Oceanic trench in the Pacific Ocean off South America
The Peru–Chile Trench, also known as the Atacama Trench, is an oceanic trench in the eastern Pacific Ocean, about off the coast of Peru and Chile. It reaches a maximum depth of below sea level in Richards Deep () and is approximately long; its mean width is and it covers an expanse of some .
The trench delineates the boundary between the subducting Nazca plate and the overriding South American plate.
Geology.
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. 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 of sediments, creating a flat bottom topography. Sediments are mainly turbidites interspersed with oceanic deposits of clay, volcanic ash, and siliceous ooze.
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.
Oceanography.
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. At times, El Niño disrupts the usual wind pattern and lessens the upwelling. The consequent loss of nutrient causes fish kills.
Biology.
In 2018, three new species of snailfish were discovered thriving in the depths of the Atacama Trench.
In 2023, a predatory crustacean was discovered in the Atacama Trench.
Associated seismicity.
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.
References.
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