Long Island: Home Sweet Home by 87N1D8m


									  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?

           Long Island Sound
                                                 Peconic Bay

                                Shinnecock Bay

                        Great South Bay
             In the beginning…
• The Atlantic Ocean basin originated ~200-135
  million years ago (mya) as the supercontinent
  Pangaea began drifting apart from seafloor
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

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’
• ~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…
 • 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
 • As the glaciers spread
   southward, they
   scraped up sediment      Wisconsonian
   (including bedrock!)
   and carried it along
   with them, depositing
   the accumulated
   material as they
   traveled and receded
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’
• The water melting from the giant ice sheet
  formed Lake Connecticut (where LIS now stands)
• As more and more of the ice sheet melted, sea
  level rose and eventually covered over the
  coastal plain creating Long Island Sound (saline)
  ~12,000 years ago
The origin of glacial deposits
    Ice Age: The Final Meltdown
• 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; September 1938
       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
• 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
• 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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