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A 300-foot-thick wall of ice formed the land we now live on


In the beginning, there was ice.

Eighteen thousand years ago, a massive wall of ice 300 feet thick extended south from the Arctic to what is now New Jersey. There was no Long Island then. There was no island at all, because the land was a solid mass covered by this enormous ice cap.

Slowly — glaciers do not move quickly — this ice cap began to pull back, retreating north, inch by inch, and scraping the land at its base to such an extent that it ground up entire boulders and reduced them to sand. This would become the topsoil that today makes the North Fork and Shelter Island the remarkable farmland that it is.

Then, perhaps around 11,000 years ago, as the earth began to warm slightly and this huge ice cap started to melt, what we now call Long Island began to take shape. That is to say, a meltwater channel formed by flowing water from the melting ice gradually filled up and became what we know today as Long Island Sound. The ancestral Hudson River was also formed by just such a channel of melting water.

Smaller meltwater streams helped form our bays and creeks. Kettle holes — deep, freshwater ponds created by large chunks of ice left behind as the glacier receded — emerged. Shelter Island’s Fresh Pond is a kettle hole pond.

So, why do the places we live — on maps the North Fork resembles a bony, arthritic finger and the Island resembles a cowboy on a bucking bronco — look the way they do? It’s because of the ice. Long Island is a byproduct of a giant, grinding ice sheet — one so powerful that a very large boulder would be reduced to particles of sand after being dragged underneath it for just 20 miles.

“I love looking at the North Fork,” said Sean Tvelia, a professor of geology and physical sciences at Suffolk County Community College. Mr. Tvelia’s enthusiasm for the forces that shaped our home is contagious. With the eye of a skilled investigator looking over a crime scene, he sees what the ice left behind thousands of years ago when he looks at the layers of sand and silt on a high bluff overlooking Long Island Sound.

“This is ground zero for the glacier,” he explained. “If you look at the coastline, if you are standing on the beach, you can understand that giant wall of ice. This was the toe of the ice.”

The birth of what we call Long Island 11,000 years ago is a mere blink in the 4-billion-year life of the planet, give or take a half-billion or so. Geologically speaking, we are too young to merit a birthday. And we are too old not to respect what brought us to this point in our long history.

But we could all gather on a Long Island Sound beach and look up at the bluff and see what the glacier left behind and raise a glass to it. On a broader scale, though, what makes the North Fork and Shelter Island unique and worth protecting — the rich farm soil, creeks and bays — is the ice. You can’t know this land without knowing how ice shaped it.

Professor Tvelia makes clear what is well known among those who study the geology of where we live: Piecing together its earliest history and establishing a timeline of events is a difficult task. After all, the answers lie in rocks and sediment, which don’t give up their stories easily. This forces the professor to become an earth detective, sifting for clues.

“There is no real good data on how long the ice was here,” he said. “We know it was in Vermont 21,000 years ago. And then gone. How long it existed is hard to know. The ice retreated south to north.”
The ice was 300 feet thick here, and maybe a mile and half in depth to our north, over what’s now Connecticut.

While one of the many unanswered questions about the ice is how far south it reached, it appears as though what is now Long Island was pretty much its southernmost reach. We were the end — or the toe, as the professor calls it. What geologists call the Ronkonkoma Moraine — essentially a ridge of sediment left by the glacier — runs across Long Island, with clear signs the ice continued across modern-day New Jersey and then west.

Perhaps even more fascinating than how the machinery of the ice formed our home is this tantalizing question: When did people first arrive here?

The so-called Clovis people — named for perfecting the Clovis point, a highly engineered killing instrument — were farther west on the continent 20,000 years ago. They moved east, perhaps following giant game like the mammoths, hugging the southern edge of the wall of ice.

We know this because their distinctive Clovis points have been found on Long Island. It is a good guess that these people were here 8,000 to 10,000 years ago. That means these people, about whom we know so little, were on this land for perhaps 9,600 years all by themselves.

John Strong, a retired Southampton College professor and an expert on eastern Long Island Indian history, said the hunter-gatherers who came here followed food sources as the ice retreated north. They became established here when there was enough food — plants and animals — for them to live on and form extended family groups.

It is also not beyond the realm of possibility that people from what is now the European continent walked here from there — following the edge of the ice until they arrived on our land mass. There is no physical proof of that, but it is a fascinating question.

But first there was ice. And then an island. This is the beginning of our story.

About this series
The History Project is a 16-part series telling the stories of the place we call home. The second chapter will be published January. 25.