1-How many half-lives are required to yield a mineral with 1,250 atoms of U238 and 18,750 atoms of Pb206?

A. 8

B. 4

C. 1

D. 16

2-Are decay rates of radioactive isotopes affected by the physical and chemical environment that the isotope is in?

A. Yes, strongly affected

B. No, not affected

C. Affected by certain chemical environments

D. Affected by certain physical environments

3-The principle of __________ states that "Layers of sediment are generally deposited in a horizontal position."

A. sediment

B. fossil succession

C. cross-bedding

D. original horizontality

E. cross-cutting relationships

4-A half-life is the time it takes for half __________.

A. the rock's crystals to be scarred by fission tracks

B. of the daughter isotope to escape

C. of the parent isotopes to become trapped in a crystal

D. of the parent isotope to decay to daughter isotopes

5-An unconformity is a gap in the stratigraphic sequence.

True

False

6-Fossils found in strata:

A. allow the correlation of strata separated by many miles

B. All of the above statements are correct.

C. are the records of ancient life

D. have been useful to geologists in creating the geologic column

7-Considering the half-life of potassium 40, which is 1.3 billion years, what fraction of the original potassium 40 can be expected within a given mineral crystal after 3.9 billion years?

A. 1/2

B. 1/8

C. 1/4

D. 1/16

8-Relative dating is determining the

A. chronological order of a sequence of events.

B. time span between geologic events.

C. length of time since the rock was formed.

D. age of a rock expressed as a certain number of years.

9-The principle of cross-cutting relationships says that ______.

A. a sediment or sedimentary rock layer is older than the layers below it and younger than the layers that lie above

B. waterborne sediments are deposited in nearly horizontal layers

C. a sediment or sedimentary rock layer is younger than the layers below it and older than the layers that lie above

D. a rock unit is older than a feature that disrupts it, such as a fault or igneous intrusion

10-Gaps in the rock record, between differently inclined layers of rock, are called:

A. erosion unconformities

B. disconformities

C. nonconformities

D. angular unconformities