Chapter 9 Geology

25 July 2022
4.7 (114 reviews)
29 test answers

Unlock all answers in this set

Unlock answers (25)
question
Which of the following is an example of a numerical date? CHOOSE ALL THAT APPLY.
answer
The limestone formed at the end of the Ordovician, The pumice is 43 million years old.
question
What is the difference between numerical dates and relative dates?
answer
Numerical dates specify an absolute age in number of years, whereas relative dates determine the order of events in relation to one another.
question
Which of the geologic principles listed here is incorrectly defined?
answer
The principle of cross-cutting relationships states that the fault or intrusion that cuts across several rock layers is older than these layers.
question
What is the significance of an unconformity
answer
An unconformity represents an interval of time that is missing from the rock record.
question
Which of the following correctly describes an angular unconformity, a disconformity, and a nonconformity?
answer
An angular unconformity consists of tilted or folded rock layers that have been eroded and overlain by horizontal sedimentary layers; a disconformity consists of horizontal sedimentary layers that have been eroded and overlain by horizontal sedimentary layers; a nonconformity consists of metamorphic rocks or igneous intrusions that have been eroded and overlain by horizontal sedimentary layers.
question
Which of the below conditions favor fossil preservation?
answer
The organism is buried quickly.
question
Petrified wood is an example of what type of fossil preservation?
answer
Permineralization
question
Which method of fossilization listed below is correctly described?
answer
Permineralization is the process where pores in bones and wood are permeated by mineral-laden water.
question
Which of the below is an example of a trace fossil?
answer
coprolite
question
What conditions favor the preservation of an organism as a fossil?
answer
The organism has or is made of hard parts, The organism is rapidly buried.
question
What are the characteristics of an index fossil?
answer
limited to a short span of geologic time but widely distributed
question
Along with being important in correlation, how else are fossils useful to geologists?
answer
Fossils can help determine the depositional environment in which the rock layer that contains them formed.
question
Which of the following statements accurately contrasts an index fossil with a fossil assemblage?
answer
An index fossil is an individual fossil used to correlate different rock layers of the same age; a fossil assemblage is a specific combination of fossils that is used to more precisely date a rock layer.
question
What is the principle of fossil succession?
answer
Fossil organisms succeed one another upward through rock layers in a definite and determinable order; therefore, any time period can be recognized by its fossil content.
question
What is the goal of correlation?
answer
to gain a more comprehensive view of the geologic history of a region
question
When a beta particle is emitted during radioactive decay, the atomic number of the isotope _____.
answer
increases by 1
question
Two isotopes of uranium, 238U and 235U, have the same number of ___, but different numbers of ___.
answer
protons; neutrons
question
Archeologists typically use ___ to date artifacts by means of radiometric dating.
answer
Carbon-14
question
For what time span does radiocarbon dating apply?
answer
70,000 years ago or younger
question
What are the descriptions of the three types of radioactive decay?
answer
Electron capture is when the atomic number decreases by 1, Beta emission is when the atomic number increases by 1, Alpha emission is when the atomic number decreases by 2 and the atomic mass decreases by 4
question
What remains after a sample undergoes two half-lives?
answer
25 percent of the sample is composed of parent atoms, and 75 percent of the sample is composed of daughter atoms.
question
Why is radiometric dating a reliable method for determining numerical dates?
answer
Each radioactive isotope used for dating has been decaying at a fixed rate since the formation of the minerals in which it occurs
question
Which of the following represents the shortest division of time?
answer
Holocene
question
Why is "-zoic" part of so many names of units in the geologic time scale?
answer
The boundaries of geologic time units with names ending in zoic have been determined by worldwide changes in life forms.
question
What description below describes all geologic time prior to the Phanerozoic eon?
answer
The earliest span of geologic time is referred to as the Precambrian, which is an informal unit of time that is so old that little detail is known about it. For this reason, the Precambrian is not divided into periods or epochs.
question
To what does the term Hadean apply?
answer
The Hadean is an informal term for the time interval at the very beginning of Earth's history, which took place before the synthesis of Earth's oldest-known rocks.
question
Which type of rock is best suited for radiometric dating?
answer
granite
question
Why is it difficult to assign a numerical age to a sedimentary rock?
answer
A radiometric date taken from a grain within a detrital sedimentary rock only gives the age of that one grain, which likely came from a source different from the other grains within the rock.
question
How might a numerical date for a layer of sedimentary rock be determined?
answer
The order of occurrence of the sedimentary layer is related to a local igneous body that has been radiometrically dated, thus yielding an age range for the sedimentary layer.