East Pacific Rise

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The East Pacific Rise (shown in light blue), extending south from the Gulf of California East Pacific Rise.jpg
The East Pacific Rise (shown in light blue), extending south from the Gulf of California

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.



East Pacific Rise, 21 degrees north. Base of "black smoker" chimney BlackSmoker.jpg
East Pacific Rise, 21 degrees north. Base of "black smoker" chimney

The oceanic crust is moving away from the East Pacific Rise to either side. Near Easter Island the rate is over 150 mm (6 in) per year which is the fastest in the world. [1] However, on the northern end, it is much slower at only roughly 60 mm (2+12 in) per year. [2] [3] On the eastern side of the rise the eastward-moving Cocos and Nazca plates meet the westward moving South American Plate and the North American Plate and are being subducted under them. The belt of volcanos along the Andes and the arc of volcanoes through Central America and Mexico are the direct results of this collision. Due east of the Baja California Peninsula, the Rise is sometimes referred to as the Gulf of California Rift Zone. In this area, newly formed oceanic crust is intermingled with rifted continental crust originating from the North American Plate.

Near Easter Island, the East Pacific Rise meets the Chile Rise at the Easter Island and Juan Fernandez microplates, trending off to the east where it subducts under the South American Plate at the Peru–Chile Trench along the coast of southern Chile. The southern extension of the East Pacific Rise (called the Pacific-Antarctic Ridge) merges with the Southeast Indian Ridge at the Macquarie Triple Junction south of New Zealand.

Parts of the East Pacific Rise have oblique spreading, that is seafloor spreading that is not orthogonal to the nearest ridge segment. [4]

Along the East Pacific Rise the hydrothermal vents called black smokers were first discovered by the RISE project in 1979, and have since been extensively studied. [5] These vents are forming volcanogenic massive sulfide ore deposits on the ocean floor. [6] [7] Many unique deep-water creatures have been found with vents, that subsist in a chemosynthetic ecosystem rather than one using photosynthesis. [8] The southern stretch of the East Pacific Rise is one of the fastest-spreading divergent boundaries on Earth. [1] [9]

See also

Related Research Articles

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<span class="mw-page-title-main">Seafloor spreading</span> Geological process at mid-ocean ridges

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.

<span class="mw-page-title-main">Divergent boundary</span> Linear feature that exists between two tectonic plates that are moving away from each other

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.

<span class="mw-page-title-main">Hydrothermal vent</span> A fissure in a planets surface from which geothermally heated water issues

A hydrothermal vent is a fissure on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hotspots. Hydrothermal deposits are rocks and mineral ore deposits formed by the action of hydrothermal vents.

<span class="mw-page-title-main">Nazca Plate</span> Oceanic tectonic plate in the eastern Pacific Ocean basin

The Nazca Plate or Nasca Plate, named after the Nazca region of southern Peru, is an oceanic tectonic plate in the eastern Pacific Ocean basin off the west coast of South America. The ongoing subduction, along the Peru–Chile Trench, of the Nazca Plate under the South American Plate is largely responsible for the Andean orogeny. The Nazca Plate is bounded on the west by the Pacific Plate and to the south by the Antarctic Plate through the East Pacific Rise and the Chile Rise respectively. The movement of the Nazca Plate over several hotspots has created some volcanic islands as well as east-west running seamount chains that subduct under South America. Nazca is a relatively young plate both in terms of the age of its rocks and its existence as an independent plate having been formed from the break-up of the Farallon Plate about 23 million years ago. The oldest rocks of the plate are about 50 million years old.

<span class="mw-page-title-main">Pacific Plate</span> Oceanic tectonic plate under the Pacific Ocean

The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million km2 (40 million sq mi), it is the largest tectonic plate.

<span class="mw-page-title-main">Cocos Plate</span> Young oceanic tectonic plate beneath the Pacific Ocean off the west coast of Central America

The Cocos Plate is a young oceanic tectonic plate beneath the Pacific Ocean off the west coast of Central America, named for Cocos Island, which rides upon it. The Cocos Plate was created approximately 23 million years ago when the Farallon Plate broke into two pieces, which also created the Nazca Plate. The Cocos Plate also broke into two pieces, creating the small Rivera Plate. The Cocos Plate is bounded by several different plates. To the northeast it is bounded by the North American Plate and the Caribbean Plate. To the west it is bounded by the Pacific Plate and to the south by the Nazca Plate.

<span class="mw-page-title-main">Mid-ocean ridge</span> Basaltic underwater mountain system formed by plate tectonic spreading

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.

<span class="mw-page-title-main">Juan de Fuca Ridge</span> Divergent plate boundary off the coast of the Pacific Northwest region of North America

The Juan de Fuca Ridge is a mid-ocean spreading center and divergent plate boundary located off the coast of the Pacific Northwest region of North America. The ridge separates the Pacific Plate to the west and the Juan de Fuca Plate to the east. It runs generally northward, with a length of approximately 500 kilometres (310 mi). The ridge is a section of what remains from the larger Pacific-Farallon Ridge which used to be the primary spreading center of this region, driving the Farallon Plate underneath the North American Plate through the process of plate tectonics. Today, the Juan de Fuca Ridge pushes the Juan de Fuca Plate underneath the North American plate, forming the Cascadia Subduction Zone.

<span class="mw-page-title-main">Galápagos Microplate</span> Very small tectonic plate at the Galapagos Triple Junction

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.

<span class="mw-page-title-main">Galápagos hotspot</span> Pacific volcanic hotspot

The Galápagos hotspot is a volcanic hotspot in the East Pacific Ocean responsible for the creation of the Galápagos Islands as well as three major aseismic ridge systems, Carnegie, Cocos and Malpelo which are on two tectonic plates. The hotspot is located near the Equator on the Nazca Plate not far from the divergent plate boundary with the Cocos Plate. The tectonic setting of the hotspot is complicated by the Galapagos Triple Junction of the Nazca and Cocos plates with the Pacific Plate. The movement of the plates over the hotspot is determined not solely by the spreading along the ridge but also by the relative motion between the Pacific Plate and the Cocos and Nazca Plates.

<span class="mw-page-title-main">Easter Microplate</span> Very small tectonic plate to the west of Easter Island

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.

This is a list of articles related to plate tectonics and tectonic plates.

<span class="mw-page-title-main">Geology of the Pacific Ocean</span> Overview about 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 geology of Panama includes the complex tectonic interplay between the Pacific, Cocos and Nazca plates, the Caribbean Plate and the Panama Microplate.

<span class="mw-page-title-main">RISE project</span> 1979 international marine research project

The RISE Project (Rivera Submersible Experiments) was a 1979 international marine research project which mapped and investigated seafloor spreading in the Pacific Ocean, at the crest of the East Pacific Rise (EPR) at 21° north latitude. Using a deep sea submersible (ALVIN) to search for hydrothermal activity at depths around 2600 meters, the project discovered a series of vents emitting dark mineral particles at extremely high temperatures which gave rise to the popular name, "black smokers". Biologic communities found at 21° N vents, based on chemosynthesis and similar to those found at the Galapagos spreading center, established that these communities are not unique. Discovery of a deep-sea ecosystem not based on sunlight spurred theories of the origin of life on Earth.

<span class="mw-page-title-main">Project FAMOUS</span> Marine scientific exploration by manned submersibles of a diverging tectonic plate boundary

Project FAMOUS was the first-ever marine scientific exploration by manned submersibles of a diverging tectonic plate boundary on a mid-ocean ridge. It took place between 1971 and 1974, with a multi-national team of scientists concentrating numerous underwater surveys on an area of the Mid-Atlantic Ridge about 700 kilometers west of the Azores. By deploying new methods and specialized equipment, scientists were able to look at the sea floor in far greater detail than ever before. The project succeeded in defining the main mechanisms of creation of the median rift valley on the Mid-Atlantic Ridge, and in locating and mapping the zone of oceanic crustal accretion.

Emily M. Klein is a professor of geology and geochemistry at Duke University. She studies volcanic eruptions and the process of oceanic crust creation. She has spent over thirty years investigating the geology of mid-ocean ridges and identified the importance of the physical conditions of mantle melting on the chemical composition of basalt.

<span class="mw-page-title-main">Marine geophysics</span>

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.


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