When this superheated water rises into the frigid ocean waters, the sudden mixing of hot and cold causes the dissolved rocks to precipitate out, forming towering, chimney-like structures containing sulfide minerals, such as pyrite, chalcopyrite and sphalerite, as well as silicates.
The largest such chimney ever observed was 140 feet tall, but most break off before they reach such heights, leaving a rubble field around their base that also provides biological niches.
When the temperature of water emerging from the vents is above 575 degrees Fahrenheit, the sulfide minerals precipitate out as microscopic particles and give the water a billowing, cloud-like appearance that inspired the name black smokers.
Life at the vents is the only life on Earth that does not depend, either directly or indirectly, on energy from the sun. Instead, bacteria in the hot seawater get their energy from hydrogen sulfide in a process called chemosynthesis. They, in turn, are the base of a food chain that leads all the way up to exotic fish, all of which ultimately rely on the toxic volcanic fumes.
Perhaps the most exotic of the creatures at the black smokers are the Pompeii worms, Alvinella pompejana, which live in papery tubes on the sides of the chimneys. The tails of the worms inside the tubes are in water temperatures as high as 185 degrees Fahrenheit, while the heads are immersed in water that is only about 76 degrees.
The worms are not only the most heat-tolerant multicellular organisms known, but they also live in the highest temperature gradient ever observed--a 109-degree drop in temperature across their bodies that most biologists did not believe could be survived. How they survive this is still a mystery.
In their recent expedition, the researchers used metal cages designed and built by Le Olson of the University of Washington. Using a remotely operated submersible, the team maneuvered the cages over the chimneys, which were strapped inside the cages with steel cable.
After the base of each chimney was severed with a chain saw, the structures were raised 7,500 feet to the surface. One was an old, cold structure that was not venting fluids, two were venting fluids hot enough (up to 176 degrees) to support a wide variety of life and the fourth was an active black smoker.
The fourth one, called Finn, "was still smoking and steaming when it reached the surface," said geologist John Delaney, a co-leader of the expedition.
