Fisher, Robert L. Geological Research Division, Scripps Institution of Oceanography, La Jolla, California.
Last reviewed:November 2019
- Geophysical exploration
- Seafloor topography and surficial processes
- Crustal composition: evidence from dredging
- Evolution: evidence from drilling
- Related Primary Literature
- Additional Reading
A long, narrow, characteristically very deep and asymmetrical depression of the seafloor, with relatively steep sides. Oceanic trenches characterize active margins at the ocean-basin–continent or ocean-basin–island-arc boundaries. They contain the greatest oceanic depths and are associated with the most active volcanism, largest negative gravity anomalies, most frequent shallow seismicity, and almost all of the intermediate and deep-focus earthquake activity. As the surface expression of the widely accepted process of subduction by which oceanic crustal material is returned to the upper mantle, they are key elements in current models of plate tectonic evolution on Earth and possibly on Venus.
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