225000 - 10000 B.C.

How Long Island was formed before we were here!

Long Island began to take shape 450 million years ago. It is relatively new considering that the earth was formed 4.6 billion years ago. Long Island is built on a three layer base. The first layer of bedrock formed 500-600 million years ago as southern Connecticut slid beneath Long Island Sound. Its second layer, is made of sand, gravel and clay which was deposited 60 to 70 million years ago by ancient rivers. The top layer which gives Long Island the shape we know consists of the debris left from the Wisconsin Glacier.

Kings Park Bluff during glacier deposit
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    60,000 years ago the Wisconsin glacier moved south across Canada and Northern United States. This huge glacier, hundreds of feet high, carried pieces of anything that was in its way, rocks, gravel, mountain tops, boulders and soil from valleys and plateaus. About the spot where the LIE is now, the earth warmed, the glacier began to melt and left huge mounds of debris which became the string of hills stretching from Brooklyn to Montauk. This is called the Ronkonkoma Terminal Moraine. It also created rivers and flatlands and caused the sea to rise separating Long Island from the mainland.

40,000 years ago the Wisconsin Glacier again advanced and again melted leaving its debris on Long Island's north shore. The Long Island we know was formed by the Wisconsin Glacier and explains why it is hilly on the north shore, flat in the center and why flat land extends from the edge of moraine to the Atlantic Ocean. This second terminal moraine runs from Brooklyn Heights to Orient Point. The Harbor Hill Moraine in Roslyn, the Terryville Outwash Plain in Port Jefferson, the Ronkonkoma Terminal Moraine, and the Hempstead Outwash Plain make up Long Island's surface. It has given us rivers, lakes, bluffs, peninsulas and kettle holes like Lake Ronkonkoma, Lake Success and Artist Lake and the large boulders and rocks called erratics which came from New England.

Always changing, 18,000 years ago Long Island was freed of ice, 12,000 years ago Long Island Sound reflooded and 8,000 to 6,000 years ago, Long Island got its fish like shape.