Off New York City’s Deep End: a Pleistocene grand canyon

Off New York City’s Deep End: a Pleistocene grand canyon

01.29.2010, 1:29 am
Filed under: Uncategorized

image:Brian Roman © clastic detritus

A canyon, comparable in depth to the Grand Canyon, exists 100 miles off the coast New York City.  It’s a submarine canyon.  Maybe that’s why most New Yorkers don’t know about it. It also has been under water for awhile.  The canyon dates to the Pleistocene and is actually an ancient extension of the Hudson River. During the Pleistocene, sea levels were 400 feet lower (in part because of all the water locked up in glaciers).  The reduced sea level meant that the Hudson flowed 100 miles further east of its present location at the terminus of Lower Manhattan. The canyon carved by the Hudson extends a remarkable 450 miles across the continental shelf, then connects with the deep ocean basin where it descends to depths of 3 to 4 kilometers. As the Wisconsin Ice sheet retreated from what is present day New York City, the mighty Hudson of the Pleistocene transported heaps of glacial discharge and carved the surrounding landscape in its path. Today the sea floor is a mix of glacial silt and the City’s industrial sludge, by-products from the rather recent past when directly dumping garbage into the River was allowed.

It’s easy to wish we could follow the ancient river’s path to the edge of the Canyon today and gaze over the plunging edge. Though today, the path would most likely be scattered with the detritus of the industrial age.

Back in the Pleistocene, the Wisconsin Ice Sheet literally stopped in what is now New York City. Long Island is a terminal moraine and marks the dramatic retreat of the Ice Sheet. The island is essentially a gigantic assemblage of what had accumulated in the glacier’s fist. Staten Island was part of Long Island until Glacial Lake Hudson, which filled the Upper New York Bay, broke through the Narrows (site of the Verrazano-Narrows Bridge) around 6,000 years ago. From there the Hudson River could take its preferred, more direct route to the Atlantic. The lower Hudson River, technically a tidal estuary, is also known as the Hudson Fjord.

Views of New York City’s very own fjord, image: CC Katy Silberger

Mesmerizing traces of the ancient River’s path, from the edge of Lower Manhattan to the depths of the Canyon, are distinctly visible from satellite view.

The Hudson River of the Pleistocene signals its route towards Hudson Canyon, image: Google Maps

The Pleistocene and the depths of the Canyon might seem far away, too deep to be known, or too remote to be relevant to our daily lives.  But modern humans and especially New Yorkers actually have a lot at stake in what goes down in relation to this geologic wonder.  Submarine canyons, due to the temperatures maintained at their frigid depths in combination with the high pressures at the sea floor, are thought to contain immense pockets of methane hydrates, a clean-burning energy source. If a way to extract the gas from the sea floor could be resolved, some researchers think that the resulting fuel could power the United States for centuries.

Image courtesy of Hudson Canyon Cruise 2002, NOAA/OER.

This is such a viable possibility that teams of scientists from the National Oceanic and Atmospheric Administration (NOAA) have been embarking on expeditions over the last decade to map the canyon and its auspicious gas reserves.  A dramatic counterpoint to the promise of a new source of energy is the reality of the gas’s intense volatility: gas pockets could cause undersea landslides and trigger tsunamis with devastating effects for the metropolitan area.  A portentous foreshadowing could be the 1929 7.2 earthquake off Newfoundland. This earthquake triggered a large submarine slump that created a tsunami that killed 28 people and ruptured 12 transatlantic cables.

underwater cable

Such undersea landslides are of immediate concern in connection with Hudson Canyon. As noted on the NOAA site, “The Hudson Canyon region is a hub of trans-Atlantic fiber-optic telecommunications cables that connect the New York-New Jersey metropolitan area to the rest of the world.”   So, if you live in New York, next time your internet goes out, let’s hope it’s not a Hudson Canyon landslide slicing through the cables that enable the metropolitan area of 18.8 million people to keep connected with the world at large.

image: UK Guardian

It’s a bit bewildering to think that a massive population of people inhabiting New York City lives in close proximity to this monumental culmination of geologic forces- AND most of us don’t even know it exists.  Becoming aware of an incredible geologic phenomenon such as Hudson Canyon creates a perspective that’s both fantastic and REAL–one that both humbles and dishes out a healthy dose of pure wonder.  When we start to see familiar icons such as the Hudson River as connections to places and times that we could never inhabit ourselves, they can become massively more interesting, perhaps even venerable.  It’s also fun, given FOP’s mandate, to sense how directly the Pleistocene continues to shape and reshape today’s world.

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