Deck 22: Plate Tectonics

Question 1

The mantle can be separated into two different portions-the lower mantle and the upper mantle. The lower mantle is

A)completely solid due to extreme pressure that prevents rocks from melting.
B)composed of putty that flows like molasses.
C)rigid and cannot flow.
D)predominantly liquid.

Answer 1

A

Question 2

Motion of a P-wave is

A)side to side.
B)transverse.
C)longitudinal.
D)up and down.

Answer 2

C

Question 3

Surface waves are useful for investigating Earth's interior because they

A)refract at the boundaries between Earth's layers.
B)reflect at the boundaries between Earth's layers.
C)cast shadows indicating Earth's layers.
D)none of the above

Answer 3

D

Question 4

Seismic waves are classified as body waves and surface waves. An example of a body wave is a

A)primary wave (P-wave).
B)Love wave.
C)Rayleigh wave.
D)tertiary wave (T-wave).

Question 5

Secondary waves can travel through all areas of the Earth except the

A)surface.
B)outer core.
C)inner core.
D)mantle.

Question 6

Earth's internal layers were discovered by studying

A)seismic waves.
B)the Mohorovicic discontinuity.
C)Rayleigh and Love waves.
D)convection cells.

Question 7

P-waves refract at the boundary between inner and outer core because

A)there is a change of phase between inner and outer core.
B)there is a change in chemical composition between inner and outer core.
C)they gain speed.
D)they lose speed.

Question 8

Body waves

A)come in two principal types.
B)refract at Earth's boundary layers.
C)travel through Earth's interior following an earthquake.
D)all of the above

Question 9

Seismic waves are like

A)X-rays, because they let us see into Earth.
B)radio waves, because they are of similar length.
C)sound waves, because they are longitudinal.
D)ocean waves, because they are transverse.

Question 10

We can say that Earth's crust floats on the mantle because

A)the mantle is very hot and flows from internal convection.
B)part of the mantle is hot enough to flow as a plastic solid.
C)the continental crust floats on the oceanic crust.
D)the mantle is below the crust.

Question 11

Because S-waves do not travel through Earth's outer core, scientists inferred that the outer core is

A)impenetrable.
B)molten liquid.
C)solid.
D)very dense.

Question 12

Which waves indicate the most extensive shadow? Why?

A)P waves-because they cannot travel through the liquid outer core
B)P waves-because they cannot travel through the solid inner core
C)S waves-because they cannot travel through the liquid outer core
D)S waves-because they cannot travel through the solid inner core

Question 13

Earth's liquid and solid layers were discovered by studying the propagation of seismic waves through Earth's interior. P-waves ________; S-waves ________.

A)compress and expand the rock as they move through it; vibrate the particles of their medium up and down and side-to-side
B)can travel through solid granite, magma, water, or air; can travel only through solids-not in fluids
C)are the fastest of all seismic waves and the first to register on a seismograph; are the second to register on a seismograph
D)all of the above

Question 14

Earth's magnetic field is attributed to the

A)flow of molten liquid in Earth's inner core.
B)flow of molten fluid in Earth's outer core.
C)movement of lithospheric plates in the outer mantle.
D)movement of lithospheric plates at Earth's surface.

Question 15

The Mohorovicic discontinuity marks the change in rock density between the

A)inner and outer core.
B)core and the mantle.
C)mantle and the crustal surface.
D)asthenosphere and lithosphere.

Question 16

The upper mantle can be divided into two zones, the

A)asthenosphere in the lower upper mantle and part of the lithosphere in the upper part of the upper mantle.
B)asthenosphere in the upper, upper mantle and the lithosphere in the lower upper mantle.
C)Moho and the lithosphere.
D)continental mantle and the oceanic mantle.

Question 17

The velocity of a seismic wave depends on

A)the type of material it travels through.
B)its amplitude.
C)its frequency.

Question 18

Earthquake P-waves are most like

A)water waves because they have crests and troughs.
B)vibrations in a string because they vibrate perpendicularly to the direction of travel.
C)light waves because they are transverse.
D)sound waves because they are longitudinal.

Question 19

The propagation of seismic waves through Earth's interior provides evidence of internal layering. The first boundary discovered was the boundary between the

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

Question 20

The fastest seismic wave is a

A)primary wave.
B)secondary wave.
C)tertiary wave.
D)Rayleigh wave.

Question 21

The inner core is solid because

A)it is composed of iron and nickel.
B)the surrounding outer layers act as a blanket to insulate the core.
C)pressure from the weight of the surrounding layers prevents the inner core from melting.
D)None of these, for the inner core is not solid, but liquid.

Question 22

The lithosphere rides on top of the asthenosphere. Lithospheric movement causes

A)earthquakes, volcanic activity, and mountain building activity.
B)the subduction of continental crust under oceanic crust.
C)hot-spot activity as found in Hawaii.
D)widespread destruction.

Question 23

The Mohorovicic discontinuity exists because

A)the temperature inside Earth changes with depth.
B)the rock at this depth transitions from lower density to higher density.
C)there is change in the physical state of rocks on both sides of the boundary.
D)there is a difference in conductivity of the rocks on either side of the boundary.

Question 24

The thickness of Earth's crust

A)varies from about 10 km under the continents to about 60 km under the oceans.
B)on average is about 10 km.
C)on average is about 60 km.
D)varies from about 5 km under the oceans to about 70 km under the continents.

Question 25

Isostasy is

A)the positioning of the crust in response to the buoyant force and gravity.
B)the buoyant force exerted on the mantle by oceanic crust.
C)the buoyant force exerted on the mantle by continental crust.
D)the force of gravity acting on the crust.

Question 26

According to the theory of seafloor spreading, large quantities of molten rock rises up along

A)the mid-ocean ridges.
B)trenches that border continental margins.
C)atolls surrounding the Pacific volcanic rim.
D)subsiding divergent margins.

Question 27

The balance of gravitational and buoyant forces acting on the crust determines its

A)weight.
B)vertical position.
C)mass.
D)plasticity.

Question 28

Alfred Wegener supported his theory of continental drift by

A)fitting together the shorelines of the African and Asian continents.
B)using satellite data to show the continents' move over time.
C)using paleomagnetic data.
D)making a connection between the rocks, rock structures, and plant and animal fossils found in both Africa and South America.

Question 29

The outer core

A)has a plastic-like flow.
B)spins, which produces Earth's magnetic field.
C)is solid as a rock.
D)transmits S-waves.

Question 30

Earth's layer with the most brittle behavior is the

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

Question 31

The mantle is composed of

A)iron and nickel.
B)iron-rich silicate rocks.
C)half liquid and half rocky material.
D)solid rock.

Question 32

Wegener's theory of continental drift

A)was first considered a monumental breakthrough in science.
B)was not accepted by the scientific community of Wegener's time
C)utilized data from several scientific disciplines. Wegener proposed that continental drift was generated from convection motion.
D)has been proven wrong.

Question 33

The core of Earth is probably composed of

A)silicate minerals.
B)aluminum oxides.
C)iron and nickel.
D)calcium magnesium sulfate.

Question 34

The theory of seafloor spreading is supported by

A)geological, biological, and climatological data.
B)paleomagnetic analysis of the ocean's floor.
C)the change in Earth's polarity.
D)none of the above

Question 35

The lithosphere floats atop the

A)mantle.
B)crust.
C)asthenosphere.
D)mohorovicic.

Question 36

Continental crust extends farther down into the mantle than oceanic crust because

A)continental crust is thicker than oceanic crust.
B)oceanic crust is buoyant and rides atop the mantle.
C)continental crust is heavier than oceanic crust.
D)continental crust sinks into the mantle and asthenosphere.

Question 37

The theory of continental drift is credited to

A)J) Tuzo Wilson.
B)Alfred Wegener.
C)H) H. Hess.
D)W) Loma Prieta.

Question 38

Earth's magnetic field

A)never appreciably changes.
B)has reversed itself many times.
C)is centered at Earth's core.
D)both B and C

Question 39

Continental crust is very buoyant compared with oceanic crust because continental crust is

A)predominantly composed of basaltic rock that contains many air bubbles from successive lava flows.
B)predominantly composed of granitic rocks, whereas oceanic crust is composed of basaltic rocks.
C)thinner than the oceanic crust, forming a thin upper skin on the oceanic crust below.
D)very young and fresh.

Question 40

The lithosphere includes

A)continental and oceanic crust.
B)the crust and the upper part of the mantle.
C)part of the mantle and the crust.
D)all of the above

Question 41

When the magnetic field of Earth is reversed,

A)Earth flips over in its orbit.
B)Earth's rotation is also reversed.
C)newly formed mineral grains on the ocean floor are magnetized according to the new orientation of the magnetic field.

Question 42

The occurrence of earthquakes in the absence of seafloor spreading, oceanic trenches, or volcanic activity is a characteristic feature of

A)convergent boundaries between plates.
B)divergent boundaries between plates.
C)subduction zones.
D)transform fault boundaries between plates.

Question 43

If the path of polar wandering recorded on two continents is not the same, then we can say that

A)Earth's magnetic history has been very complex.
B)at least one of the continents has moved.
C)our radioactive dating techniques have been inaccurate.
D)the continents have always been widely separated.

Question 44

Transform faults are areas of crustal

A)formation.
B)destruction.
C)subduction.
D)accommodation and plate movement.

Question 45

The ocean crust

A)becomes progressively younger away from the mid-ocean ridges.
B)is the same age worldwide.
C)becomes progressively older away from the mid-ocean ridges.
D)ranges in age; the oldest ocean crust is in the Atlantic and the youngest ocean crust is in the Arctic.

Question 46

Spreading centers occur along

A)trenches.
B)transform faults.
C)mid-ocean ridges.
D)the northern and western margins of the Juan de Fuca plate.

Question 47

The theory of plate tectonics states that

A)the lithosphere is broken up into several plates that move about as a result of convective motion in the asthenosphere.
B)earthquakes and volcanic activity result from convection motion in the lithosphere.
C)buoyant lithospheric plates float on top of the rigid asthenosphere.
D)the plates move in conveyor-belt fashion as new crust is generated at the continental margins and destroyed at the mid-ocean ridges.

Question 48

Magnetic surveys of the ocean floors reveal

A)alternating strips of normal and reversed polarity paralleling the mid-Atlantic ridge.
B)thin oceanic crust composed of basaltic rocks.
C)that reversed polarity is rare.
D)all of the above

Question 49

Rocks with an imprint of Earth's magnetic code contain

A)the rock's polarity, magnetic-pole direction, and the altitude of the magnetic pole.
B)polarity, latitude of origin, and the direction of the magnetic pole at the time of formation.
C)polarity, latitude of origin, and fossils indicating the age of the rock.
D)all of the above

Question 50

Most of Earth's seismic activity, volcanism, and mountain formation occur along

A)convergent boundaries.
B)divergent boundaries.
C)plate boundaries.
D)transform fault boundaries.

Question 51

What kind of forces act on the crust at divergent boundaries?

A)tensional forces that stretch the crust and generate a spreading center
B)compressional forces that crunch the crust and generate a spreading center
C)compressional forces that crunch and shorten the crust by folding and faulting
D)compressional forces due to plate collision

Question 52

Regions in which earthquakes are common are also regions in which

A)hurricanes are common.
B)volcanoes are common.
C)the geomagnetic force is strong.
D)many fossils are found.

Question 53

Oceans are about four times as deep as mountains are high. At the bottom of the ocean are

A)huge towering mountains, deep valleys, and deep ocean trenches near the continental borders.
B)thick oceanic crust at the ocean ridges that gradually thins as it nears the deep ocean trenches.
C)towering plutonic mountains created from volcanoes and fissure eruptions at the oceanic trench areas.
D)all of the above

Question 54

Divergent boundaries are areas of

A)crustal formation.
B)crustal destruction.
C)continuous, high magnitude earthquakes.
D)intense compressional forces.

Question 55

Why are plate boundaries the sites of most geologic activity?

A)Plates interact with one another at their boundaries.
B)Plate boundaries are zones of weak crustal material.
C)Heat from Earth's core escapes between tectonic plates.
D)Plate boundaries are not sites of most geologic activity.

Question 56

The longest mountain chain in the world is the

A)Mid-Ocean Ridge.
B)Himalayas.
C)Appalachians.
D)Sierra Nevada.

Question 57

Which of the following is not a type of tectonic plate boundary?

A)divergent plate boundary
B)fault plate boundary
C)transform plate boundary
D)convergent plate boundary

Question 58

Convergent boundaries are areas of

A)compressional forces that crunch the crust and generate a spreading center.
B)tensional forces that stretch the crust and generate a spreading center.
C)crustal formation.
D)plate collision.

Question 59

Convergent boundaries are

A)regions of great mountain building.
B)areas of plate subduction.
C)regions of plate collision.
D)all of the above

Question 60

According to plate tectonic theory, the San Andreas fault is a

A)convergence zone.
B)divergence zone.
C)subduction zone.
D)transform fault.

Question 61

The density of Earth's crust, mantle, and core increases moving toward Earth's center because

A)Earth's elements are distributed evenly throughout its interior.
B)Early in Earth's history, it separated into layers according to density.
C)Earth is plastic throughout its structure today and in the past.
D)The charged particles flowing in the outer core repel the lighter elements found at Earth's surface.

Question 62

The three kinds of plate convergence are

A)oceanic-oceanic, continental-oceanic, and continental-continental.
B)subduction, volcanic arc-building, and trench building.
C)transform, divergent, and convergent.
D)crashing, scraping, and splitting.

Question 63

The ultimate cause of tectonic plate motion is the

A)second law of thermodynamics.
B)tendency for heat to spread out.
C)escape of heat from Earth's interior.
D)all of the above

Question 64

Does the fact that the mantle is beneath the crust suggest that the mantle is denser than the crust? Explain.

Question 65

Organisms found in the ocean trenches

A)are unicellular.
B)are Earth's deepest dwellers.
C)must withstand low pressures.
D)do not live in trenches but fall into them accidentally.

Question 66

How does erosion and wearing away of a mountain affect the depth to which the crust extends into the asthenosphere?

Question 67

Describe the idea of continental drift.

Question 68

How did plant and animal fossils contribute to the theory of continental drift?

Question 69

Body waves can be divided into two types: primary waves and secondary waves. What is the difference between these two types of body waves?

Question 70

Conditions in oceanic trenches that are inhospitable to life include

A)lack of light, extreme heat, and high pressure.
B)lack of light, extreme cold, and toxic chemicals.
C)lack of light, extreme cold, high pressure, and scarce food.
D)lava, high pressure, and scarce food.

Question 71

Describe the theory of plate tectonics.

Question 72

Convection is a

A)mode of heat transfer that circulates heat within Earth's mantle.
B)mode of heat transfer that carries heat from Earth's core toward its surface.
C)form of insulation that maintains Earth's internal temperature.
D)form of heat transfer restricted to Earth's interior.

Question 73

New lithosphere is formed at

A)ocean trenches.
B)convergent plate boundaries.
C)transform plate boundaries.
D)spreading centers.

Question 74

Describe the seafloor spreading hypothesis.

Question 75

What is the evidence for Earth's central core being solid?

Question 76

What is isostasy? How does isostasy affect the placement of oceanic crust versus continental crust?

Question 77

What are the two major kinds of waves an earthquake produces?

Question 78

Briefly describe the different types of plate boundaries.

Question 79

Which plate subducts when oceanic and continental plates meet and why?

A)The continental plate subducts beneath the oceanic plate because the oceanic plate is most dense.
B)The continental plate subducts beneath the oceanic plate because the continental plate is most dense.
C)The oceanic plate subducts beneath the continental plate because the oceanic plate is most dense.
D)The oceanic plate subducts beneath the continental plate because the continental plate is most dense.

Question 80

Compare the relative speeds of primary and secondary seismic waves, and relate speeds of travel to the medium in which the waves travel.