Deck 27: the Earths Interior, Revisited: Seismic Layering, Gravity, and the Magnetic Field

Question 1

Which layer of the Earth has the highest density?

A) atmosphere
B) crust
C) mantle
D) core

Answer 1

D

Question 2

If an S-wave is traveling through rock when it encounters a magma chamber,the S-wave will ________.

A) slow down
B) speed up
C) remain at the same speed
D) not travel through the magma

Answer 2

D

Question 3

If a gravity anomaly is negative,what does that imply about the material underground?

A) The material is much more dense rock.
B) The material is much less dense rock.
C) The material is an underground ore.
D) The material is composed of mantle.

Answer 3

B

Question 4

If a ship weighs 52,000 tons and is in isostatic equilibrium when 6,000 tons of cargo is added,what is the total mass of water that will be displaced by the ship after the cargo is added?

A) 6,000 tons
B) 12,000 tons
C) 58,000 tons
D) 52,000 tons

Question 5

If a P-wave is traveling through the Earth and encounters a molten magma chamber,what will happen to the velocity of the P-wave?

A) It will slow down.
B) It will speed up.
C) It will stay at a constant speed.
D) It will drop to zero.

Question 6

Using the graph below,why is the outer core liquid,but the inner core solid?

A) because the inner core is made of different material than the outer core
B) because the temperature in the inner core is above that of the melting curve
C) because the temperature in the inner core is below that of the melting curve
D) because the pressure on the inner core is lower

Question 7

If a seismic wave is refracted upward at a boundary,what can be said about the material the wave is traveling through?

A) The wave is moving through two materials of the same velocity.
B) The wave is moving from a faster material into a slower material.
C) The wave is moving from a slower material into a faster material.
D) The wave is traveling through a molten magma chamber.

Question 8

A mountain range made of basalt would produce a(n)________ gravity anomaly.

A) positive
B) negative
C) isostatic
D) magnetized

Question 9

The Earth's gravity is best represented by an equipotential surface that contains bumps and depressions where areas of higher or lower gravity appear over the Earth.This representation is called the ________.

A) reference geoid
B) gravitational potential
C) isostasy
D) geoid

Question 10

You are studying the seismic data from Mars when you notice that there are no S-waves recorded from 130° through 180° on the opposite side of the planet.What does this information tell you about the interior of Mars?

A) There is a layer of solid material in the interior of Mars.
B) There is a layer of liquid material in the interior of Mars.
C) There is a layer with a higher-velocity material than the crust below.
D) There is a layer with a lower-velocity material than the crust below.

Question 11

Seismic waves travel ________ in solids than in liquids; however,unlike P-waves,S-waves ________ travel through liquids.

A) slower; can
B) slower; can't
C) faster; can
D) faster; can't

Question 12

Which of the following best describes how scientists study the interior of the Earth?

A) Scientists dig deep holes to access and study the Earth's interior.
B) Scientists use seismic waves,gravity,and magnetism to study the Earth's interior.
C) Scientists use only seismic waves and gravity to study the Earth's interior.
D) Scientists use seismic waves alone to study the Earth's interior.

Question 13

In the picture below,when the ship is filled with cargo it sinks into the water until the mass of water displaced is equal to the mass of the cargo.The ship is then said to be ________.

A) an equipotential surface
B) in freeboard balance
C) equal to the geoid
D) in isostatic equilibrium

Question 14

Identify the layers of the Earth,from the outside to the interior,using the illustration below.

A) core,mantle,crust
B) mantle,crust,core
C) core,crust,mantle
D) crust,mantle,core

Question 15

The time it takes for a seismic wave to travel from the focus to a seismometer is called the ________.

A) wave front time
B) P-S wave arrival distance
C) travel time
D) seismic ray time

Question 16

In the following graph,why does the line for S-waves NOT appear in the outer core?

A) S-waves can't travel through the outer core because it is solid.
B) S-waves can't travel through the outer core because it is liquid.
C) S-waves disappear after being reflected at the core-mantle boundary.
D) S-waves can't travel that far into the Earth due to the high amount of iron.

Question 17

What causes the velocity of a P-wave to speed up when it enters the inner core?

A) The inner core is a much more dense material than the outer core.
B) The inner core is a much less dense material than the outer core.
C) The inner core is liquid,and thus the wave speeds up.
D) The P-wave no longer has to compete with the S-wave for energy.

Question 18

The graph below shows the change in velocity of seismic waves with depth in the crust.Why does the velocity of the P-wave drop drastically at the core-mantle boundary?

A) because the core is much denser than the mantle
B) because the outer core is solid and P-waves can't pass through solids
C) because the outer core is liquid and seismic waves travel slower in liquids
D) because the S-waves are removed and that energy is transferred to the P-waves

Question 19

The core consists of two layers: the ________ inner core and ________ outer core.

A) iron; nickel
B) nickel; iron
C) solid; liquid
D) liquid; solid

Question 20

If a S-wave is traveling through sandstone and then encounters peridotite,the S-wave will ________.

A) slow down
B) speed up
C) remain at the same speed
D) not travel through the peridotite

Question 21

Kilauea Volcano in Hawaii has been erupting large volumes of basaltic lava over the past few decades.Would the magnetic anomaly associated with this recent volcanism be positive or negative? Why?

Question 22

Why would the gravity anomaly over a deep-ocean trench be negative?

A) because the bathymetry of the trench dips very far below sea level
B) because the crust being pulled into the trench is less dense than sediments above
C) because water fills the space above the subducting slab and is much less dense than rock
D) because the buoyant magma created at the subduction zones is less dense than the rock

Question 23

During the last ice age,continental glaciers covered significant portions of the North American continent.In the context of Archimedes' principle,what effect would these glaciers have had on the lithosphere relative to the asthenosphere? How was isostatic equilibrium achieved?

Question 24

A positive magnetic anomaly is produced when the measured magnetic field strength is ________ the expected magnetic field strength.

A) greater than
B) less than
C) the same as
D) the opposite of

Question 25

Imagine that you are an economic geologist,trying to find copper resources.How might gravity anomalies help you?

Question 26

Using the image below,explain why the P-wave velocity drops drastically at the core-mantle boundary.Also,explain why the P-wave velocity speeds up at the inner core-outer core boundary.

Question 27

If you measure the magnetization of an area of igneous rocks and find a large negative anomaly,what does that imply about the rocks?

A) They were formed during a time of normal polarity of the magnetic field.
B) They were formed during a time of reversed polarity of the magnetic field.
C) They were formed on the ocean floor where the rocks are closer to the core.
D) They were formed on the continental crust in a complex pattern of magnetization.

Question 28

The Earth's magnetic field is produced in the ________.

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

Question 29

Why are magnetic anomalies of continental crust so much more complicated than those of oceanic crust?

A) The continents are much older and thus have had more time for the minerals to become magnetized.
B) The continents contain abundant iron minerals,whereas the oceanic crust does not contain any iron minerals.
C) The continents contain a random orientation of minerals that become magnetized when they interact with the magnetic field.
D) The continents contain a complex distribution of igneous intrusions,lava flows,and iron-rich sediments.

Question 30

If a P-wave is traveling up from a layer of mantle peridotite to a layer of limestone crust,what will happen to the P-wave in terms of speed and direction of motion? Why?