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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 Megaannum, 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 provinces, large low-shear velocity province (LLSVP). Most of Pacific Hotspot (geology), hotspots are located above the LLSVP while the longest Pacific hotspot tra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fracture (geology)
A fracture is any separation in a geologic formation, such as a Joint (geology), ''joint'' or a Fault (geology), ''fault'' that divides the Rock (geology), rock into two or more pieces. A fracture will sometimes form a deep fissure or crevice in the rock. Fractures are commonly caused by Stress (physics), stress exceeding the rock strength, causing the rock to lose cohesion along its weakest plane. Fractures can provide Permeability (fluid), permeability for fluid movement, such as water or hydrocarbons. Highly fractured rocks can make good aquifers or Oil reservoir, hydrocarbon reservoirs, since they may possess both significant Permeability (fluid), permeability and fracture porosity. Brittle deformation Fractures are forms of brittle deformation. There are two types of primary brittle deformation processes. Tensile fracturing results in ''joints''. ''Shear fractures'' are the first initial breaks resulting from shear forces exceeding the cohesive strength in that plane. Aft ... [...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, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magellan Rise (ocean Plateau)
Magellan Rise is an oceanic plateau in the Pacific Ocean, which covers a surface area of . There is another geological structure with the same name west from the Marshall Islands. 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 linked to the deep "JASON superplume", or from the interaction of a spreading ridge with a plume. Candidate mantle plumes are the Easter hotspot and the Foundation hotspot. The volume of rocks in the Magellan Rise is very uncertain, but may be in the range of to . It apparently developed first on the Phoenix Plate before being transferred onto the Pacific Plate 125 million years ago. The Magellan Rise has never risen to shallow depths, at least since the Cretaceous, and it is covered by sediments of Tithonian/Berriasian to Quaterna ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 ( 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 l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Manihiki Plateau
The Manihiki Plateau is an oceanic plateau in the south-west Pacific Ocean. The Manihiki Plateau was formed by volcanic activity 126 to 116 million years ago during the mid-Cretaceous period at a triple junction plate boundary called the Tongareva triple junction. Initially at 125 million years ago the Manihiki Plateau formed part of the giant Ontong Java-Manihiki- Hikurangi plateau. Geological setting The Manihiki Plateau extends from 3°S to 6°S and 159°W to 169°W covering and has an estimated volume of with a crustal thickness of . Several of the Cook Islands are located on the southern part: Pukapuka, Nassau, Suwarrow, Rakahanga, and Manihiki. The Tokelau Basin borders it to the west, the Samoan Basin to the south, the Penrhyn Basin to the east, and the Central Pacific Basin to the north. It reaches up to below sea level, several kilometres shallower than the surrounding basins. The plateau can be divided into three regions. The south-eastern High Plateau is t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hikurangi Plateau
The Hikurangi Plateau is an oceanic plateau in the South Pacific Ocean east of the North Island of New Zealand. It is part of a large igneous province (LIP) together with Manihiki and Ontong Java, now located and north of Hikurangi respectively. Mount Hikurangi, in Māori mythology the first part of the North Island to emerge from the ocean, gave its name to the plateau. Geological setting The Hikurangi Plateau covers approximately and reaches below sea level. Hikurangi Plateau is cut by the Hikurangi Channel, a 2000 km abyssal channel that starts at Kaikōura and runs along the Hikurangi Trough as far as the Māhia Peninsula before crossing the plateau and ending in the South-west Pacific abyssal plain. Tectonic evolution Two models have been proposed for the formation of Hikurangi. It could be derived from the mantle plume that caused the break-up of Gondwana and the separation of Zealandia from Antarctica 107 Ma. Alternatively, it could have formed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ontong Java Plateau
The Ontong Java Plateau (OJP) is a massive oceanic plateau located in the southwestern Pacific Ocean, north of the Solomon Islands. The OJP was formed around (Ma), with a much smaller volcanic event around 90 Ma. Two other southwestern Pacific plateaus, Manihiki and Hikurangi, now separated from the OJP by Cretaceous oceanic basins, are of similar age and composition and probably formed as a single plateau and a contiguous large igneous province together with the OJP. When eruption of lava had finished, the Ontong Java–Manihiki–Hikurangi plateau covered 1% of Earth's surface and represented a volume of of basaltic magma. This "Ontong Java event", first proposed in 1991, represents the largest volcanic event of the past 200 million years, with a magma eruption rate estimated at up to per year over 3 million years, for a total several times larger than the Deccan Traps. The smooth surface of the OJP is punctuated by seamounts such as the Ontong Java Atoll, one of the l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aleutian Islands
The Aleutian Islands ( ; ; , "land of the Aleuts"; possibly from the Chukchi language, Chukchi ''aliat'', or "island")—also called the Aleut Islands, Aleutic Islands, or, before Alaska Purchase, 1867, the Catherine Archipelago—are a chain of 14 main, larger volcanic islands and 55 smaller ones. Most of the Aleutian Islands belong to the U.S. state of Alaska, with the archipelago encompassing the Aleutians West Census Area, Alaska, Aleutians West Census Area and the Aleutians East Borough, Alaska, Aleutians East Borough. The Commander Islands, located further to the west, belong to the Russian Federal subjects of Russia, federal subject of Kamchatka Krai, of the Russian Far East. The islands form part of the Aleutian Arc of the Northern Pacific Ocean, and occupy a land area of 6,821 sq mi (17,666 km2) that extends westward roughly from the Alaska Peninsula, Alaskan Peninsula mainland, in the direction of the Kamchatka Peninsula; the archipelago acts as a border between ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Anomaly
In geophysics, a magnetic anomaly is a local variation in the Earth's magnetic field resulting from variations in the chemistry or magnetism of the rocks. Mapping of variation over an area is valuable in detecting structures obscured by overlying material. The magnetic variation (geomagnetic reversals) in successive bands of ocean floor parallel with mid-ocean ridges was important evidence for seafloor spreading, a concept central to the theory of plate tectonics. Measurement Magnetic anomalies are generally a small fraction of the magnetic field. The total field ranges from 25,000 to 65,000 nanoteslas (nT). To measure anomalies, magnetometers need a sensitivity of 10 nT or less. There are three main types of magnetometer used to measure magnetic anomalies: # The fluxgate magnetometer was developed during World War II to detect submarines. It measures the component along a particular axis of the sensor, so it needs to be oriented. On land, it is often oriented vertically, wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
