How do subduction zones create deep ocean trenches?
Quick Answer
A dense oceanic plate bends and sinks beneath another plate, dragging the seafloor downward. This produces long, narrow trenches such as the Mariana Trench, which is over 11,000 meters deep.
The Full Story
At a subduction zone, one tectonic plate dives beneath another because it is colder and denser, usually as oceanic lithosphere. As the descending plate bends, it pulls the seafloor down into a trench parallel to the plate boundary. Sediments can be scraped off and piled up into an accretionary wedge, but the trench remains a dramatic surface expression of the plate collision. The Mariana Trench in the western Pacific is the deepest known, reaching roughly 11,000 meters.
Key Facts
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