The Peru–Chile Trench, also known as the Atacama Trench, is an oceanic trench in the eastern Pacific Ocean, about 160 kilometres (99 mi) off the coast of Peru and Chile.^[1] It reaches a maximum depth of 8,065 m (26,460 ft) below sea level in Richards Deep (23°10′45″S 71°18′41″W / 23.17917°S 71.31139°W / -23.17917; -71.31139) and is approximately 5,900 km (3,666 mi) long; its mean width is 64 km (40 mi) and it covers an expanse of some 590,000 km² (230,000 sq mi).

The trench delineates the boundary between the subducting Nazca Plate and the overriding South American Plate.

The trench is a result of a convergent plate boundary, where the eastern edge of the oceanic Nazca Plate is being subducted beneath the continental South American Plate.^[1] The trench is also a part of the Chile Triple Junction, an unusual junction that consists of a mid-oceanic ridge and the Chile Rise being subducted under the South American plate at the Peru-Chile Trench. Two seamount ridges within the Nazca Plate enter the subduction zone along this trench: the Nazca Ridge and the Juan Fernández Ridge.

From the Chile Triple Junction to Juan Fernández Ridge the trench is filled with 2.0–2.5 kilometres (1.2–1.6 mi) of sediments, creating a flat bottom topography. Sediments are mainly turbidites interspersed with oceanic deposits of clay, volcanic ash, and siliceous ooze.^[1]

The Peru–Chile Trench, the forearc and the western edge of the central Andean plateau (Altiplano), delineate the dramatic "Bolivian Orocline" that defines the Andean slope of southern Peru, northern Chile, and Bolivia.

Most of the time, the trade winds drive surface waters offshore near the equator, driving the Humboldt Current from the tip of southern Chile to northern Peru. This current is associated with upwelling of deep, nutrient-rich water off the coast of Peru.^[2] At times, El Niño disrupts the usual wind pattern and lessens the upwelling. The consequent loss of nutrient causes fish kills.

In 2018, three new species of snailfish were discovered thriving in the depths of the Atacama Trench.^[3][4]

The subduction of the Nazca Plate below the South American Plate along the Chile-Peru Trench is associated with numerous earthquakes. Several of these earthquakes are notable for their size, associated tsunamis, and landslides.

• 1570 Concepcion earthquake: M_w ~8.3
• 1687 Peru earthquake: M_w ~8.7
• 1730 Valparaíso earthquake M_s ~8.7
• 1746 Lima–Callao earthquake: M_w ~8.7
• 1868 Arica earthquake: M_w ~9.0
• 1877 Offshore Tarapaca, Peru:^[6] M_w ~8.3
• 1906 Valparaíso earthquake
• 1942 Peru earthquake: M_w 8.2 event associated with a tsunami, the rupture dimensions and epicenter are similar to those of a 1996 earthquake
• 1960 Valdivia earthquake: At M_w 9.5, the largest earthquake ever recorded on the earth
• November 1960 Peru earthquake: This event had a long source duration, leading to a significant discrepancy between different moment calculation methods (M_s 6.75 vs M_w 7.8)
• 1970 Ancash earthquake: This M_w7.9 event triggered a landslide with large snow and ice components, killing ~68,000 people
• 2001 southern Peru earthquake: M_w 8.4
• 2005 Tarapacá earthquake
• 2007 Tocopilla earthquake
• 2007 Peru earthquake: M_w 8.0
• 2010 Chile earthquake: M_w 8.8 event associated with a tsunami
• 2010 Pichilemu earthquake
• 2014 Iquique earthquake
• 2015 Illapel earthquake

• Oceanic trench
• Pacific Ring of Fire

• Graham, Alan (2009-09-28). "THE ANDES: A GEOLOGICAL OVERVIEW FROM A BIOLOGICAL PERSPECTIVE". Annals of the Missouri Botanical Garden. 96 (3): 371–385. doi:10.3417/2007146. ISSN 0026-6493.</ref>
• Mofjeld, Harold; Symons, Christina; Lonsdale, Peter; González, Frank; Titov, Vasily (2004-03-01). "Tsunami Scattering and Earthquake Faults in the Deep Pacific Ocean". Oceanography. 17 (1): 38–46. doi:10.5670/oceanog.2004.65. ISSN 1042-8275.
• Fisher, Robert L.; Raitt, Russell W. (1962). "Topography and structure of the Peru-Chile trench". Deep Sea Research and Oceanographic Abstracts. 9 (11–12): 423–443. doi:10.1016/0011-7471(62)90094-3. ISSN 0011-7471.
• Wortel, M.J.R.; Cloetingh, S.A.P.L. (1985). "Accretion and lateral variations in tectonic structure along the Peru-Chile Trench". Tectonophysics. 112 (1–4): 443–462. doi:10.1016/0040-1951(85)90190-8. ISSN 0040-1951.

v t e Geology of Chile
Terranes	Arequipa-Antofalla Chaitenia Chilenia Chiloé Cuyania Fitz Roy Madre de Dios Mejillonia Patagonia
Sedimentary formations and groups	Cenozoic Neogene Abanico Fm. Angostura Fm. Ayacara Fm. Bahía Inglesa Fm. Caldera Beds Caleta Godoy Fm. Caleta Herradura Fm. Campanario Fm. Chaicayán Gp. Cheuquemó Fm. Cholchol Fm. Chucal Fm. Cola de Zorro Fm. Coquimbo Fm. Cura-Mallín Gp. Farellones Fm. La Cascada Fm. Lacui Fm. La Montaña Fm. La Portada Fm. Lauca Fm. Malleco Fm. Mininco Fm. Navidad Fm. Oxaya Fm. Parga Fm. Puduhuapi Fm. Pupunahue Beds Quebrada Macusa Fm. Ranquil Fm. Río Frías Fm. San Pedro Beds Santo Domingo Fm. Temuco Fm. Traiguén Fm. Trapa-Trapa Fm. Tubul Fm. Vargas Fm. Paleogene Abanico Fm. Azapa Fm. Caleta Chonos Fm. Cheuquemó Fm. Cura-Mallín Gp. La Cascada Fm. Lebu Gp. Loreto Fm. Lupica Fm. Oxaya Fm. Parga Fm. Purilactis Gp. Pupunahue Beds Temuco Fm. Vargas Fm. Mesozoic Cretaceous Baños del Flaco Fm. Cerro Colorado Fm. Chacarilla Fm. Chañarcillo Gp. Coihaique Gp. Divisadero Gp. Dorotea Fm. Hornitos Fm. La Liga Fm. Ñirehuao Fm. Punta del Cobre Fm. Purilactis Gp. Quiriquina Fm. Viñita Fm. Way Gp. Zapata Fm. Jurassic Chacarilla Fm. Coihaique Gp. Ibáñez Fm. La Liga Fm. La Negra Fm. Nacientes del Biobío Fm. Nacientes del Teno Fm. Pan de Azúcar Fm. Tobífera Fm. Triassic Canto del Agua Fm. Choiyoi Gp. Panguipulli Fm. Santa Juana Fm. Tralcán Fm. Paleozoic Llano de Chocolate Beds
Batholiths	Coastal central Chile Elqui-Limarí Futrono-Riñihue North Patagonian Panguipulli South Patagonian Vicuña Mackenna
Metamorphic complexes	Bahía Mansa Belén Chañaral Choapa Chonos Cordillera Darwin Eastern Andes Mejillones Puerto Edén Punta de Choros Quebrada del Carrizo Trafún Tierra del Fuego
Faults	Atacama Fault Biobío-Aluminé Fault Cachet Fault Domeyko Fault El Arrayán Fault Futrono Fault Gastre Fault Lanalhue Fault Liquiñe-Ofqui Fault Magallanes-Fagnano Fault Mocha-Villarrica Fault Pichilemu Fault Reigolil-Pirihueico Fault San Ramón Fault Valeriano Fault
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