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.
|Approximate area||2,900,000 km2|
|Features||Cocos Island, Pacific Ocean|
|1Relative to the African Plate|
The Cocos Plate was created by sea floor spreading along the East Pacific Rise and the Cocos Ridge, specifically in a complicated area geologists call the Cocos-Nazca spreading system. From the rise the plate is pushed eastward and pushed or dragged (perhaps both) under the less dense Caribbean Plate, in the process called subduction. The subducted leading edge heats up and adds its water to the mantle above it. In the mantle layer called the asthenosphere, mantle rock melts to make magma, trapping superheated water under great pressure. As a result, to the northeast of the subducting edge lies the continuous arc of volcanos —also known as the Central America Volcanic Arc— stretching from Costa Rica to Guatemala, and a belt of earthquakes that extends farther north, into Mexico.
The northern boundary of the Cocos Plate is the Middle America Trench. The eastern boundary is a transform fault, the Panama Fracture Zone. The southern boundary is a mid-oceanic ridge, the Galapagos Rise. The western boundary is another mid-ocean ridge, the East Pacific Rise.
The Rivera Plate north of the Cocos Plate is thought to have separated from the Cocos Plate 5–10 million years ago. The boundary between the two plates appears to lack a definite transform fault, yet they are regarded as distinct. After its separation from the Cocos Plate, the Rivera Plate started acting as an independent microplate.
The devastating 1985 Mexico City earthquake and the 2017 Chiapas earthquake were results of the subduction of the Cocos Plate beneath the North American Plate. The devastating 2001 El Salvador earthquakes were generated by the subduction of this plate beneath the Caribbean Plate.
The 1937 Orizaba earthquake occurred on July 26 at 03:47 UTC, near Orizaba, Veracruz, Mexico. It had a magnitude of 7.3 on the surface wave magnitude scale. Thirty four people were reported dead. Damage was reported in Esperanza, Puebla. This was an intraplate earthquake within the subducting Cocos Plate.1965 Oaxaca earthquake
The 1965 Oaxaca earthquake occurred in Mexico on August 23 at 13:46 with a moment magnitude of 7.5. Five people were reported dead in Mexico City and 1 in Oaxaca. There was an anomalous change in seismic activities before the earthquake. There was a quiescent stage from late 1963 to mid-1964, and it was followed by a renewal of seismic activities before the main shock. This earthquake was a shallow thrust earthquake in the interplate subduction zone, in which the Cocos Plate is subducting beneath the North American Plate.1999 Oaxaca earthquake
The 1999 Oaxaca earthquake occurred on September 30 at 11:31 local time (16:31 UTC) in Oaxaca, Mexico, 60 km NNW of Puerto Ángel. The epicenter was located near San Agustin Loxicha. It had a magnitude of Mw 7.4. The maximum intensity reached MM VIII in southwestern Oaxaca, and could be felt strongly in Mexico City. The torrential rains preceding and following the temblor intensified the damage of this earthquake. Thirty-five people were reported dead. The archeological site of the ancient Zapotec city of Monte Alban also suffered damage in this earthquake. This was an intraplate earthquake in the Cocos Plate, with a normal-faulting mechanism. The fault plane was 90 km long and 45 km wide. The maximum slip was about 2.5 m, which was located about 20 and 40 km WNW of the hypocenter.Caribbean Plate
The Caribbean Plate is a mostly oceanic tectonic plate underlying Central America and the Caribbean Sea off the north coast of South America.
Roughly 3.2 million square kilometers (1.2 million square miles) in area, the Caribbean Plate borders the North American Plate, the South American Plate, the Nazca Plate and the Cocos Plate. These borders are regions of intense seismic activity, including frequent earthquakes, occasional tsunamis, and volcanic eruptions.Coiba Plate
The Coiba Plate is a small tectonic plate (a microplate) located off the coasts south of Panama and northwestern Colombia. It is named after Coiba, the largest island of Central America, just north of the plate offshore southern Panama. It is bounded on the west by the Cocos Plate, on the south by the Malpelo Plate, on the east by the North Andes Plate, and on the north by the Panama Plate. This microplate was previously assumed to be part of the Nazca Plate, forming the northeastern tongue of the Nazca Plate together with the Malpelo Plate. Bordering the Coiba Plate on the east are the north-south striking Bahía Solano Fault and east of that, the Serranía de Baudó, an isolated mountain chain in northwestern Chocó, Colombia.East Pacific Rise
The East Pacific Rise is a mid-oceanic ridge, 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.Farallon Plate
The Farallon Plate was an ancient oceanic plate that began subducting under the west coast of the North American Plate—then located in modern Utah—as Pangaea broke apart during the Jurassic period. It is named for the Farallon Islands, which are located just west of San Francisco, California.
Over time, the central part of the Farallon Plate was completely subducted under the southwestern part of the North American Plate. The remains of the Farallon Plate are the Juan de Fuca, Explorer and Gorda Plates, subducting under the northern part of the North American Plate; the Cocos Plate subducting under Central America; and the Nazca Plate subducting under the South American Plate.The Farallon Plate is also responsible for transporting old island arcs and various fragments of continental crustal material rifted off from other distant plates and accreting them to the North American Plate.
These fragments from elsewhere are called terranes (sometimes, "exotic" terranes). Much of western North America is composed of these accreted terranes.Galapagos Rise
The Galapagos Rise is a divergent boundary located between the South American coast and the triple junction of the Nazca Plate, the Cocos Plate, and the Pacific Plate. The volcanically active Galapagos Islands exist on the Galápagos hotspot above the Galapagos Rise. The Galapagos Microplate is a small separate plate on the rise just to the southeast of the triple junction.
The Cocos Ridge trends northeasterly from the Galapagos to the coast of Costa Rica and Panama. The Carnegie Ridge trends almost due east to the Ecuadorian coast.
The Galapagos Rise is a currently active ridge. Fernandina Volcano on Fernandina Island, the most westerly island of the chain erupted on May 12, 2005 ejecting a column of ash that rose to a height of seven km from a fissure on the west side of the volcano. Volcanic ash fell on neighboring Isabela Island. Alcedo Volcano on Isabela Island last erupted in the 1950s.Galapagos Triple Junction
The Galapagos Triple Junction is a geological area in the eastern Pacific Ocean several hundred miles west of the Galapagos Islands where three tectonic plates - the Cocos Plate, the Nazca Plate and the Pacific Plate - meet. It is an unusual type of triple junction in which the three plates do not meet at a simple intersection. Instead, the junction includes two small microplates, the Galapagos Microplate and the Northern Galapagos Microplate, caught in the junction, turning synchronously with respect to each other and separated by the Hess Deep rift.Galápagos Microplate
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.Galápagos hotspot
The Galápagos hotspot is a volcanic hotspot in the East Pacific Ocean responsible for the creation of the Galapagos 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.
The hotspot is believed to be over 20 million years old and in that time there has been interaction between the hotspot, both of these plates, and the divergent plate boundary, at the Galapagos Spreading Centre. Lavas from the hotspot do not exhibit the homogeneous nature of many hotspots; instead there is evidence of four major reservoirs feeding the hotspot. These mix to varying degrees at different locations on the archipelago and also within the Galapagos Spreading Centre.Geology of Costa Rica
The geology of Costa Rica is part of the Panama Microplate, which is slowly moving north relative to the stable Caribbean Plate.In the late Cretaceous, an oceanic trench or backarc system formed in connection with a subduction zone, situated where the Isthmus of Panama is now located. Into the early Paleogene, deep sea, open ocean sediments and basalt lava accumulated in the backarc. Volcanic activity was intense in the Cretaceous, Paleocene and Eocene. The volcanic arc that built up during the period overthrust onto the southern margin of North America.During the Oligocene, the offshore Pacific Plate fragmented into the Cocos Plate and Nazca Plate, divided by the east-west Colon spreading ridge. The tectonics of Costa Rica are more complicated because the Cocos Plate subdivided into two blocks separated by the Costa Rica Fracture Zone (running northeast onto land), with the northern block being subducted. Submarine canyons have been used to infer the path of the Panama Fracture Zone running along the coast creating wrench faults. On the Osa Peninsula, the Nicoya Complex preserves oceanic crust with basaltic lava, dolerite, gabbro, limestone, chert and argillite, obducted onto land before the Oligocene and then rearranged by Miocene wrench faults.In the Neogene the low angle subduction of the Cocos Plate led to volcanism in the now extinct Cordillera de Aguacate chain in the center of the country. The Valle Central basin formed as volcanism shifted northeastward in the Quaternary. In the Pleistocene, calderas ejected huge quantities of silica-rich ash, filling the Valle Central basin, affecting the Tarcoles Gorge and generating the Orotina debris fan at the coast. Streams rearranged and flowed more toward the Pacific, downcutting existing channels.In the past two million years, Costa Rican volcanoes have erupted andesite, rhyolite and dacite with geochemical patterns that suggest the magma may have come from the melting of metamorphosed basalt.Marine geologists have found mound-like structure offshore due to subduction related fluid venting. A lack of chlorine suggests a freshwater origin.Geology of Nicaragua
The geology of Nicaragua includes Paleozoic crystalline basement rocks, Mesozoic intrusive igneous rocks and sedimentary rocks spanning the Cretaceous to the Pleistocene. Volcanoes erupted in the Paleogeneand within the last 2.5 million years of the Quaternary, due to the subduction of the Cocos Plate, which drives melting and magma creation. Many of these volcanoes are in the Nicaraguan Depression paralleled by the northwest-trending Middle America Trench which marks the Caribbean-Cocos plate boundary. Almost all the rocks in Nicaragua originated as dominantly felsic continental crust, unlike other areas in the region which include stranded sections of mafic oceanic crust. Structural geologists have grouped all the rock units as the Chortis Block.Malpelo Plate
The Malpelo Plate is a small tectonic plate (a microplate) located off the coasts west of Ecuador and Colombia. It is the 57th plate to be identified. It is named after Malpelo Island, the only emerged part of the plate. It is bounded on the west by the Cocos Plate, on the south by the Nazca Plate, on the east by the North Andes Plate, and on the north by the Coiba Plate, separated by the Coiba Transform Fault (CTF). This microplate was previously assumed to be part of the Nazca Plate. The Malpelo Plate borders three major faults of Pacific Colombia, the north to south striking Bahía Solano Fault in the north and the Naya-Micay and Remolino-El Charco Faults in the south.Panama Fracture Zone
The Panama Fracture Zone is a major, active right lateral-moving transform fault and associated inactive fracture zone which forms part of the tectonic boundary between the Cocos Plate and the Nazca Plate. It is part of the triple junction between the Cocos Plate, Nazca Plate and Caribbean Plate which is moving in the southeastern direction at 5.5 cm/yr. It runs from the East Pacific Rise to the Middle America Trench.Panama Plate
The Panama Plate is a small tectonic plate sandwiched between the Cocos Plate and Nazca Plate to the south and the Caribbean Plate to the north. Most of its borders are convergent boundaries including a subduction zone to the west. It consists, for the most part, of the nations of Panama and Costa Rica.Phoenix Plate
The Phoenix Plate (also known as the Aluk or Drake Plate) was an ancient tectonic plate that existed during the mid-Cretaceous through early Cenozoic time. The remainder of the plate is now located east of the Drake Passage/Shackleton Fracture Zone.
The Phoenix Plate began subducting under the Antarctic Plate. The Phoenix Ridge, a mid-oceanic ridge between the Pacific and the Phoenix Plates which had a spreading rate of 18–20 cm per year until around 84 Ma. A major decrease in spreading rate, and the convergence rate with the Antarctic Plate occurred around 52.3 Ma. During the Late Cretaceous, the Phoenix Plate fragmented into the Charcot Plate, much in the same way in which the Rivera and the Cocos Plate were formed by the fragmentation of the Farallon Plate.The Antarctic-Phoenix Ridge (sometimes also called the Phoenix Ridge) consists of three extinct spreading ridge segments between the Antarctic Peninsula and the Scotia Sea. This ridge was initiated during the Late Cretaceous-Early Tertiary when the plate had divergent boundaries with the Bellingshausen and Pacific Plates. Bellingshausen was fused with the Antarctic Plate around 61 Ma and the Phoenix plate was gradually subducted by the Antarctic Plate as the Pacific-Antarctic Ridge propagated. The last collision between ridge crest segments and the subduction zone happened around 6.5 Ma and spreading had ceased entirely by 3.3 Ma when the small remnant of the Phoenix Plate was incorporated into the Antarctic Plate. The South Shetland Trough is the south-eastern boundary of the remnant and the Shackleton Fracture Zone is its north-eastern boundary.Rivera Plate
The Rivera Plate is a small tectonic plate (a microplate) located off the west coast of Mexico, just south of the Baja California Peninsula. It is bounded on the northwest by the East Pacific Rise, on the southwest by the Rivera Transform Fault, on the southeast by a deformation zone, and on the northeast by the Middle America Trench and another deformation zone.
The Rivera Plate is believed to have separated from the Cocos Plate located to its southeast about 5–10 million years ago. Seismicity and tomography images show that the Rivera plate dips at 40° beneath the forearc region and then dips ~70° beneath the Trans-Mexican Volcanic Belt. The subduction of the Rivera Plate under the North American Plate, in the Mid-American Trench, has been the cause of the strongest earthquakes in the history of Mexico, including the largest earthquake in Mexico during the 20th century which occurred on June 3, 1932 in the state of Jalisco. The quake had a magnitude of 8.2 with a magnitude 7.8 aftershock, both of which caused widespread casualties and damage.
On October 9, 1995, a magnitude 7.6 earthquake occurred beneath the Jalisco region and caused significant loss of life and property.
A 7.8 magnitude earthquake occurred on January 24, 2003 near Colima in Mexico.Volcán Atitlán
Volcán Atitlán (Spanish pronunciation: [atiˈtlan]) is a large, conical, active stratovolcano adjacent to the caldera of Lake Atitlán in the Guatemalan Highlands of the Sierra Madre de Chiapas range. It is within the Sololá Department, southwestern Guatemala.
The volcano has been quite active historically, with more than a dozen eruptions recorded between 1469 and 1853, the date of its most recent eruption. Atitlán is part of the Central American Volcanic Arc. The arc is a chain of volcanoes stretching along Central America formed by subduction of the Cocos Plate underneath the Caribbean Plate. These volcanoes are part of the Ring of Fire around the Pacific Ocean.
Volcán Atitlán is few miles south of Volcán Tolimán, which rises from the southern shore of Lake Atitlán. Volcán San Pedro rises above Lake Atitlán northwest of Volcán Atitlán. A long narrow bay separates Volcán Atitlán and Volcán Toliman from Volcán San Pedro.