"A single rock outcrop can reveal the entire geologic history of this park," he said. "And this one shows evidence of a continental collision where two of the earth's plates hit together, and then later, hot magma intruded at 1,000 degrees centigrade." He gestured toward the gray wall.

"That was great," the director, Mercedes Walker, said to Dr. Gates and his cameraman, Aaron Dubrow. "Now let's do the whole thing again."

O.K., it's not Comedy Central, or even Court TV, but that's the way it goes in science show business. Dr. Gates, chairman of the Department of Earth and Environmental Sciences at Rutgers University in Newark, is the star of a new animated video documentary chronicling the last two billion years of New York's tortured rock record.

The video is just one of the tools Dr. Gates is planning to use to make Harriman State Park, one of the last vast, geologically pristine places in the region, the main attraction at a new center for "geotourism."

"Geotourism is a relatively new phenomenon, but a lot of people are passionate about geology," Dr. Gates said. "That's why geology lovers always get into car accidents around outcrops -- they're only looking at the rocks."

For many decades, most geological researchers have given short shrift to the New York region, Dr. Gates said, thanks to the spectacular topography -- higher mountains, active volcanoes and deep canyons -- of the West.

But the stony basement of the metropolitan area is actually one of the most complex in the United States, he said, in terms of the dazzling variety of rocks and their intricate mille-feuille construction.

To spread this message, Dr. Gates and his scientific team have been working to establish a geological park in the unspoiled 50,000-acre outdoor laboratory of Harriman, in Rockland and Orange Counties.

There is already a coterie of geology lovers who visit regions of the United States and Europe that are promoted as geological parks, complete with tours and self-guided itineraries. But Dr. Gates also envisions Harriman as an educational tool for scholars, teachers, schoolchildren and the general public.

The new Web site in progress marries a Harriman hiking map with starred views of geological interest, offering information about each outcrop that attempts to satisfy interest levels ranging from grade school to grad school. It is all an outgrowth of the work of Dr. Gates and his team, who, supported by a $75,000 grant from the National Science Foundation, have been mapping the rugged landscape of Harriman for the last six years.

His ambition has been not only to compile the most detailed picture of the geological history of Harriman and its region, but also to look for clues that might unravel important mysteries of the earth's lost supercontinents.

Already, in his earth-science sleuthing, Dr. Gates has shed new light not only on the pattern of local earthquakes but also on the Harriman watershed in a time of drought. "His studies of subsurface geological fractures have helped reveal the pattern of water flows in Harriman, which is important during the drought emergency," said Ken Krieser, deputy executive director of the Palisades Interstate Park Commission.

Dr. Gates's research has also yielded new revelations about the formation of the ancient continent of Rodinia about a billion years ago. Furthermore, he has identified two-billion-year-old zircons in Harriman rocks, twice as old as any previous finds in the New York region.

This discovery has led Dr. Gates to the startling science-fictionish conclusion that "the Hudson Highlands of New York may have once been a part of South America."

The garnets discovered by Dr. Gates date to 2.045 million years ago, the record-holder for metropolitan-area geology. This raises the speculation that portions of the Hudson Highlands rocks found in Harriman could be a remnant of another continental mass that slammed into what is now metropolitan New York.

Dr. Gates has located a preliminary match in Western South America, in the headlands of the Amazon River, which offers a similar geology. It is possible that Harriman contains a remnant of what is now Brazil that was left behind when the continents pulled apart 600 million years ago.

For years Dr. Gates has also made a study of the earthquake-producing fault zones in Harriman. Though the New York area is often characterized as dormant, geologists say it presents the potential for earthquake hazard.

And so, thanks to Dr. Gates's urging, a seismograph was established in February in the Perkins Memorial Tower atop Bear Mountain, according to Dr. Won-Young Kim, research scientist at Lamont-Doherty Earth Observatory in Palisades, N.Y. "It is quite fascinating to use this in mapping the fault zones there," said Dr. Kim, who set up the seismograph.

When Dr. Gates described the boundaries in Harriman of the Ramapo Fault, which stretches from Peekskill to Tuxedo, N.Y., scientists at Lamont checked their seismological records and discovered that the fault had produced several earthquakes of 2.3 on the Richter scale in recent years.

Last year Lamont-Doherty's seismographs recorded two earthquakes in Manhattan on Jan. 17 and Oct. 27. (They measured 2.4 and 2.6 on the Richter scale, respectively.) "We never knew of any in Manhattan before," Dr. Kim said. The observatory also recorded the collapse of the World Trade Center on Sept. 11; the fall of the north tower measured 2.3. (Readers can view these records, as well as real-time seismograph measurements, on the observatory's Web site, www.ldeo.columbia.edu/LCSN.)

The Newark Museum will be incorporating the geological media presentations created by Dr. Gates and his team in the institution's new $14 million natural science hall, scheduled to open in November. "Dr. Gates has has been key to our presentation," said Dr. Ismael Calderon, director of the science department of the museum, "because he made us realize that rocks can speak."

Dr. Gates's work will also be used by the Bear Mountain Trailside Museum and Zoo, as well as at the Lautenberg Visitor Center in Warwick, N.Y., scheduled to open by the end of the year.

Currently, Dr. Gates has four researchers doing geological mapping in Harriman. And seven Rutgers students are working on computer animations for the video documentary as well as the Web site. "Seeing these continents come together, it's like science fiction," said Mark Chua, 21, who was creating the video's seven-second depiction of the collision of India and Eurasia.

Since Harriman is pretty much the way it was 12,000 years ago, after the last glacier retreated, it has become a preserve for geological study, and Dr. Gates was able to discover his "Rosetta stone."

This outcrop suggests that the Rodinian supercontinent was assembled by a series of continental collisions over time, a revelation that is being chronicled in the video documentary by Dr. Gates's crew, the first of several planned documentaries. This information will also be included on a new Rutgers Web site that will offer detailed hiking maps of Harriman.

Harriman's guardians are pleased that Dr. Gates is giving the region's geology new respect. "We support Dr. Gates's efforts to make Harriman a geological park," said Mr. Krieser of the Palisades Interstate Park Commission.

And there are plenty of East Coast geological mysteries to keep Dr. Gates's research team busy. "The Grand Canyon isn't here," he said with a shrug, "but Harriman is."