GPH 112 43 Why the Grand Canyon is Grand Stage C

GPH 112 43 Why the Grand Canyon is Grand Stage C.Question 1 2 / 2 pts How fast is the Grand Canyon widening? (or, what is the rate of cliff retreat?) Please use these places in the geovisualization. Remember, you will be measuring distances between the North Rim and the Colorado River, and then the South Rim and the Colorado River to be able to calculate rates. Please calculate your answer in centimeters per century years (cm/century). Tiyo Point on the North Rim: 36.1806, -112.1278 & Colorado River between: 36.1055, -112.1562 & Hopi Point on the South Rim: 36.0733, -112.1551 Correct! The north side of the Colorado River (from Tiyo Point) is widening at a rate of about 18 cm/century. The south side of the Colorado River (from Hopi Point) is widening at a rate about 7cm/century. None of the answers listed are even close. Thus, this is the best answer. The north side of the Colorado River (from Tiyo Point) is widening at a rate of about 1.8 centimeters per thousand years. The south side of the Colorado River (from Hopi Point) is widening at a rate about 1 cm per thousand years The north side of the Colorado River (from Tiyo Point) has widened at a rate of 1.8 meters per million years, while the south side (from Hopi Point) is widening at 1.2 meters per million years. Believe it or not, there’s only one other sort of study on rates of canyon widening in the heart of the Grand Canyon. In the Grand Canyon, researchers Ken Cole and Layer Mayer used packrat midden nests to estimate rates of cliff retreat using radiocarbon dates on the middens (that date back a few tens of thousands of years) to be about 4.5 cm/century. Although this rate is less, its in the same “ballpark” or order of magnitude. Question 2 0 / 1.5 pts How wide would the canyon be (between some future Tiyo and Hopi Points) 10 million years from now, using the rate you established in the example given in the PD file? The correct answer will be in miles, since most people understand miles at an intuitive level. About 31.5 miles You Answered About 18 miles About 10 miles Correct Answer About 23 miles What you measured for distances from Tiyo and Hopi points to the Colorado River will be different from what we measured. If you got anywhere closed 8700 meters from Tiyo Point and 3500 meters from Hopi Point (to the Colorado River), then this is how you should have done the calculations. Any measurement around 8700 meters from Tiyo Point to the Colorado River will convert to 1800 meters per million years. Thus, in 10 million years, the retreat of the rim would be 18,000 meters. Any measurement close to 3500 meters from Hopi Point to the Colorado River will lead you to a bit more than 700 meters per million years when you divide the distance by 4.8 million years. This rounded off rate of 700 m/Ma will be multiplied by 10 (million years) giving you a distance of 7000 meters. Thus, in 14.8 million years, the width of the canyon would be:  8700 m + 3500 m + 18000 m + 7000 m or  Tiyo-Colorado distance + Hopi-Colorado distance + 10 million Tiyo-Colo + 10 million HopiColo The predicted distance in 10 million years from now would be about 37,200 meters or 37.2 kilometers. Since 1 kilometer = 0.6214 miles, the best answer would be 23.36 miles, rounded off to 23 miles. Question 3 1.5 / 1.5 pts How fast did the Colorado River incise down into the Grand Canyon between 4.8 and 1.2 million years ago (or over a 3.6 million year period)? The answer should be in centimeters per century and be calculated for both Point Sublime on the North Rim and an unnamed point