by Mike Hays
You don’t have to travel to Alaska or Norway to see a fjord. Where can you go to see a glacier-created, sea-filled canyon? Down by the river. The lower Hudson River has unique geology, since it is both a fjord and, broadly speaking, a drowned river or estuary with tidal inflows.
In earlier geological eras, when the land was much higher above sea level than now, an interior sea drained to the sea via the primordial Hudson River. The riverbed carved out a clear channel. The channel bed is still visible stretching out into the continental shelf that is now underwater.
During the glaciation 15,500-20,000 years ago, the Hudson River provided an easier groove for the glacier to move further south than it did in the surrounding land. Schematics of the glaciers show a clear wall across the Northeast with an icy finger traveling down the old riverbed.
The glacier pushed stones and gravel south, forming Long Island. When the glacier retreated north during warming, waters flowed down the Hudson but were blocked from the ocean by the Long Island dam. Water from the river flowed through the Sparkill gap at Piermont, into the North Jersey lowlands. Eventually, the Long Island dam broke and the Hudson River began to flow into the Atlantic, much like it does today.
The Nyack section of the Hudson doesn’t look quite like pictures of other fjords partly because the Tappan Zee reach is very broad and the surrounding cliffs are not especially tall, particularly in Westchester. The riverbed is actually quite deep, although it is mostly filled with clay and silt.
Heading north, the river displays better fjord form. The Hudson Fjord, running from Bear Mountain to Newburgh Bay, is quite deep but mostly is filled with rocks, gravel, and silt. Storm King, on the west side of the river, and Breakneck Ridge, on the east, rise 1,300 feet above the river. Visually, this is quite dramatic and exactly what we expect to see in a fjord.
The Hudson narrows again downriver to the George Washington Bridge. A view from State Line or Alpine Lookouts brings to mind again the classic fjord; a narrow channel bounded by tall cliffs.
Many fjords are tidal. As we all know the tides are quite strong in Nyack and carry salt water all the way up to Poughkeepsie in dry weather. One of the Lenni Lenape names for the river was Mahicantuck, which means “a river that flows both ways.”
The sign above Nyack Village Hall reads Nyack-on-Hudson, although a case could easily be made to call this village “Nyack-on-Fjord,” too.
Photo credits: Mike Hays; Hook Mountain by Matt Hudson
- The Hudson by Tom Lewis, 2005
- Roadside Geology of New York State by Bradford Van Diver, 1985
Michael Hays is a 30-year resident of the Nyacks. He grew up the son of a professor and nurse in Champaign, Illinois. He has recently retired from a long career in educational publishing with Prentice-Hall and McGraw-Hill. He is an avid cyclist, amateur historian and photographer, gardener, and dog walker. He has enjoyed more years than he cares to count with his beautiful companion, Bernie Richey. You can follow him on Instagram as UpperNyackMike.