It was great getting to work with one of my best friends, Brice Lynch, on this blog.
Brice is a hydrogeologist and one of my partners in the A Year In The Sound Project!

Words by Rich Nardo w/ Brice Lynch
Photos by Rich Nardo + Brice Lynch

It was on that slender riotous island which extends itself due east of New York and where there are, among other natural curiosities, two unusual formations of land. Twenty miles from the city a pair of enormous eggs, identical in contour and separated only by a courtesy bay, jut out into the most domesticated body of saltwater in the Western Hemisphere, the great wet barnyard of Long Island Sound - The Great Gatsby

For most people familiar with the area, Long Island’s north shore conjures images of palatial estates and the serene waters of the Long Island Sound. Members of New York’s cultural elite have been making their homes on the Sound’s beautiful beaches long before F. Scott Fitzgerald drew international acclaim for his portrayal of “East Egg” and “West Egg” (based on Port Washington and Great Neck respectively) in The Great Gatsby. It’s safe to say that the “Gold Coast” has a long and storied history for New Yorkers, but what isn’t spoken about as often is the fact that the area’s geological past runs much deeper and is just as interesting. 

Origins Story

Long Island’s northern shoreline is characterized by massive coastal bluffs and glacial erratics that originated roughly 21,000 years ago during the most recent “pulse” of Wisconsin glaciation. As this last glacier made its way south, it left a huge lake (or series of lakes) that spanned from what is now Martha’s Vineyard to modern day Queens. The Long Island Sound was, at that time, part of what is referred to as Glacial Lake Connecticut. The Sound’s shoreline were shaped by way of the Harbor Hill Glacial Moraine (moraines are the accumulated dirt and rocks carried by glacial movement). 

Three types of rocks that are considered dominant throughout most of the Sound are granite, basalt and granite gneiss. Gneiss is a high grade metamorphic rock that experienced intense heat and pressure during its formation and is easily identified by the segregation of light and dark minerals that give it a banded texture. The alkali feldspar granite boulders, some of which can be as big as garages, are felsic, igneous rocks rich in potassium feldspar, commonly known as K-spar. While there are several other silicate minerals present in these boulders including quartz and, to a lesser degree, plagioclase feldspar, muscovite, biotite and hornblende, the high percentage of K-spar in these rocks is what gives a lot of them the predominant pink hue we see so often. 

Long Islanders will be the first to tell you that the north shore more closely resembled New England or Westchester than the white sandy beaches of the south shore. This is because the bedrock on which Long Island resides is the same as that of New York City and Westchester County. About 70 million years ago, during the Cretaceous Period, a shallow coastal environment was created where sand and clay spread over the surface of the bedrock. These cretaceous sands and clays continue to be covered by younger deposits nearly everywhere on Long Island and the original environment is now 400 feet below what is considered sea level. The difference in topography between Long Island’s north and south shores occurs due to the fact that the Wisconsian glacier largely stopped at what is now Long Island, causing the moraine to “spill over” in the formation of the island. Sunken Meadow State Park is the quintessential rocky and hilly terrain of the north shore while Jones Beach State Park features a perfect gentle sloping sandy outwash plain that terminates into the Atlantic Ocean exemplifying our south shores. 

The Sound Today

Today, Long Island Sound runs 110 miles from the East River out to Block Island Sound. It is 21 miles at its widest point and its depth tends to vary between 65 and 230 feet. There is an estimated 18 trillion gallons of water in the Sound, which is said to be enough to supply New York City with water for 33 years. The deepest point in the Sound is a channel known as “The Race” that reaches depths of 350 feet. “The Race” is located between Fishers Island and Little Gull Island and serves as the main entrance for the Sound. 

Long Island’s north shore is predominantly created by headland erosion. The remains of the Harbor Hill Moraine can be seen in the towering bluffs, which are constantly eroded by runoff waves and wind, resulting in the narrow strips of shoreline at their base. Erosion takes place along the Sound at an average rate of one-two feet of recession per year. That sand and silt that is lost in one area is sometimes carried by the current to other locations where it is deposited in the form of barrier spits or sand shoals and intertidal flats. This process is called longshore drift and typically occurs moving east to west in the Sound.

A Closing Anecdote from our “A Year In The Sound” project. 

When we visited Rocky Point in East Marion for the A Year In The Sound project, we came across the below massive erratic. We estimated the dimensions to be 27 feet long by 35 feet wide and 13 feet high - this would add up to be 12,285 cubic feet. The average weight of a cubic foot of a granite boulder such as this one is 175 pounds. That means the rock we’re looking at here is roughly 2,149,874 pounds. Being that this rock had to be transported here via glacier, those numbers offer an exciting glimpse into the incredible force that glaciers apply to the earth’s crust! 

References

Based largely on field research by Brice Lynch.

Additional references:

• Long Island Sound Study:  http://longislandsoundstudy.net/wp-content/uploads/2004/12/Coastal-barriers-and-beaches.pdf

• Wikipedia:  https://en.wikipedia.org/wiki/Long_Island_Sound

• The Great Gatsby (for the initial quote).