Deck 5: Plate Tectonics: A Scientific Revolution Unfolds

Question 1

Mount Hood (pictured)is part of the Cascade Range. These active volcanoes are a chain that stretches along the west coast from northern California to southern British Columbia, Canada. The Cascades are ________.

A)evidence of subduction in the Pacific Northwest of the United States
B)evidence of rifting of the North American continent
C)a product of the San Andreas Fault
D)due to a hot spot beneath Seattle

Answer 1

A

Question 2

The area of crust directly above a rising mantle plume is a(n)________.

A)convergent plate boundary
B)Curie point
C)hot spot
D)asthenosphere

Answer 2

C

Question 3

Examine the two figures. Which shows whole-mantle convection?

A)A
B)B
C)neither A nor B
D)both A and B

Answer 3

A

Question 4

Ten million years from now, the East African rift valley system will most closely resemble the modern ________.

A)Red Sea
B)Appalachian Mountains
C)Peru-Chile Trench
D)San Andreas Fault

Question 5

Which one of the following most accurately describes the volcanoes of the Hawaiian Islands?

A)volcanoes associated with subduction and a convergent plate boundary
B)volcanoes fed by a long-lived hot spot below the Pacific lithospheric plate
C)volcanoes associated with a mid-Pacific oceanic ridge and spreading center
D)volcanoes associated with a mid-Pacific transform fault

Question 6

Lithospheric plates can consist of which of the following components?

A)continental crust, oceanic crust, and ocean water
B)continental crust, lithospheric mantle, and asthenospheric mantle
C)continental crust, lithospheric mantle, and oceanic crust
D)continental crust only, NOT oceanic crust

Question 7

The temperature below which magnetic material can retain a permanent magnetization is called the ________.

A)hot spot
B)Curie point
C)fracture zone
D)Darcy temperature

Question 8

Most of the world's ________ line(s)up along plate tectonic boundaries.

A)volcanoes
B)earthquakes
C)very young oceanic crust
D)all of the above

Question 9

Why was Wegener's idea of continental drift rejected?

A)It proposed tidal forces as the mechanism for the motion of continents.
B)It implied that the continents would have plowed their way through weaker oceanic crust, like a boat cutting through a thin layer of sea ice.
C)It lacked compelling evidence that the continents had been connected in the past.
D)both A and B

Question 10

When new oceanic lithosphere is generated at an oceanic ridge, what happens to the plate it's attached to?

A)The plate gets larger.
B)The plate gets smaller.
C)The plate stays the same size.
D)The plate sinks into the lower mantle.

Question 11

Continental rifts are associated with ________ plate boundaries.

A)divergent
B)convergent
C)transform
D)all kinds of

Question 12

Linear, magnetic patterns associated with mid-ocean ridges are configured as ________.

A)concentric circles about a rising plume of hot, mantle rocks and magma
B)normal and reversed magnetized strips roughly perpendicular to the ridge axis
C)reversed magnetizations along the rift valleys and normal magnetizations on the ridge
D)normal and reversed magnetized strips roughly parallel to the ridge

Question 13

A transform plate boundary is characterized by ________.

A)two plates colliding and thrusting up a mountain range
B)two plates moving apart and opening up a new ocean basin
C)a deep, vertical fault along which two plates slide past one another in opposite directions
D)hot spot volcanism

Question 14

The ________ is an example of a modern convergent boundary where two continents meet.

A)westward movement of South America over the (subducting)Nazca plate
B)Arabian Peninsula slamming into North Africa under the Red Sea
C)northwestern movement of Baja California and a sliver of western California
D)northerly movement of India relative to Eurasia

Question 15

Cooler, older, oceanic lithosphere sinks into the mantle at ________.

A)subduction zones along convergent plate boundaries
B)transform fault zones along divergent plate boundaries
C)rift zones along oceanic ridges
D)sites of long-lived, hot spot volcanism in the ocean basins

Question 16

In the early part of the twentieth century, ________ argued forcefully for the idea of continental drift.

A)Richard Wagner
B)Alfred Wegener
C)James Hutton
D)Harry Hess

Question 17

________ was an aquatic reptile that lived in South America and Africa during the Permian period.

A)Mesosaurus
B)Lystrosaurus
C)Glossopteris
D)Tyrannosaurus

Question 18

Alfred Wegener included all of the following lines of evidence as supporting his "continental drift" hypothesis except one. Which was NOT part of Wegener's evidence?

A)the geometrical fit between South America and Africa
B)late Paleozoic glacial features
C)stripes of reverse magnetism on either side of oceanic rides
D)similar fossils on widely-separated continents

Question 19

New oceanic lithosphere is formed at ________.

A)convergent boundaries by submarine eruptions and intrusions of basaltic magma
B)divergent boundaries by submarine eruptions and intrusions of basaltic magma
C)divergent boundaries by submarine eruptions and intrusions of rhyolitic magma
D)convergent boundaries by submarine eruptions and intrusions of rhyolitic magma

Question 20

Imagine that you were given a ship equipped with a device that could measure how deep the water is. You are asked to use this ship to find a subduction zone. What would you look for as you sailed around the world's oceans?

A)an oceanic ridge
B)a mountain range
C)a continental rift
D)a deep-ocean trench

Question 21

The plate tectonics model has been verified by multiple lines of evidence.

Question 22

Hawaii is the oldest island of the Hawaiian Island chain.

Question 23

During various times in the geologic past, the polarity of Earth's magnetic field has been reversed.

Question 24

Plates move at about the same rate your fingernails grow, a few centimeters per year.

Question 25

In convection, warm material rises because it is more dense.

Question 26

The volcanoes of Hawaii are localized above a deep mantle hot spot; they are not part of the East Pacific oceanic ridge.

Question 27

A volcanic island arc is the result of ________.

A)subduction of continental crust underneath oceanic crust
B)subduction of oceanic crust underneath oceanic crust
C)subduction of oceanic crust underneath continental crust
D)subduction of continental crust underneath continental crust

Question 28

Plate tectonics implies that Earth must be expanding.

Question 29

A global positioning system (GPS)locator at site A reveals that it is moving at 2.1 centimeters per year to the east. A second GPS locator is tracking site B, which is moving at 2.0 centimeters per year to the west. What sort of plate boundary is this?

A)divergent
B)convergent
C)transform
D)impossible to tell based on this information alone

Question 30

The rate of seafloor spreading is, on the average, about two or three meters per year.

Question 31

Among the following choices, the closest match for the East Pacific Rise is ________.

A)the Mid-Atlantic Ridge
B)the San Andreas Fault
C)the Appalachian Mountains
D)the Mariana Trench

Question 32

Although several plausible models have been proposed, scientists haven't yet figured out the exact pattern of convection in Earth's mantle.

Question 33

In general, rocks of the continental crust are less dense than rocks of the oceanic crust.

Question 34

Continent-continent convergence results in subduction.

Question 35

The oldest rocks on the seafloor are much younger than the oldest rocks on the continents.

Question 36

Examine the image of the Baja Peninsula of Mexico. Red lines indicated sections of oceanic ridge. White lines indicate transform faults. Black arrows indicate the direction of relative plate motion. Is it true or false to say this is a good example of a convergent plate boundary?

Question 37

Mantle convection may occur in two layers within the mantle - the active upper mantle and
the sluggish lower mantle - as proposed in the layer cake model.

Question 38

Rock in the asthenosphere is mostly molten.

Question 39

Divergent boundaries are limited to the seafloor.

Question 40

You are dropped off by helicopter at a site on the land. You are told that it is a plate boundary. Almost immediately, you feel an earthquake. You look around and note the absence of volcanoes, but you notice an offset stream channel, and find a vertical fault with two kinds of rock on either side of it. What sort of plate boundary are you most likely on?

A)divergent
B)convergent
C)transform
D)plate interior (hot spot)

Question 41

Mt. Kilimanjaro and Mt. Kenya are ________ that occur along the East African Rift.

Question 42

Slabs of oceanic lithosphere sink at subduction zones because the subducted slab is denser than the underlying asthenosphere. In this process, called ________, Earth's gravity tugs at the slab, drawing the rest of the plate toward the subduction zone.

Question 43

The ________ is Earth's outermost rocky layer that is broken into plates.

Question 44

Some kind of ________ (upward movement of less dense material and downward movement of more dense material)appears to drive the motion of plates.

Question 45

The ________ today marks the location of the rift along which Africa separated from South America.

Question 46

Match the items in the first column with the correct descriptions in the second column.

A)rising of warm material due to lower density.
B)boundary where two plates slide past one another.
C)the condition of the magnetic field where the magnetic force flows out of Earth's south pole and back in at the north pole.
D)the crust and the stiff upper mantle combined; this is broken into plates.
E)boundary where two plates move away from one another.
F)the "weak layer" within the mantle. Motion here is thought to help drive plate tectonics.
G)the condition of the magnetic field where the magnetic force flows out of Earth's north pole and back in at the south pole.
H)boundary where two plates move towards one another.
1)lithosphere
2)asthenosphere
3)convergent
4)divergent
5)transform
6)normal polarity
7)reversed polarity
8)convection

Question 47

What evidence did Alfred Wegener use to support his hypothesis of continental drift? What additional evidence was added later (post-World War II)that suggested seafloor spreading? How do these two ideas unite to form the theory of plate tectonics?

Question 48

The ________ is weaker and less rigid than the overlying lithosphere.

Question 49

During the first two decades of the twentieth century, ________ was a vigorous proponent of continental drift.

Question 50

Label each of the features associated with this divergent plate boundary.

Question 51

Iceland sits on a(n)________ plate boundary.

Question 52

The North American plate is currently ________ in size.

Question 53

Examine the image. It shows ________, a freshwater reptile whose fossils Alfred Wegener cited as evidence of continental drift.

Question 54

A(n)________ is a long-lived, stationary, magma source deep in the mantle, well below the base of the lithosphere.

Question 55

Examine this map of the Lutgens Archipelago, a chain of hotspot-related islands atop the Tarbuck Plate in the Tasa Sea. Use the information given to determine the (a)direction and (b)rate of movement of the Tarbuck Plate.

Question 56

Alaska's Aleutian Islands formed as part of a(n)________ along a(n)________ boundary.

Question 57

The San Andreas fault in California is a good example of a(n)________ plate boundary.

Question 58

Which of these two sets of apparent polar wander paths shows the "fixed continent" model and which shows the "plate tectonics" model? Explain.

Question 59

________ was a supercontinent that existed in the late Paleozoic era of geologic time.

Question 60

The South Atlantic basin is widening by seafloor spreading. Africa and South America are moving ________.

Question 61

How wide would an ocean basin be if it formed due to the breakup of a supercontinent 200 million years ago and had an oceanic ridge in the middle that spread at a rate of 2.5 centimeters per year (25 kilometers per million years)?

Question 62

Examine the cross-section through a hypothetical ocean basin. Use the magnetic time scale at left to determine when continents A and B separated from one another. Justify your answer.