First Exam
Calculate the difference between the
two average crustal elevations
Calculate the rate of sea floor spreading
Second Quiz
Calculate the average rate of sea floor subsidence in cm/1000 yr
Calculate the difference between the two average crustal elevations.
Calculate the difference between the average elevation of continental crust (840 m above sea level) and the average elevation of oceanic crust (3800 m below sea level). Note that elevations above sea level are positive and elevations below sea level are negative.
840 m |
To receive credit for the problem in class and on the quiz, you must show your work.
Calculate the rate of sea floor spreading.
To calculate the rate of sea floor spreading for a particular lithospheric plate, the distance between two points and the difference in the ages of those two points is required. A rate is determined by the distance divided by the time: distance/time or, simply, d/t.
Rate = d/t
For example, the distance between stations A and B is 1,080 km. The difference between the ages of the rocks at station A and station B is 54,000,000 years. Calculate the average rate of sea floor spreading.
d/t = 1080 km/54,000,000 yr = 0.00002 km/yr
To better visualize this rate, it should be converted to cm/yr. First convert kilometers to meters, then meters to centimeters.
1080 km * 1000m/1 km = 1,080,000 m
1,080,000 m * 100 cm/1 m = 108,000,000 cm
Finally,
d/t = 108,000,000 cm/54,000,000 yr = 2 cm/yr
To receive credit for the problem in class and on the quiz, you must show your work.
Calculate the average rate of the sea floor subsidence in cm/1000 yr.
The average increase in depth:
Therefore, the average rate of subsidence = 4 km/100,000,000 yr.
To convert the units to centimeters, change kilometers to meters and, then, meters to centimeters.
4 km/100,000,000 yr * 1000m/1 km *100 cm/1 m = 400,000 cm/100,000,000 yr = 4 cm/1000 yr.
Scientist like to use distances that are easy to visualize, so give the units in cm/1000 yrs:
400,000 cm/100,000,000 yr = 4 cm/1000 yr.
To receive credit for the problem in class and on the quiz, you must show your work.