Deck 2: Plate Tectonics: A Unifying Theory

Question 1

How are hot spots used for determining the absolute motions of plates?

Answer 1

Hot spots appear to be fixed in the mantle relative to each other,so they can be used as a reference frame.If the age of a basalt and its distance from the hot spot is determined,then the rate of movement of that rock can be calculated.If a number of these samples are taken from various distances from the hot spot,the calculation can be quite accurate.

Question 2

How does the introduction of a geographic barrier encourage the evolution of species?

Answer 2

A population that is not separated will interbreed,so there will be little opportunity for different species to form.If a barrier separates that population and if conditions are different on either side of the barrier,natural selection will favor certain traits over others,and over time the two different populations of organisms may evolve to become different species.

Question 3

Briefly describe what happens when divergent plate boundaries form within a continent.

Answer 3

High heat flow elevates the continent and a rift valley forms,with normal faults and a central valley called a graben.Magma is intruded into fractures.As the plates diverge,basalt erupts in the rift,creating new ocean crust.Ultimately,as the plates continue to diverge,a new ocean basin forms.

Question 4

Explain how mountain ranges can be used as evidence to support continental drift.

Question 5

Why were glacially deposited strata important in the development of continental drift theory?

Question 6

Explain why submarine hydrothermal vents are interesting to scientists.

Question 7

Briefly explain how magnetic reversals in oceanic crust and fossils in ocean sediments are used to construct a magnetic time scale.

Question 8

Briefly explain why the movement of continents over geologic time was the best explanation for polar wandering.

Question 9

How does fossil evidence support continental drift?

Question 10

What is a method by which the present rate of motion between two plates can be measured accurately?

Question 11

How is the phrase "the present is the key to the past" used in creating evidence for continental drift?

Question 12

What were the major lines of evidence for continental drift as presented by Wegener in the early 20ᵗʰ century?

Question 13

Briefly explain the roles of magma and hydrothermal activity in forming ore deposits along convergent and divergent plate boundaries.

Question 14

Briefly explain why apparent polar wandering is "apparent".

Question 15

How does seafloor spreading explain the movement of the continents?

Question 16

Draw a cross-section of a continental-continental convergent plate boundary.Show the directions of relative plate motion.Put stars for the locations of earthquakes.Show the location of the mountain range.Label the subduction complex.

Question 17

Draw a cross-section of an oceanic-continental convergent plate boundary.Show the directions of relative plate motion.Put stars for the locations of earthquakes.Put triangles with smoke out the top for the locations of volcanoes.Label the trench and subduction complex.

Question 18

Draw a cross-section of an oceanic-oceanic convergent plate boundary.Show the directions of relative plate motion.Put stars for the locations of earthquakes.Put triangles with smoke out the top for the locations of volcanoes.Label the trench,back arc basin,and subduction complex.

Question 19

Briefly explain why there is so much oil in the Persian Gulf region.

Question 20

What are four of the many things that plate tectonics theory explains or whose explanations it has influenced?

Question 21

What type of motion is found at a transform plate boundary? What physical feature marks the boundary between the two plates?

Question 22

What other geological processes could have resulted in the configuration of coastlines so that South America and Africa appeared to fit together?

Question 23

Why is plate tectonic theory so widely accepted?

Question 24

Who was the first person to suggest that all of the continents had been once joined together as a supercontinent called Pangaea and when was that idea proposed?

Question 25

Why were glacially deposited strata important in the development of the continental drift hypothesis?

Question 26

What is a hot spot relative to a mantle plume? What is often found there?

Question 27

What is the reason that the presence of Glossopteris flora fossils was strong evidence for the existence of Gondwana?

Question 28

Where in the ocean basins is ocean crust youngest?

Question 29

Where is the best place to try to fit the continents together?

Question 30

What is it about a cooling lava that allows geologists to determine the location of past magnetic poles?

Question 31

List two ways that glacial deposits give strong evidence of the existence of Gondwana.

Question 32

What is the driving mechanism for plate tectonics?

Question 33

Briefly explain how convection transfers heat.

Question 34

What two features of the magnetic field do magnetic iron-bearing minerals that crystallize out of magma record?

Question 35

What do glacial striations indicate?

Question 36

What is the principal reason why Wegener's hypothesis of continental drift was rejected?

Question 37

In what ways does plate tectonics theory have economic applications?

Question 38

What are the three possible explanations for the distribution of paleomagnetic data?

Question 39

What evidence is there that ocean basins are young and old oceanic crust must be destroyed?

Question 40

The Appalachian Mountains of the eastern United States are thought to have once been joined with mountains located in which other continental regions?

Question 41

Paleomagnetism is the study of the ____________________ magnetism in rocks.When magma cools,the magnetic iron-bearing minerals align themselves with the Earth's magnetic field and record ____________________ and ____________________.

Question 42

Most of the petroleum found in the Persian Gulf area formed at a ____________________ continental margin where the remains of ____________________ were buried and converted to petroleum.

Question 43

The heat that drives thermal convection cells comes primarily from ____________________ and is supplemented by ____________________.

Question 44

Magnetic stripes in oceanic basalts are ____________________ and ____________________ around ocean ridges.

Question 45

Wegener proposed that the continents were once all together as a supercontinent he named ____________________,which then split into a northern supercontinent called ____________________ and a southern supercontinent called ____________________.

Question 46

At a convergent plate boundary,oceanic crust is ____________________.

Question 47

The process that continues to move Africa and South America apart from each other is ____________________.

Question 48

Volcanoes are found at these two types of plate boundaries: ____________________ and ____________________.

Question 49

The group of plant fossils that provides important evidence for the existence of Gondwana is ____________________.

Question 50

Where divergent plate boundaries form beneath continental masses,low areas known as ____________________ form.

Question 51

Rock sequences found on land that consist of deep-sea sediment,oceanic crust,and upper mantle are called ____________________.These sequences are used to identify ____________________ plate boundaries.

Question 52

At deep-sea trenches,____________________ is subducted back into the ____________________.

Question 53

At mid-oceanic ridges,hot magma rises from the ____________________ and forms new ____________________.

Question 54

The physical phenomenon that results from the spin of electrons that is found in some solids,particularly iron,and moving electricity is known as ____________________.The zone around substances with this property is called a ____________________.

Question 55

At divergent plate boundaries,plates are moving ____________________.At these locations,new ____________________ forms.

Question 56

Radiometric dating shows that the oldest ocean crust is ____________________ years old and the oldest continental crust is ____________________ years old.

Question 57

The temperature at which iron-bearing minerals gain their magnetic property is the ____________________.

Question 58

Paleomagnetic data plotted on a map suggested that the magnetic pole had moved over time;this phenomenon was called ____________________.

Question 59

Deviations from the average strength of Earth's present-day magnetic field are called ____________________.

Question 60

The type of plate boundary that runs through California is called ____________________,and the name of this plate boundary is the ____________________.

Question 61

Aseismic ridges have that name because they do not have earthquakes.

Question 62

The northern supercontinent consisted of:

A)North America,Europe,Asia,India,and Greenland.
B)North America,Greenland,and Europe.
C)North America,Europe,Asia,and India.
D)North America,Greenland,Asia,and India.
E)North America,Europe,Asia,and Greenland.

Question 63

Studies of paleomagnetism document:

A)changes in the Earth's gravitational field.
B)how the inner/outer core boundary has evolved.
C)how the mineral magnetite has varied through time.
D)how the Earth's magnetic poles have varied through time.
E)none of these

Question 64

Large,high mountain ranges without volcanoes are built at which type of plate boundary?

A)divergent: oceanic-oceanic
B)convergent: oceanic-continental
C)convergent: continental-continental
D)transform: continental-continental
E)divergent: oceanic-oceanic AND convergent: continental-continental

Question 65

At a mid-oceanic ridge spreading center:

A)the plates are moving past each other.
B)the plates are moving away from each other.
C)the plates are moving toward each other.
D)one plate is being subducted beneath another.
E)both plates are being subducted.

Question 66

A transform plate boundary may connect:

A)a spreading ridge and subduction zone.
B)two spreading ridges.
C)two subduction zones.
D)a spreading ridge and a subduction zone or two subduction zones.
E)a spreading ridge and a subduction zone,two spreading ridges,or two subduction zones.

Question 67

A rock will preserve its remnant magnetism as long as it is not heated above the Curie point.

Question 68

Plate tectonic processes have influenced:

A)the distribution of earthquakes and volcanoes.
B)the locations of ore deposits and mountain systems.
C)climatic patterns and ocean circulation.
D)the geographic distribution,evolution,and extinction of life forms.
E)all of these

Question 69

Around most of the Atlantic the continental slope descends into an oceanic trench but around the Pacific the continental slope merges with a more gently sloping continental rise.

Question 70

The symmetrical pattern of magnetic polarities about spreading ridges in oceanic crust basalts indicates that:

A)each plate has had an independent set of magnetic reversals.
B)basalt retains its magnetic signature for only a few million years.
C)new ocean crust is created by volcanism at oceanic ridges and old crust moves laterally away from the ridge.
D)the oceanic crust is geologically young.
E)magnetic polarity reverses but northern and southern hemispheres do not.

Question 71

The differing paleomagnetic records for each continent showed:

A)each continent had its own magnetic pole during successive geological periods.
B)that the magnetic poles for each continent had moved over geological time.
C)that the magnetic poles have remained in one location and each of the continents has moved.
D)that both the poles and the continents have moved over time.
E)none of these

Question 72

The study of paleomagnetism is possible because:

A)the magnetic minerals in rocks create the Earth's magnetic field.
B)most rocks contain no magnetic minerals.
C)the magnetic minerals in rocks disrupt the Earth's magnetic field.
D)the magnetic minerals in a cooling lava point toward the north magnetic pole.
E)none of these

Question 73

The mechanism for plate movement is:

A)conduction of heat from the core.
B)friction created by tidal forces generated by the Moon.
C)conduction of heat within the mantle.
D)convection of heat within the mantle.
E)convection of heat within the core.

Question 74

At divergent plate boundaries,the operating forces are:

A)compressional.
B)lateral shearing.
C)tensional.
D)thrusting.
E)normal.

Question 75

The 2005 Indian Ocean tsunami,the eruption of Mount Merapi in 2010 and the 9.0 magnitude earthquake that struck Japan in 2011 occurred at the same type of plate boundary.

Question 76

Earth's magnetic field is dipolar,meaning that it has two similar magnetic poles one at the north pole and one at the south pole.

Question 77

Fossil evidence linking the Gondwana continents includes the:

A)lake-dwelling Mesosaurus and large land-dwelling reptile Lystrosaurus and Cynognathus.
B)freshwater Mesosaurus and dinosaurs Brontosaurus and Tyrannosaurus.
C)freshwater crocodiles and the large amphibian Eryops.
D)reptile Dimetrodon and the first bird Archaeopteryx.
E)lake-dwelling Mesosaurus and the large land-dwelling reptiles Dimetrodon and Edaphosaurus.

Question 78

Which are not associated with a mid-oceanic ridge?

A)old ocean crust
B)shallow-depth earthquakes
C)volcanic eruptions
D)transform faults
E)hot water

Question 79

That the northern continents were once joined and located along the equator was shown by the:

A)coal-age plant fossils of North America and Europe.
B)Glossopteris flora.
C)distribution of mountain ranges.
D)distributions of Permian and Triassic reptiles.
E)distributions of northern hemisphere glacial tillites.

Question 80

Fossil evidence of the links among Gondwana continents was compelling because the species should have:

A)been found over wide regions if they were able to migrate among continents.
B)exhibited evidence of tolerance for climatic extremes.
C)shown a mechanism for widespread dispersal.
D)been found over wide regions and shown a mechanism for widespread dispersal.
E)been found over wide regions,exhibited evidence of tolerance for climatic extremes and shown a mechanism for widespread dispersal.