Beyond these three uses, there is much disagreement over when to capitalize. Every major publication and publisher has its own standards, and many writers have their own preferences (which are generally overridden by in-house rules during publication).
Deep-sea trench. Deep-sea trench, also called oceanic trench , any long, narrow, steep-sided depression in the ocean bottom in which occur the maximum oceanic depths, approximately 7,300 to more than 11,000 metres (24,000 to 36,000 feet). They typically form in locations where one tectonic plate subducts under another.
The Aleutian Trench is effectively buried east of Kodiak Island in the Gulf of Alaska. There the ocean floor is smooth and flat. To the west, farther from the sediment supply of Alaska, the trench reaches depths of more than 7 km (about 4 miles).