First Exam
Calculate the difference between the
two average crustal elevations
Calculate the rate of sea floor spreading
Calculate the average rate of sea floor
subsidence in cm/1000 yr
Calculate the deposition rate of marine
sediments in the deep-ocean basin
Second Exam
Calculate the sinking rate of sand in cm/s
Calculate the time required for the ocean
to evaporate completely, if the evaporated water did not return to the ocean
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.
Calculate the deposition rate of marine sediments in the deep-ocean basin.
To calculate the deposition rate of sediment for a region of sea floor, divide the total thickness of the sediment by the time required for the sediment to accumulate (i.e. the age of the sea floor). For example, if 1 km of sediment was deposited in 100,000,000 yr:
amt of sed/t = 1 km/100,000,000 yr * 1000 m/1 km * 100 cm/ 1 m = 0.001 cm/yr.
To better visualize this rate, multiple the annual rate by 1000 to yield 1 cm/1000 yr.
0.001 cm/yr * 1000 = 1 cm/1000 yr
To receive credit for the problem in class and on the quiz, you must show your work.
Calculate the sinking rate of sand in cm/s.
To calculate the sinking rate of a sedimentary particle, divide the distance that the particle sinks by the time required for the particle to sink to that depth. For example, if it takes 1.8 days for a sand particle to sink 4 km:
d/t = 4 km/1.8 days
To better visualize this rate, it should be converted to cm/s (centimeters per second). First convert kilometers to meters, then meters to centimeters:
4 km * 1000m/1 km = 4,000 m
4,000 m * 100 cm/1 m = 400,000 cm
Then, convert the days to hours, then the hours to minutes, and, lastly, the minutes to seconds:
1.8 days * 24 hr/day * 60 min/hr * 60 s/min = 155,520 s
Finally, divide the distance in centimeters by the time in seconds:
d/t = 400,000 cm/155,520 s = 2.6 cm/s
To receive credit for the problem in class and on the quiz, you must show your work.
Calculate the time required for the ocean to evaporate completely, if the evaporated water did not return to the ocean.
To calculate the time, divide the average depth of the ocean, 3800 m, by the average rate of evaporation, 1 m/yr:
rate = d/t
d/rate = t
3800 m/(1 m/yr) = 3800 yr
You will be asked the question only, so you must remember the average depth of the ocean, 3800 m, and the average evaporation rate, 1 m/yr.
To receive credit for the problem in class and on the quiz, you must show your work.