Chapters 9 And 10

Front 1

Which condition will tend to make rocks change by ductile deformation rather than by brittledeformation?

Back 1

Slowlyapplied stress

Front 2

Pick out the TRUE statement. TheSan Andreas Fault...

a) is a right-lateral strike-slip fault

b) has a fault plane that dips 120° to the southeast

c) is a planar structure, so its orientation should be expressed in terms of bearing and plunge d) can also properly be called the San Andreas Joint

e) All the possible answers are correct.

Back 2

Is a right-lateral strike-slip fault

Front 3

If you see small angular fragmentsof shattered rock within a linear boundary zone between two more intact massesof rock, you must be looking at:

Back 3

Fault breccias

Front 4

Faulting in the Basin and RangeProvince of Nevada, Utah, and Arizona...

a) is normal

b) is caused by crustal stretching

c) has produced elongate valleys and mountain ranges

d) is an example of continental rifting

e) all the possible answers are correct.

Back 4

All the possible answers are correct.

Front 5

Which of the following statementsis FALSE? Mountains...

a) have roots of continental crust that extend deeper than the level of crust under plains

b) are randomly distributed over Earth’s surface

c) can spread laterally under their own weight, given time

d) are created during orogenies that may last for millions of years

e) are made up of rocks that have undergone ductile deformation and brittle deformation

Back 5

Are randomly distributed over Earth’s surface

Front 6

Deformation...

a) is a characteristic of mountain belts

b) produces changes in the shape and orientation of rock grains and rock layers

c) is brittle when many chemical bonds are broken quickly and the rock pieces separate

d) may produce faults if brittle and may produce folds if ductile

e) all the possible answers are correct

Back 6

All the possible answers are correct

Front 7

Which of the following statementsis FALSE? The African Rift Valley...

a) is bordered by linear mountain ranges called fault-block mountains

b) is basically a long graben

c) is geologically similar to the Basin and Range Province of Utah, Nevada, and Arizona

d) has volcanoes along it because asthenosphere is rising under the rift and supplying heat e) is produced by compressional stress

Back 7

Is produced by compressional stress

Front 8

Mountains don't get infinitely highor exist forever because...

a) when they get exceptionally large they spread laterally

b) they experience orogenic collapse

c) erosion attacks as soon as they begin to rise

d) all the possible answers are correct

e) their own weight causes them eventually to collapse.

Back 8

All the possible answers are correct

Front 9

A shield:

a) has lots of shear zones, flow folds, and tectonic foliation

b) is part of a craton

c) contains Precambrian metamorphic and igneous rocks outcropping at ground surface

d) all the possible answers are correct

e) can be associated with a cratonic platform.

Back 9

All the possible answers are correct

Front 10

Identify the FALSE statement.Brittle deformation...

a) produces folds and faults

b) occurs above a depth of about 10 to 15 km

c) occurs above the brittle-ductile transition zone

d) structures can be found in the same outcrop as ductile deformation structures because deformation rates may change during the course of an orogeny

e) is a permanent change of shape; elastic strain is a temporary change of shape. Save

Back 10

Produces folds and faults

Front 11

Which of these is NOT acharacteristic of mountain ranges formed or found within continental rifting?

a) thinned lithosphere

b) narrow block mountains separated by valleys c) thrust and reverse faulting

d) magmatism and/or volcanism

e) deep basins filled with sediments

Back 11

Thrust and reverse faulting

Front 12

T/F Tension produces shear strain.

Back 12

False

Front 13

T/F Faulting in a thrust-fault systemshortens the crust, since slivers of Earth get pushed over each other likeoverlapping shingles.

Back 13

True

Front 14

Which of these does NOT causeisostatic adjustment?

a) delamination of a portion of lithospheric mantle

b) continental rifting

c) massive intrusion of magmas into the lower or middle crust

d) tectonic foliation in response to shearing or dynamic metamorphism

e) plate convergence

Back 14

Delamination of a portion of lithospheric mantle

Front 15

T/F Typical continental crust is 35 to40 km thick; under mountains it is thinner, typically 15 to 20 km thick.

Back 15

False

Front 16

T/F When the buoyancy force pushing upon lithosphere equals the gravitational force pulling down on it, the situationis said to show isostatic equilibrium.

Back 16

True

Front 17

T/F Isostatic compensation takes a longtime because material within Earth’s core must flow to make theadjustment, and it flows slowly because of its great depth.

Back 17

False

Front 18

An ancient part of the crust thathasn’t been affected by mountain-building processes in at least a billion yearsis called a(n)

Back 18

Craton

Front 19

T/F Exotic terranes collided with thewest edge of the North American Cordillera and those that were not subductedbecame accreted terranes; because the mountains grew laterally this way, they’recalled accretionary orogens.

Back 19

True

Front 20

T/F The Himalayas, Alps, andAppalachian Mountains are all examples of convergent boundary mountains.

Back 20

True

Front 21

What is uniformitarianism?

Back 21

it is illustrated byscientists’ seeing pillow lava form only underwater, then theorizing thatpillow lava found high in the mountains today did nevertheless form underwater.

Front 22

Before the development of isotopicdating methods, the age of the earth was estimated by...

a) counting the ages of people within successive generations as described in the Bible

b) comparing rates of change on Earth’s surface today with the geologic record

c) calculating the rate of cooling of Earth from an assumed initial temperature

d) estimating evolution rates from the fossil record

e) all the possible answers are correct

Back 22

All the possible answers are correct

Front 23

Choose the proper list of names tofit the following three descriptions: Age of Mammals, Age of Dinosaurs, andlongest named geologic unit of time.

Back 23

Cenozoic, Mesozoic, Precambrian

Front 24

An area of slightly dippingsedimentary rock layers has large inclusions and is intruded by an igneousdike. Apply the basic principles for determining relative ages, and identifythe FALSE statement.

a) The sedimentary layers started out lying flat. b) The oldest sedimentary layer is the bottom layer

c) The igneous intrusion "baked" (metamorphosed) the sedimentary rock it touched

d) The dike is younger than the sedimentary rock layers it cuts across

e) The inclusions are younger than the sedimentary rock they are in

Back 24

The inclusions are younger than the sedimentary rock they are in

Front 25

Which method ofdetermining the age of materials is a radiometric dating technique?

Back 25

measuring the proportions of certain isotopes with respect to one another

Front 26

A zircon crystal is found tocontain three times as much Pb-207 (“lead 207”) as U-235 (“uranium 235”).Zircon (ZrSiO4) crystals form with small amounts of uranium in thembut without any lead in them. The half-life for the decay of U-235 into Pb-207is 713 million years. Based on this information, how long ago was the zirconcrystal formed?

Back 26

1,426 million (i.e., 2 x 713 million) years

The information tells you that zircon crystals form with no lead in them but with some uranium in them (as an impurity, substituting for zircon). There are several types of uranium, and the isotope U-235 breaks down into lead-207 at the rate of 50 percent every 713 million years (i.e., U-235 has a half-life of 713 million years). After one half-life had gone by, half the U-235 would be gone and turned into Pb-207. After another 713 million years (or two half-lives in total), ¾ of the original U-235 would have decayed into lead-207. Two half-lives equals 1,426 million years for this decay-pair.

Front 27

What assumption that you might use in radiometric age-dating would cause you to underestimatethe age of a rock?

Back 27

Therock had been a closed system since the time it formed, but it had beenmetamorphosed enough that some daughter product—but no parent product—escaped.

Front 28

What principle allows tree ringsand often permanent snowfields (or glaciers) to be used for age-dating?

Back 28

Repeatedannual patterns

Front 29

T/F It’s not possible to say just whenan individual radioactive atom will decay, but it is possible to say when halfof an existing quantity of radioactive material will be gone.

Back 29

True

Front 30

Closure temperature is?

Back 30

Thetemperature at which a rock system ceases to interchange parent or daughterproduct with surrounding material.

Front 31

T/F The oldest rocks found so far inour solar system are 4.57-billion-year-old meteorites, leading scientists toconclude that this is the approximate age of Earth.

Back 31

True

Front 32

What are the four steps ofradiometric age dating a geologic material?

Back 32

1. collecting a rock sample

2. separating the minerals of interest

3. extracting the isotopes of interest

4. measuring the concentrations and ratio of the two or more isotopes