). "The Petrogenetic Evolution of Lavas from Easter Island and Neighbouring Seamounts, Near-ridge Hotspot Volcanoes in the SE Pacific". Journal of Petrology. 38 (6): 785–813. doi:10.1093/petrology/38.6.785.
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.

Crough Seamount

Crough Seamount (named after the geologist Thomas Crough) is a seamount in the Pacific Ocean, within the exclusive economic zone of Pitcairn. It rises to a depth of 650 metres (2,130 ft) and is paired with a taller but overall smaller seamount to the east. This seamount has a flat top and probably formed an island in the past. It is about 7-8 million years old, although a large earthquake recorded at its position in 1955 may indicate a recent eruption.

The seamount appears to be part of a long geological lineament with the neighbouring Henderson and Ducie islands, as well as the southern Tuamotus and Line Islands. Such a lineament may have been generated by a hotspot; the nearby Easter hotspot is a candidate hotspot.

Easter Fracture Zone

The Easter Fracture Zone is an oceanic fracture zone associated with the transform fault extending from the Tuamotu archipelago in the west to the Peru–Chile Trench to the east.

The Easter Fracture Zone extends roughly 5900 kilometers from 20°S,131°W to 26°S,78°W. The landscape consists of several ridges and isolated volcanos with maximal peak elevation above the seafloor of 3000m. Because the local seafloor has depths around 4000m to the north of the fracture zone and 3400m to the south of the fracture zone, most of its volcanic peaks form seamounts. They do rise above sea level at the Pitcairn Islands and Easter Island.

Easter Island

Easter Island (Rapa Nui: Rapa Nui, Spanish: Isla de Pascua) is a Chilean island in the southeastern Pacific Ocean, at the southeasternmost point of the Polynesian Triangle in Oceania. Easter Island is most famous for its nearly 1,000 extant monumental statues, called moai, created by the early Rapa Nui people. In 1995, UNESCO named Easter Island a World Heritage Site, with much of the island protected within Rapa Nui National Park.

It is believed that Easter Island's Polynesian inhabitants arrived on Easter Island sometime near 1200 AD. They created a thriving and industrious culture, as evidenced by the island's numerous enormous stone moai and other artifacts. However, land clearing for cultivation and the introduction of the Polynesian rat led to gradual deforestation. By the time of European arrival in 1722, the island's population was estimated to be 2,000–3,000. European diseases, Peruvian slave raiding expeditions in the 1860s, and emigration to other islands, e.g. Tahiti, further depleted the population, reducing it to a low of 111 native inhabitants in 1877.Chile annexed Easter Island in 1888. In 1966, the Rapa Nui were granted Chilean citizenship. In 2007 the island gained the constitutional status of "special territory." Administratively, it belongs to the Valparaíso Region, constituting a single commune of the Province Isla de Pascua. The 2017 Chilean census registered 7,750 people on the island, of whom 3,512 (45%) considered themselves Rapa Nui.Easter Island is one of the most remote inhabited islands in the world. The nearest inhabited land (around 50 residents in 2013) is Pitcairn Island, 2,075 kilometres (1,289 mi) away; the nearest town with a population over 500 is Rikitea, on the island of Mangareva, 2,606 km (1,619 mi) away; the nearest continental point lies in central Chile, 3,512 kilometres (2,182 mi) away.

Easter Island is considered part of Insular Chile.

Galápagos Islands

The Galápagos Islands (official name: Archipiélago de Colón, other Spanish name: Las Islas Galápagos, Spanish pronunciation: [las ˈislas ɣaˈlapaɣos], local pronunciation: [laz ˈihlah ɣaˈlapaɣoh]), part of the Republic of Ecuador, are an archipelago of volcanic islands distributed on either side of the equator in the Pacific Ocean surrounding the centre of the Western Hemisphere, 906 km (563 mi) west of continental Ecuador. The islands are known for their large number of endemic species and were studied by Charles Darwin during the second voyage of HMS Beagle. His observations and collections contributed to the inception of Darwin's theory of evolution by means of natural selection.

The Galápagos Islands and their surrounding waters form the Galápagos Province of Ecuador, the Galápagos National Park, and the Galápagos Marine Reserve. The principal language on the islands is Spanish. The islands have a population of slightly over 25,000.The first recorded visit to the islands happened by chance in 1535, when Fray Tomás de Berlanga, the Bishop of Panamá, was surprised with this undiscovered land during a voyage to Peru to arbitrate in a dispute between Francisco Pizarro and Diego de Almagro. De Berlanga eventually returned to the Spanish Empire and described the conditions of the islands and the animals that inhabited them. The group of islands was shown and named in Abraham Ortelius's atlas published in 1570. The first crude map of the islands was made in 1684 by the buccaneer Ambrose Cowley, who named the individual islands after some of his fellow pirates or after British royalty and noblemen. These names were used in the authoritative navigation charts of the islands prepared during the Beagle survey under captain Robert FitzRoy, and in Darwin's popular book The Voyage of the Beagle. The new Republic of Ecuador took the islands from Spanish ownership in 1832, and subsequently gave them official Spanish names. The older names remained in use in English-language publications, including Herman Melville's The Encantadas of 1854.

Geology of Chile

The geology of Chile is a characterized by processes linked to subduction such as volcanism, earthquakes and orogeny. The buildings blocks of Chile's geology assembled during the Paleozoic Era. Chile was by then the southwestern margin of the supercontinent Gondwana. In the Jurassic Gondwana begun to split and the ongoing period of crustal deformation and mountain building known as the Andean orogeny begun. In the Late Cenozoic Chile definitely separated from Antarctica, the Andes expienced a great rise accomplained by a cooling climate and the onset of glaciations.

The subduction interactions shaped four main morphostructures of Chile: the Andes; the Intermediate Depression, the Coast Range, and the Peru–Chile Trench off the coast. Since Chile is on an active continental margin, it has many volcanoes. Almost the entire country is subject to earthquakes arising from strains in the Nazca and Antarctic Plates or shallow strike-slip faults. Northern Chilean mineral resources are a major economic resources, and the country is the leading producer of copper, lithium and molybdenum. Most of these mineral deposits were created from magmatic hydrothermal activity. The water required to form those deposits derived from the subducted slab of the oceanic crust beneath the Andes.

The Chilean Easter Island and Juan Fernández Archipelago are volcanic hotspot islands in the eastward-moving Nazca plate. The geology of the Chilean Antarctic Territory has various commonalities with that of mainland Chile.

Geology of the Pacific Ocean

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).

Hotspot (geology)

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.

Isla Salas y Gómez

Isla Salas y Gómez, also known as Isla Sala y Gómez, is a small uninhabited Chilean island in the Pacific Ocean. It is sometimes considered the easternmost point in the Polynesian Triangle.

Isla Salas y Gómez and its surrounding waters are a Marine Protected Area called Parque Marino Salas y Gómez, with a surface area of 150,000 km2.

Juan Fernández hotspot

The Juan Fernández hotspot is a volcanic hotspot located in the southeastern Pacific Ocean. The hotspot created the Juan Fernández Ridge which includes the Juan Fernández Archipelago and a long seamount chain that is being subducted in the Peru–Chile Trench at the site of Papudo giving origin to the Norte Chico Volcanic Gap.

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 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.

Moai (seamount)

The Moai Seamount is a submarine volcano, the second most westerly in the Easter Seamount Chain or Sala y Gómez ridge. It is east of Pukao seamount and west of Easter Island. It rises over 2,500 metres from the ocean floor to within a few hundred metres of the sea surface. The Moai seamount is fairly young, having developed in the last few hundred thousand years as the Nazca Plate floats over the Easter hotspot.

The Moai seamount was named after the moai statues of neighbouring Easter Island.

Pukao (seamount)

The Pukao Seamount is a submarine volcano, the most westerly in the Easter Seamount Chain or Sala y Gómez ridge. To the east are Moai (seamount) and then Easter Island. It rises over 2,500 metres from the ocean floor to within a few hundred metres of the sea surface. The Pukao Seamount is fairly young, and believed to have developed in the last few hundred thousand years as the Nazca Plate floats over the Easter hotspot.

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