After one half life youve gone from 400 parents to

After one half-life, you've gone from 400 parents to 200; after a second half-life you go from 200
parents to 100, and after a third half-life you go from 100 parents to 50. (Typical studies of
radioactive decay use many more atoms, to avoid statistical fluctuations, but the question says
"on average", so we asked you about 400 rather than 400,000,000,000,000 to make the math
easier.)
Points Earned: 1/1
9. In age dating, geologists use:

A. Radiometric techniques and layer-
for relative dating of events that h
the last 100,000 years, and other r
techniques for relative dating of m
events.
B. Radiometric techniques for absolute dating of events that happened in the las
years, and other radiometric techniques and layer-counting for absolute datin
older events.
C. Radiometric techniques for relative dating of events that happened in the last
years, and layer-counting for relative dating of events that happened billions
ago.
D. Cross-cutting relationships for absolute ages, and uniformitarianism for relati
E. Radiometric techniques and layer-counting for absolute dating of events that
the last 100,000 years, and other radiometric techniques for absolute dating o
older events.
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.
Points Earned: 1/1
10. What is indicated by the yellow lines in the image above?

John Wesley Powell, of the United States Geological Survey, and the leader of the first boat trip
through the Grand Canyon, called the feature marked by the yellow lines "The Great
Unconformity". It separates horizontal Paleozoic sedimentary rocks, above, from inclined
Precambrian sedimentary rocks, below.
Points Earned: 1/1
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. Near the bottom, where the river has
through rocks that were cooked, sque
and partially melted deep in an old
mountain range.
B. Near the west end, where lava that came up pull-apart faults folded while flow
before hardening fully.
C. In the gift shop, where artists have painted the cliff to look like real rocks.
D. About halfway between the top and the river, where a large fault has dragged
rocks and caused the fold.
E. Near the top, in sedimentary rocks that slumped downhill when they were sof
folding the 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.
Correct Answer: A
Your Response: A
Points Earned: 1/1