WASHINGTON — Scientists have launched a project to
construct a highly accurate calendar of key events in what they
call “deep time,” the almost unimaginable span since
Earth was born 4.5 billion years ago.

Sponsors think a precise prehistoric time scale can help them
better interpret what is happening to our planet and predict what
may lie ahead as the world gets warmer. For example, they hope the
project, called CHRONOS (Greek for “time”), will help
settle arguments over the causes and effects of climate change on
the evolution and extinction of species.

Project director Bruce Wardlaw, a geologist at the U.S. Geologic
Survey in Reston, Va., said the purpose was to “produce a
global time scale of Earth’s history to solve problems for
the benefit of society.”

Researchers are counting on tools and technologies developed
over the last 10 years to greatly increase the accuracy of the
geologic time scale, said Samuel Bowring, a geology professor at
the Massachusetts Institute of Technology in Cambridge.

Bowring told a deep-time conference in Washington in October
that the goal is to achieve a resolution of 1/10th of 1
percent—far better than the existing errors of 2 percent or
more—by 2015. That would cut some uncertainties from millions
to thousands of years.

Scientists from multiple disciplines are involved in the effort.
Physicists are perfecting their ability to determine the age of a
rock by the rate of decay of radioactive elements. Geologists
recently learned how to relate periodic switches in the magnetism
of the seafloor to events on land. Chemists can precisely date lava
and ashes from ancient volcanoes. Biologists have learned to read
the “molecular clocks” in living cells that tell when a
species was created. Astronomers connect regular changes in
Earth’s orbit around the sun to geologic records.

Researchers say a finer time scale is needed because existing
geologic “clocks” are notoriously inaccurate, sometimes
off by millions of years. They are based mostly on evidence
contained in layers of rock laid down eons ago, as can be seen
vividly in the walls of Grand Canyon.

Project scientists say a special concern is the risk of an
abrupt climate change—a rapid rise or fall of 10 to 20
degrees Fahrenheit in global temperature in less than a
century—as happened repeatedly in the distant past.

The fear is that the gradual climate warming over the last 150
years could eventually reach a tipping point, as when hot water
suddenly turns to steam, and send the world’s temperatures
soaring.

“Climate can change on a dime,” said Gerilyn
Soreghan, who teaches geology at the University of Oklahoma in
Norman.
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