Deck 3: Igneous Rocks

Question 1

The lithospheric plates in modern plate tectonic theory differ significantly from Wegener's

A) they are significantly thinner
B) we now know that the plate motions are driven by massive magnetic reversals
C) several of the largest plates include both continental and oceanic crust
D) it is the oceans that do all of the moving, not the continents

Answer 1

C

Question 2

Most transform faults are located .

A) in the ocean basins connecting offsets along the mid- ocean ridge system
B) within continents at old continental sutures or along continental margins
C) at ridge- ridge- ridge triple junctions
D) along the crests of mountain ranges like the Alpine fault in New Zealand

Answer 2

A

Question 3

This plate boundary has the least amount of volcanism.

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

Answer 3

A

Question 4

Where lithosphere is sinking into the mantle, it is a plate boundary.

A) convergent
B) divergent
C) strike- slip
D) transform

Question 5

In the early part of the 20th century, argued forcefully for continental drift.

A) Bill Kohl
B) Alfred Wegener
C) Peter Rommel
D) Karl Wagner

Question 6

Early results of the Deep Sea Drilling Project clearly justified the conclusion that .

A) the oceans have not always contained most of Earth's water
B) Proterozoic rocks are found only as seamounts in the deepest parts of the ocean basins
C) the youngest sediments were deposited directly on the oldest seafloor basalts
D) the ocean basins are geologically young (

Question 7

What kind of geologic studies were the primary focus of the Glomar Challenger and JOIDIES Resolution's international investigations?

A) drilling the seafloor sediments and underlying ocean crust to determine the history and development of different oceanic regions
B) conducting swath multi- beam bathymentry and other underway geophysical surveys to map the ocean basins
C) resource mapping on the continental shelves of Canada and other contributing member nations
D) satellite mapping of the sea surface and spectroscopic analysis of surface currents for global current circulation and geochemistry

Question 8

Plates are sliding past one another horizontally along a plate boundary.

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

Question 9

Early results of the Deep Sea Drilling Program clearly justified the conclusion that .

A) the oceans have not always contained most of Earth's water
B) proterozoic rocks are found only as seamounts in the deepest parts of the ocean basins
C) the ocean basins are relatively young; most ocean basin rocks and sediments are Cretaceous or younger in age
D) the youngest sediments were deposited directly on the oldest seafloor basalts

Question 10

Which of the following most accurately describes the volcanoes of the Hawaiian Islands?

A) composite cone volcanoes associated with a mid- Pacific transform fault
B) shield volcanoes fed by a long- lived hot spot below the Pacific plate
C) composite cone volcanoes associated with subduction and a convergent plate boundary
D) shield volcanoes associated with a mid- Pacific ridge and spreading centre

Question 11

If the North Atlantic began to rift about 200 m.y. ago, initiating the break up of Pangaea, where are the Jurassic basalts from that initial rifting?

A) on the Mid- Atlantic Ridge under Iceland
B) as outcrops and as basement to the continental shelves' sediment sequences along the eastern seaboard of North America and along the western coast of north Africa
C) subducted beneath the Bermuda triangle
D) There aren't any left; they all got recycled back into the mantle along subduction zones underneath western Europe and Brazil.

Question 12

was never proposed as evidence supporting the existence of Pangaea.

A) Late Paleozoic glacial features
B) The Glossopteris flora
C) Geometric fit between South America and Africa
D) Islands of Proterozoic rocks along the Mid- Atlantic Ridge

Question 13

Deep ocean trenches are surficial evidence for .

A) sinking of oceanic lithosphere into the mantle at subduction zones
B) rising of hot asthenosphere from deep in the mantle
C) transform faulting between an oceanic plate and a continental plate
D) rifting beneath a continental plate and the beginning of continental drift

Question 14

The largest mostly oceanic plate is the .

A) Antarctic
B) Scotian
C) Atlantic
D) Pacific

Question 15

The Aleutian Islands occur at .

A) a transform boundary where North America has moved towards Alaska
B) a convergent, continental margin with uplifted fault blocks, much like those of the Basin and Range Province
C) a divergent boundary where shield volcanoes are forming
D) an ocean- ocean convergent boundary on a volcanic arc above a northward- subducting Pacific plate

Question 16

Why were Wegener's continental drift ideas rejected by many contemporary and later scientists?

A) The ocean basins were well known to be geologically young, Mesozoic and Cenozoic features.
B) His drift mechanism seemed impossible on the basis of known physical processes.
C) Land bridges were proven to have aided in animal and plant migrations.
D) The gravitational attractions of the Sun and Moon were not strong enough to move the continents from the southern to the northern hemisphere.

Question 17

The "big bend" in the Hawaii- Emperor seamount chain occurred at about 45 m.y. ago. What is the most likely explanation for this change in the orientation of the hot spot track across the Pacific plate?

A) The hot spot abruptly changed its direction. It used to move straight south, and since 45 m.y. ago it has been moving SE through the upper mantle.
B) The Devil put this line of volcanoes here to confuse us and subvert us from the true path. Everyone knows Earth isn't really that old.
C) From Cretaceous through 45 my. (Eocene), the Pacific seafloor used to move northwards as it subducted down a trench near the present Aleutians. Since then the Kurile- Kamchatka trench began subducting and the Pacific plate began moving NW instead.
D) They are two unrelated hot spot tracks that intersect. Originally there was an Emperor hot spot, then it died while the Hawaiian hot spot started up and moved in a new direction.

Question 18

Deep- focus earthquakes are associated with plate boundaries.

A) convergent (subducting)
B) strike- slip
C) divergent
D) transform

Question 19

What do the Appalachians have in common tectonically with the Himalayas?

A) They are both unusual places where ocean crust overrode the continent.
B) They are both active, convergent, continental- margin arc systems.
C) They both formed by continent- continent collision.
D) They both formed by continental rifting.

Question 20

New oceanic crust and lithosphere are formed at .

A) divergent boundaries by submarine eruptions and intrusions of mafic magma
B) divergent boundaries by submarine eruptions and intrusions of felsic magma
C) convergent boundaries by submarine eruptions and intrusions of felsic magma
D) convergent boundaries by submarine eruptions and intrusions of mafic magma

Question 21

What was the unexpected contribution of Keith Runcorn and his students to the continental drift controversy?

A) Apparent polar wander paths for rocks of various ages in Europe demonstrated that either the magnetic pole, or the continent's position, had wandered with time.
B) Magnetic stripes on the seafloor demonstrated magnetic reversals and seafloor spreading.
C) Reversed magnetic north directions preserved in rocks demonstrated that the location of Earth's axis had changed markedly throughout time, implying periodic cataclysms that shifted the continents during pole reversals.
D) Discordance of the Earth and Moon's magnetic pole orientations proved that the poles of one or both had drifted with the lithosphere since they were formed.

Question 22

What is the inclination of Earth's magnetic field as recorded in a recent lava flow near 59 degrees north in Yukon?

A) nearly horizontal and pointing north
B) nearly horizontal and pointing south
C) steeply inclined and pointing north
D) nearly vertical and pointing south

Question 23

Plates are moving apart from one another with a plate boundary.

A) convergent
B) divergent
C) transform
D) strike- slip

Question 24

Cooler, older, oceanic lithosphere sinks into the mantle at .

A) transform fault zones along divergent plate boundaries
B) rift zones along mid- ocean ridges
C) sites of long- lived, hot spot volcanism in the ocean basins
D) subduction zones along convergent plate boundaries

Question 25

The mid- Atlantic ridge is a plate boundary.

A) strike- slip
B) convergent
C) transform
D) divergent

Question 26

The were formed in the late Paleozoic when sediments in a marine basin were squeezed and crumpled between converging continents.

A) Urals in Russia
B) northern Rockies in Canada and the United States
C) Andes in South America
D) Alps in Europe

Question 27

Anywhere in the world, most effectively outline the edges of the lithospheric plates.

A) the locations of deep mantle hot spots
B) lines of earthquake epicentres
C) lines of active composite cone volcanoes
D) margins of the continental shelves

Question 28

A transform plate boundary is characterized by .

A) composite cone volcanoes on the edge of a plate and shield volcanoes on the adjacent plate
B) a deep, vertical strike- slip fault along which two plates slide past one another in opposite directions
C) a divergent boundary where the continental plate changes to an oceanic plate
D) two, converging, oceanic plates meeting head- on and piling up into a mid- ocean ridge

Question 29

The volcanoes and deep valleys of east Africa are related to a .

A) continental rift along which parts of the African continent are beginning to slowly separate
B) fault allowing Arabia to slip westward past east Africa and penetrate into Turkey
C) continental collision zone between Africa and the Zagros Mountains along the southern margin of Eurasia
D) transform fault aligned with the Red Sea carrying the Arabian and African blocks in opposite directions

Question 30

Linear, magnetic patterns associated with mid- ocean ridges are configured as .

A) normal and reversed magnetized stripes roughly parallel to the ridge
B) normal and reversed magnetized stripes roughly perpendicular to the ridge axis
C) concentric circles about a rising plume of hot, mantle magma
D) reversed magnetizations along the present day rift valleys and normal magnetizations along the adjacent ridge

Question 31

The top of the asthenosphere is closest to the surface .

A) along a transform fault
B) along the length of a deep mantle plume
C) along a subduction zone
D) along a mid- ocean ridge

Question 32

Why is so much mafic magma erupted along mid- ocean ridges?

A) The subducting, oceanic slab sinks so deep that eventually it melts, producing massive quantities of mafic magma.
B) Basaltic mantle under the ridge is hot enough to completely melt if seawater is added.
C) Lowered pressures decrease the temperatures at which mafic magma can partially melt from massive, extensive, rising plumes of mantle peridotite.
D) The mantle beneath the ridges is enriched in thorium, uranium, and potassium, causing strong heating due to energy from radioactive decay.

Question 33

Pangaea was .

A) a super continent that formed in the late Paleozoic and broke apart in Triassic time
B) a large, ocean basin that opened in the Triassic and closed in the Paleocene
C) a huge mountain range formed when Africa pushed northward into Europe in Eocene time
D) a large, Precambrian shield area in Africa and South America that broke apart late in the Proterozoic Eon

Question 34

The west coast of South America is associated with a plate boundary.

A) divergent
B) transform
C) strike- slip
D) convergent

Question 35

What is the tectonic environment for the volcanoes Kilimanjaro and Mt. Kenya?

A) continental rift
B) mid- ocean ridge seamounts
C) within- plate hot spot type
D) continental margin volcanic arc

Question 36

Deep-focus earthquakes are associated with plate boundaries.

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

Question 37

Wegener's supercontinent that began to break up about 200 million years ago was named .

A) Rodinia
B) Pangaea
C) Gondwanaland
D) Laurasia

Question 38

plate boundaries have the largest magnitude earthquakes.

A) Transform and convergent
B) Divergent and transform
C) Divergent and convergent
D) All plate boundaries have large magnitude earthquakes.

Question 39

The modern- day Red Sea is explained by plate tectonics theory because it is .

A) a rare example of a two continent subduction zone where both the African and Arabian continental plates are both sinking under the Red Sea plate
B) a tiny remnant of a once immense ocean that was closed as Africa moved into Asia
C) a rift zone that may eventually open into a major ocean if Arabia and Africa continue to separate
D) the site of a transform fault along which Arabia is moving away from Africa

Question 40

Following technologic advances in ocean mapping that came from the Cold War in the 1950s and 1960s the new data from the ocean basins led to propose the first model for seafloor spreading.

A) Alfred Wegener
B) Keith Runcorn
C) Harry Hess
D) Sir Edward Bullard

Question 41

What do the data points signify on the apparent polar wandering curves for Eurasia and North America?

A) where the north magnetic pole appears to be located as viewed from various locations on different continents of the northern hemisphere today
B) laboratory locations where Eurasian and North America rock samples were taken to be tested
C) the apparent positions for the north magnetic pole at various times in the past, from paleomagnetic measurements on different rock sequences in Eurasia and North America
D) where the north magnetic pole will be at various times in the future if North America keeps moving east and Eurasia keeps moving west

Question 42

From the list below, which contribution did J. Tuzo Wilson make to Plate Tectonic theory?

A) that the largest earthquake zones were over dipping oceanic plates
B) the existence of mid- ocean ridges and the correlation of magnetic stripes to seafloor spreading
C) the existence of fracture zones in the ocean crust, and intraplate hot spots
D) the rifting of continents like Pangaea and Gondwanaland

Question 43

How can you tell from the apparent polar wandering curves for Eurasia and North America, when they were last together and had just started to drift apart?

A) more than 500 million years ago, because the curves are separated then
B) just recently, when the curves came together
C) about 300 million years ago, because the curves really bend before that
D) about 200 million years ago because, for times older than that, their curves remain parallel and about the same distance apart

Question 44

New oceanic crust and lithosphere are formed at .

A) divergent boundaries by submarine eruptions and intrusions of basaltic magma
B) convergent boundaries by submarine eruptions and intrusions of rhyolitic magma
C) divergent boundaries by submarine eruptions and intrusions of rhyolitic magma
D) convergent boundaries by submarine eruptions and intrusions of basaltic magma

Question 45

Pull- apart, rift zones are generally associated with a plate boundary.

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

Question 46

Deep-oceanic trenches are most abundant around the rim of the ocean basin.

A) Indian
B) Arctic
C) Pacific
D) Atlantic

Question 47

Which of the following energy sources is thought to directly drive the lateral motions of Earth's lithospheric plates?

A) rotational spinning of the Earth, with the plates dragging behind
B) tidal gravitational attractive forces of the Sun and Moon
C) export of heat from deep in the mantle to the top of the asthenosphere and descending cold material in a solid state convective flow
D) electric and magnetic fields generated in and radiating from the inner core

Question 48

plate boundaries are characterized by arcs of explosive composite cones and deep- ocean trenches.

A) Convergent
B) Strike- slip
C) Divergent
D) Transform

Question 49

What does the plate reconstruction, with the Atlantic Ocean closed up, do to the apparent polar wandering paths for Eurasia and North America, and what can we infer from this?

A) It really indicates that, because opposite polarities attract, the curves became stuck together.
B) It makes them overlap but they are still strangely curved, implying the poles have still shifted so continental drift doesn't solve anything.
C) It indicates that the poles drift counterclockwise with time, implying Earth used to revolve the other way.
D) It makes them coincide, demonstrating that the opening of the Atlantic was the cause for the divergence seen today.

Question 50

What important physical and chemical process occurs to subducted seafloor as it reaches a depth of 100 to 150 kilometres depth in the upper mantle?

A) Heat from the surrounding mantle drives off water and other volatiles from the slab, which escape upwards, lowering the melting point of the overlying asthenospheric mantle.
B) The cooling of the ocean crust from the cold, deep ocean water of the trenches causes the subducted crust to freeze the mantle, cracking and freezing it to generate the largest earthquakes.
C) It experiences nearly a doubling in its density as the subducted basalt recrystallizes to peridotite.
D) The subducted seafloor entirely melts generating a line of explosive volcanoes.

Question 51

How does the polar wander curve for Eurasia confirm Wegener's hypothesis that the Carboniferous (300 m.y.) coal beds were originally deposited when that land mass was near the equator?

A) This means that Eurasia used to sit in the middle of the north Pacific Ocean 300 m.y. ago where the climate is warmer.
B) To have that pole position, the 300 m.y. coal beds must have had a steep magnetic inclination.
C) 300 m.y. ago, the equator and magnetic poles had switched positions, so Eurasia was tropical then.
D) To restore the 300 m.y. paleopole to today's north magnetic pole pushes Eurasia about 40 degrees of latitude farther south than it is today.

Question 52

Mount St. Helens and the other Cascade volcanoes from Mt. Shasta in northern California to Mt. Garibaldi in southwestern B.C. are .

A) a row of young, active, shield volcanoes built as western North America moved over a hot spot deep in the mantle
B) young, active composite cones built on a continental margin above a sinking slab of oceanic lithosphere
C) old, deeply eroded composite cones built before the Pacific Ocean existed
D) old, deeply eroded, basaltic shield volcanoes built when western North America was over the present- day site of the Hawaiian hot spot

Question 53

Deep- focus earthquakes, those between 300 and 700 km below the surface, occur only in association with .

A) mid- ocean ridges
B) hot spots
C) subduction zones
D) transform faults

Question 54

The is (are) a logical evolutionary analog of the African Rift Valleys ten million years from now.

A) Peru-Chile trench
B) Red Sea
C) Ural Mountains
D) San Andreas fault

Question 55

What is the cause of the magmas currently erupting in the Hawaiian Islands?

A) flux- melting associated with subduction and a convergence between two sub- plates in the Pacific basin
B) shallow decompression melting along a mid- Pacific ridge, spreading NE- SW
C) shear melting associated with a mid- Pacific transform fault
D) shallow decompression melting of a fixed mantle plume, with magmas rising through the NW- moving Pacific plate

Question 56

What is the inclination of Earth's magnetic field as recorded in a recent lava flow on a volcano in northern Peru?

A) nearly vertical and pointing south
B) nearly horizontal and pointing north
C) nearly vertical and pointing north
D) nearly horizontal and pointing south

Question 57

In the nomenclature of J. Tuzo Wilson, a very long- lived magma source rising from deep in the mantle is called a(n) _.

A) melt welt
B) old flame
C) hot spot
D) basalt fount

Question 58

first related the symmetrical magnetic patterns in seafloor basalts to seafloor spreading at a mid- ocean ridge.

A) Wegener, Holmes, and Wilson
B) Rodgers, Gershwin, and Hammerstein
C) Morley, Vine, and Matthews
D) Evans, Smith, and Novak

Question 59

The distance between Halifax and London UK each year due to plate movements.

A) increases two metres
B) increases two centimetres
C) decreases eight meters
D) decreases two centimetres

Question 60

A curved line of volcanic islands spaced about 80 km apart along the edge of one plate where two oceanic plates meet is called a(n) .

A) oceanic volcanic rift zone
B) volcanic island arc
C) subsided and failed continental rift
D) hot spot track

Question 61

The former, late Paleozoic super continent is known as .

A) Pangaea
B) Pandemonia
C) Panatopia
D) Pancakea

Question 62

The chaotic accumulation of deformed oceanic sediments, and scraps of ocean crust found plastered onto a convergent continental margins, like that where the Cocos plate subducts beneath western Mexico, is called .

A) a wedgie
B) an accretionary wedge
C) the scrapie
D) a continental margin arc

Question 63

Which one of the following is an important fundamental assumption underlying the plate tectonic theory?

A) Earth's magnetic field originates in the outer core.
B) Earth's diameter has been essentially constant over time.
C) Earth's ocean basins are very old and stable features.
D) Radioactive decay slows down at the extreme pressures of the inner core.

Question 64

Which of the following is not part of the accepted driving mechanism of plate tectonic motions?

A) The Earth's unequal distribution of internal heat is what drives the mantle convection and provides the heat engine.
B) All of the heat for the mantle convection comes from small amounts of radioactive elements in the inner core.
C) Solid state convective flow in the rocky mantle, warm regions rising and cold regions sinking, is the basic driving force for plate motions.
D) Oceanic plates descend and constitute the downward- moving portion of Earth's internal convective flow.

Question 65

The is an example of an active, continent- continent collision.

A) northern movement of Queen Charlotte Islands toward the Aleutian Trench
B) Arabian Peninsula slamming into North Africa under the Red Sea
C) westward movement of the South American plate over the Nazca plate
D) northward movement of India under Eurasia

Question 66

What is the ultimate source for the plate tectonic motions?

Question 67

Provide an example of Wegener's conjectures about continental drift for which there is no evidence.

Question 68

Deep focus earthquakes are associated with a plate boundary.

Question 69

Where is the inclination of Earth's magnetic field the steepest?

A) at the north and south poles
B) in the Bermuda triangle
C) latitudes between 45 and 50 degrees
D) at the equator

Question 70

A typical rate of seafloor spreading in the Atlantic Ocean is .

A) 2 centimetres per year
B) 20 metres per year
C) 2 kilometres per year
D) 2 metres per year

Question 71

plate boundary is characterized by arcs of explosive composite cone volcanoes and deep- ocean trenches.

A) Subduction
B) Divergent
C) Transform
D) Convergent

Question 72

The were formed in the late Paleozoic when sediments in a marine basin were squeezed and crumpled between the converging continents of Europe and Asia.

A) Urals in Russia
B) Andes in South America
C) Alps in Europe
D) northern Canadian Rockies

Question 73

All of the following are evidence supporting the theory of plate tectonics except for .

A) hot spots
B) changes in the Moon's orbit due to shifting plates
C) ocean floor drilling
D) measurements of plate motions

Question 74

Approximately major lithospheric plates exist today.

A) 11
B) 2
C) 4
D) 7

Question 75

What is the most likely explanation for why there are no islands, only deep seamounts and guyots NW of Kauai towards Midway?

A) The Pacific plate moved much faster during the period in question and there wasn't time to build tall volcanoes over the Hawaiian hot spot.
B) The seafloor farther from the current hot spot has aged and cooled off, so the volcanoes eroded and sank below sea level.
C) The hot spot was less vigorous from 27 to 65 m.y. than subsequently.
D) The intervening seafloor is thinner so it sat higher and eroded off all the volcanoes.

Question 76

discovered tranform faults and first proposed that Earth's outer shell comprises several rigid plates.

A) J. Tuzo Wilson
B) James Hutton
C) Charles Darwin
D) Harry Hess

Question 77

Where is the inclination of Earth's magnetic field horizontal?

A) at the equator
B) latitudes between 45 and 50 degrees
C) at the north and south poles
D) in the Bermuda triangle