Deck 10: Motion Inside Earth

Question 1

Which of the following factors is most influential in causing convection in the outer core?

A) The outer core has a low viscosity, approximately equal to that of water at room temperature.
B) The outer core has a high heat conductivity.
C) Compositional differences create a difference in density.
D) Heating causes expansion of fluids.

Answer 1

C

Question 2

Which is not a factor that leads geologists to expect that convection in the mantle is likely?

A) Viscosity in the lithosphere is high.
B) Viscosity beneath the lithosphere is lower because the rock is close to its melting temperature.
C) Some of the lithosphere is denser than the asthenosphere.
D) The thickness and mass of the mantle are huge.

Answer 2

A

Question 3

How is Earth's magnetic field oriented?

A) almost parallel to the rotation axis
B) almost parallel to the equator
C) almost perpendicular to the rotation axis
D) almost perpendicular to the equator

Answer 3

A

Question 4

How do geologists know that the magnetic field of Earth has changed constantly over time?

A) by the direction of historical lava flows, which they have been able to date with radioactive dating methods
B) by crystals that have formed in metamorphic rocks
C) by records kept in magnetic rock-forming minerals
D) by analyzing and extrapolating records kept by scientists since the 1600s

Question 5

The magnetic north pole migrates about

A) 40 km per decade.
B) 40 cm per day.
C) 40 m per month.
D) 40 km per year.

Question 6

Which property most inhibits convection?

A) elasticity
B) viscosity
C) density
D) rigidity

Question 7

What is the name for a period of time when the magnetic field is oriented in the opposite direction?

A) a magnetic reversal
B) a reversed polarity interval
C) a normal polarity reversal
D) an underage polarity

Question 8

Evaluate the following statement. "Convection is a method of heat transfer that requires movement and is not possible in the solid rock regions of Earth."

A) This statement is true; however, convection occurs in the pliable regions of Earth and causes earthquakes to move solid rock.
B) This statement is false; convection occurs in all three states of matter.
C) The statement is true; heat transfer occurs only by other methods in the solid rock regions of Earth.
D) The statement is false; solid rock movement is possible at a slow rate.

Question 9

What is declination?

A) the angle of decrease of the axis of rotation in relation to latitude
B) the horizontal angle between the magnetic and geographic north poles
C) the vertical angle between the field-force line and Earth's surface
D) the angle of increase of the axis of magnetism in relation to latitude

Question 10

Which type of heat transfer occurs without any movement of matter?

A) transduction and radiation
B) conduction and radiation
C) transference and conduction
D) convection and radiation

Question 11

The average polarity interval between magnetic reversals over the last 15 million years has been

A) 20,000 years.
B) 200,000 years.
C) 2,000,000 years.
D) 2,000 years.

Question 12

Evaluate the statement. "Convection occurs because of conduction and radiation at the boundaries of a liquid."

A) This statement is true in the laboratory but not true for Earth processes.
B) This statement is false because the three types of heat transfer operate separately.
C) This statement is true in the laboratory and for Earth processes.
D) This statement is false and should say, "Conduction occurs because of convection and radiation at the boundaries of a liquid."

Question 13

Parcels of rising mantle are always ________ than adjacent rocks, and parcels of sinking upper mantle are always ________ than adjacent rocks.

A) more dense; less dense
B) heavier; lighter
C) warmer; cooler
D) more basaltic; less basaltic

Question 14

Which combination of factors would best lead to convection?

A) low viscosity, low mass, and low heat conductivity
B) high viscosity, high mass, and high heat conductivity
C) low heat conductivity, low mass, and high viscosity
D) low viscosity, low heat conductivity, and high mass

Question 15

Geologists in the early 1900s concluded that heat flow through continents should be greater than heat flow through ocean floors. Evaluate this hypothesis.

A) True. The granite of the continental crust contains more radioactive elements than the basalt of the ocean floor, so more heat is produced in continental crust.
B) True. Continental crust is thicker than ocean crust, so more heat is produced in the thicker layer.
C) False. The lithosphere is thinner beneath oceans than continents, so heat flows more easily up from the mantle.
D) False. The basalt of the ocean floor has a better insulating quality than continental crust granite.

Question 16

What happens as mantle rock rises?

A) It cools and sinks again almost immediately.
B) It cools and contracts.
C) It expands at decreased pressure.
D) It melts and continues to push upward.

Question 17

Which observation indicates that heat is integral to the movement of fluid in a lava lamp?

A) The lava moves upward when it reaches 50C.
B) The liquids expand as heat is applied.
C) The density of the lava decreases as it reaches 50C.
D) There is no movement of fluid in a cold lava lamp.

Question 18

Which statement about the formation of the magnetic field of Earth is true?

A) Its formation is a result of magnetic materials in the core.
B) Its formation is a result of the movement of magnetic materials in the core.
C) It constantly forms, is lost, and is regenerated.
D) It is more strongly observable at relatively low temperatures.

Question 19

In most cases, the distance between the seismically slow upwelling zone and the closest downwelling zone is

A) much greater than the thickness of the convecting mass.
B) much less than the thickness of the convecting mass.
C) about the same as the thickness of the convecting mass.
D) about the same as the thickness of the mantle.

Question 20

Which of the following is not an effect of convection of Earth's outer core?

A) Earth's plates move with tectonic action.
B) Humans are able to navigate using compasses.
C) Animals follow continuous migration patterns.
D) Hazardous cosmic radiation is deflected from Earth.

Question 21

Evaluate the following statement. "Simplified models such as Glatzmaier and Roberts' computer simulation cannot falsify a hypothesis."

A) This statement is false because the failure of a correlation between the model and the hypothesis could be due to an error in the model, not the hypothesis.
B) This statement is false because the failure of a correlation between the model and the hypothesis shows that there must be some error in the hypothesis.
C) This statement is true because the failure of a correlation between the model and the hypothesis could be due to an error in the model, not the hypothesis.
D) This statement is true because the failure of a correlation between the model and the hypothesis shows that there must be some error in the hypothesis.

Question 22

How many years were required for a magnetic reversal to occur according to Glatzmaier and Roberts' computer simulation?

A) 500
B) 1,000
C) 20,000
D) 200,000

Question 23

Approximately how long has it been since the last magnetic reversal?

A) 1,780 years
B) 17,800 years
C) 780,000 years
D) 1.768 million years

Question 24

Judge the following sentence according to the criteria given below. Ice cubes rise to the top of a glass of water because ice is less dense than water.

A) The assertion is correct but the reason is incorrect.
B) The assertion is incorrect but the reason is correct.
C) The assertion and the reason are both correct, and the reason is valid.
D) The assertion and the reason are both correct, but the reason is invalid.
E) Both the assertion and the reason are incorrect.

Question 25

What substitution did Glatzmaier and Roberts make in their model?

A) straight-angled rotation of Earth for its real tilted axis
B) average density in place of specific densities
C) the viscosity of water for the viscosity of the outer core
D) thermal convection for compositional convection

Question 26

Which factor is not included in Glatzmaier and Roberts' model?

A) Earth's rotation
B) compositional convection
C) convective motion
D) electricity and magnetism

Question 27

What hypothesis has been presented for the close parallel relationship of the magnetic field and the rotation axis?

A) Rotation causes spiraling convection currents in the outer core.
B) Rotation causes spiraling convection currents in the outer mantle.
C) Rotation causes spiraling convection currents in the inner mantle.
D) Rotation causes spiraling convection currents in the inner core.

Question 28

Judge the following sentences according to the criteria given below. Ice cubes are dropped in a glass of warm water and float to the top. The ice cubes rose to the top of the glass of warm water because the frozen ice is colder than the warm water.

A) The assertion is correct but the reason is incorrect.
B) The assertion is incorrect but the reason is correct.
C) The assertion and the reason are both correct, and the reason is valid.
D) The assertion and the reason are both correct, but the reason is invalid.
E) Both the assertion and the reason are incorrect.

Question 29

Liquid metal at the base of the outer core moves upward due to ________ convection.

A) thermal
B) chemical
C) brittle
D) elastic

Question 30

What happened to the initial magnetic field introduced into the computer simulation by Glatzmaier and Roberts?

A) It faded away.
B) It increased.
C) It decreased.
D) It became self-sustaining.

Question 31

What is a possible effect of a magnetic reversal on Earth's organisms?

A) Species become extinct as they lose their navigational ability.
B) Organisms are subjected to greater amounts of cosmic radiation.
C) Organisms are subjected to greater amounts of radioactivity.
D) Organisms will change their habitats with the accompanying climate change.

Question 32

What occurred to magnetic field strength in Glatzmaier and Roberts' model during polarity reversals?

A) it decreased
B) it stayed the same
C) it increased
D) it disappeared

Question 33

The property of matter that describes its resistance to flow is called

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

Question 34

Which of the following is a hypothesis regarding the initial formation of Earth's magnetic field?

A) The magnetic field was transferred from the Sun.
B) Magnetite and other magnetic iron minerals aligned during solidification of the magma ocean.
C) The magnetic field was generated by Earth's rotation.
D) The magnetic field originated with Earth.

Question 35

How long did the supercomputer require to run Glatzmaier and Roberts' original simulation of 45,000 years?

A) a day
B) a week
C) a month
D) a year

Question 36

What did Glatzmaier and Roberts' model suggest as a reason for magnetic reversal?

A) interactions between magnetic fields in the inner and outer cores
B) alterations to forces on Earth by other planets
C) alterations to forces on Earth by changes in the Sun
D) metamorphism of rocks in the crust

Question 37

The shape of Earth's magnetic field resembles

A) a bar magnet.
B) a horseshoe magnet.
C) an elliptical magnet.
D) a spherical magnet.

Question 38

Judge the following sentences according to the criteria given below. On average, heat flow through oceanic crust is greater than heat flow through continental crust because mantle heat is transferred towards the surface by convection.

A) The assertion is correct but the reason is incorrect.
B) The assertion is incorrect but the reason is correct.
C) The assertion and the reason are both correct, and the reason is valid.
D) The assertion and the reason are both correct, but the reason is invalid.
E) Both the assertion and the reason are incorrect.

Question 39

What is a dynamo?

A) a rotating body containing fluid whose movement maintains the rotation
B) a rotating magnet whose magnetism maintains the rotation
C) a rotating device that changes motion energy to electrical energy
D) a rotating body that contains fluid and magnetism

Question 40

Conduction dominates everywhere within the lithosphere.

Question 41

"Why create a computer simulation of Natural Processes?"

Question 42

Although we don't know for sure, changes in the strength and orientation of earth's magnetic field are most likely due to

A) fluctuations in outer-core convection.
B) variations in sea-floor spreading rates.
C) the total number of mantle hot spots.
D) changes in the velocity of subducting plates.

Question 43

A self-sustaining geodynamo in the outer core generates Earth's magnetic field.

Question 44

What key features have emerged through the examination of the map of Earth's magnetic field?

Question 45

"How does convection work?"

Question 46

The shape of Earth's magnetic field resembles that produced by a laboratory bar magnet.

Question 47

Low viscosity does not favor convection.

Question 48

Have you ever made a convection cell? What about when you boil water for pasta?

Question 49

Rising mantle material will ultimately stop because, at lower pressures, decompression causes the material to expand, cool and contract.

Question 50

Seismic tomography shows regions of the mantle where seismic waves travel slightly slower or slightly faster than in adjacent rock.

Question 51

During periods of magnetic reversals your compass needle would point south rather than north.

Question 52

Without convection, there would be no volcanoes on Earth because

A) all the convecting material spurts out at the surface.
B) rising mantle material undergoes decompression melting.
C) molten outer-core melts the lower continental crust.
D) volcanoes sink down into Earth near down-going convention cells.

Question 53

Judge the following sentence according to the criteria given below. Earth is long overdue for a magnetic reversal because during the past 15 million years Earth's magnetic field reversed every 200,000 years, on average, and the last reversal was 780,000 years ago.

A) The assertion is correct but the reason is incorrect.
B) The assertion is incorrect but the reason is correct.
C) The assertion and the reason are both correct, and the reason is valid.
D) The assertion and the reason are both correct, but the reason is invalid.
E) Both the assertion and the reason are incorrect.

Question 54

Conduction is the transfer only of heat from hot regions to cold regions.

Question 55

Why is the lower mantle thicker than the upper mantle?

Question 56

How could the mantle be too thin to prevent convection?

Question 57

Judge the following sentences according to the criteria given below. A student disputes the process of mantle convection. They argue that rock is solid and cannot flow. They challenge their classmates to provide evidence for present day mantle convection. A classmate shows them a seismic tomographic map and cross section showing variations in S-wave velocities.

A) The seismic tomographic map and cross section do show evidence for present day mantle convection and offers a strong affirmation of mantle convection.
B) The seismic tomographic map and cross section do show evidence present day mantle convection but this data cannot be used as evidence for mantle convection.
C) The seismic tomographic map and cross section has a random pattern of S-wave velocities and offers no evidence for anything.
D) The seismic tomographic map and cross section shows evidence for mantle convection in the past but not for present day mantle convection.

Question 58

What processes transport heat without moving matter?

A) convection and conduction
B) radiation and convection
C) radiation and conduction
D) radiation, conduction and convection

Question 59

Judge the following sentence according to the criteria given below. Earth's magnetic field is due to a big mass of magnetized material inside Earth because magnets function only at relatively low temperatures.

A) The assertion is correct but the reason is incorrect.
B) The assertion is incorrect but the reason is correct.
C) The assertion and the reason are both correct, and the reason is valid.
D) The assertion and the reason are both correct, but the reason is invalid.
E) Both the assertion and the reason are incorrect.

Question 60

Mantle convection occurs because upward-moving rock expands more by decompression than it contracts by cooling.

Question 61

"What does mantle convection look like?"

Question 62

"How does outer-core convection generate the magnetic field?"