Carla Helfferich is a science writer at the Institute. With the aftershocks from the latest earthquakes in San Francisco and China, millions of people received lessons about seismic events. For one thing, the sea would be poisonously briny without them. Proving that requires considering first why the sea is salty. An old Scandinavian folktale says that a magic salt grinder was tossed into the ocean, where it functions eternally for want of the right charm to stop it.
Oceanographers joke that the tale is quite true, except for details.
In the real world, the grinding is done by rivers and their tributaries. As rains wash the land, they carry some of it away. Raw material for the sea's salt, minerals slip into the waterways and head downhill to the ocean. The oceans steadily evaporate, providing water vapor to the air. As fog and rain clouds, the water comes ashore again.