“It was biblical,” Mr. Horenstein said. The wave created the Narrows, which now connects the Atlantic Ocean to one of the world’s largest natural harbors.
In the metropolitan area, the southern tip of Staten Island overlooks the Arthur Kill and Raritan Bay, and represents the southernmost part of the glacial rise. The site hosts the Conference House Park. It takes its name from an unsuccessful peace conference held there in 1776 during the Revolutionary War.
As we walked past a stone manor house where the meeting took place, Mr. Horenstein pointed to the rounded rocks in its walls and, based on color and texture, proceeded to tick off their likely sites of origin — some from upstate New York, some from New Jersey, and so on.
What fraction came from the glacial ridge?
“All of them,” he replied. “It was the local building material.”
We walked down to the nearby beach and wandered a few hundred feet to where the land formed a sandy bluff. It offered a rare glimpse into the heart of the ridge: a jumble of clay, silt, pebbles and boulders in a fragile matrix laid bare by the action of tides, hurricanes and pounding waves.
In all of New York City, “this is the only place you can see the moraine clearly,” Mr. Horenstein said, leaning into the wind. “This is it, the southernmost end.”
Mr. Horenstein held up a rounded stone. Somehow, it ended up in reporter’s backpack as a souvenir of the day.