The Tonga Trench is an oceanic trench located in the southwestern Pacific Ocean. It is the deepest trench in the Southern hemisphere and the second deepest on Earth after the Mariana Trench. The fastest plate-tectonic velocity on Earth is occurring at this location, as the Pacific Plate is being subducted westward in the trench.
A large igneous province (LIP) is an extremely large accumulation of igneous rocks, including intrusive and extrusive, arising when magma travels through the crust towards the surface. The formation of LIPs is variously attributed to mantle plumes or to processes associated with divergent plate tectonics. The formation of some of the LIPs in the past 500 million years coincide in time with mass extinctions and rapid climatic changes, which has led to numerous hypotheses about causal relationships. LIPs are fundamentally different from any other currently active volcanoes or volcanic systems.
The Early Cretaceous or the Lower Cretaceous is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma.
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 116 million years ago (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 80 million km3 (19 million cu mi) 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 22 km3 (5.3 cu mi) per year over 3 million years, 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 largest atolls in the world.
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.
The Kermadec Trench is a linear ocean trench in the south Pacific Ocean. It stretches about 1,000 km (620 mi) from the Louisville Seamount Chain in the north (26°S) to the Hikurangi Plateau in the south (37°S), north-east of New Zealand's North Island. Together with the Tonga Trench to the north, it forms the 2,000 km (1,200 mi)-long, near-linear Kermadec-Tonga subduction system, which began to evolve in the Eocene when the Pacific Plate started to subduct beneath the Australian Plate. Convergence rates along this subduction system are among the fastest on Earth, 80 mm (3.1 in)/yr in the north and 45 mm (1.8 in)/yr in the south.
The Phoenix Plate was a tectonic plate that existed during the early Paleozoic through late Cenozoic time. It formed a triple junction with the Izanagi and Farallon plates in the Panthalassa Ocean as early as 410 million years ago, during which time the Phoenix Plate was subducting under eastern Gondwana.
The Galapagos Microplate (GMP) is a geological feature of the oceanic crust located at 1°50' N, offshore of the west coast of Colombia. The GMP is collocated with the Galapagos Triple Junction, which is an atypical ridge-ridge-ridge triple junction. At the Galapagos Triple Junction, the Pacific Plate, Cocos Plate, and Nazca Plate meet incompletely, forming two counter-rotating microplates at the junction of the Cocos-Nazca, Pacific-Cocos, and Pacific-Nazca spreading ridges.
The Caribbean large igneous province (CLIP) consists of a major flood basalt, which created this large igneous province (LIP). It is the source of the current large eastern Pacific oceanic plateau, of which the Caribbean-Colombian oceanic plateau is the tectonized remnant. The deeper levels of the plateau have been exposed on its margins at the North and South American plates. The volcanism took place between 139 and 69 million years ago, with the majority of activity appearing to lie between 95 and 88 Ma. The plateau volume has been estimated as on the order of 4 x 106 km³. It has been linked to the Galápagos hotspot.
The Afar Triple Junction is located along a divergent plate boundary dividing the Nubian, Somali, and Arabian plates. This area is considered a present-day example of continental rifting leading to seafloor spreading and producing an oceanic basin. Here, the Red Sea Rift meets the Aden Ridge and the East African Rift. The latter extends a total of 6,500 kilometers (4,000 mi) from the Afar Triangle to Mozambique.
The Owen Fracture Zone (OFZ), though misnamed a fracture zone, is a transform fault in the northwest Indian Ocean that separates the Arabian and African Plates from the Indian Plate. Extending north-northeast from where the Carlsberg Ridge meets the Sheba ridge in the south to the Makran Subduction Zone in the north, it represents the port side of the northward motion of the Indian subcontinent during the Late Cretaceous–Palaeogene break-up of Gondwana. Slip along the Owen Fracture Zone is occurring at 2 mm (0.079 in)/yr, the slowest rate on Earth, which means the Arabian Plate moves northward faster than the Indian Plate.
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 3,000 km (1,900 mi) and 3,500 km (2,200 mi) 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.
The Tongareva triple junction, also called the Pacific-Farallon-Phoenix triple junction, was a geologic triple junction in the southwestern Pacific Basin where three tectonic plates met: the Pacific Plate, the Farallon Plate, and the Phoenix Plate. It existed throughout the mid-Cretaceous period and consisted of three mid-ocean ridges. A volcanic episode from 125 to 120 million years ago created an oceanic plateau east of Samoa called the Manihiki Plateau.
The Balmoral Reef Plate is a small tectonic plate (microplate) located in the south Pacific north of Fiji. Clockwise from the north, it borders the Pacific Plate, the Australian Plate, Conway Reef Plate, and the New Hebrides Plate. The northern and western borders are a divergent boundary while the rest of the borders are transform and convergent boundaries. The Balmoral Reef Plate's ocean crust is less than 12 million years old and is spreading between the New Hebrides and Tonga subduction. The plate forms the west central part of the seafloor of the North Fiji Basin.
The Shatsky Rise is Earth's third largest oceanic plateau, located in the north-west Pacific Ocean 1,500 km (930 mi) east of Japan. It is one of a series of Pacific Cretaceous large igneous provinces (LIPs) together with Hess Rise, Magellan Rise, and Ontong Java-Manihiki-Hikurangi. It was named for Nikolay Shatsky (1895-1960), a Soviet geologist, expert in tectonics of ancient platforms.
The Tonga-Kermadec Ridge is an oceanic ridge in the south-west Pacific Ocean underlying the Tonga-Kermadec island arc. It is a result of the most linear, fastest converging, and seismically active subduction boundary on Earth, the Kermadec-Tonga subduction zone, and consequently has the highest density of submarine volcanoes.
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 geological structure with the same name west from the Marshall Islands.
The Wishbone scarp is a Pacific Ocean floor feature in the oceanic crust, that if it were on land would be similar to a mountain range fault system over 1,000 km (620 mi) long. It commences in the north near the Osbourn Trough although it is likely to be related tectonically to the Manihiki scarp somewhat to its north. To the south it splits into west and east scarps that have been intercepted by the Louisville hotspot with the West Wishbone scarp continuing until it intercepts the Chatham Rise. There is now evidence that the entire scarp has a fracture zone origin resolving previous uncertainty on this issue.
The Osbourn Trough, is a 900 km (560 mi)-long extinct mid-ocean ridge, that may have stopped spreading as recently as 79 million years ago. It is a west-to-east oriented sea floor feature, located to the east of the present Tonga-Kermadec Ridge where the present Pacific Plate is under going subduction under a micro-plate of the Australian Plate. The Osbourn Trough is key to understanding the postulated breakup mechanism of the historic massive Ontong Java-Manihiki-Hikurangi large igneous province (LIP), as it has been shown to be the spreading centre that lead to the separation of the Manihiki Plateau to its north and the Hikurangi Plateau to its south close to New Zealand.
