Geology 101- Geologic Time Practice

30 million years old

A rock contains 7000 daughter atoms and 1000 radioactive parent atoms. If the half-life for the radioactive reaction is 10 million years, how old is the rock?

11,460

A shell in a sedimentary rock contains 1/4 of its original carbon-14. If carbon-14 has a half-life of 5730 years, then we can determine that the sediment was deposited __________ years ago.

the increase in temperature with increasing depth of burial and compression

In regional metamorphism the source of increased temperature and pressure is _________ .

granite (unit 1)

In this diagram, the contact between the granite (unit 1) and the lowest layer (unit 2) is depositional and the dike (unit 6) cuts across both units. What is the oldest unit?

A and B

In what site on this figure would you expect high pressure/low temperature metamorphism?

D and E

In what site on this figure would you expect regional metamorphism?

Determine the exact age of rocks.

Index fossils allow geologists to

protons, neutrons

Isotopes of an element have the same number of _________ but a different number of __________.

Phyllite

Name the metamorphic rock from the following picture.

Quartzite

Name the metamorphic rock from the following picture.

Slate

Name the metamorphic rock from the following picture.

gneiss

Name the rock from the following picture

Quartzite

Name the rock from the following picture:

Schist

Name the rock from the following picture:

Shale

Name the rock from the following picture:

phyllite

Name the rock from the following picture:

the granite (4)

Of the following numbered units, which is the oldest?

Unit 9

Of the following numbered units, which is the youngest?

the fault and fault scarp (3)

Of the following numbered units, which is the youngest?

Is an unconformity Represents erosion or no deposition Represents some missing time

The contact at the base of unit F in both columns:

a dark and light color banding

The foliation shown in a gneiss is

fault (feature F)

This figure has rock units and geologic features that are assigned letters that are not in any particular order. From the geologic relations, what is the oldest unit or feature of those listed below?

granite (unit G)

This figure has rock units and geologic features that are assigned letters that are not in any particular order. From the geologic relations, what is the oldest unit?

lava flow (unit L)

This figure has rock units and geologic features that are assigned letters that are not in any particular order. From the geologic relations, what is the youngest unit or feature of those listed below?

The boundary between the two units indicates that for a time there was either erosion or no deposition.

This figure shows a unconformity between an upper dark layer (being deposited by the sea) and a lower light-colored layer. What happened to form this unconformity?

Some units were deposited in the left section but not in the right one or were eroded away.

This figure shows two sections that represent the same age range and contain some of the same fossils. If you compare the two sections, what conclusions do you come to?

The upper unit is younger because it is on top The upper unit is younger because it contains pieces of the underlying unit The lower unit is older because it was tilted and eroded before deposition of the upper unit

This photograph shows an upper unit with fragments and a lower unit with tilted layers. Which of the following statements is true?

Trace

Tracks and burrows are examples of ________ fossils.

it was not deposited or was eroded away

Unit C is present in the left column but not the right column because:

3

Using the data in this table, calculate the number of half-lives that have passed for the granite (unit G on this table)?

1,500,000,000

Using the data in this table, determine the age of the granite (unit G on this table).

an unconformity between the two layers

What evidence might suggest a time interval between two rock layers?

~50,000 years

What is the maximum age limit of radiocarbon dating?

C

What letter(s) corresponds to areas high temperature but low pressure metamorphism?

unconformity

What type of feature is represented by the boundary between geologic units 2 and 3?

unconformity

What type of feature is shown in this photograph of Siccar Point, Scotland?

tilted layers

Which is the oldest feature in the diagram?

B

Which letter corresponds to high pressure but low temperature metamorphism?

1

Which location on this diagram would most likely record contact metamorphism in shallow levels of the crust?

3

Which location on this diagram would most likely record metamorphism along a subduction zone?

Mica

Which mineral is responsible for the strong foliation in a schist?

differential pressure

Which of the following causes a foliation in a metamorphic rock?

tilted layers

Which of the following features is older than fault 1?

lava flow and granite

Which of the following features is younger than fault 1?

deposits along the fault

Which of the following features is younger than fault 2?

lived for a long period of geologic time

Which of the following is not a characteristic of an index fossil?

tilted layers

Which of the following is older than fault 2?

C-14

Which of the following isotopes of carbon is radioactive?

gneiss, schist, phyllite, slate

Which of the following lists is arranged in order from highest to lowest grade of metamorphic rock?

shale-slate

Which of the following matches a sedimentary rock with a possible metamorphic equivalent?

Quartzite

Which of the following metamorphic rocks can not form from a shale?

slate-basalt

Which of the following metamorphic rocks is not paired with its true parent rock?

gneiss

Which of the following rocks represents the highest metamorphic grade?

unit 6

Which of the numbered units is the oldest?

1

Which of the numbers on this figure indicates low pressure/high temperature metamorphic conditions?

4

Which of these conditions could form rocks that are partly metamorphic and partly igneous?

Law of Inclusions

Which relative dating technique allowed you to determine which of the features in the cross-section is the oldest?

Law of Cross-cutting relations

Which relative dating technique allowed you to determine which of the features in the cross-section is the youngest?

they have different histories of erosion and deposition

Why don't these two sequences of fossil-bearing rocks match exactly?

40 million years old

An igneous rock formed with 144 radioactive (parent) atoms, but contains only 36 radioactive (parent) atoms today. If the half life for the radioactive element is 20 million years, how old is the rock?

125 million years

An mineral contains 60 parent atoms and 260 daughter atoms. If the half life for the radioactive element is 50 million years, how old is the rock?

20 million years

An mineral contains 900 parent atoms and 300 daughter atoms. If the half-life for the radioactive element is 40 million years, how old is the rock?

basalt dike

Examine the geologic cross section above. Which feature is the youngest?

sandstone(5)

Examine the geologic cross section above. Which of the following features is the oldest?

caused by a directed pressure

Foliated metamorphic rocks are always

Sedimentary

Fossils are most common in which rock types?

~ 8%

If a radioactive element has decayed for 3.5 half-lives, the amount of radioactive parent material remaining is what fraction of the original?