Ever wonder why the ocean doesn’t get saltier, even though it’s continually evaporating?
I’m Jim Metzner, and this is the Pulse of the Planet, presented by the American Museum of Natural History. Helping us shed some light on this question is Charles Langmuir, a professor of Earth and Environmental Science at Columbia University.
“Seawater is salty , but it’s not too salty. Its saltiness is just perfect for the life that lives in it. And the saltiness hasn’t changed very much over hundreds of millions of years. Now how could that happen, because we’re continually eroding the continents; we’re continually sticking more salts into the ocean, and yet somehow the ocean is able to maintain itself in this steady state, despite all this stuff being added.”
Most of the Earth’s volcanic activity is located on the bottom of the ocean along the chain of ocean ridges which circle the earth. It turns out that these volcanoes actually help regulate the salinity of the ocean.
“One of the principle ways that this happens is because these volcanoes at the bottom of the ocean put very, very hot molten rock in very close contact with very cold seawater. And so this seawater circulates through the cracks in the ocean crust and gets heated up to very high temperatures. At these very high temperatures, the water reacts with the rock and removes certain things from the seawater, which makes the seawater stay in balance, chemically. So in this way erosion, volcanoes on the sea floor, the chemical composition of seawater and its capacity to remain in a state conducive to living organisms are all intimately related to one another.”
Pulse of the Planet is presented by the American Museum of Natural History. Additional funding for this series has been provided by the National Science Foundation. I’m Jim Metzner.