The downflow zone is thought to have been formed initially by a kink in the ridge, which stresses the rock enough to crack it mechanically. Seawater, forced down into the resulting space, eventually gets heated by the magma, then rises back to the seafloormuch the same process seen in a pot of boiling water. Tolstoy and her coauthors believe the water travels not through large faultsthe model previously favored by some scientists--but through systems of tiny cracks. Furthermore, their calculations suggest that the water moves a lot faster than previously thoughtperhaps a billion gallons per year through this particular system. Their chart of the waters route is reinforced by biologists observations from submersible dives that the area around the downflow chimney is more or less lifeless, while the surging vents are a riot of bacterial mats, mussels, tubeworms, and other weird creatures that thrive off the heat and chemicals.
Its an exciting and substantial contribution. It begins to look at some really big questions, said Dan Fornari, a marine geologist at Woods Hole Oceanographic Institution who was not involved in the study. Among other things, it is a mystery where vent organisms came from-
|Contact: Kevin Krajick|
The Earth Institute at Columbia University