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Washington: An
international team of researchers has discovered melt-glass
material, dating back nearly 13,000 years and forming at
temperatures between 1,700 and 2,200 degrees Celsius, which was
the outcome of a cosmic body hitting the earth.
The discovery was made by an 18-member international team of
researchers including James Kennett, professor of earth science at
University of California Santa Barbara (UCSB).
Found in a thin layer of sedimentary rock in South Carolina and
Syria, the material provides the latest evidence to support the
controversial Younger Dryas Boundary (YDB) hypothesis, proposing
that a cosmic impact occurred 12,900 years ago at the onset of an
unusual cold climatic period called the Younger Dryas.
This episode occurred at or close to the time of major extinction
of the North American megafauna, including mammoths and giant
ground sloths; and the disappearance of the prehistoric and widely
distributed Clovis culture, the journal Proceedings of the
National Academy of Sciences reports.
"These scientists have identified three contemporaneous levels
more than 12,000 years ago, on two continents yielding siliceous
scoria-like objects (SLOs)," said H. Richard Lane, programme
director of National Science Foundation's Division of Earth
Sciences, which funded the research.
"SLOs are indicative of high-energy cosmic airbursts/impacts,
bolstering the contention that these events induced the beginning
of the Younger Dryas. That time was a major departure in biotic,
human and climate history," said Lane.
Morphological and geochemical evidence of the melt-glass confirms
that the material is not cosmic, volcanic, or of human-made
origin. "The very high temperature melt-glass appears identical to
that produced in known cosmic impact events such as Meteor Crater
in Arizona, and the Australasian tektite field," said Kennett of
UCSB, according to a California statement.
"The melt material also matches melt-glass produced by the Trinity
nuclear airburst of 1945 in Socorro, New Mexico," Kennett
continued. "The extreme temperatures required are equal to those
of an atomic bomb blast, high enough to make sand melt and boil."
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