Deck 8: Telling Time Geologically

Question 1

All of the following radiometric dating methods are useful for rocks older than 100,000 years EXCEPT:

A) uranium- lead dating.
B) carbon- 14 dating.
C) potassium- argon dating.
D) rubidium- strontium dating.

Answer 1

B

Question 2

We believe the age of the Earth to be about 4.6 billion years old. This theory is confirmed by all of the following EXCEPT:

A) radiometric dating of meteorites that have struck the Earth.
B) extrapolation from radiometric dating of the oldest rocks found on Earth.
C) radiometric dating of rocks found on the Moon.
D) the proportional amount of lead isotopes on the Earth.

Answer 2

D

Question 3

The primary reason the principle of original horizontality can be applied by geologists is:

A) rocks are often found in overturned positions.
B) sediments tend to be deposited in horizontal layers.
C) vast areas have been deformed by tectonic activity.
D) lava flows tend to disrupt horizontally deposited sediments.

Answer 3

B

Question 4

An eroded fault offsets a dike, which intrudes sedimentary layers. Which event occurred last?

A) Erosion of the fault surface.
B) Intrusion of sedimentary layers.
C) Deposition of sedimentary layers.
D) Faulting and offsetting of a dike.

Question 5

If the half- life of a radioactive isotope is 1 billion years, and we measure a parent- to- daughter ratio of 1:3 in a particular sample, the age of the sample would be about:

A) 1 billion years old.
B) 3 billion years old.
C) 4 billion years old.
D) 2 billion years old.

Question 6

According to the principle of faunal succession, one would expect:

A) very old rocks to contain fossils of complex organisms, while younger rocks would contain fossils of both simple and complex organisms.
B) simple organisms to be found in sedimentary rocks more often than complex organisms.
C) the success of an organism determines the abundance of its fossils.
D) very old rocks to contain fossils of only simple organisms, while younger rocks would contain fossils of both simple and complex organisms.

Question 7

A rock or mineral becomes a closed system when it completely cools and crystallizes. Which rock type would become a closed system most rapidly?

A) Basalt.
B) Gneiss.
C) Schist.
D) Granite.

Question 8

The oldest remains of life have been found in:

A) 3.77- billion- year- old chert in Australia.
B) 3.96- billion- year- old gneiss of Canada.
C) 3.46- billion- year- old chert in Australia.
D) 670- million- year- old sandstone of Australia.

Question 9

The oldest rocks found on Earth are dated at:

A) 4.6 billion years.
B) 570 million years.
C) 3.77 billion years.
D) 3.96 billion years.

Question 10

According to the principle of cross- cutting relationships, if a dike is found cutting across sedimentary strata, the reasonable conclusion would be that:

A) the dike may be either younger or older than the sedimentary strata.
B) the dike is younger than the sedimentary strata.
C) the dike and the sedimentary strata are the same age.
D) the dike is older than the sedimentary strata.

Question 11

The principle of _ states that in any undisturbed sequence of rock strata, the youngest strata will be at the top and the oldest at the bottom.

A) superposition
B) cross- cutting relationships
C) inclusions
D) original horizontality

Question 12

All of the following are important causes of mass extinction EXCEPT:

A) volcanic flood basalts.
B) methane emissions from the sea floor.
C) ice ages.
D) meteorite impact.

Question 13

The principle of _ states that the present is the key to the past.

A) original horizontality
B) uniformitarianism
C) superposition
D) fossils have evolved over time

Question 14

Evidence of the oldest continental landscape includes all of the following EXCEPT:

A) an eroded surface indicating an unconformity.
B) fossilized sea creatures.
C) rocks containing paleosols.
D) sedimentary rocks containing shallow- water ripples.

Question 15

Evidence of the Earth's early atmosphere was contained in the:

A) 3.46- billion- year- old sedimentary rocks.
B) paleosols preserved on the unconformity surface.
C) 3.96- billion- year- old gneisses.
D) 3.52- billion- year- old granites and greenstones.

Question 16

The most dramatic mass extinction event on Earth occurred:

A) 10,000 years ago (Pleistocene- Holocene).
B) 65 million years ago (Cretaceous- Tertiary).
C) 55 million years ago (Paleocene- Eocene).
D) 250 million years ago (Permo- Triassic).

Question 17

Determining a specific age for a geologic event, feature, or rock unit using quantitative data is called:

A) age dating.
B) geometric dating.
C) relative dating.
D) absolute dating.

Question 18

Which of the following statements about relative dating by weathering features is NOT true?

A) The relative age of a landscape can be determined by observing the surface topography.
B) Younger landscapes have a higher number of surface boulders.
C) Soil is composed of completely weathered material and is of little use in this type of dating.
D) Highly weathered rocks emit a dull thud when struck with a rock hammer, while unweathered rocks emit a ringing sound.

Question 19

The half- life of a radioactive isotope refers to:

A) the time it takes for half of the parent isotopes to decay to daughter isotopes.
B) the time it takes for the ratio of parent to daughter isotopes to be 1:2 (half as many parent isotopes as daughter isotopes).
C) one- half of the total lifespan of a parent isotope.
D) the time it takes for the ratio of parent to daughter isotopes to be 2:1 (twice as many parent isotopes as daughter isotopes).

Question 20

Of the following organisms, the best index fossils would be:

A) bacteria, because they have existed in widespread geographic areas since life first began.
B) a specific type of trilobite that existed for only a short geologic time in widespread geographic areas.
C) cockroaches, because they have existed in widespread geographic areas almost since the first appearance of insects.
D) a specific type of bryzoa that existed for only a short geologic time in very limited geographic areas.

Question 21

If a mineral sample is dated using the potassium- argon dating method, and if some of the argon- 40 gas has escaped, the mineral's age:

A) will appear to be younger than it really is.
B) will not be affected.
C) will appear to be older than it really is.
D) can be determined by measuring the quantity of parent material present.

Question 22

Which of the following statements about lichenometry is NOT true?

A) Lichen dating is calibrated for an area by observing lichens on surfaces of known ages such as old tombstones.
B) Lichen dating is accomplished by counting the number of lichen colonies growing on the surface of a rock.
C) Lichenometry is useful for dating young glacial deposits, rockfalls, and mudflows.
D) Lichen dating is useful only for surfaces younger than about 9000 years.

Question 23

Fission- track dating is accomplished by observing the paths left by subatomic particles released during radioactive decay. Which characteristic of these tracks is used to determine the age of a sample?

A) The direction of the tracks.
B) The shape of the tracks.
C) The number of tracks.
D) The length of the tracks.

Question 24

Correlation of rock units is used to determine:

A) the ages of similar fossils found in geographically distant rocks.
B) which geographically distant rock units are the same type of rock.
C) which geographically distant rock units were formed under approximately the same environments.
D) which geographically distant rock units are approximately the same age.

Question 25

The proper order of the divisions of the geologic time scale from largest to smallest is:

A) eon, era, period, epoch.
B) era, eon, epoch, period.
C) epoch, period, eon, era.
D) eon, epoch, period, era.

Question 26

All of the following are tectonic events that occur very slowly EXCEPT:

A) opening of ocean basins.
B) collision of continents.
C) earthquakes.
D) building of mountains.

Question 27

Comparing certain characteristics to determine the ages of rocks and other geological features is called:

A) absolute dating.
B) relative dating.
C) age dating.
D) geometric dating.

Question 28

The divisions of the geologic time scale were based primarily on:

A) differences in fossil assemblages.
B) differences in sedimentary rock structures.
C) differences in types of rocks.
D) differences in minerals.

Question 29

All of the following represent examples of unconformities EXCEPT:

A) horizontal sedimentary strata overlying crystalline rocks.
B) tilted sedimentary strata offset by a fault.
C) horizontal sedimentary strata overlying tilted sedimentary strata.
D) horizontal sedimentary strata overlying eroded horizontal sedimentary strata.

Question 30

Which of the following statements about unconformities is NOT true?

A) The sedimentary rock record of most regions represents only 1% to 5% of Earth's existence.
B) Virtually every sequence of sedimentary rock layers contains one or more unconformities.
C) No single place on Earth contains all of the rock strata composing the entire geologic record.
D) Unconformities occur when plate- tectonic forces cause sediments to be deposited at an angle instead of horizontally.

Question 31

Which of the following statements about carbon- 14 dating is NOT true?

A) The bodies of organisms take in carbon- 14 throughout their lives and after death until they are isolated from the atmosphere by burial.
B) Carbon- 14 dates are determined by measuring the activity of carbon- 14 and comparing to the initial activity.
C) Rocks dated by the carbon- 14 method are generally in the 100- to 70,000- year age range.
D) Cosmic bombardment changes the rate of production of carbon- 14.

Question 32

According to the principle of inclusions, if a rock is found embedded within an igneous pluton, the reasonable conclusion would be that:

A) it cannot be determined whether the rock or the pluton is older.
B) the rock is the same age as the pluton.
C) the rock is younger than the pluton.
D) the rock is older than the pluton.

Question 33

The earliest known life forms on Earth are believed to have lived:

A) 3.96 billion years ago.
B) 3.77 billion years ago.
C) 570 million years ago.
D) 4.6 billion years ago.

Question 34

Which of the following statements about varve chronology is NOT true?

A) Summer sediment layers are dark- colored, while winter sediments are light- colored.
B) Varve layers are examined in cores extracted from the bottom of a lake.
C) Varves are more apparent in lakes that freeze in winter than in those that do not.
D) Varves can be used to date geologic events that had an effect on a lake.

Question 35

Comparison of weathering rinds in rocks from different regions is most accurate for which rock type?

A) Basalt.
B) Sandstone.
C) Limestone.
D) Granite.

Question 36

Dendrochronology can be used to date all of the following EXCEPT:

A) landslides.
B) droughts.
C) house posts.
D) an ax handle.

Question 37

All of the following examples illustrate preservation of original parts EXCEPT:

A) preservation in frozen permafrost.
B) preservation in underground burrows.
C) preservation in hardened tree sap.
D) preservation in tar pits.

Question 38

Dendrochronology is most useful in which regions?

A) Polar regions.
B) Desert regions.
C) Temperate climates.
D) Equatorial regions.

Question 39

The primary change in the Earth's environment that allowed more complex life forms to come into being was:

A) the addition of sufficient dissolved mineral and nutrients in the oceans.
B) the development of hospitable climatic belts.
C) a change in the Sun's emission of ultraviolet radiation.
D) the development of a protective atmosphere.

Question 40

Which type of rock is most likely to contain fossils?

A) Metamorphic rocks.
B) Igneous rocks.
C) Sedimentary rocks.
D) All of the above.

Question 41

Numerical age of fossiliferous marine strata could best be determined by using:

A) weathering rinds of fossil- bearing sandstone concretions.
B) isotopic dates from interbedded layers of volcanic ash.
C) the temperature- time relationships of nearby metamorphic rocks.
D) isotopic dates from nearby igneous intrusions.

Question 42

How is carbon- 14 dating different from the other types of radiometric- dating systems?

Question 43

Explain how weathering features may indicate the relative ages of rocks, landscapes, and soils.

Question 44

What causes are proposed for the several mass extinction events in the Earth's past?

Question 45

Briefly discuss how fossils form.

Question 46

How was the geologic time scale originally organized? What events define its major boundaries?

Question 47

Explain the means by which correlation of geographically separated sedimentary rock units is accomplished.

Question 48

We can apply the principle of uniformitarianism to conclude that:

A) volcanoes have always erupted lava.
B) Earth has always rotated at the same speed.
C) Earth has always had continents.
D) Earth has always had rivers.

Question 49

Describe the basic principles of radiometric dating.

Question 50

Why do we find neither rocks nor evidence of life as old as the age of the Earth?

Question 51

What qualities make a radioactive isotope unsuitable or suitable for use in radiometric dating?

Question 52

Discuss how unconformities develop and describe the three types of unconformities.