Deck 14: Exploring Earths Interior

Question 1

What principle is based on the continents being less dense than the underlying mantle?

A)epeirogeny
B)isostasy
C)superposition
D)tomography

Answer 1

B

Question 2

Continental crust beneath mountains can be up to ___ kilometers thick.

A)10
B)40
C)70
D)100

Answer 2

C

Question 3

How thick is the oceanic crust?

A)approximately 7 km
B)approximately 70 km
C)approximately 35 km
D)approximately 240 km

Answer 3

A

Question 4

Which of the following statements about the Mohorovičić discontinuity (Moho)is false?

A)The Moho marks the top of a partially molten layer.
B)The Moho separates denser rocks below from less dense rocks above.
C)The Moho separates the crust from the mantle.
D)The speed of seismic waves increases as they pass down through the Moho.

Question 5

Why is the average elevation of the continents higher than the average elevation of the seafloor?

A)because melting of large ice caps has caused isostatic rebound of the continents
B)because oceanic crust is composed of denser rocks than the continental crust
C)because the continents are supported by upwelling mantle currents
D)because subduction pulls down the seafloor

Question 6

Where do P waves travel fastest?

A)in the upper mantle
B)in the outer core
C)in the lower mantle
D)in the inner core

Question 7

The S-wave shadow zone extends from ____ to 180° angular distance from the earthquake focus.

A)45°
B)75°
C)105°
D)145°

Question 8

How thick is average lithosphere?

A)25 km
B)100 km
C)250 km
D)1000 km

Question 9

Which of the following statements is true?

A)Liquids do not transmit P waves.
B)P-wave velocities are greater in the core than in the mantle.
C)Seismic waves follow straight paths through the interior of Earth.
D)The S-wave shadow zone is larger than the P-wave shadow zone.

Question 10

Which of the following regions in Earth consists primarily of olivine and pyroxene?

A)the crust
B)the upper mantle
C)the lower mantle
D)the inner core

Question 11

Which of the following correctly lists the three rock types in order of increasing P-wave velocity?

A)gabbro.granite,peridotite
B)granite,peridotite,gabbro
C)granite,gabbro,peridotite
D)peridotite,gabbro,granite

Question 12

The oceanic crust consists mostly of

A)felsic rocks.
B)mafic rocks.
C)sedimentary rocks.
D)ultramafic rocks.

Question 13

Which of the following statements about the asthenosphere is false?

A)The asthenosphere lies beneath the lithosphere.
B)The asthenosphere is stronger than the lithosphere.
C)The asthenosphere rises close to the surface beneath mid-ocean ridges.
D)The asthenosphere is partially molten.

Question 14

Which of the following seismic waves will arrive at a seismograph first?

A)P
B)S
C)PP
D)SS

Question 15

What is the approximate distance from the surface to the center of Earth?

A)700 km
B)2900 km
C)6400 km
D)24,000 km

Question 16

How fast do P waves travel through granite?

A)4 kilometers per second
B)6 kilometers per second
C)8 kilometers per second
D)12 kilometers per second

Question 17

After melting of a continental ice cap,the surface of the continent will tend to

A)rise.
B)sink.
C)rise or sink depending on the thickness of the ice cap.
D)remain the same.

Question 18

Which of the following statements is false?

A)P waves travel slower in the crust than in the mantle.
B)The crust is denser than the mantle.
C)The crust-mantle boundary is called the Mohorovičić discontinuity.
D)The oceanic crust consists of basalt and gabbro.

Question 19

Which layer in Earth does not transmit S waves?

A)the crust
B)the inner core
C)the mantle
D)the outer core

Question 20

Which of the following marks the boundary between the crust and the mantle?

A)a decrease in P-wave velocity and a change in rock type
B)an increase in P-wave velocity and a change in rock type
C)a decrease in P-wave velocity,but no change in rock type
D)an increase in P-wave velocity,but no change in rock type

Question 21

Above what temperature do materials lose their permanent magnetism?

A)100°C
B)500°C
C)1000°C
D)5000°C

Question 22

Approximately how often does Earth's magnetic field reverse itself?

A)every 50 years
B)every 5000 years
C)every 500,000 years
D)every 50,000,000 years

Question 23

Seismic wave speeds increase with

A)decreasing density and temperature.
B)decreasing density and increasing temperature.
C)increasing density and decreasing temperature.
D)increasing density and temperature.

Question 24

According to a recent hypothesis,mantle plumes that feed hot spots originate from

A)the asthenosphere-lithosphere boundary.
B)the core-mantle boundary.
C)the crust-mantle boundary.
D)the inner core-outer core boundary.

Question 25

What drives plate tectonics?

A)erosion
B)solar energy
C)thermal conduction
D)thermal convection

Question 26

Which of the following regions is hottest?

A)the crust
B)the inner core
C)the mantle
D)the outer core

Question 27

At what depth does the transition from the upper mantle to the lower mantle occur?

A)approximately 100 kilometers
B)approximately 3000 kilometers
C)approximately 700 kilometers
D)approximately 5000 kilometers

Question 28

Who first proposed that Earth acted as a large magnet whose field forces the needle of a magnetic compass to align north-south?

A)Charles Darwin
B)William Gilbert
C)James Hutton
D)Charles Lyell

Question 29

The boundary between the mantle and the core lies at a depth of approximately

A)300 kilometers.
B)1000 kilometers.
C)3000 kilometers.
D)10,000 kilometers.

Question 30

The temperature at the center of Earth is approximately

A)200°C.
B)500°C.
C)2000°C.
D)5000°C.

Question 31

Based on seismic tomographic images,how deep do subducting slabs extend?

A)to the crust-mantle boundary
B)to the upper mantle-lower mantle boundary
C)to the core-mantle boundary
D)to the inner core-outer core boundary

Question 32

Which of the following regions is the source of most basaltic magma?

A)the asthenosphere
B)the lithosphere
C)the lower mantle
D)the outer core

Question 33

What cause large-scale variations in Earth's geoid?

A)variations in gravity
B)variations in radioactivity
C)variations in magnetism
D)variations in solar energy

Question 34

What causes the sharp increases in the velocity of S waves at a depth of 400 and 660 km in the mantle?

A)changes in the composition of the mantle
B)changes in the mineral structures
C)changes in the pressure of the mantle
D)changes in the temperature of the mantle

Question 35

Where is Earth's magnetic field generated?

A)in the crust
B)in the mantle
C)in the outer core
D)in the inner core

Question 36

Over geologic time,most of the heat lost from Earth's interior has been transported by

A)conduction.
B)convection.
C)radioactive decay.
D)solar radiation.

Question 37

The mechanical transfer of heat by vibration of atoms and molecules is called

A)conduction.
B)convection.
C)magnetism.
D)radiation.

Question 38

Which of the following statements about Earth's core is true?

A)The inner core and the outer core are both liquid.
B)The inner core and the outer core are both solid.
C)The inner core is liquid and the outer core is solid.
D)The inner core is solid and the outer core is liquid.

Question 39

What element makes up most of Earth's core?

A)iron
B)oxygen
C)magnesium
D)silicon

Question 40

Seismic tomography has revealed that seismic waves in the uppermost mantle are relatively

A)fast beneath both mid-ocean ridges and subduction zones.
B)fast beneath mid-ocean ridges and slow beneath subduction zones.
C)slow beneath mid-ocean ridges and fast beneath subduction zones.
D)slow beneath both mid-ocean ridges and subduction zones.

Question 41

How much of Earth's magnetic field can be described by a simple dipole?

A)10%
B)25%
C)75%
D)90%

Question 42

The graphical curve that describes how temperature changes with depth in Earth is called the

A)tempotherm.
B)heating gradient.
C)geoid gradient.
D)geotherm.

Question 43

The area on the surface of Earth where P waves and S waves are not recorded by seimograms following an earthquake event are referred to as

A)reflection zones.
B)aseismic areas.
C)geoid highs.
D)shadow zones.

Question 44

A P wave that travels from the earthquake focus through the mantle,outer core,back through the mantle,and to Earth's surface is labeled a=

A)PcP wave.
B)PKP wave.
C)PKS wave.
D)PcS wave.

Question 45

What do sound,light,and seismic waves have in common?

A)They can travel trough all types of materials.
B)They travel at the same speeds.
C)Their speed depends on the materials they travel through.
D)Their speeds are independent of the material they travel through.

Question 46

Seismic tomography has revealed a superplume rising from the core-mantle boundary below

A)Iceland.
B)South Africa.
C)the Himalayas.
D)Mount St.Helens.

Question 47

Using a compositional model of pure iron-nickel alloy for the inner core renders the inner core ________ to match the data for the outer core.

A)too dense
B)not dense enough
C)too magnetic
D)not magnetic enough

Question 48

Seismic waves that bounce off a boundary between two different materials are said to be ________,whereas seismic waves that cross the boundary and are bent are said to be ________.

A)refracted; reflected
B)reflected; transmitted
C)reflected; refracted
D)refracted; transmitted

Question 49

Which of the following statements is false?

A)S waves slow down as they travel through the mantle.
B)P waves slow down in the outer core.
C)S waves cannot transmit through the outer core.
D)P waves travel through the inner core.

Question 50

Which of the following processes is responsible for the recording of the magnetic reversals on the seafloor?

A)depositional remanent magnetism
B)tectonosilicate magnetism
C)metamorphic magnetism
D)thermoremanent magnetism

Question 51

Earth's magnetic field shields the surface of Earth from

A)asteroids.
B)solar winds.
C)intergalactic radio waves.
D)geotherms.

Question 52

How many mineralogical phase changes do scientists interpret to occur in the mantle based on the jumps in S-wave speeds?

A)one
B)two
C)three
D)four

Question 53

An S wave that is reflected once off the surface of Earth is labeled an ______ wave.

A)SR
B)SP
C)SS
D)SK

Question 54

The P wave shadow extends from 105° to roughly __________distance from an earthquake's focus.

A)120°
B)130°
C)140°
D)160°

Question 55

Evidence for the internal structure of Earth is mostly based on

A)heat flow measurements.
B)waves generated by earthquakes.
C)existence of a magnetic field.
D)deep mines and drilling.

Question 56

Which of the following Earth systems powers Earth's magnetic field?

A)the climate system
B)the plate tectonic system
C)the geodynamo system
D)all of the above

Question 57

When was there a 35-million-year period during which Earth's magnetic field did not undergo reversals?

A)the Cretaceous
B)the Eocene
C)the Miocene
D)the Pliocene-Pleistocene

Question 58

The P wave shadow extends from roughly __________ to 142° distance from an earthquake's focus.

A)25°
B)50°
C)100°
D)125°

Question 59

Variations in the pull of gravity at the surface of Earth are linked to

A)variations in latitude.
B)variations in the liquid outer core.
C)variations in lithospheric densities.
D)variations in the mantle temperature.

Question 60

Exploring Earth's interior using seismic tomography is analogous to exploring the human body using a(n)

A)CAT scanner.
B)MRI machine.
C)stethoscope.
D)fMRI machine.

Question 61

Earth's inner core was discovered by seismologist

A)Beno Gutenberg.
B)Andrija Mohorovičić.
C)Hugo Benioff.
D)Inge Lehmann.

Question 62

The P wave shadow extends from roughly ___ to roughly ____ distance from an earthquake's focus.

A)60°; 100°
B)100°; 140°
C)140°; 180°
D)180°; 220°

Question 63

What sort of geothermal gradient is consistent with having convection in the mantle?

A)0.5°C/km
B)2.5°C/km
C)25°C/km
D)250°C/km

Question 64

Let's assume that the inner core was liquid and the outer core was solid.What would one expect to see in terms of P and S wave shadows in terms of distance from an earthquake focus?

A)P-wave and S-wave shadows would be the same size.
B)S-wave shadow would start where the P-wave shadow ends.
C)P-wave shadow would start where the S-wave shadow ends.
D)There would only be a P-wave shadow.

Question 65

Given that the P wave velocities are related to rock density,choose the sequence that shows the rocks in terms of increasing P wave speeds.Rock densities are: rock I = 2.9 gm/cc,rock II = 2.6 gm/cc,and rock III = 3.3 gm/cc.

A)I,II,III
B)II,III,I
C)I,III,II
D)II,I,III

Question 66

Recently scientists have suggested that __________,thus acting like a "planet within a planet."

A)mantle spins faster than the core
B)outer core spins faster than the mantle
C)inner core spins faster than the mantle
D)lower mantle spins faster than the outer core

Question 67

Which portion of the mantle is relatively free of seismic discontinuities?

A)30 to 100 km
B)100 to 400 km
C)400 to 1000 km
D)1000 to 2500 km

Question 68

Over time,the size of the inner core will __________ and the size of the outer core will __________.

A)grow; grow
B)shrink; shrink
C)shrink; grow
D)grow; shrink

Question 69

Which of the following foods would best serve a proxy for Earth's layering?

A)apple
B)orange
C)peach
D)onion

Question 70

Calculations suggest that the inner core

A)spins at a faster rate than the rest of Earth.
B)spins in the opposite direction of the rest of Earth.
C)spins at the same rate as Earth.
D)does not spin at all.

Question 71

Where,inside Earth,is the largest change in material density?

A)base of the crust
B)base of the lithosphere
C)core-mantle boundary
D)outer core-inner core boundary

Question 72

Assume you are astronaut geophysicist working on Titan (Moon of Saturn)and measure a P-wave velocity of 8 km for the moon's crust.Assuming what you know from Earth,what kind of rock is this surface made of?

A)granite
B)basalt
C)gabbro
D)peridotite

Question 73

In a deep mine,temperatures increase at the rate of approximately ______ per kilometer.

A)2.5°C
B)25°C
C)250°C
D)2500°C

Question 74

Geologists have discovered a simple mathematical equation that relates the depth of the seafloor to crustal age.This relationship implies that the oceanic lithosphere

A)floats on the asthenosphere.
B)cools by conduction.
C)cools by convection.
D)is rigid.

Question 75

Which of the following layers will not transmit S waves?

A)crust
B)mantle
C)outer core
D)inner core

Question 76

As seismic waves travel through Earth,they generally

A)curve upward.
B)travel in straight lines.
C)curve downward.
D)travel along irregular paths.

Question 77

The base of transition zone layer marks the beginning of the

A)outer core.
B)inner core.
C)lower mantle.
D)upper mantle.

Question 78

According to the principle of isostasy

A)oceanic crust should stand higher than continental crust.
B)continental crust should be thinner than oceanic crust.
C)crustal thickness is directly related to surface elevation.
D)elevation is independent of crust type.

Question 79

Geologists have formulated a simple mathematical equation that can predict the depth of oceans.According to their equation,on what does the water depth primarily depend?

A)distance from shore
B)age of the seafloor
C)distance from the nearest mid-ocean ridge
D)none of the above

Question 80

Between 410 and 670 km depths,S-waves show several jumps attributed to phase changes in the upper mantle.What do geophysicists call this region?

A)the seismic jump region
B)the sudden change zone
C)the low-velocity zone
D)the transition zone