Name: ____________________________________
Class: _____________
Date: _____________
Self Assessment: Determining the Age of Rocks
1. The law of superposition states that in an undeformed sequence of sedimentary rocks, each bed is _____.
a) dateable based on index fossils for which an age is known
b) deposited in a horizontal position
c) a complete set of conformable strata
d) older than the one above it and younger than the one below
2. If two rock masses are adjacent, and one contains inclusions from the other, what is most likely true?
a) The mass that contains the inclusions is the younger of the two.
b) The two masses must have been separated by a third layer which has eroded.
c) The mass that contains the inclusions is the older of the two.
d) The two masses must be close to the same age.
3. A gap between layers of horizontal rock is called a _____.
a) horizontal unconformity
b) disconformity
c) nonconformity
d) angular unconformity
4. In a hypothetical rock formation, four layers are in evidence. From the bottom they will be labeled A, B, C,
and D. Layers A and B exist at an angle to the upper layers and the plane of Earth's crust. Layer C lies flat
across the jagged edges of the lower layers. Layer D lies flat above C, and is being made jagged at its
surface by erosion. What most likely caused the unconformity beneath layer C?
a) a period of uplift and the erosion of all overlying rocks
b) a period of deformation and erosion during a pause in deposition
c) a long period of continuous sedimentation
d) a pause in erosion during which large amounts of deposition occurred
PAGE 1
Name: ____________________________________
Class: _____________
Date: _____________
Self Assessment: Determining the Age of Rocks
5. The process of alpha emission involves _____.
a) emission of a particle composed of one neutron and one proton, which decreases the mass number of
the isotope by two, and the atomic number by one
b) the combination of an electron and proton, which forms a neutron and decreases the atomic number by
one
c) emission of a particle composed of two neutrons and two protons, which decreases the mass number of
the isotope by four, and the atomic number by two
d) emission of an electron from a neutron, which results in the creation of a proton, and increases the
atomic number by one
6. The nucleus of every radioactive element disintegrates over time. This process is called _____.
a) electron capture
b) radiation
c) radioactive decay
d) half life
7. Carbon 14 decay takes place over thousands of years, making it a useful tool for measuring the age of
_____.
a) human artifacts
b) dinosaur fossils
c) volcanic rock
d) sedimentary rock
8. Carbon 14 has a half life of 5,730 years. What does this figure mean?
a) It takes 5,370 years for half of the nuclei in a sample of Carbon 14 to decay.
b) It takes 5,370 years for all of the nuclei in a sample of Carbon 14 to decay.
c) It takes 5,370 years for half of the electrons in a sample of Carbon 14 to decay.
d) It takes 5,370 years for all of the electrons in a sample of Carbon 14 to decay.
PAGE 2
Name: ____________________________________
Class: _____________
Date: _____________
Self Assessment: Determining the Age of Rocks
9. During radioactive decay, a parent element degenerates into a daughter product. When the ratio of parent
element to daughter product is 1:7, how many half lives have passed?
a) 2
b) 3
c) 6
d) 7
10. Geologic time is the stretch of time over which Earth's geologic development has taken place. This span
of time is approximately _____.
a) 4.6 trillion years
b) 4.6 billion years
c) 460 thousand years
d) 4.6 million years
PAGE 3
ANSWER KEY
1. d
2. a
3. b
4. b
5. c
6. c
ANSWER KEY Page 1
7. a
8. a
9. b
10. b