Deck 2: Plate Tectonics: a Unifying Theory

Question 1

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

Answer 1

Plate tectonics explains, at least to some extent, all of the following phenomena: the distribution of earthquakes and volcanoes, the locations of ore deposits and mountain systems, climate and ocean circulation patterns, and the geographic distribution, evolution, and extinction of life forms.

Question 2

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

Answer 2

The major line of evidence being: A) Glaciations on Gondwana continents could only have occurred if the continents were joined, since the centers of the glaciers would have been in the ocean if they were not. B) The shape of continents, such as eastern coast of South America and the western coast of Africa, match as pieces of a jigsaw puzzle. Fossil evidence both plant and animals on the margins of the continents that are currently separated by oceans, once lived in adjacent regions when they were alive. C) Also the similarity of rock types on the margins of the two continents (composition and age) provides additional evidence for continental drift.

Question 3

How does seafloor spreading explain the movement of the continents?

Answer 3

With seafloor spreading, the continents and oceanic crust move together as part of large plates. The plate is pushed apart by the formation of new ocean crust and pulled by the subduction of old ocean crust. New crust is generated due to seafloor spreading and the old crust is being recycled (for example live convection current or a conveyor belt).

Question 4

Briefly describe what happens at transform plate boundaries and what geological phenomenon is generally associated with it along with an example.

Question 5

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

Question 6

Briefly explain why apparent polar wandering is "apparent".

Question 7

Explain why submarine hydrothermal vents are interesting to scientists.

Question 8

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 9

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

Question 10

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

Question 11

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

Question 12

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

Question 13

How does fossil evidence support continental drift?

Question 14

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

Question 15

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 16

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

Question 17

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

Question 18

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

Question 19

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

Question 20

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 21

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

Question 22

Briefly explain how convection transfers heat.

Question 23

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

Question 24

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

Question 25

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

Question 26

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

Question 27

Why is plate tectonic theory so widely accepted?

Question 28

What is the driving mechanism for plate tectonics?

Question 29

Where in the ocean basins is ocean crust youngest?

Question 30

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

Question 31

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

Question 32

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

Question 33

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

Question 34

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

Question 35

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

Question 36

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

Question 37

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

Question 38

What do glacial striations indicate?

Question 39

In what ways does plate tectonics theory have economic applications?

Question 40

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

Question 41

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

Question 42

At a divergent plate boundary, oceanic crust is ____________________.

Question 43

At a convergent plate boundary, oceanic crust is ____________________.

Question 44

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

Question 45

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

Question 46

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

Question 47

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

Question 48

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

Question 49

Completion
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 50

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

Question 51

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

Question 52

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

Question 53

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

Question 54

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

Question 55

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

Question 56

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

Question 57

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 58

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

Question 59

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

Question 60

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 61

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 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

At divergent plate boundaries, the operating forces are:

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

Question 64

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 generated by volcanism at oceanic ridges and old crust moves laterally away from the ridge and is subsequently destroyed via the process of subduction.
D) the oceanic crust is geologically young.
E) magnetic polarity reverses but northern and southern hemispheres do not.

Question 65

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 66

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 67

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 68

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 69

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 70

True/False
Earthquakes, tsunamis, and volcanic eruptions occur due to interactions with tectonic plates.

Question 71

True/False
Aseismic ridges have that name because they do not indicate occurrences of earthquakes.

Question 72

Multiple Choice 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 73

True/False
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 74

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 75

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 76

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

Question 77

True/False
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 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

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.

Question 80

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.