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Ngatemato Seamounts
Ngatemato seamounts (Name derived from a ruling family in Rapa) are a series of seamounts in the southern Pacific Ocean. These seamounts have the shape of ridges and display calderas. The Aureka () and Make () seamounts are part of the Ngatemato track. Dredged rocks are weakly tholeiitic basalts of Oligocene age. They are about high and wide at their base. Despite being smaller in size than the Macdonald seamounts however the Ngatemato seamounts have larger volumes which is masked by stronger plate deformation; the magma output that created the Ngatemato and Taukina chains when summed up is about . The seamounts were discovered in 1996 by the RV Maurice Ewing in the Austral Islands. Potassium-argon dating yields ages of about 30 million years; the seamounts developed close to the East Pacific Rise. Away from the Austral Islands the Ngatemato seamounts merge with the Foundation seamounts, with which they may share an origin. Macdonald seamount and associated seamounts as well ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rapa Iti
Rapa, also called Rapa Iti, or "Little Rapa", to distinguish it from Easter Island, whose Polynesian name is Rapa Nui, is the largest and only inhabited island of the Bass Islands in French Polynesia. An older name for the island is Oparo. The total land area including offshore islets is . As of the 2017 census, Rapa had a population of 507.Répartition de la population en Polynésie française en 2017 Institut de la statistique de la Polynésie française The island's highest point is at elevation at Mont Perahu. Its main town is Ahuréi. The inhabitants of Rapa Iti speak their own Polynesian language called the |
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 East Pacific Rise near Easter Island is the fastest spreading mid-ocean ridge, with a spreading rate of over 15 cm/yr. The Pacific Plate moves generally towards the northwest at between 7 and 11 cm/yr while the Juan De Fuca Plate has an east-northeasterly movement of some 4 cm/yr. Most subduction zones around the rim of the Pacific are directed away from a large area in the southern Pacific. At the core–mantle boundary below this area there is a large low-shear velocity province (LLSVP). Most of Pacific hotspots are located above the LLSVP while the longest Pacific hotspot tracks are located at or near its boundaries pointing at the positi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mantle Plume
A mantle plume is a proposed mechanism of convection within the Earth's mantle, hypothesized to explain anomalous volcanism. Because the plume head partially melts on reaching shallow depths, a plume is often invoked as the cause of volcanic hotspots, such as Hawaii or Iceland, and large igneous provinces such as the Deccan and Siberian Traps. Some such volcanic regions lie far from tectonic plate boundaries, while others represent unusually large-volume volcanism near plate boundaries. Concepts Mantle plumes were first proposed by J. Tuzo Wilson in 1963 and further developed by W. Jason Morgan in 1971 and 1972. A mantle plume is posited to exist where super-heated material forms ( nucleates) at the core-mantle boundary and rises through the Earth's mantle. Rather than a continuous stream, plumes should be viewed as a series of hot bubbles of material. Reaching the brittle upper Earth's crust they form diapirs. These diapirs are "hotspots" in the crust. In particular, the conc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Foundation Hotspot
Foundation Seamounts are a series of seamounts in the southern Pacific Ocean. Discovered in 1992, these seamounts form a long chain which starts from the Pacific-Antarctic Ridge. Some of these seamounts may have once emerged from the ocean. The Foundation Seamounts were probably formed by a now-weakening mantle plume called the Foundation hotspot that is located close to the Pacific-Antarctic Ridge. It is possible that this hotspot generated additional volcanoes, such as the Ngatemato and Taukina seamounts farther west. The oldest volcanism on the Foundation Seamounts occurred 21 million years ago, while the youngest volcanism appears to be hydrothermal venting and the eruption of a lava flow between 1997 and 2001 where the Foundation Seamounts intersect the Pacific-Antarctic Ridge. Name and discovery The Foundation Seamounts were discovered in 1992 through satellite altimetry observations. They are named after the National Science Foundation, a name-giving inspired to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hotspot (geology)
In geology, hotspots (or hot spots) are volcanic locales thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle. Examples include the Hawaii, Iceland, and Yellowstone hotspots. A hotspot's position on the Earth's surface is independent of tectonic plate boundaries, and so hotspots may create a chain of volcanoes as the plates move above them. 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 alternative plate theory is that the mantle source beneath a hotspot is not anomalously hot, rather the crust above is unusually weak or thin, so that lithospheric extension permits the passive rising of melt from shallow depths. Origin The origins of the concept of hotspots lie in the work of J. Tuzo Wilson, who postulated in 1963 that the formation of the Hawaiian Islands resulted from the slow movement of a tecton ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pacific Plate
The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate. The plate first came into existence 190 million years ago, at the triple junction between the Farallon, Phoenix, and Izanagi Plates. The Pacific Plate subsequently grew to where it underlies most of the Pacific Ocean basin. This reduced the Farallon Plate to a few remnants along the west coast of North America and the Phoenix Plate to a small remnant near the Drake Passage, and destroyed the Izanagi Plate by subduction under Asia. The Pacific Plate contains an interior hot spot forming the Hawaiian Islands. Boundaries The north-eastern side is a divergent boundary with the Explorer Plate, the Juan de Fuca Plate and the Gorda Plate forming respectively the Explorer Ridge, the Juan de Fuca Ridge and the Gorda Ridge. In the middle of the eastern side is a transform boundary with the North American Plate along the San Andreas Fault, and a boundary with the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Taukina Seamounts
Taukina seamounts are a series of seamounts on the Pacific Plate. The Macdonald hotspot and the Ngatemato seamounts are located nearby. The Taukina and Ngatemato seamounts were discovered in 1996 by the RV Maurice Ewing and both are named after families in Rapa Iti. The Taukina seamounts are formed by small volcanoes, with heights of and widths of . They often feature a caldera on their summit. Tholeiitic rocks make up the seamounts. The shape of the Taukina seamounts resembles that of the seamounts that form on the East Pacific Rise. An alternate theory of origin is that the Ngatemato seamounts deformed the Pacific plate enough with their weight to trigger the eruption of magma. References {{Reflist, refs= {{Cite book, title=Oceanic Hotspots, last=Jordahl, first=K., last2=Caress, first2=D., last3=McNutt, first3=M., last4=Bonneville, first4=A., date=2004, publisher=Springer, Berlin, Heidelberg, isbn=9783642622908, location=, pages=22, language=en, doi=10.1007/978-3-642-18782-7 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Foundation Seamounts
Foundation Seamounts are a series of seamounts in the southern Pacific Ocean. Discovered in 1992, these seamounts form a long chain which starts from the Pacific-Antarctic Ridge. Some of these seamounts may have once emerged from the ocean. The Foundation Seamounts were probably formed by a now-weakening mantle plume called the Foundation hotspot that is located close to the Pacific-Antarctic Ridge. It is possible that this hotspot generated additional volcanoes, such as the Ngatemato and Taukina seamounts farther west. The oldest volcanism on the Foundation Seamounts occurred 21 million years ago, while the youngest volcanism appears to be hydrothermal venting and the eruption of a lava flow between 1997 and 2001 where the Foundation Seamounts intersect the Pacific-Antarctic Ridge. Name and discovery The Foundation Seamounts were discovered in 1992 through satellite altimetry observations. They are named after the National Science Foundation, a name-giving inspired to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
East Pacific Rise
The East Pacific Rise is a mid-ocean rise (termed an oceanic rise and not a mid-ocean ridge due to its higher rate of spreading that results in less elevation increase and more regular terrain), a divergent tectonic plate boundary located along the floor of the Pacific Ocean. It separates the Pacific Plate to the west from (north to south) the North American Plate, the Rivera Plate, the Cocos Plate, the Nazca Plate, and the Antarctic Plate. It runs south from the Gulf of California in the Salton Sea basin in Southern California to a point near 55° S, 130° W, where it joins the Pacific-Antarctic Ridge trending west-southwest towards Antarctica, near New Zealand (though in some uses the PAR is regarded as the southern section of the EPR). Much of the rise lies about 3200 km (2000 mi) off the South American coast and rises about 1,800–2,700 m (6,000–9,000 ft) above the surrounding seafloor. Overview The oceanic crust is moving away from the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Austral Islands
The Austral Islands (french: Îles Australes, officially ''Archipel des Australes;'' ty, Tuha'a Pae) are the southernmost group of islands in French Polynesia, an overseas country of the French Republic in the South Pacific. Geographically, they consist of two separate archipelagos, namely in the northwest the Tupua'i islands (french: Îles Tubuaï) consisting of the Îles Maria, Rimatara, Rūrutu, Tupua'i Island proper and Ra'ivāvae, and in the southeast the Bass Islands (french: Îles basses) composed of the main island of Rapa Iti and the small Marotiri (also known as Bass Rocks or Îlots de Bass). Inhabitants of the islands are known for their pandanus fiber weaving skills. The islands of Maria and Marotiri are not suitable for sustained habitation. Several of the islands have uninhabited islets or rocks off their coastlines. Austral Islands' population is 6,965 on almost . The capital of the Austral Islands administrative subdivision is Tupua'i. History Whaling ves ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seamount
A seamount is a large geologic landform that rises from the ocean floor that does not reach to the water's surface (sea level), and thus is not an island, islet or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise abruptly and are usually found rising from the seafloor to in height. They are defined by oceanographers as independent features that rise to at least above the seafloor, characteristically of conical form.IHO, 2008. Standardization of Undersea Feature Names: Guidelines Proposal form Terminology, 4th ed. International Hydrographic Organization and Intergovernmental Oceanographic Commission, Monaco. The peaks are often found hundreds to thousands of meters below the surface, and are therefore considered to be within the deep sea. During their evolution over geologic time, the largest seamounts may reach the sea surface where wave action erodes the summit to form a flat surface. After they have subsided and sunk below the sea surface such flat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
