Calculate the difference in average elevation between continental crust $($granite$,40$ km thick$)$ and oceanic crust $($basalt$,7$ km thick$)?$ In this case, the asthenosphere is the compensation layer. How does this compare to the average depth of the ocean basins $($the abyssal plain$)?($note: the black solid line is not sea level $–$which depends on the amount of water in the Ocean$).$