Editing Oceanic trench (section)

=== Sedimentation ===
Trench morphology is strongly modified by the amount of sedimentation in the trench. This varies from practically no sedimentation, as in the Tonga-Kermadec trench, to completely filled with sediments, as with the Cascadia subduction zone. Sedimentation is largely controlled by whether the trench is near a continental sediment source.{{sfn|Kearey|Klepeis|Vine|2009|p=251}} The range of sedimentation is well illustrated by the Chilean trench. The north Chile portion of the trench, which lies along the [[Atacama Desert]] with its very slow rate of weathering, is sediment-starved, with from 20 to a few hundred meters of sediments on the trench floor. The tectonic morphology of this trench segment is fully exposed on the ocean bottom. The central Chile segment of the trench is moderately sedimented, with sediments onlapping onto pelagic sediments or ocean basement of the subducting slab, but the trench morphology is still clearly discernible. The southern Chile segment of the trench is fully sedimented, to the point where the outer rise and slope are no longer discernible. Other fully sedimented trenches include the Makran Trough, where sediments are up to {{convert|7.5|km||sp=us}} thick; the Cascadia subduction zone, which is completed buried by {{convert|3 to 4|km||sp=us}} of sediments; and the northernmost Sumatra subduction zone, which is buried under {{convert|6|km||sp=us}} of sediments.{{sfn|Geersen|Voelker|Behrmann|2018|pp=412–416}}

Sediments are sometimes transported along the axis of an oceanic trench. The central Chile trench experiences transport of sediments from source fans along an axial channel.{{sfn|Völker|Geersen|Contreras-Reyes|Reichert|2013}} Similar transport of sediments has been documented in the Aleutian trench.{{sfn|Stern|2005}}

In addition to sedimentation from rivers draining into a trench, sedimentation also takes place from landslides on the tectonically steepened inner slope, often driven by [[megathrust earthquake]]s. The Reloca Slide of the central Chile trench is an example of this process.{{sfn|Völker|Weinrebe|Behrmann|Bialas|2009}}