Réunion hotspot

The Réunion hotspot is a volcanic hotspot which currently lies under the island of Réunion in the Indian Ocean. The Chagos-Laccadive Ridge and the southern part of the Mascarene Plateau are volcanic traces of the Réunion hotspot.[1]

The hotspot is believed to have been active for over 65 million years. A huge eruption of this hotspot 65 million years ago is thought to have laid down the Deccan Traps, a vast bed of basalt lava that covers part of central India, and opened a rift which separated India from the Seychelles Plateau. The Deccan Traps eruption coincided roughly with the nearly antipodal Chicxulub impactor and the Cretaceous–Paleogene extinction of the dinosaurs, and there is considerable speculation that the three events were related.[2][3] As the Indian plate drifted north, the hotspot continued to punch through the plate, creating a string of volcanic islands and undersea plateaux. The Laccadive Islands, the Maldives, and the Chagos Archipelago are atolls resting on former volcanoes created 60–45 million years ago that subsequently submerged below sea level. About 45 million years ago the mid-ocean rift crossed over the hotspot, and the hotspot passed under the African Plate.

The hotspot appears to have been relatively quiet 45–10 million years ago, when activity resumed, creating the Mascarene Islands, which include Mauritius, Réunion, and Rodrigues. Mauritius and Rodrigues Ridge were created 8–10 million years ago, and Rodrigues and Réunion Islands in the last two million years. Piton de la Fournaise, a shield volcano on the southeastern corner of Réunion, is one of the most active volcanoes in the world, erupting last in February 2019.[4]

Piton de la Fournaise 1
Piton de la Fournaise, an active shield volcano formed by the Réunion hotspot

References

  1. ^ E. V. Verzhbitsky (2003). "Geothermal regime and genesis of the Ninety-East and Chagos-Laccadive ridges". Journal of Geodynamics. 35 (3): 289–302. Bibcode:2003JGeo...35..289V. doi:10.1016/S0264-3707(02)00068-6.
  2. ^ Renne, P. R.; et al. (2015). "State shift in Deccan volcanism at the Cretaceous-Paleogene boundary, possibly induced by impact". Science. 350 (6256): 76–78. Bibcode:2015Sci...350...76R. doi:10.1126/science.aac7549. PMID 26430116.
  3. ^ Sprain, Courtney J.; Renne, Paul R.; Vanderkluysen, Loÿc; Pande, Kanchan; Self, Stephen; Mittal, Tushar (21 February 2019). "The eruptive tempo of Deccan volcanism in relation to the Cretaceous-Paleogene boundary". Science. 363 (6429): 866–870. doi:10.1126/science.aav1446.
  4. ^ Klemetti, Erik (2014). "New Eruption at Piton de la Fournaise on Reunion Island". Wired. Archived from the original on 22 June 2014.

External links

Coordinates: 21°06′S 55°30′E / 21.1°S 55.5°E

Central Indian Ridge

The Central Indian Ridge (CIR) is a north-south-trending mid-ocean ridge in the western Indian Ocean.

Chagos-Laccadive Ridge

The Chagos-Laccadive Ridge (CLR), also known as Chagos-Laccadive Plateau, is a prominent volcanic ridge and oceanic plateau extending between the Northern and the Central Indian Ocean.

Extending from c. 10°S to 15°N, the CLR includes the Laccadive, Maldives, and Chagos archipelagos and can be divided into three corresponding blocks, of which the first is continental and the two latter are oceanic. The CLR is asymmetrical with a steeper eastern slope and has an average depth of less than 1,000 m (3,300 ft). It formed south of or near the Equator together with the remaining western continental margin of India, when India separated first from Madagascar in the Mid-Cretaceous and then from the Seychelles in the Late Cretaceous.

Deccan Traps

The Deccan Traps are a large igneous province located on the Deccan Plateau of west-central India (17–24°N, 73–74°E). They are one of the largest volcanic features on Earth. They consist of multiple layers of solidified flood basalt that together are more than 2,000 m (6,600 ft) thick, cover an area of c. 500,000 km2 (200,000 sq mi), and have a volume of c. 1,000,000 km3 (200,000 cu mi). Originally, the Deccan Traps may have covered c. 1,500,000 km2 (600,000 sq mi), with a correspondingly larger original volume.

East Australia hotspot

The East Australia hotspot is a volcanic hotspot that forces magma up at weak spots in the Indo-Australian Plate to form volcanoes in Eastern Australia. It does not produce a single chain of volcanoes like the Hawaiian Islands. Unlike most hotspots, the East Australia hotspot has explosive eruptions, as well as the runny lava flows of the Hawaii hotspot, the Iceland hotspot and the Réunion hotspot. The hotspot is explosive because basaltic magma interacts with groundwater in aquifers below the surface producing violent phreatomagmatic eruptions.

Tweed Volcano in New South Wales is a large shield volcano that was formed by the hotspot about 23 million years ago and has one of the biggest erosion calderas in the world.

A number of the volcanoes in the province have erupted since Aboriginal settlement (46,000 BP). The most recent eruptions were about 5,600 years ago, and memories of them survive in Aboriginal folklore. These eruptions formed the volcanoes Mount Schank and Mount Gambier in the Newer Volcanics Province. There have been no eruptions on the Australian mainland since European settlement.

Geography of Seychelles

The Seychelles is a small island nation located in the Somali sea northeast of Madagascar and about 835 mi (1,344 km) from Mogadishu, Somalia, its nearest foreign mainland city, while Antsiranana is the nearest foreign city overall. Seychelles lies between approximately 4ºS and 10ºS and 46ºE and 54ºE. The nation is an archipelago of 115 tropical islands, some granite and some coral. the majority of which are small and uninhabited. The landmass is only 452 km2 (175 sq mi), but the islands are spread wide over an Exclusive Economic Zone of 1,336,559 km2 (516,048 sq mi). About 90 percent of the population of 90,000 live on Mahé, 9 percent on Praslin and La Digue. Around a third of the land area is the island of Mahé and a further third the atoll of Aldabra.

There are two distinct regions, the granitic islands, the world's only oceanic islands of granitic rock and the coralline outer islands. The granite islands are the world’s oldest ocean islands, while the outer islands are mainly very young, though the Aldabra group and St Pierre (Farquhar Group) are unusual, raised coral islands that have emerged and submerged several times during their long history, the most recent submergence dating from about 125,000 years ago

Geology of India

The geology of India is diverse. Different regions of India contain rocks belonging to different geologic periods, dating as far back as the Eoarchean Era. Some of the rocks are very deformed and altered. Other deposits include recently deposited alluvium that has yet to undergo diagenesis. Mineral deposits of great variety are found in the Indian subcontinent in huge quantity. Even India's fossil record is impressive in which stromatolites, invertebrates, vertebrates and plant fossils are included.

India's geographical land area can be classified into the Deccan Traps, Gondwana and Vindhyan.

The Deccan Traps covers almost all of Maharashtra, a part of Gujarat, Karnataka, Madhya Pradesh and Andhra Pradesh marginally. During its journey northward after breaking off from the rest of Gondwana, the Indian Plate passed over a geologic hotspot, the Réunion hotspot, which caused extensive melting underneath the Indian Craton. The melting broke through the surface of the craton in a massive flood basalt event, creating the Deccan Traps. It is also thought that the Reunion hotspot caused the separation of Madagascar and India.

The Gondwana and Vindhyan include within its fold parts of Madhya Pradesh, Chhattisgarh, Odisha, Bihar, Jharkhand, West Bengal, Andhra Pradesh, Maharashtra, Jammu and Kashmir, Punjab, Himachal Pradesh, Rajasthan and Uttarakhand. The Gondwana sediments form a unique sequence of fluviatile rocks deposited in Permo-Carboniferous time. The Damodar and Sone river valleys and Rajmahal hills in eastern India contain a record of the Gondwana rocks.

The Geological Survey of India has published the List of National Geological Monuments in India.

Geology of Réunion

Réunion is a mafic island formed as a result of the Réunion hotspot in the Indian Ocean, the same hotspot that produced the massive basalt flows of the Deccan Traps, when it was beneath India more than 66 million years ago.

Geology of the Maldives

The geology of the Maldives formed beginning 68 million years ago as a hotspot which produced the Deccan Traps in India. As India moved northward, the hotspot generated an island chain in the Indian Ocean, which includes Mauritius and Réunion. The Réunion hotspot trail was offset by the Central Indian Ridge 35 million years ago. The hotspot theory is supported by the fact that the basement basalts underlying the atolls of the Maldives are younger in the south, toward Réunion.

Gondwana

Gondwana ( ) or Gondwanaland was a supercontinent that existed from the Neoproterozoic (about 550 million years ago) until the Jurassic (about 180 million years ago).

It was formed by the accretion of several cratons. Eventually, Gondwana became the largest piece of continental crust of the Paleozoic Era, covering an area of about 100,000,000 km2 (39,000,000 sq mi). During the Carboniferous Period, it merged with Euramerica to form a larger supercontinent called Pangaea. Gondwana (and Pangaea) gradually broke up during the Mesozoic Era. The remnants of Gondwana make up about two thirds of today's continental area, including South America, Africa, Antarctica, Australia, Indian Subcontinent and Arabia.

The formation of Gondwana began c. 800 to 650 Ma with the East African Orogeny, the collision of India and Madagascar with East Africa, and was completed c. 600 to 530 Ma with the overlapping Brasiliano and Kuunga orogenies, the collision of South America with Africa and the addition of Australia and Antarctica, respectively.

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.

Indian Ocean

The Indian Ocean is the third-largest of the world's oceanic divisions, covering 70,560,000 km2 (27,240,000 sq mi) (19.8% of the water on the Earth's surface). It is bounded by Asia on the north, on the west by Africa, on the east by Australia, and on the south by the Southern Ocean or, depending on definition, by Antarctica.

Kerguelen Plateau

The Kerguelen Plateau ( , ) is an oceanic plateau and a large igneous province (LIP) located on the Antarctic Plate, in the southern Indian Ocean. It is also a microcontinent and submerged continent. It is about 3,000 km (1,900 mi) to the southwest of Australia and is nearly three times the size of Japan. The plateau extends for more than 2,200 km (1,400 mi) in a northwest–southeast direction and lies in deep water.

The plateau was produced by the Kerguelen hotspot, starting with or following the breakup of Gondwana about 130 million years ago. A small portion of the plateau breaks sea level, forming the Kerguelen Islands (a French territory) plus the Heard and McDonald Islands (an Australian territory). Intermittent volcanism continues on the Heard and McDonald Islands.

Mascarene Islands

The Mascarene Islands (English: , French: Mascareignes) or Mascarenes or Mascarenhas Archipelago is a group of islands in the Indian Ocean east of Madagascar consisting of Mauritius, Réunion and Rodrigues. Their name derives from the Portuguese navigator Pedro Mascarenhas, who first visited them in April 1512. The islands share a common geologic origin in the volcanism of the Réunion hotspot beneath the Mascarene Plateau and form a distinct ecoregion with a unique flora and fauna.

Piton de la Fournaise

Piton de la Fournaise (French for "Peak of the Furnace") is a shield volcano on the eastern side of Réunion island (a French department) in the Indian Ocean. It is currently one of the most active volcanoes in the world, along with Kīlauea in the Hawaiian Islands, Stromboli and Etna in Italy and Mount Erebus in Antarctica. A previous eruption began in August 2006 and ended in January 2007. The volcano erupted again in February 2007, on 21 September 2008, on 9 December 2010, which lasted for two days, and on 1 August 2015. The most recent eruption began on 11 August 2019. The volcano is located within Réunion National Park, a World Heritage site.

Piton de la Fournaise is often known locally as le Volcan ("the Volcano"); it is a major tourist attraction on Réunion island.

Piton des Neiges

The Piton des Neiges (Snow Peak) is a massive 3,069 m (10,069 ft) shield volcano on Réunion, one of the French volcanic islands in the Mascarene Archipelago in the southwestern Indian Ocean. It is located about 800 kilometres (500 mi) east of Madagascar. Piton des Neiges is the highest point on Réunion and is considered to be the highest point in the Indian Ocean. The volcano was formed by the Réunion hotspot and emerged from the sea about two million years ago. Now deeply eroded, the volcano has been inactive for 20,000 years and is surrounded by three massive crater valleys, the Cirques. Piton des Neiges forms the northwestern two thirds of Réunion, with the very active Piton de la Fournaise comprising the rest. As it name suggests, snow is occasionally seen on its summit in winter.

The volcanic island is considered to be about three million years old (Pliocene); the other two islands in the archipelago, Mauritius and Rodrigues, are 7.8 million (Miocene) and 1​1⁄2 million (Pleistocene) years old, respectively. The island possesses a high endemism of flowering plants (about 225); this has justified the creation of a biological reserve on the lower slopes of the Piton des Neiges.

Saya de Malha Bank

The Saya de Malha Bank (also Sahia de Malha Bank, Modern Portuguese: saia de malha, English mesh skirt) is the largest submerged ocean bank in the world, part of the vast undersea Mascarene Plateau.

Shiva crater

The Shiva Crater is a geologic structure, which is hypothesized by Sankar Chatterjee and colleagues to be a 500-kilometre (310 mi) diameter impact structure. This geologic structure consists of the Bombay High and Surat Depression. They lie beneath the Indian continental shelf and the Arabian Sea west of Mumbai, India. Chatterjee named this structure after Shiva, the Hindu god of destruction and renewal.

Supervolcano

A supervolcano is a large volcano that has had an eruption with a Volcanic Explosivity Index (VEI) of 8, the largest recorded value on the index. This means the volume of deposits for that eruption is greater than 1,000 cubic kilometers (240 cubic miles).

Supervolcanoes occur when magma in the mantle rises into the crust but is unable to break through it and pressure builds in a large and growing magma pool until the crust is unable to contain the pressure. This can occur at hotspots (for example, Yellowstone Caldera) or at subduction zones (for example, Toba). Large-volume supervolcanic eruptions are also often associated with large igneous provinces, which can cover huge areas with lava and volcanic ash. These can cause long-lasting climate change (such as the triggering of a small ice age) and threaten species with extinction. The Oruanui eruption of New Zealand's Taupo Volcano (about 26,500 years ago) was the world's most recent VEI-8 eruption.

Timeline of volcanism on Earth

This timeline of volcanism on Earth is a list of major volcanic eruptions of approximately at least magnitude 6 on the Volcanic Explosivity Index (VEI) or equivalent sulfur dioxide emission around the Quaternary period (from 2.58 Mya to the present).

Some eruptions cooled the global climate—inducing a volcanic winter—depending on the amount of sulfur dioxide emitted and the magnitude of the eruption. Before the present Holocene epoch, the criteria are less strict because of scarce data availability, partly since later eruptions have destroyed the evidence. Only some eruptions before the Neogene period (from 23 Mya to 2.58 Mya) are listed. Known large eruptions after the Paleogene period (from 66 Mya to 23 Mya) are listed, especially those relating to the Yellowstone hotspot, the Santorini caldera, and the Taupo Volcanic Zone.

Active volcanoes such as Stromboli, Mount Etna and Kilauea do not appear on this list, but some back-arc basin volcanoes that generated calderas do appear. Some dangerous volcanoes in "populated areas" appear many times: so Santorini, six times and Yellowstone hotspot, twenty-one times. The Bismarck volcanic arc, New Britain, and the Taupo Volcanic Zone, New Zealand, appear often too.

In addition to the events listed below, are many examples of eruptions in the Holocene on the Kamchatka Peninsula, which are described in a supplemental table by Peter Ward.

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