Answer to Question 1The mantle responds to short-term stresses, such as seismic waves, like a solid, but responds to longterm
stresses, such as those of isostatic rebound, like a viscous liquid.
Answer to Question 2Isostatic rebound is the re-equilibration of the crust by rebounding to the level at which it floats
again in the mantle after a mass has been removed. The melting of glaciers after the end of the ice age
has caused the crust they were sitting on to rebound upward.