Why does the lithosphere sink back into the earth at trenches, which form the surface trace of subduction zones? A.
lithosphere is always lighter than the asthenosphere

B, the mantle is filled with gas

C. as the lithosphere moves away from the heat of the rift valley, it gets older and loses heat, ultimately giving it a higher density than the portion of the mantle which composes the asthenosphere

D. Because warm lithosphere has a higher density than the portion of the mantle which composes the asthenosphere.

answer; ///(a) ;

the species living around the vents are especially good at dispersal.  

deep-sea vent originates on the floor of the ocean when seawater circulates through hot volcanic rocks, usually situated where the new oceanic crust is being produced.  

biological dispersal refers to the movement of species from their location of birth to their site of breeding, or from breeding site to another. similarly, the oceanic dispersal refers to the movement of the species from one land mass to another by sea crossing.