Any long, narrow, steep-sided depression in the ocean bottom in which maximum oceanic depths (24,000–36,000 ft, or 7,000–11,000 m) occur. The deepest known depression of this kind is the Mariana Trench. Most trenches occur at subduction zones, where one tectonic plate is thrust under another.
Variants of DEEP-SEA TRENCH
deep-sea trench or oceanic trench
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