Deck 2: The Way the Earth Works: Plate Tectonics

Question 1

Younger oceanic crust will have ________ ocean sediments,while older oceanic crust will have ________ oceanic sediments.

A)older;younger
B)carbonate;silicic
C)thicker;thinner
D)thinner;thicker

Answer 1

D

Question 2

Evidence that glaciers once covered an area might include ________.

A)till and striations
B)backwash and striations
C)till and grabens
D)backwash and grabens

Answer 2

A

Question 3

Seafloor spreading is driven by volcanic activity ________.

A)in the middle of abyssal plains
B)along mid-ocean ridges
C)at the edges of continental shelves
D)along fracture zones

Answer 3

B

Question 4

Seafloor spreading occurs at ________ boundaries.

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

Question 5

The discovery of seafloor spreading finally provided a mechanism for ________.

A)subduction zones
B)continental drift
C)transgressions
D)normal faulting

Question 6

Late Paleozoic glacial deposits are NOT found in which of the following places?

A)India
B)southern Africa
C)North America
D)South America

Question 7

Regions of the seafloor with positive magnetic anomalies were formed during times when Earth's magnetic field ________.

A)was exceptionally strong
B)was exceptionally weak
C)had normal polarity
D)had reversed polarity

Question 8

Seafloor spreading ________.

A)recycles old oceanic crust
B)closes ocean basins
C)creates new continental crust
D)creates new oceanic crust

Question 9

In the geologic past,the polarity of Earth's magnetic field is ________.

A)unknown,but it is assumed to have been identical to today's
B)known to have stayed constant through geologic time,as shown by remnant magnetization of iron-rich minerals in rocks
C)known to have experienced numerous reversals,as shown by remnant magnetization of iron-rich minerals in rocks
D)known to have stayed constant through time,based on theoretical calculations

Question 10

The apparent tendency of the north (or south)magnetic pole to vary in position over time is termed ________.

A)dipole
B)magnetic declination
C)magnetic inclination
D)polar wander

Question 11

Consult the figure below.Abundant swamps led to the formation of coal during the Late Paleozoic in which of the following places?

A)India
B)southern Africa
C)North America
D)Antarctica

Question 12

In Wegener's evidence for continental drift,continents were proposed to fit together,such as the east coast of South America with the ________.

A)west coast of Europe
B)east coast of Africa
C)west coast of Greenland
D)lower west coast of Africa

Question 13

Limestone reefs and salt deposits are important rocks in the reconstruction of Earth's history because they ________.

A)can be used to infer the ancient climate of Earth;they are deposited in environments that are restricted to warm climates
B)automatically provide age information;all such deposits occurred between 200 and 400 million years ago
C)are deposited in warm climates today,but there is good reason to think that they were deposited in cold climates millions of years ago
D)pinpoint the locations of old subduction zones

Question 14

Wegener's idea of continental drift was rejected by American geologists because ________.

A)his English was too poor to be understood by them
B)he could not conceive of a valid mechanism that would cause continents to shift positions
C)he had relatively little evidence supporting the existence of a supercontinent
D)the apparent fit of continental coastlines is blurred when the margins are defined by the edges of continental shelves rather than sea level

Question 15

Marine magnetic anomalies can be used to estimate the ________.

A)rate of seafloor spreading
B)rate of seafloor subsidence
C)age of the seafloor sediments
D)rate of Earth's expansion

Question 16

What does an ordinary compass indicate?

A)magnetic inclination
B)magnetic declination
C)magnetic north
D)true north

Question 17

According to the figure below,marine magnetic anomalies lay roughly ________ to mid-ocean ridges.

A)perpendicular
B)parallel
C)adjacent
D)at an obtuse angle

Question 18

If a geologist discovered coal in a modern-day cold,snowy location,he or she could conclude that ________.

A)a meteorite must have struck the area
B)the area was once covered with swamps and/or jungles
C)the area was once covered with an ocean
D)this discovery was anomalous

Question 19

The rate of seafloor spreading exactly matches the rate of ________.

A)ocean subsidence
B)transgression
C)subduction
D)erosion of the seafloor

Question 20

If a geologist discovered striations (scratches)on bedrock surfaces and small hills composed of poorly sorted sediment,what could he or she conclude about the area?

A)that a fault used to run through the area
B)that the area used to be a beach along an ocean
C)that glaciers had once covered the area
D)that mountains had once covered the area

Question 21

Which of these parts of the deep-ocean floor is flat and nearly featureless?

A)ridge axis
B)abyssal plain
C)guyot
D)trench

Question 22

The distribution of ________ across the globe provides the primary indicator of boundaries between all tectonic plates.

A)mountain ranges
B)volcanoes
C)mid-ocean ridges
D)earthquakes

Question 23

According to the image below,where is new oceanic crust being formed?

A)A
B)B
C)C
D)D

Question 24

Transform boundaries occur most frequently along ________boundaries in order to break the ________ into segments so as to accommodate motion on a sphere.

A)convergent;accretionary prisms
B)convergent;deep ocean trenches
C)divergent;mid-ocean ridges
D)divergent;magnetic anomalies

Question 25

Unlike the lithosphere,the asthenosphere ________.

A)is able to flow over long periods of time
B)has a density similar to the core
C)varies in thickness from place to place
D)is relatively cool

Question 26

Deformed (bent,stretched,or cracked)lithosphere occurs ________.

A)randomly over the surface of Earth
B)primarily within the interiors of tectonic plates
C)primarily on the margins of tectonic plates
D)primarily at hot spots

Question 27

Which of the following was NOT used as evidence for seafloor spreading?

A)high heat flow at mid-ocean ridges
B)jigsaw puzzle fit of the continents
C)progressive change in age of crust
D)changes in thickness of sediments

Question 28

A geologist aboard a deep-sea research vessel has collected several drill cores of oceanic crust from the bottom of the ocean.The cores are collected in order from east to west along the bottom of the basin and are labeled A1,B1,C1,and D1,respectively.Core A1 has 2.88 meters (m)of clay and siliceous ooze covering 4.86 m of pillow basalt.Core B1 has 2.37 m of muddy,clayey ooze covering 3.57 m of basalt.Core C1 has 2.11 m of clay and siliceous ooze followed by 3.2 m of basalt.Core D1 has 1.87 m of siliceous ooze over 2.54 m of basalt.Which core is closest to the mid-ocean ridge?

A)A1
B)B1
C)C1
D)D1

Question 29

Continental coastlines that occur within the interior of a tectonic plate are called ________ margins.

A)internal
B)passive
C)active
D)inert

Question 30

With increasing distance from a mid-ocean ridge,the age of oceanic crust ________.

A)increases
B)decreases
C)stays constant
D)varies randomly

Question 31

Why was the discovery of marine magnetic anomalies so important to the theory of seafloor spreading?

A)because they show a record of marine fossils,which can be linked to geologic time
B)because they proved that Earth's magnetic field reverses polarity throughout history
C)because they show an accurate record of the creation and movement of oceanic crust
D)because they allowed geologists to record the amount of oceanic crust formed

Question 32

The primary difference between lithospheric and asthenospheric mantle that gives rise to numerous different patterns of physical behavior is ________.

A)physical state: the lithosphere is solid;the asthenosphere is liquid
B)chemical composition: the lithosphere is mafic;the asthenosphere is felsic
C)temperature: the lithosphere is cooler than the asthenosphere
D)chemical composition: the lithosphere is felsic;the asthenosphere is mafic

Question 33

Under the theory of plate tectonics,the plates themselves are ________.

A)discrete pieces of lithosphere at the surface of the solid Earth that move with respect to one another
B)discrete layers of lithosphere that are vertically stacked one atop the other
C)composed only of continental rocks that plow through the weaker oceanic rocks
D)very thick (approximately one-quarter of Earth's radius)

Question 34

At a subduction zone,the down-going (subducting)plate ________.

A)is always composed of continental lithosphere
B)is always composed of oceanic lithosphere
C)may be composed of either oceanic or continental lithosphere
D)is composed entirely of asthenosphere

Question 35

Using the image below,which marine magnetic anomalies show a reversed polarity?

A)A,D,E
B)A,B,F
C)B,C,F
D)C,D,F

Question 36

Compared to typical oceanic lithosphere,the thickness of continental lithosphere is ________.

A)less
B)greater
C)approximately the same
D)There is not a consistent pattern of lithospheric thickness.

Question 37

The theory of ________ states that the lithosphere is broken into a series of plates that move relative to each other.

A)plate drift
B)seafloor spreading
C)continental drift
D)plate tectonics

Question 38

The thickness of oceanic lithosphere is ________.

A)nearly uniformly 100 kilometers
B)greatest at the geographic poles and least near the equator
C)greatest near the mid-ocean ridges and thins out away from the ridges
D)least near the mid-ocean ridges and thickens away from the ridges

Question 39

Beneath a blanket of sediments,oceanic crust is primarily composed of ________.

A)granite
B)basalt
C)limestone
D)coal

Question 40

Slab pull occurs because subducting slabs are ________.

A)less mafic,and therefore less dense,than surrounding asthenosphere
B)cooler,and therefore more dense,than surrounding asthenosphere
C)hotter,and therefore more dense,than surrounding asthenosphere
D)cooler,and therefore less dense,than surrounding asthenosphere

Question 41

Which basic type of plate boundary is shown in the image below?

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

Question 42

The rate of motion of a lithospheric plate with respect to a stationary location inside Earth is termed ________ plate velocity,while the motion of a plate with respect to another is termed ________ plate velocity.

A)absolute;relative
B)relative;absolute
C)Both are measures of absolute velocity.
D)Both are measures of relative velocity.

Question 43

Consult the figure below.Hawaii is an example of ________.

A)hot-spot volcanism
B)mid-ocean-ridge volcanism
C)a volcanic island arc formed by subduction
D)transform margin

Question 44

Describe the process of seafloor spreading,making sure to address why the diameter of Earth is not growing.

Question 45

At transform plate boundaries,________.

A)earthquakes are common but volcanoes are absent
B)volcanoes are common but earthquakes do not occur
C)both earthquakes and volcanoes are common
D)neither earthquakes nor volcanoes are common

Question 46

The image below shows a view of a typical segmented mid-ocean ridge.Which letter below marks the location of the active transform fault?

A)A
B)B
C)C
D)D

Question 47

Discuss where transform boundaries are primarily found and what their main purpose is.

Question 48

Summed over the entire surface of Earth,the rate of spreading at divergent boundaries is ________ lithospheric consumption at subduction zones.

A)faster than
B)slower than
C)equal to
D)This cannot yet be measured by geologists.

Question 49

Hot spots can occur ________.

A)only within continental plates
B)only within oceanic plates
C)within either continental or oceanic plates
D)only when the thickness of the crust is less than 10 km

Question 50

The mid-ocean ridges are elevated above the surrounding seafloor because ________.

A)ridge rocks are hot and therefore have relatively low density
B)the lithosphere is thickest at the ridges so they stand up taller
C)rising ocean currents create a vacuum that pulls ridges up
D)ridge rocks are mafic,which are less dense than ultramafic ocean basin rock

Question 51

A geologist measures the amount of seafloor produced along a MOR to be 45 km.The oldest crust produced is 4.5 Ma.What is the spreading rate of the MOR in cm/yr? Show your work.

Question 52

What would happen if the rate of seafloor spreading was faster than the rate of subduction?

A)Arc volcanoes would not form.
B)The ocean basins would shrink.
C)The Earth would become smaller.
D)The Earth would grow larger.

Question 53

Explain why Wegener's theory of continental drift was not originally accepted by geologists of his time?

Question 54

Plate tectonics theory is often referred to as the "unifying" theory in geology.Explain why plate tectonics is such an important theory to the study of Earth.

Question 55

Which basic type of plate boundary is shown in the image below?

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