B., 200.
C., 100.
D., 50.
E., 25.
After one half-life, you’ve gone from 800 parents to 400 parents; after a second half-life you go from 400 parents to
200. . (Typical studies of radioactive decay use many more atoms, to avoid statistical fluctuations, but the question
says “on average”, so we asked you about 800 rather than 800,000,000,000,000 to make the math easier.)
, Points Earned:, 1/1
Correct Answer:, B
Your Response:, B
9., You are asked to assign as accurate a numerical age as possible (how many years old) to a sedimentary deposit. You would be wise to use:, A., Uniformitarian techniques if the deposit is old, and counting of annual layers if the deposit is young.
B., Uniformitarian techniques.C., Either counting of annual layers or radiometric techniques if the deposit is old (more than about 100,000 years), and radiometric techniques if the deposit is young (less than about 100,000 years).D., Either counting of annual layers or radiometric techniques if the deposit is young (less than about 100,000 years), and radiometric techniques if the deposit is old (more than about 100,000 years).E., Counting of annual layers if the deposit is old (more than about 100,000 years), and radiometric techniques if the deposit is young (less than about 100,000 years).
If you want an absolute date (number of years) rather than older/younger, you can count layers for young things, or
use radiometric techniques for young things or for old ones. Uniformitarian calculations aren’t very accurate.
, Points Earned:, 1/1
Correct Answer:, D
Your Response:, D

,
10., John Wesley Powell, who led the first boat trip through the Grand Canyon, called the feature marked by the
yellow lines above “The Great _________”. What did he put in the blank?
, A., Pull-apart fault.
B., Intrusion.
C., Unconformity.
D., Trompe L’Oeil.
E., Thrust Fault.
This is The Great Unconformity, separating inclined sedimentary rocks below from horizontal sedimentary rocks
above. The rocks above are from the Paleozoic, and those below from the Precambrian. A Trompe L’Oeil painting is
designed to fool the eye, but this is real.
, Points Earned:, 1/1
Correct Answer:, C
Your Response:, C

,
11., In the photograph above, a portion of cliff about 30 feet high is shown. From what location in the Grand Canyon did Dr. Alley take this image?, A., In the gift shop, where artists have painted the cliff to look like real rocks.
This is the Vishnu Schist and Zoroaster Granite, rocks from the heart of a mountain range. The river is just barely
out of the picture to the bottom.
, Points Earned:, 1/1
Correct Answer:, E
Your Response:, E

,
12., The picture above shows a region of hard rock about six inches across from the Grand Canyon. The shape and
polish of the rock are interesting.

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- Fall '08
- ALLEY,RICHARDBANANDAKRISHNAN,SR
- Geology