Deck 2: Earth Structure and Plate Tectonics

Question 1

Identify all of the different observations used to support Harry Hess's theory of seafloor spreading.

A) Seafloor magnetic anomalies
B) Geographic fit of the continents
C) Studies of fossil plants and animals
D) Dipping zones of earthquakes at ocean trenches
E) Patterns of glaciation
F) Shallow earthquakes along transform faults
G) Matching bodies of rock on either side of the Atlantic
H) Alignment of mountain ranges when the Atlantic is closed
J) High heat flow at oceanic ridges

Answer 1

A, D, F, J

Question 2

The steeper profile of the Mid-Atlantic Ridge compared to the East Pacific Rise indicates that the Mid-Atlantic Ridge is the faster spreading center.

Answer 2

False

Question 3

The North Atlantic Ocean was the first modern ocean to open during the breakup of Pangaea.

Answer 3

False

Question 4

Oceanic-type crust is more dense than continental-type crust.

Question 5

The thickness of deep-sea sediments increases with distance from a spreading center.

Question 6

The mid-ocean ridges and rises are spreading centers where new oceanic crust is created.

Question 7

Deep earthquakes, (below 100 km, or 60 mi) are usually associated with oceanic ridges.

Question 8

The largest lithospheric plate is the Pacific Plate.

Question 9

Identify all of the different observations Alfred Wegener used to support his theory of continental drift.

A) Seafloor magnetic anomalies
B) Geographic fit of the continents
C) Studies of fossil plants and animals
D) Dipping zones of earthquakes at ocean trenches
E) Patterns of glaciation
F) Shallow earthquakes along transform faults
G) Matching bodies of rock on either side of the Atlantic
H) Alignment of mountain ranges when the Atlantic is closed
J) High heat flow at oceanic ridges

Question 10

The edge of an active continental margin bordered by a deep-sea trench is wide and shallow with deep deposits of land-derived sediments.

Question 11

Isostatic columns of crustal material produce equal pressures deep within the mantle.

Question 12

Identify all of the types of plate boundaries that are associated with active volcanism.

A) Divergent
B) Ocean-Ocean Convergent
C) Transform
D) Continent-Continent Convergent
E) Ocean-Continent Convergent

Question 13

Earth's inner core is liquid whereas its outer core is solid.

Question 14

The age of the seamounts from Hawaii to Midway Island increases in age from east to west.

Question 15

The continental landmasses are less dense than the mantle and are buoyed up by depressing the underlying mantle.

Question 16

The San Andreas Fault is an example of a transform fault.

Question 17

The refraction and shadow patterns of seismic P-waves and S-waves indicate the dimensions and properties of Earth's layers.

Question 18

Epicenters are points on Earth's surface directly above a hot spot.

Question 19

Volcanic activity associated with subduction zones is more gentle and less explosive than volcanic activity associated with hot spots and mid-ocean ridges.

Question 20

Shear waves do not pass through a solid-liquid boundary between Earth's layers. Compressional waves can pass this type of boundary.

Question 21

Volcanic activity is common at transform plate boundaries.

Question 22

P waves travel more quickly than S waves.

Question 23

Which of Earth's layers contains the greatest volume of material?

A) Inner core
B) Outer core
C) Mantle
D) Lithosphere
E) Outer crust

Question 24

Based on the current directions of plate motion, China and the West Coast of the United States are getting closer.

Question 25

Spreading at mid-ocean ridges tends to occur in increments rather than continuously.

Question 26

The Moho is located between the ________.

A) lithosphere and the asthenosphere
B) crust and the mantle
C) mantle and the outer core
D) inner and outer cores
E) continental margin and the abyssal plain

Question 27

The deepest earthquakes occur in subduction zones at oceanic-oceanic plate convergent boundaries.

Question 28

P waves travel only along the surface of the Earth.

Question 29

The density of Earth materials ________ as the core is approached.

A) remains the same
B) decreases
C) increases
D) increases then decreases
E) decreases then increases

Question 30

California is an example of a passive continental margin.

Question 31

The deep mantle below the asthenosphere is called the mesosphere.

Question 32

Deposits of sediments are usually thicker along passive continental margins.

Question 33

Hess's 1960s theory of mantle convection and seafloor spreading was essentially correct.

Question 34

S waves are able to travel through both solid and liquid.

Question 35

The taller a mountain is, the deeper its root will extend into the asthenosphere.

Question 36

Continental crust is generally thicker and less dense than oceanic crust.

Question 37

Which of the following help us believe that Earth's mass is distributed spherically and uniformly around Earth's center?

A) Lack of roughness of Earth's surface
B) Earth's spherical shape
C) Lack of rotational wobble
D) Earth's spherical shape and lack of rotational wobble
E) Lack of roughness of Earth's surface, Earth's spherical shape, and lack of rotational wobble

Question 38

The oldest oceanic crust is generally in the center of the ocean basin near the mid-ocean ridge or rise system.

Question 39

The thickness of oceanic crust increases with age.

Question 40

Sediment thickness on the oceanic crust tends to be greatest in the center of ocean basins.

Question 41

A program of deep-sea drilling for cores from the ocean's bottom is carried out by the ________.

A) Kon-Tiki
B) Fram
C) JOIDES Resolution
D) Calypso
E) Beagle

Question 42

During the next magnetic reversal, the magnetic force field surrounding Earth will shift by about ________.

A) 45°
B) 90°
C) 180°
D) 270°
E) 360°

Question 43

Seafloor spreading is continuing at a rate of approximately ________.

A) 1 to 10 cm/year
B) 1 to 10 m/year
C) 1 to 10 km/year
D) 1 to 100 cm/year
E) 1 to 100 m/year

Question 44

The trailing margin of a continental landmass ________ than its leading margin.

A) is wider
B) shows less tectonic activity
C) is more stable
D) is wider and is more stable
E) All of these choices are correct.

Question 45

The mechanism causing lithospheric plates to move is thought to be ________.

A) convection in the mantle
B) slab pull caused by a subducting lithosphere
C) tidal forces
D) Earth's rotation
E) a combination of convection in the mantle and slab pull caused by subducting lithosphere

Question 46

Which of the following occurred during the Paleozoic era?

A) Landmasses were strung along Earth's equator.
B) Landmasses drifted across the South Pole.
C) Landmasses came together to form Pangaea.
D) All of these are correct.
E) None of these is correct.

Question 47

Higher seafloor heat flow values are found ________.

A) along coastlines
B) in the middle of ocean basins
C) near ocean ridge systems
D) associated with abyssal hills
E) along the edges of trenches

Question 48

The Pacific Plate is carrying Baja California and the coastal cities of Southern California ________ the continent of North America.

A) away from (west)
B) toward (east)
C) southward along
D) northward along
E) None of these is correct; there is no motion in this region.

Question 49

The motion between the two sides of a transform fault is greatest ________.

A) outside the adjacent ridge axes
B) north of the adjacent ridge axes
C) between the adjacent ridge axes
D) south of the adjacent ridge axes
E) east or west of the adjacent ridge axes

Question 50

Thinning of Earth's crust and the resulting faulting is called ________.

A) convection
B) subduction
C) folding
D) rifting
E) trailing

Question 51

Magnetic stripes on the seafloor are created at ________.

A) subduction zones
B) spreading centers
C) abyssal plains
D) subduction zones and spreading centers
E) subduction zones, spreading centers, and abyssal plains

Question 52

Which of the following are found along subduction zones?

A) Oceanic trenches
B) Active earthquake zones
C) Island arc systems
D) All of these are correct.
E) None of these is correct.

Question 53

The theory of drifting continents was proposed by ________.

A) John Murray
B) Matthew
F) Maury C) Alfred Wegener
D) Charles Darwin
E) Robert Ballard

Question 54

The oceans' oldest sediments are found ________.

A) adjacent to a rift valley
B) on top of the basalt layer, far from spreading centers
C) adjacent to a transform fault
D) at the surface of sediment layers, far from spreading centers
E) in hot spots

Question 55

The deepest portion of the lithosphere is formed from ________.

A) oceanic basalt
B) terrestrial granite
C) a combination of basalt and granite
D) mantle material
E) the Moho

Question 56

Plates move horizontally past each other along ________.

A) transform faults
B) convergent plate boundaries
C) divergent plate boundaries
D) the rift valley
E) hot spots

Question 57

Which method is being used to investigate the structure of the mantle?

A) Isostasy
B) Measurement of seafloor heat flow
C) Seismic tomography
D) Subduction
E) Radiometric dating

Question 58

A fixed volcanic hot spot on Earth tends to produce a ________ on a moving plate.

A) series of volcanic peaks
B) high landmass with a fixed location
C) transform fault system
D) submarine canyon and associated abyssal hills
E) trench

Question 59

The present oceans have been created during the last ________.

A) 2250 million years
B) 225 million years
C) 20 million years
D) 2 million years
E) 2 billion years

Question 60

The deep-ocean trenches are usually associated with ________.

A) volcanism
B) island arc systems
C) earthquakes
D) All of these are correct.
E) None of these is correct.

Question 61

Which statement is true about continental crust?

A) It is composed of granitic-type rock and has a higher density than oceanic crust.
B) It is composed of basaltic-type rock and has a higher density than oceanic crust.
C) It is composed of granitic-type rock and has a lower density than oceanic crust.
D) It is composed of basaltic-type rock and has a lower density than oceanic crust.
E) It is composed of granitic-type rock and has the same density as oceanic crust.

Question 62

Seismic surface waves travel at about the same speed as ocean waves.

Question 63

The crust and the mantle are divided into the following layers in order of increasing depth:

A) mesosphere, lithosphere, asthenosphere
B) asthenosphere, lithosphere, mesosphere
C) lithosphere, mesosphere, asthenosphere
D) lithosphere, asthenosphere, mesosphere
E) asthenosphere, mesosphere, lithosphere

Question 64

Fracture zones ________.

A) are characterized by volcanism
B) are characterized by earthquakes
C) separate plates that move in different directions
D) are a source of high heat flux
E) None of these is correct.

Question 65

Which layer is believed to behave most like a liquid?

A) Outer core
B) Mantle
C) Crust
D) Lithosphere
E) Inner core

Question 66

The east coast of the United States is an example of a(n) ________ continental margin.

A) passive
B) active
C) trailing
D) leading
E) passive and trailing

Question 67

Why does Earth have dry land?

A) There is not enough water to cover the surface completely.
B) All planets of the solar system have dry land.
C) Earth has continental crust, which rides isostatically higher than oceanic crust because it is relatively thick and less dense.
D) The mid-ocean ridges push up the bottom of the seafloor above sea level. Eventually there will not be any ocean left.
E) All of these are correct.

Question 68

Evidence supporting the theory of continental drift includes ________.

A) the fit of continental margins on opposite sides of the Atlantic Ocean
B) the presence of similar mountain belts along continental margins across oceanic basins
C) the distribution of fossil organisms
D) the presence of similar glacial patterns across oceanic basins
E) All of these are correct.

Question 69

Which of the Earth's layers has the greatest density?

A) Core
B) Mantle
C) Crust
D) Lithosphere
E) Asthenosphere

Question 70

Before Pangaea, there was an earlier supercontinent we call ________.

A) Panthalassa
B) Gorda
C) Rodinia
D) Lefse
E) Neogenia

Question 71

What is the approximate length of the mid-ocean ridge system that extends around the globe through all of the major ocean basins?

A) 6500,000 km
B) 650,000 km
C) 65,000 km
D) 6,500 km
E) 650 km

Question 72

The density of the inner core reaches a maximum of about ________ grams/cm³.

A) 150
B) 70
C) 52
D) 31
E) 16

Question 73

Which layer of the Earth contains the greatest mass?

A) Core
B) Mantle
C) Crust
D) Lithosphere
E) Asthenosphere

Question 74

Earthquakes occur at all of the following except ________.

A) convergent boundaries between two oceanic plates
B) continental rift valleys
C) convergent boundaries between two continental plates
D) mid-ocean ridges
E) Earthquakes occur at all of the above settings

Question 75

When talking about plate tectonics, which of the Earth's layers comprises the plates?

A) Crust
B) Mantle
C) Core
D) Lithosphere
E) Asthenosphere

Question 76

Over 170 reversals of Earth's magnetic field have been recorded in the past 80 million years.

Question 77

List the following plates in order of largest to smallest:

A) North American, Pacific, Australian, Caribbean, Indian
B) Pacific, Indian, North American, Australian, Caribbean
C) Indian, Pacific, North American, Caribbean, Australian
D) Pacific, North American, Australian, Indian, Caribbean
E) Pacific, Australian, North American, Indian, Caribbean

Question 78

Throughout time, continents break apart and collide and ocean basins open and close. This cyclical process is known as the ________.

A) Wilson cycle
B) Wegener cycle
C) lithospheric cycle
D) Benioff cycle
E) Richter cycle

Question 79

Seafloor spreading can be detected by ________.

A) changes in water temperature
B) changes in water chemistry
C) acoustic monitoring
D) submersible observation of the seafloor
E) All of these are correct.

Question 80

Volcanic activity occurs at all of the following except ________.

A) convergent boundaries between two oceanic plates
B) continental rift valleys
C) convergent boundaries between two continental plates
D) mid-ocean ridges
E) convergent boundary between a continental and oceanic plate