Deck 9: Geologic Time: Concepts and Principles

Question 1

Both relative time and absolute time have been critical for geology to develop as a science.

Answer 1

True

Question 2

Relative time involves the sequencing of geologic events on the basis of the theory of relativity.

Answer 2

False

Question 3

Radiometric dating is the most common means of assigning absolute ages to rocks.

Answer 3

True

Question 4

Creation of the geologic time scale required the technology and knowledge associated with radiometric dating and absolute dating.

Question 5

Assigning an age to the earth is as simple as calculating the salinity of ocean water since the salts were originally derived from continents.

Question 6

The principle of uniformitarianism is premised on the assumption that earth processes have been the same over geologic time.

Question 7

The principles of uniformitarianism and superposition are both critical to assigning relative ages to a sequence of sedimentary rocks.

Question 8

The principles of superposition, original horizontality, and lateral continuity apply to all rocks in the rock cycle.

Question 9

Unconformities represent a gap in time.

Question 10

A catastrophic flood might produce a disconformity.

Question 11

If dike A cuts across sill B, beds above and below the sill are older than A and B

Question 12

Correlation is the process of matching similar rock types.

Question 13

Marine fossils are easily identified, geographically extensive, and existed over a short interval of geologic time.

Question 14

Well cuttings enable geologists to correlate rock units in the subsurface.

Question 15

In two half-lives, 25 percent of the parent element is left.

Question 16

Accurate radiometric dates are possible from any rock type that includes radioactive elements.

Question 17

Radiometric dates are most accurate from igneous rocks.

Question 18

Radiometric dates from closed systems are more accurate that from open rock systems.

Question 19

Radioactive decay is the process by which an unstable atomic nucleus is transformed into a different, more stable nucleus.

Question 20

Carbon 14 dates would be useful to date rocks from the Precambrian.

Question 21

The geologic time scale describes rock type and ages for rocks around the world.

Question 22

James Hutton developed the geologic time scale.

Question 23

Geologists have calculated that 500 million years ago, in Earth's geologic past, days were

A) 17 hours long.
B) 20 hours long.
C) 24 hours long.
D) 27 hours long.
E) 30 hours long.

Question 24

Geology and astronomy differ from all other sciences in that

A) phenomena occur on a global to universal scale.
B) they are historical sciences.
C) they are concerned with phenomena that occur within a deep time framework.
D) B and C
E) all of the above

Question 25

Once the concept of a linear time and history were established

A) the earliest estimates of Earth's age were based on inference from the Bible.
B) the earliest estimates of Earth's age were based on inference from the rates of observable geologic processes.
C) the earliest estimates of Earth's age were based on direct statements from the Bible.
D) the earliest estimates of Earth's age were based on faith.
E) the earliest estimates of Earth's age were based on fossils

Question 26

Sedimentary rock unit A is cut by igneous rock unit B and is on top of sedimentary rock unit C. Which of the following sequences, from oldest to youngest is correct?

A) A, B, C
B) C, B, A
C) A, C, B
D) C, A, B

Question 27

Which of the following was not among the early scientific attempts to determine Earth's age?

A) the cooling rate of a molten iron sphere of Earth's diameter
B) the rate of sediment deposition
C) the rate at which water precipitation accumulated in the ocean
D) the geologic principles and the inferred rates of change necessary to explain the fossil record
E) the rate of salt accumulation in the ocean

Question 28

Lyell's publication of Hutton's ideas were important at the time not only to geology but also to

A) astronomy.
B) Darwin's theory of evolution.
C) plate tectonics.
D) continental drift.
E) the geocentric model of the solar system.

Question 29

Working in a complex of horizontal sedimentary rocks and intrusive igneous rocks, which of the following principles might you use to determine relative ages of the rocks?

A) uniformitarianism
B) cross-cutting relations
C) superposition
D) unconformities
E) A, B, and C
F) B and C

Question 30

Which of the following is NOT a method of subsurface correlation?

A) electric resistivity logs
B) seismic profiles
C) well cores
D) well cuttings
E) gravity logs

Question 31

The time equivalence of rock units separated by great distances (e.g., an ocean) or where outcrop is minimal can be determined by

A) lateral tracing of units
B) key beds or marker beds
C) index fossils
D) rock sequences
E) all of the above

Question 32

Assemblage zones are used in fossil correlation because

A) most fossils have long geologic ranges.
B) most fossils are very rare.
C) most fossils are geographically restricted.
D) most fossils are not common.
E) most fossils are not well preserved.

Question 33

Which of the following rock types would typically produce the most accurate radiometric date?

A) igneous rock
B) sedimentary rock
C) metamorphic rock
D) A, B, and C

Question 34

The most accurate radiometric dates are obtained from (igneous, sedimentary, ___________metamorphic)rocks. Only in very unusual circumstances can (igneous, sedimentary, metamorphic) ___________ rocks be radiometrically dated.

Question 35

Explain Lord Kelvin's reasoning for calculating the age of Earth? Include in your explanation the flaw(s) in his argument.

Question 36

Why does the principle of uniformitarianism lead to the conclusion that Earth's age is great? What are some of the critical assumptions on which it is based?

Question 37

What is the possibility that the geologic time scale will change in the future? Explain your reasoning.

Question 38

Describe the conditions necessary for a rock to be appropriate for radiometric dating. Which condition is most limiting relative to the reliability of given age estimate?

Question 39

Time is conceived of and measured in several different manners depending upon culture, knowledge, application and purpose. What is meant by the term "deep time"as it is used by geologists and astronomers?

Question 40

dating is the most common method of obtaining absolute age dates.

Question 41

What are the two different frames of reference used by geologists in speaking of geologic time?

Question 42

What is the age of Earth which was calculated using biblical scriptures?

Question 43

Who, by virtue of a mathematical model, concluded that Earth could not be older than 100 million years and no younger than 20 million years?

Question 44

Does the principle of uniformitarianism mean that nothing which has not happened in recorded history could have happened in the past? Explain.

Question 45

Does the principle of uniformitarianism exclude the effects of catastrophic events as important agents of formation and change in Earth history? Explain.

Question 46

What is a hiatus?

Question 47

What is an unconformity?

Question 48

What are three types of unconformities?

Question 49

What is a nonconformity?

Question 50

What is a disconformity?

Question 51

What is the importance of the principle of superposition?

Question 52

What is the principle of fossil succession?

Question 53

Why is the principle of fossil succession important?

Question 54

Is the principle of fossil succession based on an assumption of organic evolution? Explain.

Question 55

What is a index fossil?

Question 56

Explain why it is possible to correlate rocks among several regions when the strata being correlated between two of the regions are not of the same age?

Question 57

What is the principle of fossil succession?

Question 58

Why is the principle of fossil succession considered important in geology?

Question 59

Why are fossils found almost exclusively in sedimentary rocks (as opposed to other types of rocks)?

Question 60

What are isotopes of an atom?

Question 61

How are well logs used to correlate subsurface rocks?

Question 62

What is alpha decay?

Question 63

What is beta decay?

Question 64

What is the half-life of a radioactive isotope?

Question 65

What is the maximum age limit for radiocarbon dating of fossils?

Question 66

Fossils cannot usually be dated using radiometric dating methods. Why not?

Question 67

What 2 types of elements must we be able to measure very accurately when we determine the radiometric age of a rock?

Question 68

How old is Earth (what is a geologically reasonable maximum age)?

Question 69

Why are tree-rings useful for dating recent events?

Question 70

Did the development of the geologic time scale depend on development of radiometric dating techniques? Explain.