Read through each question and test yourself.Then, click on ìanswersî to see how well you did.I did not make these questions upóthey came from a ìtest bankî.SoÖ. the phrasing and style of the questions on the midterm will differ from these ­they will be more similar to the first quiz youíve already taken ­but I will use several of these questions on the midterm.

At this point in our course, you should be able to answer most of these questionsóbut there are some that we wonít get to until next week.Good luck!

1.Mauna Loa, the largest known volcano in the Hawaiian Islands, is an example of a _____.
 

A.stratovolcano

B.cinder cone

C.shield volcano

2.Basaltic lavas _____.

A. contain more iron and magnesium than rhyolitic lavas

B.contain more silica than rhyolitic lavas

C.are more viscous than rhyolitic lavas

D.contain a greater proportion of trapped volatiles than rhyolitic lavas

3.Of the three primary forms of subaerial (on land) volcanoes, _____ consist of a simple, conical pile of ejected debris.
 

A.stratovolcanoes

B.cinder cones

C.shield volcanoes

4.Basaltic lavas which solidify at the surface before flow ceases fracture irregularly, producing a sharp-surfaced lava rock named _____.
 

A.pahoehoe

B.aa

C.pumice

D.pillow

5.Of the three primary forms of subaerial (on land) volcanoes, _____ have the most gently sloping sides, due to the low viscosity of the basaltic lavas which form them.
 

A.stratovolcanoes

B.cinder cones

C.shield volcanoes

6.   Of the three primary forms of subaerial volcanoes, _____ are sometimes referred to as "composite volcanoes."
 

A.stratovolcanoes

B.cinder cones

C.shield volcanoes

7.Hot-spot volcanoes _____.

A.can arise from the ocean floor

B.can arise on continents

C.may arise in the interior of lithospheric plates

D.All of the above are possibilities.

8.As compared to subaerial basaltic lavas, submarine basaltic lavas differ in that they _____.

A.always produce violent pyroclastic debris flows

B.produce large crystals of pyroxene and plagioclase

C.form pillow-like mounds because they cannot flow as far from their source

D.All of the above are correct.

9.The hot-spot track associated with the Hawaiian Islands and Emperor Seamounts _____.

A.shows that the Pacific Plate has been stationary over the last 30 million years

B.occurs along a divergent plate boundary

C.occurs along a convergent plate boundary

D.shows that the Pacific Plate has been moving northwest for the last 30 million years

10.Pahoehoe _____.

A.forms when basaltic lava flows solidify and cease flow simultaneously

B.has a smoother texture than aa

C.is easier to walk on than aa is

D.All of the above are correct.

11.Of the three primary forms of subaerial volcanoes, _____ are the largest in areal extent.
 

A.stratovolcanoes

B.cinder cones

C.shield volcanoes

12.Eruptions emitted through elongate cracks at the surface, as opposed to through the vents of volcanic cones, are termed _____.
 

A.hot-spot eruptions	B.fissure eruptions
C.phreatomagmatic eruptions	D.pyroclastic eruptions

13.Mt. Fuji in Japan is an example of a _____.
 

A.stratovolcano	B.cinder cone	C.shield volcano

14.Ash, cinders, and blocks are all types of _____.
 

A.pyroclastic debris	B.lava flows
C.Pele's hair	D.volcanoes

15.Pillow lavas are associated with _____.
 

A.continental rhyolitic eruptions	B.continental basaltic eruptions
C.submarine rhyolitic eruptions	D.submarine basaltic eruptions

16.Of the three primary forms of subaerial volcanoes, _____ consist of alternating layers of pyroclastic materials and solidified lava.
 

A.stratovolcanoes

B.cinder cones

C.shield volcanoes

17.Explosive or voluminous eruptions may cause the volcano to collapse upon the floor of the (now empty) magma chamber, producing a broad depression termed a _____.
 

A.crater

B.lahar

C.caldera

D.fissure

18.Whether an eruption will primarily produce lava flows or pyroclastic debris is influenced by _____.
 

A.the viscosity of the lava	B.the composition of the lava
C.the proportion of volatiles within the lava	D.All of the above are correct.

19.All volcanic eruptions pass through the crater at the volcanic summit.
 

A.true

B.false

20.A fast moving flow consisting of a mixture of water and volcanic debris is termed a _____.
 

A.lahar	B.glowing avalanche
C.flood basalt	D.stratovolcano

21.Volcanoes produce no other hazards besides lava flows and pyroclastic debris.
 

A.true

B.false

22.Marine magnetic anomaly belts are widest when and where _____.

A.continents are joined to form supercontinents

B.sea-floor spreading rates are relatively rapid

C.sea-floor spreading rates are relatively slow

23.The magnetic field of Earth in the geologic past _____.

A.is unknown, but it is assumed to have been identical to today's

B.is known to have been constant through geologic time, due to remnant magnetization of iron-rich minerals in rocks

C.is known to have experienced numerous polarity reversals, due to remnant magnetization of iron-rich minerals in rocks

D.is known to have been constant through time, on the basis of theoretical calculations

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

A.he didnít like donuts

B.he could not conceive of a 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

25.Sea-floor 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

26.Volcanoes which have submerged beneath the surface of the sea are termed _____.
 

A.mid-ocean ridges	B.seamounts
C.fracture zones	D.continental rises

27.The age of oceanic crust _____ with increasing distance from a mid-ocean ridge.
 

A.increases

B.decreases

28.Marine magnetic anomaly belts run parallel to _____.
 

A.mid-ocean ridges	B.fracture zones
C.continental coastlines	D.continental shelves

29.The grain size of an igneous rock is determined primarily by _____.

A.its mineral composition

B.its volatile content

C.its pressure during formation

D.how rapidly it cooled during crystallization

30.Bombs, ash, and cinders are all examples of _____.
 

A.intrusive igneous rocks	B.hot-spots
C.volatiles	D.pyroclastic debris

31.Most commonly, silicic igneous rocks _____.

A.contain more iron and magnesium than intermediate rocks

B.are lighter in color than mafic rocks

C.are darker in color than mafic rocks

D.are found in oceanic crust

32.Igneous rocks _____.

A.are formed through the freezing of melt

B.can be produced at the surface of the Earth as well as deep below the surface

C.are the most common type of rocks within the Earth

D.All of the above are correct.

33.The difference between lava and magma is that _____.

A.magma is light in color and lava is darker

B.magma usually has mafic composition and lava usually has silicic composition

C.magma is found beneath the Earth's surface, whereas lava has reached the surface

D.magma flows more quickly than lava

34.A famous example of hot-spot volcanism occurs at _____.
 

A.the Aleutian Islands of Alaska	B.the Andes Mountains
C.Hawaii	D.Mt. St. Helens, Washington

35.Coarse-grained gabbro is most similar in mineral composition to fine-grained _____.
 

A.andesite	B.basalt
C.komatiite	D.rhyolite

36.If the volatile content of magma is increased, its viscosity will _____.
 

A.increase

B.decrease

C.stay the same

37.If a body of magma cools, its viscosity will _____.
 

A.increase

B.decrease

C.stay the same

38.An island volcanic arc occurs at _____.
 

A.the Aleutian Islands of Alaska	B.the Andes Mountains
C.Hawaii	D.Mt. St. Helens, Washington

39.Coarse-grained granite is most similar in mineral composition to fine-grained _____.
 

A.andesite	B.basalt
C.komatiite	D.rhyolite

40.Volatiles refer to substances that _____.

A.crystallize most rapidly out of a melt

B.melt immediately upon contact with a hot body of magma

C.have a tendency to evaporate and are stable as gases

41.Coarse-grained diorite is most similar in mineral composition to fine-grained _____.
 

A.andesite	B.basalt
C.komatiite	D.rhyolite

42.A sill is _____.

A.a horizontal tabular intrusion that lies parallel to exiting layers

B.a cooled layer of lava

C.an intrusion formed within the magma chamber of volcano

D.a vertical tabular intrusion that cuts across preexisting layers

43.Pieces of country rock absorbed by an intrusive body and that do not melt form _____.
 

A.porphyroblasts	B.phenocrysts
C.xenoliths	D.gastroliths

44.Pillow basalts attain their distinctive blob-like shapes because their parent lavas do not travel far prior to solidification.This is because _____.

A.the parent lavas are completely devoid of volatiles and thus travel slowly

B.the parent lavas erupt underwater and thus cool very quickly

C.the parent lavas are highly silicic and thus travel slowly

D.the parent lavas are ultramafic and thus freeze at exceptionally high temperatures

45.All other factors being equal, intrusive rocks that form deep within the Earth _____ than intrusive rocks that cool near the surface.

A.are more silicic

B.contain a smaller proportion of volatiles

C.cool more slowly

D.cool more rapidly

46.A dike is _____.

A.a horizontal tabular intrusion that lies parallel to exiting layers

B.a cooled layer of lava

C.an intrusion formed within the magma chamber of volcano

D.a tabular intrusion that cuts across preexisting layers

47.A continental volcanic arc occurs at _____.
 

A.the Aleutian Islands of Alaska	B.the Andes Mountains
C.Hawaii	D.Japan

48.Obsidian _____.

A.is volcanic glass

B.possesses conchoidal fracture

C.typically is silicic in composition

D.All of the above are correct.

49.If a body of magma becomes more silicic, its viscosity will _____.
 

A.increase

B.decrease

C.stay the same

50.When magma crystallizes, _____ are formed.
 

A.intrusive igneous rocks	B.extrusive igneous rocks
C.volatiles	D.pyroclastic debris

51.The most abundant minerals belong to chemical group termed the _____.
 

A.silicates	B.carbonates
C.halides	D.oxides

52.Cleavage in minerals refers to _____.

A.a tendency to break in an irregular pattern

B.a tendency to break along planes of weakness

C.the sharpness of edges between crystal faces

D.the development of distinct crystal faces

53.All minerals are chemical compounds, i.e., are composed of one or more than one element.
 

A.true

B.false

54.Which common mineral is found in most kitchens?
 

A.flour

B.sugar

C.halite

D.mustard

55.At a divergent plate boundary, two opposed plates _____.

A.move towards one another

B.move away from one another

C.slide past one another

56.Subduction zones are _____.

A.convergent plate boundaries

B.divergent plate boundaries

C.transform plate boundaries

57.Seamount chains are the remnants of volcanoes formed within the interior of lithospheric plates; these volcanoes form by _____.
 

A.cinder cones	B.hot spots
C.butte volcanoes	D.deep-hole volcanoes

58.Sliding motion along transform faults caused the segments of the mid-ocean ridges to become dislocated with respect to one another.
 

A.true

B.false

59.At a convergent plate boundary, two opposed plates _____.

A.move towards one another

B.move away from one another

C.slide past one another

60.Tectonic plates might consist of _____.

A.continental lithosphere only

B.oceanic lithosphere only

C.either oceanic or continental lithosphere, or a combination of both

D.either oceanic or continental lithosphere, but not both

61.On average, continental lithosphere _____.

A.is thicker than oceanic lithosphere

B.contains more mafic rocks than does oceanic lithosphere

C.is more dense than oceanic lithosphere

D.contains no crustal material, consisting solely of lithified upper mantle

62.When two bodies of continental lithosphere are pulled together at a convergent boundary, the result is _____.
 

A.subduction

B.collision and mountain formation

63.At a subduction zone, the overriding 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

64.If a continental rift successfully breaks a single continent into two discrete pieces, the former rift valley becomes a _____.
 

A.subduction zone	B.mid-ocean ridge
C.transform fault zone	D.hot spot

65.At a transform plate boundary, _____.

A.old lithosphere is consumed

B.new lithosphere is created

C.A and B are both correct.

D.None of the above

66.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

67.The youngest sea floor occurs _____.

A.along passive margins

B.along active margins

C.along mid-ocean ridges

D.randomly distributed over the entire ocean basin

68.Hawaii is an example of a _____.
 

A.hot-spot volcano	B.mid-ocean ridge volcano
C.volcanic island arc	D.transform margin

69.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

70.At a transform plate boundary, two opposed plates _____.

A.move towards one another

B.move away from one another

C.slide past one another

71.Tectonic plates move at rates that are approximately _____.
 

A.1-5 cm every 1,000 years	B.1-15 cm / year
C.1-15 m / year	D.10-100 m / year

72.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, which plow through the weaker oceanic rocks

D.very thick (approximately 1/4 of the Earth's radius)

73.The average thickness of continental lithosphere is about _____.
 

A.30 km

B.60 km

C.150 km

D.10,000 km

74.Mid-ocean ridges are _____.

A.convergent plate boundaries

B.divergent plate boundaries

C.transform plate boundaries

75.At a subduction zone, the downgoing (subducting) plate _____.

A.is always composed of continental lithosphere

B.is always composed of oceanic lithosphere

C.may be composed or either oceanic or continental lithosphere