Which of the following causes the different densities of oceanic crust and continental crust?
a. ocean depth
b. types of rock
c. age of the rock
d. temperature of the rock

What's a recharge area? a. the part of an aquifer where groundwater meets a lake or stream b. the part of an aquifer where surface water reaches the water table c. the part of an aquifer that's located between two aquicludes d. the part of an aquifer that's located at a lower elevation