Earth: An Introduction to Physical Geology, 11e (Tarbuck)
Chapter 12 Earth’s Interior
12.1 Multiple-Choice Questions
1) Which physical property is responsible for determining how Earth materials separate out into
interior layers?
A) Density
B) Color
C) Molecular charge
D) Tensile strength
2) What is the range in densities between the top and bottom of the mantle?
A) 2.7-3.0 g/cm3
B) 3.0-3.3 g/cm3
C) 3.3-5.6 g/cm3
D) 10-12.1 g.cm3
3) What is a mineral phase change?
A) When a mineral melts from a solid state to a liquid state
B) The exterior of a mineral weathers and changes color
C) A mineral changes density because of the addition of water
D) Atoms in a mineral are rearranged into a more stable and denser structure
4) Which atom is easier to compress when pressure is squeezing a rock?
A) Negative ion
B) Positive ion
C) Isotope
5) ________ is the process where materials separate into different layers due to density.
A) Shearing
B) Differentiation
C) Phase change
D) Tensional stress
6) What do scientists use to determine the layering of the interior of the Earth?
A) Drill cores
B) Volcanic rocks
C) Sonar
D) Seismic waves
7) What is the minimum magnitude an earthquake can have in order for it to be picked up by
seismographs around the world?
A) M 6
B) M 7
C) M 8
D) M 9
8) What will happen to a seismic wave when it is reflected?
A) The wave will be bent
B) The wave will undulate
C) The wave will be bounced back toward its source
D) Nothing will change the wave
9) What will happen to a seismic wave when it is refracted?
A) The wave will be bent
B) The wave will undulate
C) The wave will be bounced back toward its source
D) Nothing will change the wave
10) What is the velocity of a P-wave?
A) 5-8 km/sec
B) 10-12 km/sec
C) 1-2 km/sec
D) 15 km/sec
11) What is the average velocity of an S-wave?
A) 1-2 km/sec
B) 3-4 km/sec
C) 5-8 km/sec
D) 10-12 km/sec
12) Where is the thinnest continental crust in the United States?
A) Appalachian Mountains
B) Mississippi River Valley
C) Basin and Range region
D) Colorado Plateau
13) Where is the thickest continental crust in the United States?
A) Appalachian Mountains
B) Rocky Mountains
C) Basin and Range region
D) Great Basin
14) Where is oceanic crust generated?
A) Along divergent plate boundaries
B) Where volcanic lava meets the sea
C) Where continents collide
D) Where magma bodies are emplaced deep in the crust
15) The ________ is a seismic boundary between the crust and the mantle where there is a
dramatic increase in seismic wave velocity.
A) Schrodinger Discontinuity
B) Greenschist Facies
C) Low-velocity pathway
D) Moho Boundary
16) Which layer of the Earth makes up more than 82% of the volume of the planet?
A) Outer Core
B) Crust
C) Mantle
D) Inner Core
17) Which layer or layers of the interior are believed to have convection cells?
A) Mantle alone
B) Mantle and Outer Core
C) Mantle and Inner Core
D) Outer Core and Inner Core
18) How does water get from the surface to the middle of the mantle?
A) Percolation via pores and fractures
B) Subterranean streams
C) Seawater seeping into the interior at mid-ocean rifts
D) Subducting oceanic lithosphere
19) Of the three mechanisms of heat transfer, which is the only one that does not operate in the
interior of the Earth?
A) Convection
B) Radiation
C) Conduction
20) What is the average geothermal gradient in the crust?
A) 20° C/km
B) 30° C/km
C) 45° C/km
D) 100° C/km
21) What is the average geothermal gradient in the mantle?
A) 0.3° C/km
B) 0.7° C/km
C) 1° C/km
D) 1.3° C/km
22) ________ is a technique to view three-dimensional changes in composition and density by
using seismology.
A) Magnetometry
B) Paleomagnetism
C) Chemical convection
D) Seismic tomography
23) How is the shape of the Earth affected by its rotation?
A) The Earth is perfectly round
B) The poles are further from the center of the Earth than the Equator
C) The Equator is further from the center of the Earth than the poles
24) Which of the following materials would cause the greatest gravity anomaly?
A) Quartz
B) Water
C) Granite
D) Metallic ore
25) Which of the following will not result in a seismic velocity anomaly when using seismic
tomography?
A) Magnetism
B) Composition
C) Temperature
D) Water content
26) A ________ is when an iron-rich fluid in the core is electrically charged and flowing, which
generates a magnetic field.
A) Geotherm
B) Geodynamo
C) Geophysical anomaly
D) Geosyncline
12.2 True/False Questions
1) The Inner Core and the Outer Core are compositionally the same. The major difference
between them is the states of matter in which they exist.
2) There are density changes between different parts of the same layer because certain materials
may compress when overlying rock squeezes them.
3) P-waves cannot penetrate the Outer Core.
4) Oceanic crust is compositionally more similar to the mantle than to continental crust.
5) The portion of the mantle closest to the Core-Mantle Boundary is hypothesized to be partially
molten because the S-wave velocities decrease by 30%.
6) The dominant mineral in the lower mantle is perovskite.
7) The core is composed of pure nickel and iron.
8) The inner core is shrinking.
9) Short-lived radioactive isotopes are responsible for the heat generated in the interior today.
10) Most rocks are poor conductors of heat, therefore conduction is not an efficient way to move
heat through most of the Earth.
11) Seismic tomography requires only the data from one recording station in order to “see” all
parts of the Earth’s interior.
12.3 Short Answer Questions
1) What is the average density of continental crust?
2) What is the average density of oceanic crust?
3) When olivine is undergoing a mineral phase change due to pressure, what mineral will it
form?
4) Circle the correct answer: Which material will seismic waves travel faster through: high-
density material or low-density material?
5) What physical property of continents makes them difficult to subduct?
6) Outside of the crust, the layer that scientists know the most about is the mantle. Other than via
seismic waves, how else do geologists obtain information about the composition of the mantle?
7) Since humans cannot access the core, what objects do scientists use as a proxy to determine
the composition of the inner and outer core?
8) Which process is responsible for Earth’s magnetic field? In which layer does this occur?
9) Name two sources of heat for the interior of the Earth.
10) How does temperature change between Earth’s core and the surface?
11) If according to the geothermal gradient there is an increase in temperature with increasing
depth, why isn’t the entire interior of the planet molten?
12) What are the three main mechanisms of convective flow in the outer core?