Seafloor spreading or Seafloor spread is a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge.
A seamount is a large geologic landform that rises from the ocean floor that does not reach to the water's surface, 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 1,000–4,000 m (3,300–13,100 ft) in height. They are defined by oceanographers as independent features that rise to at least 1,000 m (3,281 ft) above the seafloor, characteristically of conical form. 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-top seamounts are called "guyots" or "tablemounts".
In plate tectonics, a divergent boundary or divergent plate boundary is a linear feature that exists between two tectonic plates that are moving away from each other. Divergent boundaries within continents initially produce rifts, which eventually become rift valleys. Most active divergent plate boundaries occur between oceanic plates and exist as mid-oceanic ridges.
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.
The East Pacific Rise is a mid-ocean ridge, a divergent tectonic plate boundary located along the floor of the Pacific Ocean. It separates the Pacific Plate to the west from 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. 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.
A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics. It typically has a depth of about 2,600 meters (8,500 ft) and rises about 2,000 meters (6,600 ft) above the deepest portion of an ocean basin. This feature is where seafloor spreading takes place along a divergent plate boundary. The rate of seafloor spreading determines the morphology of the crest of the mid-ocean ridge and its width in an ocean basin.
Axial Seamount is a seamount and submarine volcano located on the Juan de Fuca Ridge, approximately 480 km (298 mi) west of Cannon Beach, Oregon. Standing 1,100 m (3,609 ft) high, Axial Seamount is the youngest volcano and current eruptive center of the Cobb–Eickelberg Seamount chain. Located at the center of both a geological hotspot and a mid-ocean ridge, the seamount is geologically complex, and its origins are still poorly understood. Axial Seamount is set on a long, low-lying plateau, with two large rift zones trending 50 km (31 mi) to the northeast and southwest of its center. The volcano features an unusual rectangular caldera, and its flanks are pockmarked by fissures, vents, sheet flows, and pit craters up to 100 m (328 ft) deep; its geology is further complicated by its intersection with several smaller seamounts surrounding it.
Easter Plate is a tectonic microplate located to the west of Easter Island off the west coast of South America in the middle of the Pacific Ocean, bordering the Nazca Plate to the east and the Pacific Plate to the west. It was discovered from looking at earthquake distributions that were offset from the previously perceived Nazca-Pacific Divergent boundary. This young plate is 5.25 million years old and is considered a microplate because it is small with an area of approximately 160,000 square kilometres (62,000 sq mi). Seafloor spreading along the Easter microplate's borders have some of the highest global rates, ranging from 50 to 140 millimetres /yr.
The Izu–Bonin–Mariana (IBM) arc system is a tectonic plate convergent boundary in Micronesia. The IBM arc system extends over 2800 km south from Tokyo, Japan, to beyond Guam, and includes the Izu Islands, the Bonin Islands, and the Mariana Islands; much more of the IBM arc system is submerged below sealevel. The IBM arc system lies along the eastern margin of the Philippine Sea Plate in the Western Pacific Ocean. It is the site of the deepest gash in Earth's solid surface, the Challenger Deep in the Mariana Trench.
The Hawaiʻi hotspot is a volcanic hotspot located near the namesake Hawaiian Islands, in the northern Pacific Ocean. One of the best known and intensively studied hotspots in the world, the Hawaii plume is responsible for the creation of the Hawaiian–Emperor seamount chain, a 6,200-kilometer (3,900 mi) mostly undersea volcanic mountain range. Four of these volcanoes are active, two are dormant; more than 123 are extinct, most now preserved as atolls or seamounts. The chain extends from south of the island of Hawaiʻi to the edge of the Aleutian Trench, near the eastern coast of Russia.
Continental crustal fragments, partly synonymous with microcontinents, are pieces of continents that have broken off from main continental masses to form distinct islands that are often several hundred kilometers from their place of origin.
The Southwest Indian Ridge (SWIR) is a mid-ocean ridge located along the floors of the south-west Indian Ocean and south-east Atlantic Ocean. A divergent tectonic plate boundary separating the Somali Plate to the north from the Antarctic Plate to the south, the SWIR is characterised by ultra-slow spreading rates combined with a fast lengthening of its axis between the two flanking triple junctions, Rodrigues in the Indian Ocean and Bouvet in the Atlantic Ocean.
Zealandia, also known as Te Riu-a-Māui (Māori) or Tasmantis, is an almost entirely submerged mass of continental crust that subsided after breaking away from Gondwanaland 83–79 million years ago. It has been described variously as a submerged continent, a continental fragment, and a continent. The name and concept for Zealandia was proposed by Bruce Luyendyk in 1995, and satellite imagery shows it to be almost the size of Australia. A 2021 study suggests Zealandia is 1 billion years old, about twice as old as geologists previously thought.
The volcanology of Eastern Canada includes the hundreds of volcanic areas and extensive lava formations in Eastern Canada. The region's different volcano and lava types originate from different tectonic settings and types of volcanic eruptions, ranging from passive lava eruptions to violent explosive eruptions. Eastern Canada has very large volumes of magmatic rock called large igneous provinces. They are represented by deep-level plumbing systems consisting of giant dike swarms, sill provinces and layered intrusions. The most capable large igneous provinces in Eastern Canada are Archean age greenstone belts containing a rare volcanic rock called komatiite.
The South China Sea Basin is one of the largest marginal basins in Asia. South China Sea is located to the east of Vietnam, west of Philippines and the Luzon Strait, and north of Borneo. Tectonically, it is surrounded by the Indochina Block on the west, Philippines Sea plate on the east, Yangtze Block to the north. A subduction boundary exists between the Philippines Sea Plate and the Asian Plate. The formation of the South China Sea Basin was closely related with the collision between the Indian Plate and Eurasian Plates. The collision thickened the continental crust and changed the elevation of the topography from the Himalayan orogenic zone to the South China Sea, especially around the Tibetan Plateau. The location of the South China Sea makes it a product of several tectonic events. All the plates around the South China Sea Basin underwent clockwise rotation, subduction and experienced an extrusion process from the early Cenozoic to the Late Miocene.
The Adare Basin is a geologic structural basin located north-east of Cape Adare of Antarctica, for which its named, and north of the western Ross Sea. The Adare Basin is an extensional rift basin located along a seafloor spreading center that forms the failed arm of the Tertiary spreading ridge separating East and West Antarctica, known as the West Antarctic Rift System and similar in structure to the East Africa Rift System. Centrally located in the Adare Basin is the Adare Trough. The extension of this rift system is recorded in a series of magnetic anomalies which run along the seafloor at the extinct, north–south trending, Adare spreading axis. The Adare spreading system continues unbroken into the Northern Basin underlying the adjacent Ross Sea continental shelf.
The Bransfield Basin is a back-arc rift basin located off the northern tip of the Antarctic Peninsula. The basin lies within a Northeast and Southwest trending strait that separates the peninsula from the nearby South Shetland Islands to the Northwest. The basin extends for more than 500 kilometres from Smith Island to a portion of the Hero Fracture Zone. The basin can be subdivided into three basins: Western, Central, and Eastern. The Western basin is 130 kilometres long by 70 kilometres wide with a depth of 1.3 kilometres, the Central basin is 230 kilometres long by 60 kilometres wide with a depth of 1.9 kilometres, and the Eastern basin is 150 kilometres long by 40 kilometres wide with a depth of over 2.7 kilometres. The three basins are separated by the Deception Island and Bridgeman Island. The moho depth in the region has been seismically interpreted to be roughly 34 kilometres deep.
Pito Seamount is a seamount in the Pacific Ocean. It rises to a depth of 2,250 metres (7,380 ft) and features hydrothermal activity in the form of black smokers, which were discovered in 1993.
The Canadian Arctic Rift System is a major North American geological structure extending from the Labrador Sea in the southeast through Davis Strait, Baffin Bay and the Arctic Archipelago in the northwest. It consists of a series of interconnected rifts that formed during the Paleozoic, Mesozoic and Cenozoic eras. Extensional stresses along the entire length of the rift system have resulted in a variety of tectonic features, including grabens, half-grabens, basins and faults.
Marine geophysics is the scientific discipline that employs methods of geophysics to study the world's ocean basins and continental margins, particularly the solid earth beneath the ocean. It shares objectives with marine geology, which uses sedimentological, paleontological, and geochemical methods. Marine geophysical data analyses led to the theories of seafloor spreading and plate tectonics.
