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
Click on image for full
size
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.