Final answer:
Mid-ocean ridges are higher in elevation than the surrounding ocean floor because of the process of seafloor spreading at divergent plate boundaries. Magma from the mantle rises to fill the gap created by the moving tectonic plates, pushing the existing crust upward. This occurs due to decompression melting and buoyancy of the magma.
Step-by-step explanation:
Mid-ocean ridges are higher in elevation than the surrounding ocean floor because of the process of seafloor spreading at divergent plate boundaries. At these boundaries, tectonic plates are moving apart, creating a gap where new crust is formed. Magma from the mantle rises to fill this gap, forming new crust and pushing the existing crust upward.
This occurs due to decompression melting, where the reduced pressure in the mantle causes the magma to rise. The magma is less dense than the surrounding mantle material, making it buoyant and causing it to push up the ocean floor.
A similar process occurs at hotspots, where mantle plumes generate increased temperature and cause melting of the lithospheric region. The resulting volcanoes can be found anywhere in the world. In both cases, the formation of new crust and the upwelling of magma contribute to the higher elevation of mid-ocean ridges.