Slabs of oceanic lithosphere sink at subduction zones because the subducted slab is denser than the underlying asthenosphere. In this process, called ________, Earth's gravity tugs at the slab, drawing the rest of the plate toward the subduction zone.
A) slab pull
B) ridge push
C) convection
D) reverse polarity
Question 2
The ________ is weaker and less rigid than the overlying lithosphere.
A) crust
B) lower mantle
C) upper mantle
D) asthenosphere