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 Pacific-Antarctic Ridge is a divergent tectonic plate boundary located on the seafloor of the South Pacific Ocean, separating the Pacific plate from the Antarctic plate. It is regarded as the southern section of the East Pacific Rise in some usages, generally south of the Challenger fracture zone which is associated with a triple junction between the Juan Fernández microplate, the Pacific plate and the Antarctic plate. It stretches from there in a general southwesterly direction to the Macquarie Triple Junction south of New Zealand.
The South American plate is a major tectonic plate which includes the continent of South America as well as a sizable region of the Atlantic Ocean seabed extending eastward to the African plate, with which it forms the southern part of the Mid-Atlantic Ridge.
The East Pacific Rise (EPR) is a mid-ocean rise, at 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°S130°W, where it joins the Pacific-Antarctic Ridge (PAR) trending west-south-west towards Antarctica, near New Zealand. Much of the rise lies about 3,200 km (2,000 mi) off the South American coast and reaches a height about 1,800–2,700 m (5,900–8,900 ft) above the surrounding seafloor.
The Scotia plate is a minor tectonic plate on the edge of the South Atlantic and Southern oceans. Thought to have formed during the early Eocene with the opening of the Drake Passage that separates Antarctica and South America, it is a minor plate whose movement is largely controlled by the two major plates that surround it: the Antarctic plate and the South American plate. The Scotia plate takes its name from the steam yacht Scotia of the Scottish National Antarctic Expedition (1902–04), the expedition that made the first bathymetric study of the region.
A fracture zone is a linear feature on the ocean floor—often hundreds, even thousands of kilometers long—resulting from the action of offset mid-ocean ridge axis segments. They are a consequence of plate tectonics. Lithospheric plates on either side of an active transform fault move in opposite directions; here, strike-slip activity occurs. Fracture zones extend past the transform faults, away from the ridge axis; are usually seismically inactive, although they can display evidence of transform fault activity, primarily in the different ages of the crust on opposite sides of the zone.
The Galápagos Rise is an extinct spreading centre located about 1,000 km southsouthwest of the Galápagos islands, and 2,000 km west of Peru which was active in the Miocene period. It developed shortly after the Farallon plate broke into two parts, forming the Cocos and Nazca plates. During its existence as a spreading centre the Galápagos Rise formed the eastern boundary of the Bauer microplate.
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.
An oceanic core complex, or megamullion, is a seabed geologic feature that forms a long ridge perpendicular to a mid-ocean ridge. It contains smooth domes that are lined with transverse ridges like a corrugated roof. They can vary in size from 10 to 150 km in length, 5 to 15 km in width, and 500 to 1500 m in height. Their counterparts on land are metamorphic core complexes, which form in areas of continental crustal extension or stretching.
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 (only exceeding those of the Gakkel Ridge in the Arctic) combined with a fast lengthening of its axis between the two flanking triple junctions, Rodrigues (20°30′S70°00′E) in the Indian Ocean and Bouvet (54°17′S1°5′W) in the Atlantic Ocean.
The Bouvet triple junction is a geologic triple junction of three tectonic plates located on the seafloor of the South Atlantic Ocean. It is named after Bouvet Island, which lies about 250 km (160 mi) to the east. The three plates which meet here are the South American plate, the African plate, and the Antarctic plate. The Bouvet triple junction although it appears to be a R-R-R type, that is, the three plate boundaries which meet here as mid-ocean ridges: the Mid-Atlantic Ridge (MAR), the Southwest Indian Ridge (SWIR), and the South American-Antarctic Ridge (SAAR) is actually slightly more complex and in transition.
The South American–Antarctic Ridge or simply American-Antarctic Ridge is the tectonic spreading center between the South American plate and the Antarctic plate. It runs along the sea-floor from the Bouvet triple junction in the South Atlantic Ocean south-westward to a major transform fault boundary east of the South Sandwich Islands. Near the Bouvet triple junction the spreading half rate is 9 mm/a (0.35 in/year), which is slow, and the SAAR has the rough topography characteristic of slow-spreading ridges.
The Macquarie triple junction is a geologically active tectonic boundary located at 61°30′S161°0′E at which the historic Indo-Australian plate, Pacific plate, and Antarctic plate collide and interact. The term triple junction is given to particular tectonic boundaries at which three separate tectonic plates meet at a specific, singular location. The Macquarie triple junction is located on the seafloor of the southern region of the Pacific Ocean, just south of New Zealand. This tectonic boundary was named in respect to the nearby Macquarie Island, which is located southeast of New Zealand.
The Juan Fernández plate is a small tectonic plate (microplate) in the Pacific Ocean. With a surface area of approximately 10×105 km2 (3.9×105 sq mi), the microplate is located between 32° and 35°S and 109° and 112°W. The plate is located at a triple junction between the Antarctic plate, the Nazca plate, and the Pacific plate. Approximately 2,000 km (1,200 mi) to the west of South America, it is, on average, 3,000 metres (9,800 feet) deep with its shallowest point coming to approximately 1,600 metres (5,200 feet), and its deepest point reaching 4,400 metres (14,400 feet).
This is a list of articles related to plate tectonics and tectonic plates.
The Eltanin fault system is a series of six or seven dextral transform faults that offset the Pacific-Antarctic Ridge, a spreading zone between the Pacific plate and the Antarctic plate. This is extending by up to 7.93 cm/year (3.12 in/year). It was named after the oceanographic ship USNS Eltanin.
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.
Overlapping spreading centers are a feature of spreading centers at mid-ocean ridges.
The Chile Ridge, also known as the Chile Rise, is a submarine oceanic ridge formed by the divergent plate boundary between the Nazca plate and the Antarctic plate. It extends from the triple junction of the Nazca, Pacific, and Antarctic plates to the Southern coast of Chile. The Chile Ridge is easy to recognize on the map, as the ridge is divided into several segmented fracture zones which are perpendicular to the ridge segments, showing an orthogonal shape toward the spreading direction. The total length of the ridge segments is about 550–600 km.
