Niagara Falls

Steven Dutch, Professor Emeritus, Natural and Applied Sciences, University of Wisconsin - Green Bay

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Geologic History

At present the Falls flow over the resistant Lockport Dolomite, which maintains the sharp edge of the Falls. The softer rocks below are eroded by turbulence, chemical weathering and feeze-thaw action. Periodically they retreat enough to allow a chunk of the lip to fall off and the falls retreat, about a meter a year on the Canadian side. As the falls retreat south, the slope of the Lockport Dolomite means it will become thicker, the Salina Group will be less exposed, and the retreat will slow down. In about 7,000 years, the falls will have retreated so they begin cutting into the soft Salina Group. There will still be a small falls at the present location but the gorge will begin extending south into the Salina Group.

By about 28,000 years from now, the gorge will have begun cutting into more resistant rocks again close to the Lake Erie outlet and another falls will form.

Around 12,000 years ago the glaciers retreated north of the Niagara Escarpment (brown) and the Niagara River began flowing over the Escarpment. Niagara Falls formed. The falls was protected by resistant rocks with softer rocks beneath. As the soft rocks were eroded, the falls retreated at about a meter per year.

A few thousand years in the future, the falls will reach the tip of Grand Island and there will briefly be a triple falls. After that, there will still be two falls, but they will be too far apart to see at the same time. The falls will also begin cuting a gorge into the soft rocks above the Lockport Dolomite. Eventually the Dolomite will be so reduced in height that the falls will stop retreating and become quasi-stationary falls. The animation shows the gorge after that in purple. The Canadian side, with more flow, will entrench faster than the American side and eventually capture all the water. Just before reaching Lake Erie, the gorge will encounter another series of resistant rocks and another falls, here called Final Falls, will form. Probably by then a new ice advance will have occurred.

Reference: What Future for Niagara Falls?
Shailer S. Philbrick; Geological Society of America Bulletin (1974) 85 (1): 91–98 (January, 1974).
https://doi.org/10.1130/0016-7606(1974)85<91:WFFNF>2.0.CO;2

Canadian (Horseshoe) Falls

American Falls (left), Canadian or Horseshoe Falls, right.

American Falls

Niagara Gorge

Right and below: looking upstream at the Falls from the gorge.
The Maid of the Mist is the classic Niagara Falls excursion
An inclined railroad leads to the pier
You will get wet.
The excursion pier.
Above: Hydroelectric station outlets	Below: Looking downstream in the gorge.
Below: Sightseeing boats.
	Rubble at the base of American Falls
	Winter ice buildup

Rainbows

Observation Tower

Night Views

History

Above: present views of Niagara Falls from the air. Right: The Falls retreat about a meter per year, so 3000 years ago they would have been three kilometers upstream (extreme top of the picture.
By about the time of Christ they were two klometers upstream
By the Battle of Hatings they were a kilometer upstream
By the time Columbus arrived the Falls were close to dividing around Goat Island
By the time of the American Revolution they were separate
Present Day
In a few centuries, the Canadian Falls will have retreated further. The Ameican Falls, which carry only 10% of the water, will have retreated only a little.
Eventually the Canadian Falls will retreat past Goat Island
When the Canadian Falls have retreated entirely beyond Goat Island, the American Falls will be completely deserted

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Created 7 April 2003, Last Update 31 May 2020