Define the terms: Provide concise definitions for each option:
- Oceanic trenches: Narrow, deep depressions in the ocean floor, often formed at subduction zones where tectonic plates converge.
- Seamounts: Underwater mountains formed by volcanic activity, typically not as deep as trenches.
- Abyssal plains: Flat, expansive regions of the ocean floor, located at great depths but not the deepest.
- Continental shelves: Shallow, submerged edges of continents, much closer to the surface compared to other features.