Press Release 05-149
New Images Suggest Oceanic Crust Generated from Several Magma Sources
August 25, 2005
Some of the highest quality images ever taken of the Earth's
lower crust reveal that the upper and lower crust form in two
distinctly different ways.
"This new way of studying the ocean crust is the equivalent of a new
telescope in astronomy," said Bruce Malfait, head of the National
Science Foundation (NSF)'s marine geosciences section, which funded the
research. "It allows us to look at Earth processes and composition at a
remarkable new level of detail."
To form the images, the researchers, led by a team from Columbia
University's Lamont-Doherty Earth Observatory (LDEO), analyzed sound
waves bounced off structures deep in the Earth, a process similar to
creating an ultrasound image. They published the results of their work
in the Aug. 25 issue of the journal Nature.
The Earth's oceanic crust is formed from molten rock, or magma,
located beneath mid-ocean ridges. Magma chambers located in the
mid-crust are known to be responsible for generating the upper-oceanic
crust. But it has so far been unclear if the lower crust is formed from
the same magma source, or if it arises primarily from "magma
lenses"--smaller bodies located at or near the base of the crust.
The resulting images are the first of their kind to show solidified
lenses and sills--narrow lateral intrusions of magma--embedded within
the crust-mantle boundary known as the Moho transition zone. The
presence of such lenses and sills deep near a mid-ocean ridge suggests
the lower crust is at least partially formed from several smaller
sources of magma rather than from a single large source located in the
middle of the crust.
"This demonstrates that the process of crustal formation is more
complex than believed," said LDEO scientist and lead author of the
study, Mladen Nedimovic. "It also favors the emerging view that
volcanoes have a complicated plumbing system consisting of many
interconnected sills and magma conduits. We still have a lot to learn
about what goes on beneath the surface of the Earth."
Researchers from LDEO as well as the Scripps Institution of
Oceanography and the Woods Hole Oceanographic Institution collected
seismic data from the oceanic crust beneath the sea floor off the coast
of Wash., Ore., and northern Calif.
The study was also funded by a grant from the Doherty Foundation.
-NSF-
Media Contacts
Cheryl Dybas, NSF (703) 292-7734 cdybas@nsf.gov
Ken Kostel, LDEO (212) 854-9729 kkostel@ei.columbia.edu
Cindy Clark, SIO (858) 534-3624 cclark@ucsd.edu
Shelley Dawicki, WHOI (508) 289-2270 sdawicki@whoi.edu
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