Embargoed until 2 p.m., EDT
July 11, 2001
NSF PR 01-56

Media Contacts:
Cheryl Dybas, NSF
(703) 292-8070/cdybas@nsf.gov
Sandra Hines, UW
(206) 543-2580/shines@u.washington.edu


Program Contacts:
Phil Taylor
(703) 292-8582/prtaylor@nsf.gov
Dave Epp
(703) 292-8581/depp@nsf.gov


Scientists Discover Secrets Of 'Lost City'
New class of hydrothermal vents formed differently
Note: Images available at: http://www.nsf.gov/od/lpa/news/press/pr0156.htm


     Hydrothermal vent structures serendipitously discovered last
December in the mid-Atlantic Ocean, including a massive 18-story
vent taller than any seen before, are formed in a very different
way than ocean-floor vents studied since the 1970s.  The findings
are published by National Science Foundation (NSF)-funded
researchers in the July 12 edition of Nature.  This new class of
hydrothermal vents apparently forms where circulating seawater
reacts directly with mantle rocks, as opposed to where seawater
interacts with basaltic rocks from magma chambers beneath the
seafloor.


     "This discovery is a tremendous example of the results of
targeted exploration of the ocean," says Margaret Leinen, NSF
assistant director for geosciences.  "We knew that the areas of
great faults on the seafloor were interesting, but did not
realize that hydrothermal activity of this sort could be taking
place on seafloor generated millions of years ago."


     No one had previously seen a field quite like this, but
Deborah Kelley, a University of Washington (UW) oceanographer and
lead author of the Nature paper, says this kind of vent may be
common on the seafloor. If so, scientists may have
underestimated the extent of hydrothermal venting, the amount of
heat and chemicals pouring into the world's oceans and the
abundance of life that thrives in such conditions.


     "Rarely does something like this come along that drives home
how much we still have to learn about our own planet," Kelley
says. "We need to shed our biases in some sense about what we
think we already know."

      The Lost City Field, named partly because it sits on
the seafloor mountain Atlantis Massif, was discovered December 4,
2000, during an NSF-funded expedition led by Scripps Institution
of Oceanography's Donna Blackman, UW's Kelley and Duke
University's Jeffrey Karson. Blackman and Karson are among the
paper's co-authors.


     Lost City is like other hydrothermal vent systems where
seawater circulates beneath the seafloor and gains heat and
chemicals until there is enough heat for the fluids to rise
buoyantly and vent back into the ocean.  As the warm fluids mix
with cold seawater the chemicals separate from the vent fluids
and solidify, sometimes piling up into impressive mounds, spires
and chimneys of minerals.

      It was immediately clear, however, that the Lost City
Field is unlike other hydrothermal vent systems in a number of
ways.  First, there is the height attained by some of the
structures - the mighty 180-foot vent scientists named Poseidon
compares to previously studied vents that reach 80 feet or less.
The new vents are nearly 100 percent carbonate, the same material
as limestone in caves, and range in color from a clean white to
cream or gray, in contrast to black smoker vents that are a
darkly mottled mix of sulfide minerals.  And perhaps the Lost
City's most distinctive feature is that it is sitting on 1.5
million-year-old crust formed from mantle material.