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 hotspot 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 hotspot,the calculation can be quite accurate.

Question 2

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

Answer 2

A mountain range forms under the same geological conditions along its length.This means that the same or nearly the same rock types are found along the range's length in the same or nearly the same sequence.The processes that form mountain ranges tend to create somewhat linear,elevated features.So a mountain range that has been split,even if it has been separated by an ocean,is fairly easy to recognize.

Question 3

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

Answer 3

(1)The continent remained fixed and the north magnetic pole moved; (2)the north magnetic pole stayed still and the continent moved; (3)both the continent and north magnetic pole moved.

Question 4

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

Question 5

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

Question 6

Briefly explain how convection transfers heat.

Question 7

How does fossil evidence support continental drift?

Question 8

Describe the features of oceanic trenches.For what geological reasons do the trenches appear like this?

Question 9

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

Question 10

What are four of the many things that plate tectonics theory explains?

Question 11

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

Question 12

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

Question 13

Briefly explain why apparent polar wandering is "apparent."

Question 14

Describe how the two models for the driving force of plate motion are the same.How are they different?

Question 15

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

Question 16

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

Question 17

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

Question 18

What is one geologic method for determining the average rate of seafloor spreading?

Question 19

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

Question 20

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

Question 21

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

Question 22

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

Question 23

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

Question 24

The three kinds of boundaries there can be between adjacent plates are ____________________,____________________,and ____________________.

Question 25

Paleomagnetism is the study of the ____________________ magnetism in rocks.

Question 26

The three types of convergent plate boundaries are ____________________-____________________,____________________-____________________,and ____________________-____________________.

Question 27

At a convergent plate boundary,oceanic crust is ____________________.

Question 28

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

Question 29

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

Question 30

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

Question 31

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

Question 32

In what ways does plate tectonics theory have economic applications?

Question 33

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

Question 34

How does seafloor spreading explain the movement of the continents?

Question 35

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

Question 36

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

Question 37

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

Question 38

When magma cools,the magnetic iron-bearing minerals align themselves with the Earth's magnetic field and record ____________________ and ____________________.

Question 39

What are the heat sources for each of the two mantle convection models for plate tectonics?

Question 40

Why is plate tectonic theory so widely accepted?

Question 41

The names of the plates on either side of the plate boundary that passes through California are ____________________ and ____________________.

Question 42

The transition zone from the exposed land to the ocean floor is called the

A) oceanic trench.
B) continental margin.
C) continental slope.
D) abyssal plain.

Question 43

If the continents were once joined together,rocks and mountain ranges on the margins of each should have ____.

A) formed under the same conditions
B) formed the same sequences
C) formed at the same time
D) the same structural trends and forces
E) all of these

Question 44

Glacial deposits gave strong evidence of the existence of Gondwana because ____.

A) a single continent in high latitudes was more sensible than low latitude glaciation on several continents
B) glacial striations showed that all glaciers on each continent had flowed from a central location
C) fossil plants indicated tropical climate in the northern continents
D) a single continent in high latitudes was more sensible than low latitude glaciation on several continents AND glacial striations showed that all glaciers on each continent had flowed from a central location
E) a single continent in high latitudes was more sensible than low latitude glaciation on several continents AND fossil plants indicated tropical climate in the northern continents

Question 45

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

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

Question 46

Fossil evidence of the links among Gondwana continents was compelling because the species ____.

A) should have been found over wide regions if they were able to migrate among continents
B) should have exhibited evidence of tolerance for climatic extremes
C) should have shown a mechanism for widespread dispersal
D) should have been found over wide regions if they were able to migrate among continents AND should have shown a mechanism for widespread dispersal
E) all of these

Question 47

The name given to the northern supercontinent was ____.

A) Laurasia
B) Luentia
C) Laurotia.
D) Laurentia
E) northern Pangaea

Question 48

The type of plate boundary at which many of the world's major metallic ore deposits are associated is ____________________.

Question 49

One of the most general conclusions to be drawn from plate tectonic theory is that ____.

A) the Earth is gradually losing heat
B) the Earth's geography has continually changed
C) the Earth is slowly expanding
D) the Earth is slowly shrinking
E) all the ocean basins are gradually enlarging

Question 50

Which group of fossils is considered evidence for the former existence of Gondwana?

A) Glossaurus
B) Pecopteris
C) Neuropteris
D) Glossopteris
E) Messopteris

Question 51

Fossil evidence linking the Gondwana continents includes which animal fossils?

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 52

Which of the following was not evidence for Wegener's continental drift hypothesis?

A) glacial deposits of Gondwana continents
B) fit of African and South American shorelines
C) paleomagnetic striping of the oceanic crust
D) fossil plant and animal distributions
E) similar rock sequences and mountain ranges

Question 53

The first person to suggest that all of the continents had originally been joined together as the supercontinent Pangaea was who?

A) Alexander du Toit, 1937
B) Frank Taylor, 1910
C) Alfred Wegener, 1912
D) Snider- Pelligrini, 1858
E) Harry Hess, 1962

Question 54

The proposal that the coastline fit of South America and Africa was evidence of continental drift was criticized because it could have been due to what?

A) chance
B) shoreline erosion
C) the sinking of a land bridge
D) ocean currents
E) the distribution of resistant rock types

Question 55

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

Question 56

Mountain building events occur along ____________________-____________________ or ____________________-____________________ plate boundaries.

Question 57

Two sets of mountain ranges,which are continuous once the continents on either side of the Atlantic are joined,are located where?

A) eastern North America and Greenland/ Australia and East Africa
B) east Africa and Europe/ eastern North America and the Soviet Union
C) Australia and Southeast Asia/ Arabia and the Persian Gulf
D) South Africa and Brazil/ eastern North America and Great Britain
E) Central and South America/ Central and North America

Question 58

Plate tectonic processes have influenced which of the following?

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 59

The southern supercontinent consisted of which current continents?

A) South America, Africa, Australia, Antarctica, and India
B) Africa, South America, Antarctica, and Australia
C) South America, Africa, India, and Australia
D) South Africa, India, Africa, and Australia
E) South America, Central America, India, Antarctica, Africa, and Australia

Question 60

Glacially deposited strata were important in the development of continental drift theory because ____.

A) the distribution of glacial deposits indicated that the entire Earth must have been glaciated
B) the distribution of coal-swamp deposits indicated that the entire Earth must have been very warm
C) the glacial deposits indicated that there must have been many very large glaciers on several continents
D) the glacial deposits indicated that all of the southern continents must have been closer to the South Pole and contiguous
E) the glacial deposits indicated that climate can change dramatically over geologic time

Question 61

Magnetic iron-bearing minerals that crystallize out of magma ____.

A) align themselves with the Earth's magnetic field and only record direction
B) record the strength of the Earth's magnetic fields
C) become easily altered and lose their magnetic properties
D) record both direction and strength of the Earth's magnetic field at time of crystallization
E) none of these

Question 62

What was the driving mechanism proposed by Hess to explain sea floor spreading?

A) downwelling oceanic currents
B) hydrothermal cells
C) thermal convection cells
D) motions in the outer core
E) thermal convection cells AND motions in the outer core

Question 63

Geologists know that oceanic ridges are geologically very active because they ____.

A) have high heat flow
B) have many small earthquakes
C) are the site of recent volcanic eruptions
D) have many small earthquakes and are the site of recent volcanic eruptions
E) all of these

Question 64

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 65

The seafloor spreading hypothesis indicates what as the primary cause of continental movement?

A) volcanism in the ocean crust
B) convergence of tectonic plates
C) the formation and destruction of ocean basins
D) the convection of mantle heat
E) the decay of radioactive isotopes

Question 66

Geologists recognize which three major types of plate boundaries?

A) resurgent, divergent, and emergent
B) convergent, divergent, and transform
C) transcurrent, oblique, and resurgent
D) emergent, transform, and convergent
E) transform, transcurrent, and translateral

Question 67

Certain rock types can be used to determine the locations of past magnetic poles because ____.

A) the Earth's magnetic poles have reversed many times during its history
B) the magnetic poles and geographic poles differ slightly
C) iron-bearing minerals align themselves in the direction of the current magnetic field when the rock cools below the Curie point
D) lava flows in Europe all showed that the continent was once located in the southern hemisphere
E) the north magnetic poles of each continent are identical for each geological period

Question 68

At a mid-ocean ridge spreading center,what happens?

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 69

What did the differing paleomagnetic records for each continent show?

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 70

Old,cold,and dense oceanic crust is ____.

A) created at spreading ridges
B) found closest to continental margins
C) destroyed at subduction zones
D) eventually becomes incorporated into continental crust
E) always found on plate margins

Question 71

The Earth's magnetic field is due to ____.

A) the presence of magnetic iron and nickel in the core
B) gravity
C) the occurrence of magnetite in all rocks
D) convection in the liquid outer core
E) none of these

Question 72

At divergent plate boundaries,what are the operating forces?

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

Question 73

That the oceanic crust is geologically young and the parallel magnetic striping pattern of basalts is symmetrical about oceanic ridges was conclusively shown by what?

A) radiometric dating of oceanic basalts and sequences from continents
B) the unusually thin layer of oceanic sediments and ages of contained fossils
C) the existence of the same magnetic anomaly patterns in all ocean basins
D) radiometric dating of oceanic basalts and sequences from continents AND the unusually thin layer of oceanic sediments and ages of contained fossils
E) all of these

Question 74

A volcanic hill that is on the seafloor and has a flat top is best called a

A) guyot.
B) seamount.
C) aseismic ridge.
D) microcontinent.

Question 75

What do studies of paleomagnetism show?

A) the northern and southern hemispheres have reversed position many times
B) the ocean basins are young
C) each continent once had its own magnetic pole
D) the continents remain fixed and the north magnetic pole has moved
E) all of these

Question 76

Lithospheric plates move on the Earth's surface because ____.

A) warm mantle ascends at ridges and cool mantle descends at subduction zones
B) convection occurs only in the asthenosphere
C) cool mantle ascends at ridges and warm mantle descends at subduction zones
D) warm mantle ascends at ridges and cool mantle descends at subduction zones AND convection occurs only in the asthenosphere
E) convection occurs only in the asthenosphere AND cool mantle ascends at ridges and warm mantle descends at subduction zones

Question 77

Who proposed the idea of seafloor spreading?

A) Harry Hess
B) Frederick Vine
C) Oliver and Sykes
D) Fred Taylor
E) Hess and Matthews

Question 78

Which are not associated with a mid-ocean ridge?

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

Question 79

The fact that no oceanic crust older than 180 million years (Jurassic)has been found indicates what?

A) The break-up of Pangaea must have occurred before the Jurassic Period.
B) The ocean basins must be older than Jurassic age.
C) The movement of continents must have begun no earlier than the Jurassic Period.
D) The break-up of Pangaea must have begun at about the same time as these oldest basalts were formed.
E) The movement of continents must have begun no earlier than the Jurassic Period AND The break-up of Pangaea must have begun at about the same time as these oldest basalts were formed.

Question 80

What is the driving mechanism for plate tectonics?

A) heat deep within the Earth
B) tidal forces caused by the moon
C) volcanoes and earthquakes at plate boundaries
D) a little man with a steering wheel in Tierra del Fuego
E) none of these