Question

by which mechanism does older oceanic rock move at a ridge?
magnetic forces move the rock.
continents drift and move the rock.
the ridge subducts and moves the rock.
new molten material rises and moves the rock.

Explanation:

At mid - ocean ridges, new molten material (magma) rises from the mantle. As this magma cools and solidifies, it forms new oceanic crust. The continuous addition of new material at the ridge causes the older oceanic rock to move away from the ridge. This is a key process in seafloor spreading. Magnetic forces do not directly move the rock in this context. Continental drift is a broader concept related to the movement of continents, not specifically the movement of oceanic rock at a ridge. Subduction occurs at trenches, not at ridges.

Answer:

D. New molten material rises and moves the rock.