yes
both
In a process taking tens of millions of years, part of the ocean floor sinks back into the mantle at deep ocean trenches.
At deep-ocean trenches, subduction allows part of the ocean floor to sink back into the mantle. The ocean floor does not just keep spreading. Instead, it sinks beneath deep underwater canyons called deep-ocean trenches. Where there are trenches, subduction takes place.
At deep-ocean trenches, subduction allows part of the ocean floor to sink back into the mantle. The ocean floor does not just keep spreading. Instead, it sinks beneath deep underwater canyons called deep-ocean trenches. Where there are trenches, subduction takes place.
The Young Ocean Floor is the part of the mantle showing between the 2 split tectonic plates.
sea floor
Along constructive/divergent plate boundaries. This is where the new ocean floor comes from. This is the youngest part of the ocean floor that is.
The crust contains the ocean floor and also the continents on Earth.
Continental Shelf.
reef
The bottom of the ocean is part of a tectonic plate or continental shelf, or can be on the breach line between two shelves.