Geologic evidence indicates that the Niagara River began to cut its gorge (Niaga

Question

Geologic evidence indicates that the Niagara River began to cut its gorge (Niagara Gorge) about 11,000 years ago as the Laurentide Ice Sheet retreated from the area. The ice started at the Niagara Escarpment shown in figure 5.9 and receded north to form the basin of Lake Ontario. The Niagara Gorge started at the Niagara Escarpment and retreated south to its present location. Based on this geochronology and the length of Niagara Gorge, calculate the average rate of falls retreat in cm/year.

This is the only picture i have that coincides with the question.

Queanston Shale (Browr Whirlpool Sandstone Narth Lockport Dolostane Green Niagara Gorge 2 km Goat & Nia Ningara River FIGURE 5.9 Geology of the Niagara Gorge Region. The Niagara River flows from Lake Erie north to Lake Ontario and forms the border between the United States and Canada. Niagara Falls is located on the Niagara River at the head of Niagara Gorge, about half way between the two lakes.

Explanation / Answer

From the given information we can only calculate the average rate of retreat of Niagara falls, but this rate must be variable in the history of Niagara falls.

The average rate of retreat of the Niagara falls= distance from the previous location to present location/ time duration

According to the scale of the map, the distance between earlier location and today's location is about 8500kms and time duration is 11000 years.

So, the average rate of retreat of Niagara falls= 8500/11000= 0.773 km/yr=773m/yr

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