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 how much sea level could rise
if the polar ice caps melt because of global warming
Calculate the time required for the ocean
to evaporate completely, if the evaporated water did not return to the ocean
Calculate the residence time of a seawater
constituent
Final Exam
Determine if a chemical equation
is balanced
Convert a surface current flow rate
from m/s to km/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
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 how much sea level could rise if the polar ice caps melt because of global warming
This question would be asked without providing values or formulas. To obtain a rough estimate of potential sea level rise, you must know that 97% of the water on Earth is in the ocean and 2% is in the polar ice caps. Given that the average depth of the ocean is 3800 m, you can calculate 2% of 3800 m:
3800 m x 0.02 = 76 m
This is a very rough estimate; however it shows you that sea level can rise well over 100 feet.
To receive full credit for this math problem, you must write all of the values in this problem, as well as solve the equation.
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.
Calculate the residence time of a seawater constituent
To calculate the residence time of a seawater constituent, divide the total amount of a constituent in the ocean by its input rate or its output rate. At steady state, the input rate equals the output rate.
Residence time = amount of a constituent in the ocean/input rate (or the output rate)
Calculate the resident time of Na in the ocean given that the total amount of Na is 6.08 x 1020 mol and the input rate of Na by rivers is 1.18 x 1013 mol/yr.
Residence time of Na = 6.08 x 1020 mol Na/1.18 x 1013 mol Na/yr = 5.15 x 107 yr = 51,500,000 yr
To receive credit for the problem in class and on the quiz, you must show your work.
Determine if a chemical equation is balanced
Matter cannot be created nor destroyed, so all matter must be accounted for. For example, for an equation to be balanced, both sides (reactants and products) must have the same number of constituents.
Example A
CO2 + H2O = CH2O + O2
Reactants C - 1, O - 3, H - 2
Products C - 1, O - 3, H - 2
Equation is balanced.
Example B
CO2 + H2O = CH2O
Reactants C - 1, O - 3, H - 2
Products C - 1, O - 1, H - 2
Equation is not balanced.
To receive credit for the problem in class and on the quiz, you must show your work.
Convert a surface current flow rate from m/s to km/yr
Given a surface current flow rate of 1 m/s, convert this rate to km/yr. You must convert the meters => kilometers and the seconds => minutes => hours => days => years. The conversions can be done together or separately.
Together:
1 m/s x 1 km/1000 m x 60 s/min x 60 min/hr x 24 hr/d x 365 d/yr = 31,536 km/yr
Separately:
1 m/s x 1 km/1000 m = 0.001 km
1 s x 1 min/60 s x 1 hr/60 min x 1 d/24 hr x 1 yr/365 = 3.171 x 10-8 yr
0.001 km/3.171 x 10-8 yr = 32,000 km/yr
Note that the math seems easier when the conversions are done together.
To receive credit for the problem in class and on the quiz, you must show your work.