The mid-ocean ridges are elevated above the surrounding seafloor because Ridge rocks are hot and therefore of relatively less dense than adjacent cooler oceanic crust.
I hope this helps you! :)
In geology subduction is the process whereby one tectonic plate is forced underneath another tectonic plate along a convergent boundary. Places where this type of plate interaction occurs are called subduction zones. Subduction zones have a high rate of volcanism, earthquakes, and mountain building.
