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Long Island Sound. Peconic Bay. Shinnecock Bay. Great South Bay. www.loving-long-island.com. Long Island: Home Sweet Home. You know that Long Island is an island, but do you know about the origin of Long Island and the coastal features that surround it?. In the beginning….

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Long island home sweet home

Long Island Sound

Peconic Bay

Shinnecock Bay

Great South Bay

www.loving-long-island.com

Long Island: Home Sweet Home

  • You know that Long Island is an island, but do you know about the origin of Long Island and the coastal features that surround it?


In the beginning
In the beginning…

  • The Atlantic Ocean basin originated ~200-135 million years ago (mya) as the supercontinent Pangaea began drifting apart from seafloor spreading

    http://upload.wikimedia.org/wikipedia/commons/8/8e/Pangea_animation_03.gif


The geological history of long island
The geological history of Long Island

  • When Pangaea broke apart, it separated what is now South America and Africa, leaving the Appalachian Mountains* as the western border of the emerging Atlantic Ocean basin

    * themselves created ~480 mya from plate collisions that culminated in the construction of Pangaea; once volcanoes


http://en.wikipedia.org/wiki/Allegheny_Plateau

http://www.fossilmuseum.net/fossilrecord/Appalachian-Orogenyb.htm


The geological history of long island1
The geological history of Long Island

  • 200 million years of weathering drastically reduced these mountains in size and deposited large amounts of sediment along the edge of the expanding Atlantic Ocean

  • Gradually, Long Island originated as a river valley as sediments were supplied by the erosion of these coastal plains and the Appalachian Mountains

    • served as a foundation for present-day Long Island


The last ice age
The Last ‘Ice Age’

  • ~110,000 - ~10,000 years ago marked the last (most recent) glacial period

  • During this time, much of the Northern Hemisphere (and to a lesser extent, the Southern Hemisphere) was covered in glaciers

  • Under the extremely cold conditions, these glaciers grew, or advanced


And you thought this winter was cold
And you thought this winter was cold…

  • Glaciers originating from Canada advanced southward toward present-day Long Island

  • This extensive ice sheet reached Connecticut ~26,000 years ago and the river valley of (now) Long Island ~21,000 years ago

  • This glacier (commonly called the Wisconsin Ice Sheet) covered CT and the surrounding area, widening and deepening the river valley that eventually became Long Island Sound


Stuck between a rock and a hard place

Wisconsonian Glacier

Stuck between a rock and a hard place

  • As the glaciers spread southward, they scraped up sediment (including bedrock!) and carried it along with them, depositing the accumulated material as they traveled and receded


Stuck between a rock and a hard place1
Stuck between a rock and a hard place

  • The melting of the Wisconsin ice sheet ~20,000 years ago deposited rocks and sediment from within the rocks forming glacial moraines

  • Forms LI’s north shore and ‘backbone’

*

*

*Moraines



The origin of glacial deposits
The origin of glacial deposits Connecticut (where LIS now stands)


Ice age the final meltdown
Ice Age: The Final Meltdown Connecticut (where LIS now stands)

  • Long Island is now surrounded by unique marine environments, but is still changing

  • Currents transport sediments creating barrier beaches, and salt marshes line its estuaries

  • Storms (hurricanes, in particular) are constantly reshaping the profile of Long Island, and even occasionally creating new inlets!


Shinnecock bay june 1938
Shinnecock Bay; June 1938 Connecticut (where LIS now stands)


Shinnecock bay september 1938 after the great hurricane
Shinnecock Bay; September 1938 Connecticut (where LIS now stands)after the Great Hurricane

Shinnecock Inlet

Storm surge carved out a large section of the barrier island separating Shinnecock Bay from the Atlantic Ocean


The geological future of long island
The geological Connecticut (where LIS now stands)future of Long Island

  • As sea levels rise, more and more of Long Island will become submerged (why you need flood insurance if own a house on the south shore…)

  • Alternatively, if sea levels decline, more and more of Long Island would be exposed

  • Earthquakes from isostatic rebound and ancient faults continue to occur


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