Scientists seek lost continent near the Hudson

Rock outcrop yields clues to the rise and fall of ancient Rodinia

November 25, 1999|By New York Times News Service

TOWN OF RAMAPO, N.Y- a billion years ago, or so the prevailing geological theory has it, the Earth's continental plates collided, pushing up mountains the height of the Himalayas and creating a supercontinent that geologists call Rodinia.

In time, the breakup of Rodinia created an ocean, Iapetus, that was itself destroyed when the continents collided and formed yet another supercontinent, Pangaea.

Eventually, Pangaea split up, creating North America, Europe, Africa, and the Atlantic Ocean. Finally, erosion and the burden of mile-high glaciers flattened much of the landscape, including present-day metropolitan New York.

'The Rodinian story'

These days, Alexander Gates, a professor of geology at Rutgers University in Newark, N.J., is navigating that landscape, rock hammer in hand. Ranging the forests of New York's Harriman State Park in Rockland and Orange counties, scribbling observations in his leather-bound field notebook, he is, by his description, "looking to piece together the Rodinian story."

For the last three years, Gates and his research team have been mapping the tortured history of one of the last vast, geologically pristine places in the region an inventory of significant rock-types, features and geological faults, photographing them and collecting rock samples.

Their ambition is not only to compile the most detailed picture of the geological history of Harriman and its region, but also to look for clues to important mysteries in the story of the earth's lost supercontinents, which had a history of violent assembly and reassembly as dizzying as the slam-dance of bumper cars in an amusement park.

On the urbanized, suburbanized, exurbanized face of it, New York and environs might not seem to be the most fertile geological ground. Lately, according to Gates, the region "has been neglected by geologists." But, he added, the basement rock of the metropolitan area is actually some of the most complex in the United States. in terms of the dazzling variety of rocks, their spectacular deformation by wind, water, ice and volcanic fire, and their intricate, baffling, Rubik's Cube construction.

Harriman is place to be

And when it comes to studying that local geology, Harriman is the place to be. Across the region, development has obscured most of what geologists refer to as "exposures." Harriman, though, "is pretty much the way it was left, after the glacier retreated" 12,000 years ago, said Yngvar Isachsen, principal scientist for the Geological Survey of the New York State Museum in Albany. "In geology, it doesn't get much better than that," he said.

Already, Gates said, the project has yielded revelations about the formation of the ancient continent of Rodinia, including at least one "Rosetta stone," a Harriman rock outcrop that provides significant information on the supercontinent's formation.

The research could have practical applications as well. As seismologists study the origins of the recent earthquake in Turkey, they are calling for intensified research to gauge the likelihood of future seismic events in the metropolitan area. Though the region is often characterized as dormant, geologists say it presents the potential for earthquake hazard.

And because Harriman had to close its hiking trails until recently because of the drought, Gates' work "can be very helpful to us," said Carol Ash, executive director of the Palisades Interstate Park Commission, which administers 100,000 acres of forest in New York and New Jersey, including Harriman.

"We hope that Dr. Gates' study of fissures in the rock will give us a greater understanding of the park's ground-water system, and help us to manage it better," Ash said.

Some scientists say this focus on New York's geology is long overdue. Geologists "paid a lot of attention to the New York region at the turn of the century, especially when the city's water tunnels were being built," said Leonardo Seeber, a research scientist at the Lamont-Doherty Earth Observatory of Columbia University in Palisades, N.Y.


Later, the region became "unfashionable," Seeber said. High mountains, active volcanoes, petroleum reserves and pure-science research drew many academics elsewhere.

"Other areas are trendier, and they get better funding," Isachsen said. These days, thanks to budget cuts, the Geological Survey cannot even afford to assign a geological specialist to the New York metropolitan area.

As they carry out their project, Gates and his team are also studying and reinterpreting the observations of generations of geologists who toiled before the era of plate tectonics, the evolving theory that, since the 1960s, has viewed the earth's rock record in the context of the interaction of the earth's continental plates. The metropolitan area "has always been where the action is," said Gates, but now, he noted, geologists can finally make sense of what all that action meant.

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