Cosmic impact wiped out mammoths A study of rocks in
Pennsylvania, South Carolina and Syria provides powerful support
for the theory that a major impact helped wipe out mammoths and
other megafauna, and destroyed a major prehistoric culture.
They've discovered melt-glass material dating back nearly 13,000
years, and formed at temperatures of 1,700 to 2,200 degrees
Celsius. The new data backs up the controversial Younger Dryas
Boundary (YDB) hypothesis, which proposes that a cosmic impact
took place at the onset of an unusual cold climatic period
called the Younger Dryas. This was around the time of several
major extinctions, including mammoths and giant ground sloths,
and the disappearance of the widely distributed Clovis culture.
"These scientists have identified three contemporaneous levels
more than 12,000 years ago, on two continents yielding siliceous
scoria-like objects (SLOs)," says H Richard Lane, program
director of the National Science Foundation's Division of Earth
Sciences. "SLOs are indicative of