Ancient Meteor Blast May Have Caused Extinctions (Forwarded)

University of California-Santa Barbara

CONTACT
Gail Gallessich, 805-893-7220

FEATURED RESEARCHER
Luann Becker, 206-465-1005

May 23, 2007

Ancient Meteor Blast May Have Caused Extinctions, Report UC Santa Barbara
Scientists

Santa Barbara, Calif. -- New scientific findings suggest that a large,
extraterrestrial rock may have exploded over North America 13,000 years
ago, explaining riddles that scientists have wrestled with for decades,
including an abrupt cooling of the atmosphere and the extinction of large
mammals.

Two scientists from the University of California, Santa Barbara presented
the discovery today, along with two other researchers at a news conference
at the annual meeting of the American Geophysical Union being held in
Acapulco, Mexico. Over 20 scientists contributed to the discovery.

James Kennett, paleoceanographer and professor emeritus in the Department
of Earth Science at UC Santa Barbara, said that the discovery potentially
explains three of the most-debated controversies of recent decades.

"This is what happens when you do interdisciplinary science," said Luann
Becker, research scientist with UC Santa Barbara's Institute of Crustal
Studies. "You can solve some of the bigger problems."

The time period in question is called the "Younger Dryas," a time of
abrupt cooling that lasted for about 1,000 years and occurred during an
inter-glacial warm period. Evidence for the temperature change is recorded
in ice cores.

According to the scientists, the extraterrestrial rock must have been
about five kilometers across, and either exploded in the atmosphere or
directly hit the Laurentide ice sheet located in the Northeastern section
of North America. Wildfires across the continent would have resulted from
the fiery impact, killing off the vegetation that was the food supply of
many of the larger mammals like the woolly mammoths, causing them to go
extinct. Since the Clovis people of North America hunted the mammoths as a
major source of their food, they too were affected by the impact and their
culture died out, explained Becker.

The scientific team visited over a dozen archaeological sites in North
America where they found high concentrations of iridium, an element that
is rare on Earth, and is almost exclusively associated with meteors. They
found microspherules of glass-like carbon, which form at high temperatures
and are thought to be a result of the impact blast. Also present were
another type of impact tracer -- carbon molecules called fullerenes with
gases trapped inside.

The team concluded that the impact of the space rock melted a large
portion of the Laurentide ice sheet, causing enormous amounts of cool,
fresh water to flow into the Atlantic and Arctic Oceans. This would have
caused a major disruption of the circulation of warm and cold water in
these oceans, leading to a cooler atmosphere and the glaciation of the
Younger Dryas period.

The scientists found evidence for the impact as far west as the Santa
Barbara Channel Islands. Kennett said that the best examples from the West
Coast were found at a site on Santa Rosa Island.

The Paleoclimate Program of the National Science Foundation and NASA
funded this research.