It’s no secret that water shapes the world around us. Rivers etch great canyons into the Earth’s surface, while glaciers reorganize the topography of entire mountain ranges. But water’s influence on the landscape runs much deeper than this: Water explains why we have land in the first place.

You might think of land as the bits of crust that just happen to jut up above sea level, but that’s mostly not the case. Earth’s continents rise above the seas in part because they are actually made of different stuff than the seafloor. Oceanic