The Nazca Ridge is a submarine ridge , located on the Nazca Plate off the west coast of South America . This plate and ridge are currently subducting under the South American Plate at a convergent boundary known as the Peru-Chile Trench at approximately 7.7 cm (3.0 in) per year. The Nazca Ridge began subducting obliquely to the collision margin at 11°S, approximately 11.2 Ma, and the current subduction location is 15°S. The ridge is composed of abnormally thick basaltic ocean crust , averaging 18 ±3 km thick. This crust is buoyant, resulting in flat slab subduction under Peru . This flat slab subduction has been associated with the uplift of Pisco Basin and the cessation of Andes volcanism and the uplift of the Fitzcarrald Arch on the South American continent approximately 4 Ma.
41-472: The Nazca Ridge is approximately 200 km (120 mi) wide, 1,100 km (680 mi) long, and has 1,500 m (4,900 ft) of bathymetric relief. The gradient of the slopes is 1-2 degrees. The ridge is located at a depth of 4,000 m (13,000 ft) below sea level, above the carbonate compensation depth . It is blanketed in a thin covering of 300 to 400 m (980 to 1,310 ft) thick pelagic calcareous ooze . Based on Rayleigh wave analysis,
82-452: A 7,000-km-long convergent boundary where the oceanic Nazca Plate subducts or dives beneath the continental South American Plate . The Peru–Chile Trench marks the location where the two plates meet and converge. Subduction at the plate boundary rate varies throughout the 7,000 km length, at 65 mm/yr towards the north, and up to 80 mm/yr in the south. The presence of active subduction can produce large earthquakes when elastic energy along
123-421: A height of 24 to 26 meters have been debunked and concluded as exaggerations. A more accurate height of the tsunami has been estimated at 5 meters. The tsunami was also confused as being an orphan tsunami reported along Japan's Sanriku coast due to erroneous cataloging of historical tsunamis, which also led to the confusion that it was from the 1586 Tenshō earthquake ; a large Japanese earthquake. The presence of
164-448: A layer of siliceous ooze or abyssal clay deposited on top of the carbonate layer. The exact value of the CCD depends on the solubility of calcium carbonate which is determined by temperature , pressure and the chemical composition of the water – in particular the amount of dissolved CO 2 in the water. Calcium carbonate is more soluble at lower temperatures and at higher pressures. It
205-671: A tsunami at the Sanriku coast however, was reported in June 1585, now thought to be from the 1585 Aleutian Islands earthquake . At a monument in Tokura village near the Sanriku coast in Miyagi Prefecture , a stone monument stated that a tsunami between 1 and 2 meters in height struck the coast; the tsunami has been inferred to be of the 1585 event. Modelling of the tsunami from the 1586 earthquake in Peru suggest
246-462: Is also more soluble if the concentration of dissolved CO 2 is higher. Adding a reactant to the above chemical equation pushes the equilibrium towards the right producing more products: Ca and HCO 3 , and consuming more reactants CO 2 and calcium carbonate according to Le Chatelier's principle . At the present time the CCD in the Pacific Ocean is about 4200–4500 metres except beneath
287-423: Is called the "age" of the water mass . Thermohaline circulation determines the relative ages of the water in these basins. Because organic material, such as fecal pellets from copepods , sink from the surface waters into deeper water, deep water masses tend to accumulate dissolved carbon dioxide as they age. The oldest water masses have the highest concentrations of CO 2 and therefore the shallowest CCD. The CCD
328-658: Is estimated that the magma was sourced at approximately 95 km depth from a 7% partial melt . The Nazca Ridge has a conjugate feature on the Pacific Plate , the Tuamotu Plateau . Magnetic anomalies have shown that there was symmetrical spreading at the Pacific-Farallon/Nazca center, so the Tuamotu Plateau can be used as a proxy for the pre-subducted Nazca Ridge geometry. The Nazca Plate began subducting into
369-563: Is relatively shallow in high latitudes with the exception of the North Atlantic and regions of Southern Ocean where downwelling occurs. This downwelling brings young, surface water with relatively low concentrations of carbon dioxide into the deep ocean, depressing the CCD. In the geological past the depth of the CCD has shown significant variation. In the Cretaceous through to the Eocene
410-401: Is the depth, in the oceans, at which the rate of supply of calcium carbonates matches the rate of solvation . That is, solvation 'compensates' supply. Below the CCD solvation is faster, so that carbonate particles dissolve and the carbonate shells ( tests ) of animals are not preserved. Carbonate particles cannot accumulate in the sediments where the sea floor is below this depth. Calcite
451-445: Is the least soluble of these carbonates, so the CCD is normally the compensation depth for calcite. The aragonite compensation depth ( ACD ) is the compensation depth for aragonitic carbonates. Aragonite is more soluble than calcite, and the aragonite compensation depth is generally shallower than both the calcite compensation depth and the CCD. As shown in the diagram, biogenic calcium carbonate (CaCO 3 ) tests are produced in
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#1732848675172492-596: The forearc basin has resulted in the loss of 110 km (68 mi) of the South American Plate since 11 Ma. The forearc basin of Pisco located above the subducting ridge has experienced uplift since the Late Pliocene or Pleistocene an uplift that is attributed to the subduction of the Nazca Ridge. The flat slab subduction associated with the Nazca Ridge has been linked to the cessation of volcanism in
533-425: The photic zone of the oceans (green circles). Upon death, those tests escaping dissolution near the surface settle, along with clay materials. In seawater, a dissolution boundary is formed as a result of temperature, pressure, and depth, and is known as the saturation horizon . Above this horizon, waters are supersaturated and CaCO 3 tests are largely preserved. Below it, waters are undersaturated, because of both
574-433: The solubility increases dramatically with depth and pressure. By the time the CCD is reached all calcium carbonate has dissolved according to this equation: Calcareous plankton and sediment particles can be found in the water column above the CCD. If the sea bed is above the CCD, bottom sediments can consist of calcareous sediments called calcareous ooze , which is essentially a type of limestone or chalk . If
615-574: The Andes Mountains at about 4 Ma. The subduction has also been linked with the formation of the Fitzcarrald Arch, which is a 400,000 km (150,000 sq mi), 400 to 600 m (1,300 to 2,000 ft) high, domed topographic feature that defines the Amazon drainage Basin. Studies indicate that the uplift of the arch also began 4 Ma. The uplift of the Fitzcarrald Arch intersects with
656-575: The Andes Mountains where there is a shift from high-gradient topography to the low-gradient Amazon Basin . This topographic uplift effectively divides the Amazon drainage basin into three sub-basins, the Ucayali to the northwest, the Acre to the northeast, and the Madre De Dios to the southeast. It's hypothesized that significant modifications to sedimentary, erosional, and hydrological processes have resulted from
697-411: The CCD to rise, with zones of downwelling first being affected. Ocean acidification , which is also caused by increasing carbon dioxide concentrations in the atmosphere, will increase such dissolution and shallow the carbonate compensation depth on timescales of tens to hundreds of years. On the sea floors above the carbonate compensation depth, the most commonly found ooze is calcareous ooze ; on
738-412: The CCD was much shallower globally than it is today; due to intense volcanic activity during this period atmospheric CO 2 concentrations were much higher. Higher concentrations of CO 2 resulted in a higher partial pressure of CO 2 over the ocean. This greater pressure of atmospheric CO 2 leads to increased dissolved CO 2 in the ocean mixed surface layer. This effect was somewhat moderated by
779-501: The Pacific-Farallon/Nazca spreading center, and has been attributed to hot spot volcanism. There is some debate as to where this hot spot was originally located however, with locations near Easter Island and Salas y Gomez both being proposed. The ridge is primarily composed of mid-ocean ridge basalt, which erupted on the Nazca Plate when the plate was already 5-13 Ma old. Based on isotopic ratios and rare earth element composition, it
820-519: The Peru-Chile trench 11.2 Ma at 11°S. Due to the oblique orientation of the ridge to the Nazca-South American plate collision zone, the ridge has migrated south along the active margin to its current location at 15°S. Based on Tuamotu Plateau mirror relationship, it is estimated that 900 km (560 mi) of the Nazca Ridge has already subducted. The speed of migration has slowed over time, with
861-428: The Peru-Chile trench due to the ridge subduction beyond a shallowing from 6,500 to 5,000 m (21,300 to 16,400 ft) above the ridge location. However, this is a tectonic erosion margin. There is no accretionary wedge forming in the trench, and what sediment is found there is from continental sources, based on fossil assemblage. The calcareous ooze blanketing Nazca Ridge is completely subducted. Crustal erosion of
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#1732848675172902-464: The area around the Nazca Ridge subduction zone, known at the Peru megathrust . These include, but are not limited to, a magnitude 8.1 earthquake in 1942 , a magnitude 8.0 earthquake in 1970, a magnitude 7.7 earthquake in 1996, a magnitude 8.4 earthquake in 2001, and a magnitude 8.0 earthquake in 2007 . Earthquake records for this area of subduction go back to 1586 . All of these ruptures were located either on
943-451: The buoyancy effect can be seen in oceanic crust aged from 30-40 Ma. The Nazca Plate is dated to 45 Ma where it subducts into the Peru-Chile trench. The extreme thickness of the buoyant ridge is responsible for the flat slab subduction of the older underlying plate. Modeling has shown that this type of subduction is only concurrent with submarine ridges, and accounts for approximately 10% of convergent boundaries. The most recent estimate of
984-520: The capital Lima . A section of the Peruvian coast, stretching from Caravelí to Trujillo , north to south, was severely damaged by the earthquake . Major destruction occurred in the capital city Lima as well. The estimated moment magnitude (M w ) 8.1 earthquake triggered a locally damaging tsunami up to 5 m (16 ft). This was the first major earthquake to strike the city of Lima since its establishment in 1535 . The coast of Peru lies
1025-479: The coast of Peru or within the Peru-Chile Trench between 9°S and 18°S, coincidental with the subducting Nazca Ridge, and include both intraplate and interplate rupturing. No large earthquakes have been located between 14°S and 15.5°S, where the bathymetric high of the ridge is subducting. Interplate earthquakes do not occur in direct conjunction with the Nazca Ridge. There has been little geomorphic affect to
1066-421: The deep oceans' elevated temperatures during this period. In the late Eocene the transition from a greenhouse to an icehouse Earth coincided with a deepened CCD. John Murray investigated and experimented on the dissolution of calcium carbonate and was first to identify the carbonate compensation depth in oceans. Increasing atmospheric concentration of CO 2 from combustion of fossil fuels are causing
1107-499: The earthquake occurred over a 1,000 km long by 120 km wide area near the coast. The earthquake was also felt in the cities Cusco and Huánuco . The earthquake reportedly caused the collapse of the towers of a cathedral in the city of Lima. Significant rockslides occurred at Cerro San Cristobal ( es ) in the Rímac District of Lima Province . The earthquake also severely damaged the residence of Fernando Torres de Portugal y Mesía ,
1148-562: The equatorial upwelling zone, where the CCD is about 5000 m. In the temperate and tropical Atlantic Ocean the CCD is at approximately 5000 m. In the Indian Ocean it is intermediate between the Atlantic and the Pacific at approximately 4300 meters. The variation in the depth of the CCD largely results from the length of time since the bottom water has been exposed to the surface; this
1189-415: The exposed sea bed is below the CCD tiny shells of CaCO 3 will dissolve before reaching this level, preventing deposition of carbonate sediment. As the sea floor spreads, thermal subsidence of the plate, which has the effect of increasing depth , may bring the carbonate layer below the CCD; the carbonate layer may be prevented from chemically interacting with the sea water by overlying sediments such as
1230-412: The increasing solubility with depth and the release of CO 2 from organic matter decay, and CaCO 3 will dissolve. The sinking velocity of debris is rapid (broad pale arrows), so dissolution occurs primarily at the sediment surface. At the carbonate compensation depth, the rate of dissolution exactly matches the rate of supply of CaCO 3 from above. At steady state this depth, the CCD, is similar to
1271-415: The plate boundary (megathrust) is released suddenly after decades or centuries of accumulated strain. Earthquakes rupturing the megathrust are known as megathrust earthquakes; capable of generating tsunamis when there is sufficient and sudden uplift of the seafloor, in turn lead to the sudden displacement of the sea. The shock from the quake was felt at 19:00 local time on July 9, a Wednesday . The shock
Nazca Ridge - Misplaced Pages Continue
1312-503: The portion of the Nazca Ridge that is currently exposed dates from 31 ± 1 Ma at the Peru-Chile trench, to 23 ± 1 Ma where the Nazca Ridge and Easter Seamount Chain are adjacent. Basalt composition has also been used to show that the Nazca Ridge and Easter Seamount Chain formed from the same magma source, with the formation of the Easter Seamount Chain occurring after the Nazca Plate changed direction. Formation began along
1353-412: The ridge has an average crustal thickness of 18 ±3 km, but could have a localized maximum thickness up to 35 km (22 mi). This is abnormally thick for oceanic crust. By comparison, the underlying Nazca Plate adjacent to the ridge ranges from 6 to 8 km (3.7 to 5.0 mi) thick, and is comparable to the worldwide average of around 7 km (4.3 mi) thick. Based on basalt ages,
1394-425: The ridge migrating at 7.5 cm (3.0 in) per year until 10.8 Ma, then slowing to 6.1 cm (2.4 in) per year from 10.8-4.9 Ma. The current ridge migration rate is 4.3 cm (1.7 in) per year. The current plate subduction rate is 7.7 cm (3.0 in) per year. The ridge is buoyant, resulting in flat slab subduction of the Nazca Plate underneath Peru. Buoyancy is related to crustal age, and
1435-405: The sea floors below the carbonate compensation depth, the most commonly found ooze is siliceous ooze . While calcareous ooze mostly consists of Rhizaria , siliceous ooze mostly consists of Radiolaria and diatoms . 1586 Lima%E2%80%93Callao earthquake The 1586 Lima–Callao earthquake ( Spanish : Terremoto de Lima y Callao de 1586 ) occurred on July 9 along the coast of Peru , near
1476-399: The snowline (the first depth where carbonate-poor sediments occur). The lysocline is the depth interval between the saturation and carbonate compensation depths. Calcium carbonate is essentially insoluble in sea surface waters today. Shells of dead calcareous plankton sinking to deeper waters are practically unaltered until reaching the lysocline , the point about 3.5 km deep past which
1517-439: The subduction angle for the Nazca Plate is 20° to a depth of 24 km (15 mi) at 110 km (68 mi) inland. At 80 km (50 mi) depth, approximately 220 km (140 mi) inland, the plate shifts to a horizontal orientation, and continues to travel horizontally for up to 700 km (430 mi) inland, before resuming subduction into the asthenosphere . Large magnitude earthquakes occur in association with
1558-497: The then viceroy of Peru . Ground fissures formed in the city when the shaking was ongoing. The associated tsunami was documented by the viceroy of Peru in which he said the waves picked up and smashed homes, and inundated up to 250 meters inland. Even when the waves retreated, the some parts of the city was so severely flooded that it was impossible to ride a horse through. At Callao , the earthquake and tsunami destroyed many docks and warehouses. Ships were dragged far inland during
1599-411: The tsunami inundation. Many trees and bushes were uprooted from the ground and deposited far inland by the tsunami. The 1586 earthquake ruptured a 175-km-long section of the Peru-Chile subduction zone , similar in size to the 1974 earthquake . The shock had an estimated moment magnitude (M w ) of 8.1, and a tsunami magnitude (M t ) of 8.5. Older descriptions of the tsunami having
1640-479: The uplift of the Fitzcarrald Arch. Evolutionary paths for freshwater fish began to diverge in the Amazon sub-basins approximately 4 Ma as well. The uplift of the Fitzcarrald Arch could also be the catalyst that lead to these differing evolutionary paths, effectively isolating fish populations from each other. 18°S 79°W / 18°S 79°W / -18; -79 Carbonate compensation depth The carbonate compensation depth ( CCD )
1681-410: Was accompanied by loud noises which frightened many residents, driving them out of their homes. Most residents were able to evacuate in time during the earthquake, such that the death toll was small, although there were many individuals that suffered injuries. When the quake struck, many of the residents were already out in the streets or gardens where they were safe from collapse. Damage and effects from