Look carefully at the Horseshoe Falls. What Is the maximum elevation? What is th
ID: 284738 • Letter: L
Question
Look carefully at the Horseshoe Falls. What Is the maximum elevation? What is the minimum elevation? What Is the drop of the falls? [9a - 9b] This drop is for the whole gorge where the contour lines merge to a thick line. From 1842 to 1896, the falls moved back or receded 220 feet. How many years did this recession take? What Is the average recession rate [AVR]? AVR = Total recession [foot]/number of years. Find the length of the gorge in miles. Go from Horseshoe Falls to the bridge at Queenstown. Find the length of the gorge in feet 19c. X 8, 280 feel Assuming that the AVR has held since the falls began at the Niagara Escarpment, calculate the total time for the gorge to form. 19d/19b 20. Radiocarbon dates of beach deposits at Queenstown show the start date of Niagara Falls as >> minus 12,000 years. Find a new AVR [19d/12,000]Explanation / Answer
18a. The elevation of the crest of the horse shoe fall is 517' as indicated on the map. Since the crest is the highest elevated part of any formation therefore the maximum elevation of horseshoe fall is 517'.
18b. The elevation of the foot of the horseshoe fall is given on the map is 357'. So the minimum elevation of the horseshoe fall is 357'.
18c. The drop of the fall is calculated by subtracting the elevation of the contous where the line is thickened. Drop of the fall is 540-520=20 feet.
19B. Rate of recession= distance receded/number of years
Distance receded=220 feet
Number of years during 1842 to 1896=54 years
Rate of recession=220/54=4.07 feet/year
therefore average recession rate =4.07 feet/year
19c Length of gorge can be calculated on the google earth map by calculating the distance between the two points i.e. horse shoe fall and the Queenston bridge which comes to around 7 miles
19d. Since we know the length of gorge=7 miles
Now length of gorge in feet=7*5280 feet=36960 feet
19e. the total time for the gorge to form=length of gorge in feet/average recession rate
length of gorge in feet=36960 feet
average recession rate=4.07 feet/year
Total time taken=36960ft/4.07ft/year
=9081 years
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