Confirmed: Oldest Fragment of Early Earth is 4.4 Billion Years Old [View all]

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http://news.yahoo.com/confirmed-oldest-fragment-early-earth-4-4-billion-180642066.html;_ylt=AwrBJSCrSwtTTFUAB3zQtDMD

By By Becky Oskin, Staff Writer 19 hours ago

Confirmed: Oldest Fragment of Early Earth is 4.4 Billion Years Old

Ever heard this life advice? When solving a big problem seems impossible, break it into smaller steps.

Well, scientists just took one of geology's biggest controversies and shrunk it down to atomic size. By zapping single atoms of lead in a tiny zircon crystal from Australia, researchers have confirmed the crystal is the oldest rock fragment ever found on Earth — 4.375 billion years old, plus or minus 6 million years.

"We've proved that the chemical record inside these zircons is trustworthy," said John Valley, lead study author and a geochemist at the University of Wisconsin, Madison. The findings were published today (Feb. 23) in the journal Nature Geoscience.

Confirmation of the zircon age holds enormous implications for models of early Earth. Trace elements in the oldest zircons from Australia's Jack Hills range suggest they came from water-rich, granite-like rocks such as granodiorite or tonalite, other studies have reported. That means Earth cooled quickly enough for surface water and continental-type rocks just 100 million years after the moon impact, the massive collision that formed the Earth-moon system. [How Was The Moon Formed?]

"The zircons show us the earliest Earth was more like the Earth we know today," Valley said. "It wasn't an inhospitable place."

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