Into the Deep
The big question in chemical oceanography is, "What controls the chemistry of seawater?" Scientists want to know why oceans are just as salty as they are, why seawater contains certain chemicals and not others, and where those chemicals come from. "This matters because ocean chemistry largely determines what kind of life can thrive in the sea and how well the oceans can buffer changes in the climate system," Von Damm observes. "We now know that seafloor hydrothermal activity is a big piece of the puzzle."
As water percolates down through cracks in the ocean floor at a hydrothermal site, it is rapidly heated by contact with hot rock, and its chemistry changes radically: some chemicals are removed from the water and others are absorbed from the rock. Then the superheated water blasts back out of the seafloor through a vent, like a black smoker, precipitating minerals as it cools. You can't understand the chemistry of the ocean if you don't understand what happens at hydrothermal vents.
In 1981, Von Damm went back to 21º North to collect the data that would become her Ph.D. thesis--the first basic description of vent chemistry. It was on that cruise that she got her first chance to dive in the submersible Alvin and to see a black smoker up close. She remembers the way the seafloor glittered in the sub's strobe lights. It was covered with fool's gold--pyrite, or iron sulfide--that had snowed out of the inky cloud of water. And she remembers pulling up in front of the smoker itself, a large glittering mound with three chimneys sticking out of it like oversized candlesticks.
"The pilot turned around and said, 'Well, before we start working, why don't we eat lunch?'" Von Damm says. "So we sat there and ate our peanut butter and jelly sandwiches with this black smoker sitting right outside the sub. It reminded me of those old photographs of Victorian scientists in their morning coats, having a little picnic with their umbrellas in front of some fantastic geologic exposure."
A century ago, in Victorian times, there were still fantastic new places to be seen on land.
Today, many people think that the Earth has been fully explored. But there are a few who know that
an unexplored world lies beneath the sea, and who make a point of going there.
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