The following illustration is a Holocene Sea Level chart plotting sea level over the past 9,000 years.
Vol. 325, No. 1586 (Jun. 13, 1988), pp. 357-388
The edge of the Falls is much longer at its ledges than the width of the gorge through which it has cut. The flow of water over the ledges is now much shallower, with correspondingly fewer pressures than existed, say, 3,000 years ago, when the Falls were in the gorge. Consequently, the regression rate of the erosion and undermining of the cataract is less now than during the early period of gorge existence. The regression speed during the creation of the gorge was equivalent to the regression of the Canadian Falls, where the speed, weight and pressure of the cascade are more concentrated than the average over the entire Falls.
The Commissioners of the State Reservation at Niagara Falls employed Robert S. Woodward in 1891 to estimate the time required for the creation of the Niagara River gorge. Woodward was a man of superior competence as well as unquestioned integrity and later became president of the Carnegie Institution of Washington, D.C. Woodward reported that less than 8,000 years had been required to cut the gorge of the Niagara River.
Woodward noted that “Assuming an average regression speed of 2.2 feet per year, which is one quarter foot per year faster than the regression of the Canadian Falls, we obtain 7,800 years for the approximate life span of the Niagara Gorge”. However, the Falls at Lewiston were approximately 280 feet higher than they are now. Consequently, with a significantly higher regression rate in its early cycle, and a slower current rate, estimated age of the Niagara Falls Gorge is about 7,000 years.
Geologists have also identified two additional river beds at higher levels than the current Niagara River. The highest terrace is 24 feet above the river, and the lower twelve feet lower, with identical fresh water shells found at both terraces extending to the whirlpool. This suggests that Goat Island was under water at some earlier Epoch, which tends to support successive world cataclysms.
Early explorers - first Hennepin and later Carver, provided information regarding the locations of the Falls, and from these records we know that the Falls regressed, up to 1856, at an estimated rate of about five feet per year. Approximately 8,000 years elapsed from the time when the Falls started at Fort Snelling, to their current location at the north end of the gorge.
The Falls of St. Anthony were 110 feet above the current river bed when they were located at Fort Snelling. Now the Falls are less than 40 feet high. From these facts it is logical to assume that there was a greater amount of undercutting of the Falls when they were higher with the flow landing with much greater force on the base rocks, causing faster upstream regression during the earlier stages of the Falls than during its later stages. (The probable profiles of the Falls at various times in the past, with plan and elevations, are shown in Geological Survey, Folio 201, Minneapolis St. Paul, Minn.)
Summary – Evidence of the Event