Cornwall – The hikers caught in the rock slide yesterday were on the 2,500 acres of property on Schunnemunk Mountain that the state is buying from the Open Space Institute, a New York City-based conservation group.

The land has roughly 30 miles of hiking trails with varying degrees of difficulty. A Palisades Interstate Park ranger patrols them, mostly on weekends, the busiest hiking time. Joseph Martens, president of the Open Space Institute, said he knew of no previous rock slides on the property, most of which was bought from Storm King Art Center in April 1996.

"This is a first," he said.

A rock slide is "a common occurrence in the Adirondacks, less common in the Catskills, and it hardly ever happens in the metropolitan area," said Walter Daniels, a trail supervisor and Web master for the New York-New Jersey Trail Conference, based in Mahwah, N.J.

Daniels said the hikers in Cornwall yesterday started out on Dark Hollow Trail, which he said stretches nearly a mile and a half from the railroad tracks to near the mountain summit, at 1,660 feet. The trail has some rocky stretches but is "not particularly steep or difficult," he said.

He believes the rock slide occurred on a "talus slope," which is covered with rock blocks created when water seeped into cracks and froze, breaking up the rock face. Such ground is usually stable, Daniels said.

Gov. George Pataki announced in March last year that the state will buy the 2,500 acres to preserve as park land. But the purchase has been delayed because the state has not had the funding, Martens said.

"We still hope to convey the property to the state in the coming months," he said.

The two main parking areas are in Cornwall on Otter Kill Road and Taylor Road, where the hikers caught in the rock slide yesterday had parked.