Deck 6: The Active Earth: Plate Tectonics

Question 1

Alfred Wegener proposed in his __________ __________ theory that Earth's continents were once joined together and later split and moved apart.

Answer 1

continental drift

Question 2

The Earth's __________ is about 2,900 kilometers thick.

Answer 2

mantle

Question 3

The __________ __________ is the undersea mountain chain located halfway between North and South America to the west, and Europe and Africa to the east.

Answer 3

Mid-Atlantic Ridge

Question 4

The Hawaiian Island chain is an example of a volcanic center at a __________ __________.

Question 5

Alfred Wegener named the northern part of the supercontinent __________ consisting of what is now North America and Eurasia.

A) Pangea
B) Laurasia
C) Gondwanaland
D) Arctica

Question 6

Alfred Wegener named his supercontinent __________.

Question 7

The __________ includes Earth's crust and the uppermost strong and rigid part of the mantle.

A) lithosphere
B) asthenosphere
C) atmosphere
D) biosphere

Question 8

The layer of the Earth that is as hot as the surface of the Sun is the inner __________.

Question 9

The __________ __________ system is an undersea mountain chain encircling the planet that forms at divergent plate boundaries.

Question 10

A divergent plate boundary is also called a/an __________ __________ or a/an __________ __________.

Question 11

A continent can be pulled apart at a divergent boundary in a process called __________ __________.

Question 12

The mantle makes up about __________ percent of the Earth's volume.

A) 8
B) 80
C) 20
D) 0.8

Question 13

Magnetic orientation that is the same as that of the Earth's current magnetic field is known as __________ __________ __________.

Question 14

A portion of a plate with continental crust composing its uppermost layer is thicker than one bearing __________ crust.

Question 15

The asthenosphere extends from a depth of about __________ km down to a depth of about __________ km below the surface of the Earth.

A) 1, 3.5
B) 10, 35
C) 100, 350
D) 1000, 3500

Question 16

The __________ is the Earth's thinnest layer.

Question 17

The __________ is the hot, weak, and plastic uppermost portion of the mantle.

Question 18

Average oceanic crust is __________ kilometers thick, whereas average continental crust is __________ kilometers thick.

A) 20 to 40, 5 to 10
B) 50 to 100, 200 to 400
C) 4 to 7, 20 to 40
D) 200 to 400, 50 to 100

Question 19

The San Andreas Fault is an example of a/an __________ plate boundary.

Question 20

A/an __________ __________ is a long narrow trough in the sea floor formed where a portion of an oceanic plate sinks into the mantle.

Question 21

Where two plates carrying continental crust converge, they form:

A) huge mountain ranges.
B) a subduction zone, and one plate sinks into the mantle.
C) a transform boundary.
D) a mantle plume.

Question 22

A mantle plume is a __________.

A) convergent boundary between two plates
B) divergent boundary between two plates
C) transform boundary between two plates
D) rising column of hot, plastic mantle rock
Multiple Choice

Question 23

Magnetic orientation in rocks that is opposite to the current orientation of Earth's magnetic field is called __________ magnetic polarity.

A) normal
B) reversed
C) regular
D) irregular

Question 24

The Earth's outer core is:

A) cool and brittle.
B) composed of helium.
C) molten because the pressure is very high.
D) as hot as the surface of the Sun.

Question 25

The outer 75 to 125 kilometers of the Earth, including both the crust and upper mantle, consists of:

A) molten iron and nickel of the outer core.
B) weak, plastic rock of the asthenosphere.
C) hard, strong rock of the lithosphere.
D) solid iron and nickel of the inner core.

Question 26

At a divergent boundary between spreading tectonic plates in oceanic crust:

A) one plate subducts beneath the other.
B) rock and magma rise to form the Mid-Oceanic Ridge.
C) rock sinks to form an oceanic trench.
D) rock rises to form continents.

Question 27

The first supercontinent formed by collisions of microcontinents and island arcs probably about __________ years ago.

A) 4.5 billion
B) 2 to 1.8 billion
C) 543 million
D) 5 million

Question 28

The asthenosphere is:

A) hot, weak, and plastic.
B) mostly liquid magma.
C) composed mostly of sedimentary rocks.
D) hard, strong rock.

Question 29

Continental crust is composed mainly of:

A) granite.
B) iron and nickel.
C) basalt.
D) shale and limestone.

Question 30

When a plate carrying continental crust converges with a plate carrying oceanic crust:

A) the oceanic plate floats above the continental plate.
B) the continental plate sinks into the mantle.
C) a divergent boundary forms.
D) the oceanic plate sinks beneath the continental plate and dives into the mantle.

Question 31

The lithosphere is:

A) hot, plastic, but solid rock.
B) mostly liquid magma.
C) composed mostly of sedimentary rocks.
D) cool, hard, and strong.

Question 32

Tectonic plates typically move at rates of 1 to 16 __________ per year.

A) millimeters
B) meters
C) centimeters
D) kilometers

Question 33

Where two lithospheric plates of different densities converge, the denser one sinks into the mantle beneath the other in a process called __________.

A) submission
B) subduction
C) rifting
D) spreading

Question 34

The Mid-Oceanic Ridge is elevated above the surrounding sea floor because it is:

A) made of the oldest, coolest, and most dense lithosphere.
B) made of the newest, hottest, and lowest-density lithosphere.
C) full of gas bubbles.
D) very old.

Question 35

According to the theory of isostasy, the __________ is in floating equilibrium on the __________.

A) core, asthenosphere
B) asthenosphere, mantle
C) lithosphere, asthenosphere
D) inner core, outer core

Question 36

The Himalayan Mountain Range is an example of a __________ boundary.

A) convergent
B) divergent
C) transform
D) rift valley

Question 37

The entire mantle-lithosphere system circulates in great __________ cells.

A) spreading
B) reversal
C) plume
D) convection

Question 38

Alfred Wegener realized that:

A) the African and South American coastlines fit together like pieces of a jigsaw puzzle.
B) Africa and South America must have once been one continent.
C) there must have been one big supercontinent that he named Pangea.
D) all of the above

Question 39

__________ have occurred on average every 500,000 years over the past 65 million years of Earth's history.

A) Supercontinents
B) Major mass extinctions
C) Banded iron formations
D) Magnetic reversals

Question 40

Where two plates move horizontally toward each other, they form a __________ boundary.

A) convergent
B) rift
C) divergent
D) transform

Question 41

Where two plates carrying ocean crust converge:

A) they form a Mid-Oceanic Ridge.
B) both plates stop moving.
C) the older, denser one sinks into the mantle at an oceanic subduction zone.
D) the crust collides to form a large mountain range.

Question 42

Reversed magnetic polarity is the opposite of the Earth's current magnetic field.

Question 43

The inner core is molten.

Question 44

A plate is a segment of the lithosphere; thus, it includes the uppermost mantle and all of the overlying crust.

Question 45

Supercontinents may assemble, split apart, and reassemble every 5,000 to 7,000 years.

Question 46

Oceanic crust is thicker than continental crust.

Question 47

A single plate can carry both oceanic and continental crust.

Question 48

The Mid-Atlantic Ridge is a leg of the Mid-Oceanic Ridge system that divides the Atlantic Ocean.

Question 49

The Mid-Oceanic Ridge forms along transform plate boundaries.

Question 50

Fossil distribution on continents had no bearing on Alfred Wegener's theory about continental drift.

Question 51

The Mid-Oceanic Ridge is elevated above surrounding sea floor because it is made of hot and low-density lithosphere.

Question 52

The asthenosphere is a rigid, brittle rock layer.

Question 53

According to the supercontinent model:

A) at some future time, all continents will join together in a single supercontinent, and plate tectonics activity will cease.
B) continental fragments have migrated around the globe and then reassembled as a supercontinent at least three times in Earth history.
C) the breakup of a future supercontinent will lead to the destruction of all continental crust in subduction zones.
D) all the geologic provinces in a supercontinent have the same radiometric age. True/False

Question 54

The Hawaiian Islands are an example of:

A) a microcontinent.
B) a volcanic center at a hot spot.
C) isostasy.
D) a convergent boundary.

Question 55

The lithosphere floats on the asthenosphere.

Question 56

Vertical movement in the lithosphere occurs due to:

A) mantle plumes.
B) hot spots.
C) isostatic adjustment.
D) mantle convection.

Question 57

At a convergent boundary, asthenosphere rock oozes upward to fill the gap between separating plates.

Question 58

A mantle plume is a vertical column of plastic rock rising from the mantle.

Question 59

At a transform boundary:

A) one plate subducts into the mantle.
B) a Mid-Oceanic Ridge forms.
C) two plates slide horizontally past each other.
D) earthquakes are rare.

Question 60

If two converging plates are both covered with oceanic crust, subduction will occur.