1.3 Geological time

Question 1

in an undisturbed sequence of sedimentary rocks, younger layers overlie older layers, according to the principle of …

Answer 1

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Question 2

summarise the development of geological time?

Answer 2

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Question 3

dendrochronology involves dating of historic and geologic events through the study of …

Answer 3

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Question 4

accurate radiometric dating is possible only if a rock contains a measurable amount of …

Answer 4

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Question 5

what geologic principle is a direct result of gravity

Answer 5

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Question 6

why is radiocarbon dating only rarely applied in geological work?

Answer 6

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Question 7

within the world’s sedimentary rocks, fossils ….

Answer 7

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Question 8

if the lithology and fossil content of 2 bodies of rock on opposite sides of a canyon are identical, then these remaining outcrops were likely physically connected at one time and formed part of an extensive, sheet like layer of rock. this idea summarises the principle of …

Answer 8

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Question 9

magma has intruded into some limestone, and a marble rind framed surrounding the granite pluton. the marble rind must be younger than the limestone according to the principle of …

Answer 9

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Question 10

if horizontal sedimentary strata overlie tilted strata (and no fault is present), the surface between the horizontal and tilted strata must be a(n) ________.

Answer 10

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Question 11

If a basalt body cuts across a fault, what are the relative ages of the basalt and the fault?

Answer 11

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Question 12

If the relative ages of two formations are known, what else about them can be inferred?

Answer 12

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Question 13

Two atoms of a single element that differ in number of neutrons are said to represent two distinct ________ of that element.

Answer 13

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Question 14

A radiometric age for a mineral crystal within an igneous rock measures the amount of time that has passed since the ________.

Answer 14

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Question 15

Basaltic clasts within the basal layers of a conglomerate imply

Answer 15

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Question 16

what geologic principle is not a result of gravity?

Answer 16

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Question 17

James Hutton, the “father of geology,” put forth the principle of ________.

Answer 17

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Question 18

When an unstable parent isotope decays

Answer 18

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Question 19

The closure temperature represents the point when ________.

Answer 19

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Question 20

what is the same for different isotopes of a single element?

Answer 20

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Question 21

Numerical ages for boundaries between time units on the geologic time scale primarily resulted from the study of ________, in conjunction with relative age data.

Answer 21

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Question 22

The principle of ________ explains the occurrence of older rock within a newer igneous body.

Answer 22

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Question 23

The surface below sedimentary rocks that overlie igneous or metamorphic rocks is termed a(n) ________.

Answer 23

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Question 24

If an igneous dike cuts across a sequence of sedimentary beds, ________.

Answer 24

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Question 25

In the area immediately surrounding an igneous intrusion, a host limestone is locally metamorphosed to produce marble.

Answer 25

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Question 26

Can the age of Earth be reliably estimated from sediment thicknesses?

Answer 26

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Question 27

If a sandstone lies on top of a shale, ________.

Answer 27

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Question 28

Magnetostratigraphy takes advantage of the fact that Earth’s magnetic field ________.

Answer 28

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Question 29

Basaltic clasts within a conglomerate have been radiometrically dated to 50 million years ago. Is this a reliable age for the conglomerate?

Answer 29

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Question 30

Which method of correlation is most reliable for determining age equivalence among bodies of rock that are physically separated by vast distances?

Answer 30

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Question 31

Uniformitarianism is succinctly summarized by which phrase?

Answer 31

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Question 32

If all of Earth’s history were compressed into a single year, Homo sapiens would first appear on ________.

Answer 32

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Question 33

Which eon of geologic time is represented by rocks containing abundant shelly fossils?

Answer 33

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Question 34

Buried erosional surfaces between parallel sedimentary strata are termed ________.

Answer 34

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Question 35

Relative ages expressed on the geologic time scale primarily resulted from the study of ________.

Answer 35

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Question 36

As understood by modern geologists, the principle of uniformitarianism implies that ________.

Answer 36

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Question 37

Radiometric dates applied to sedimentary rocks produce ages that ________.

Answer 37

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Question 38

Concerning the relative ages of the granite and sandstone, ________.

Answer 38

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Question 39

After one half-life has passed, what is the ratio of parent isotopes to daughter isotopes?

Answer 39

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Question 40

Seasonal changes create layering in glaciers known as ________.

Answer 40

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Question 41

How much of a radioactive parent isotope will remain after three half-lives have passed?

Answer 41

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Question 42

In an unweathered sample of rock, the ratio of an unstable isotope to its stable daughter isotope is 1:15. If no daughters were present at the time the rock cooled below closure temperature, and the half-life of the isotope is 50 million years, how old is the rock?

Answer 42

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Question 43

How is the half-life of a radioactive parent isotope defined?

Answer 43

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