Question

Which of the following correctly describes seafloor spreading?

A. New oceanic crust is formed at midocean ridges, pushed away from the ridge, and destroyed at deep-sea trenches.

B. New oceanic crust is formed at seamounts and spreads outward in all directions.

C. New oceanic crust is formed at deep-sea trenches, pushed away from the trench, and destroyed at midocean ridges.

D. New oceanic crust is formed in the middle of tectonic plates and then spreads outward in bands.

Answer 1

The answer is B. This occurs at mid-ocean ridges, where two tectonic plates are moving away from each other. As they move in opposite directions, the magma from the mantle below rises to fill the void/space left above. As the magma rises, it cools and forms a new crust. This volcanic activity continues as long as the tectonic plates are moving away from each other and new crust is formed spreading outwards from the ridge, with time.

Answer 2

Option D correctly describes seafloor spreading. Seafloor spreading is a process which typically occur at middle ocean ridges where new oceanic crusts are formed as a result of volcanic activity. These oceanic crusts then gradually move away from the ridge.