Deck 27: the Earths Interior, revisited: Seismic Layering, gravity, and the Magnetic Field

Question 1

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 outer core is above melting
C)because the inner core melts at a much higher temperature
D)because the pressure on the inner core is much greater

Answer 1

C

Question 2

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 2

B

Question 3

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

Answer 3

D

Question 4

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 5

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 6

The following picture is a gravity map of the United States.What do the dark gray regions mean in terms of the density of the material below?

A)high-density rock
B)low-density rock
C)rock of high magnetization
D)rock of low magnetization

Question 7

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 8

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 9

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

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

Question 10

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

Question 11

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 12

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 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)a self-exciting dynamo
C)equal to the geoid
D)in isostatic equilibrium

Question 14

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

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

Question 15

Which layer of the Earth has the highest density?

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

Question 16

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 17

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 18

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 19

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 20

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 the same speed.
D)It will drop to zero.

Question 21

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 22

If a ship towing a magnetometer passes over a piece of crust with a "normal" polarity,what will the magnetic anomaly look like?

A)The magnetic anomaly will be greater than Earth's.
B)The magnetic anomaly will be lower than Earth's.
C)The magnetic anomaly will exactly match Earth's.
D)The magnetic anomaly will be exactly zero.

Question 23

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 24

Earth's magnetic field is produced in the ________.

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

Question 25

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.