Chapter 20, Unit 15 Mountain Belts & Continental Crust

_____ are chains thousands of kilometers long composed of numerous mountain ranges. A. Mid-oceanic ridge
B. Volcanic arcs
C. Back arcs
D. Valley and Ridge Province E. Mountain belts

E

During the last couple of decades, geologist have used a _____ approach to gain insight into the growth and wearing away of mountains.
A. tectonic
B. erosional
C. weathering D. system
E. climatic

D

The once deep-seated roots of former Precambrian mountain belts are the _____ rock for the now stable, central part of the continent.
A. cratonic
B. basement
C. core
D. platform E. isostatic

B

In many mountainous regions are found ____, which are characterized by large thrust faults stacked one upon another.
A. fold and thrust belts
B. numerous rock types
C. evidence of intrusions D. patterns of deformation E. volcanic landforms

A

____, intermixed granitic and metamorphic rock, may represent those parts of mountain belts that were once at even deeper levels of the crust.
A. Pegmatites
B. Sutures
C. Migmatites
D. Extensional fabric E. Subduction patterns

C

Frequent earthquakes, offshore trenches, and active volcanoes perched on top of older rock are all indications of ____.
A. old mountain belts
B. stable craton
C. platform
D. Precambrian shield
E. active mountain ranges

E

Geologists believe that when the thick and high part of a mountain belt becomes too high and gravitationally unstable _____ occurs.
A. massive landslides
B. gravitational collapse and spreading
C. volcanic eruptions D. rapid downcutting E. basalt flows

B

In some mountain belts the crust breaks into fault-bounded blocks resulting in _____ mountain ranges.
A. fault-block
B. extremely high
C. extensional
D. isostatically adjusted E. metamorphic

A

The _____ is(are) the product of oceanic-continental convergence and Earth's second highest mountain belt.
A. Appalachians
B. Himalayas
C. Andes
D. Basin and Range E. Sierra Nevada

C

A _____ is a group of closely spaced mountains or parallel ridges that may show a history of intrusive tectonic activity.
A. volcano
B. mountain range
C. back-arc basin
D. spreading center E. any uplifted region

B

The continental crust is _______ beneath mountain belts than under the craton. A. thinner
B. thicker
C. the same thickness
D. more felsic E. more dense

B

Most of the world's mountains existing today are a result of ____. A. intense deformation
B. isostasy
C. weathering and erosion
D. intense deformation and isostasy
E. intense deformation, isostasy, and weathering and erosion

E

Extension and normal faulting take place in a mountain range ____. A. during their early stage of formation
B. when rock at high level flows outward
C. before folding and metamorphism
D. randomly throughout the range's history
E. and is always related to late stage intrusions

B

The region of a continent that has been structurally stable for a long period of time is called the ______.
A. dome
B. basin
C. Precambrian shield D. craton
E. mountain range

D

The _____ resulted from the collision of Asia and Europe. A. Alps
B. Pyrenees
C. Caledonide Mountains
D. Ural Mountains
E. Himalayan Mountains

D

The sedimentary sequences that form on passive margins are predominantly ____. A. shale
B. limestone
C. sandstones
D. andesitic flows
E. shale, limestone, and sandstones

E

Volcanic rocks, mostly _______, accumulate near a convergent plate boundary. A. shales
B. sandstones
C. granites
D. andesites E. marbles

D

The Himalayan Mountains formed as the result of ______ convergence. A. ocean-continent
B. arc-continent
C. ocean-ocean
D. arc-ocean
E. continent-continent

E

A _____ terrane has rock types and ages that do not seem to be related to the rest of the geology of a mountain belt.
A. mixed
B. coupled
C. partial
D. integrated E. suspect

E

If the San Andreas Fault remains active, Los Angeles will continue northward and crash into ___.
A. Alaska
B. Japan
C. the Imperial Valley D. British Columbia E. Hawaii

A

Terranes that can be shown to have traveled great distances are known as _____ terranes. A. accreted
B. exotic
C. suspect
D. cratonic E. shield

B

Late stage normal faulting in a mountain range is a result of _______. A. volcanism
B. igneous intrusions
C. vertical uplift or extension
D. sea-floor spreading
E. geosyncline formation

C

Migmatites must have been transported much higher in the crust during and after ____. A. normal faulting
B. volcanism
C. emplacement of plutons
D. an orogeny E. subduction

D

At the close of the Paleozoic, eastern North America was attached to what is now _______.
A. Europe and Asia
B. China and South America
C. India and Antarctica D. Africa and China
E. Europe and Africa

E

_____ is the detachment of part of the mantle portion of the lithosphere beneath a mountain belt.
A. Delamination
B. Mantle convection
C. Terrane shift
D. Isostatic adjustment E. Craton formation

A

_____ faults in the Tibetan plateau indicate that gravitational collapse is taking place. A. Normal
B. Reverse
C. Thrust
D. Strike-slip
E. High-angle thrust

A

________ beneath the Basin and Range helps to explain the extensive rhyolitic and basaltic eruptions that occurred tens of millions of years after the last orogeny.
A. Obduction
B. Delamination
C. Wilson Cycles
D. Subduction
E. Thickening of the continental crust by "rooting"

B

The cycle of splitting of a supercontinent, opening of an ocean basin, followed by closing of the basin and collision of the continents, is known as a ________.
A. Wegener plan
B. Wilson Cycle
C. delamination plan
D. Hess Process
E. Vine-Mathews system

B

A ______ is the source of sedimentary and volcanic material accumulating along a convergent boundary.
A. subduction zone
B. magmatic arc
C. suspect terrane
D. mid-oceanic ridge
E. folded mountain range

B

Continents grow bigger as _______.
A. accretionary wedges form at the margins
B. gravitational collapse and spreading widens the craton C. mountain belts evolve along their margins
D. uplift and block-faulting takes place
E. isostacy lifts them up

C

Major mountain belts with higher mountain ranges tend to be geologically ___________ relative to those where the mountains are lower.
A. the same age
B. younger than
C. random in age D. older than

B

Geologists regard most bodies of ultramafic rock as being _______. A. intrusions formed during the accumulation stage
B. due to gravitational collapse and spreading
C. due to lithospheric delamination
D. areas left by block faulting and uplift
E. mantle material faulted into the crust during orogeny

E

The present ________ represent rejuvenation following uplift in Late Tertiary time. A. Appalachian Mountains
B. Alps
C. Himalayan Mountains
D. Ural Mountains
E. Sierra Nevada Mountains

A

The system approach regards mountains as the products of three closely interdependent components. Which of the following is not one of those components?
A. plate tectonics
B. meteor impacts
C. climate D. erosion

B

Of the two major mountain belts in North America, the _______ are in the West. A. Urals
B. Himalyan
C. Appalachians
D. North American Cordillera E. Andes

D

A(n) __________ is an episode of intense deformation of the rocks of a region. A. isostatic adjustment
B. geosyncline
C. orogeny
D. buoyancy event
E. basin to dome event

C

The Grand Canyon, Ozark dome, Black Hills, and Adirondacks expose ________. A. a fold and thrust belt
B. ophiolites
C. a Precambrian basement
D. an ancient magmatic arc E. the result of delamination

C

Most of the _____ of the United States has/have a very thin blanket - only 1000 to 2000 meters - of sedimentary rock layers.
A. craton
B. Gulf Coast
C. Rocky Mountain region D. Oregon-Washington coast E. Blue Ridge Mountains

A

According to the concept of ____, lighter less dense continental crust "floats" higher on the mantle than denser oceanic crust.
A. delamination
B. gravitational collapse
C. geosynclines D. block faulting E. isostacy

E

A(n) _________ mountain range, such as the Basin and Range and Tetons, implies a horizontal extension strain.
A. fault block
B. erosional
C. volcanic D. fold
E. strike-slip.

A

Orogenies are associated with ________.
A) convergent plate boundaries
B) divergent plate boundaries
C) transform plate boundaries

A) convergent plate boundaries

Where is the highest plateau in the world?
A) Iceland
B) Australia
C) Western South America
D) Western North America
E) Southwest China

D) Western North America

The Precambrian shield consists of ________.
A) very recent sediments
B) ancient metamorphic and plutonic rocks
C) thick layers of sedimentary rocks
D) flood basalts

B) ancient metamorphic and plutonic rocks

Sedimentary rocks that contain a significant amount of igneous material and outcrop in
mountain belts suggest formation ________.
A) along a passive continental margin
B) along an active continental margin
C) in the Precambrian
D) on the deep ocean floor
E) near a hot spot

B) along an active continental margin

The continental crust is thicker ________.
A) under the craton than under mountain belts
B) under older mountain belts than under younger ones
C) under younger mountain belts than under older ones
D) under the U.S. Midwest than under the western states
E) underneath the Appalachians than under the Rockies

C) under younger mountain belts than under older ones

A flipping subduction zone is most closely associated with ________.
A) the collision of an arc with a continent
B) gravitational collapse and spreading
C) seafloor spreading
D) continental collision
E) fold and thrust belts

A) the collision of an arc with a continent

The Alps are dominated by ________.
A) normal faults
B) reverse faults
C) transverse faults

B) reverse faults

Which of the following is not associated with a fault-block mountain range?
A) Normal faults
B) Extension
C) The Sierra Nevada
D) The Tetons
E) Rapid uplift

E) Rapid uplift

What is an accreted terrane?
A) A sequence of rocks with an unknown origin
B) A sequence of rocks that did not form at its present site
C) A sequence of sedimentary rocks formed on a continent
D) A sequence of sedimentary rocks formed on the ocean floor
E) A sequence of rocks that has been uplifted in an orogeny

E) A sequence of rocks that has been uplifted in an orogeny

The mountain belt that forms the western part of North America is called the
A) Appalachians
B) North American Cordillera
C) Himalaya
D) Andes
E) Rockies

B) North American Cordillera

The North American craton
A) covers the central part of the United States and Canada
B) has only 1,000-2,000 meters of sedimentary rock overlying basement rock
C) has rock beneath any sedimentary rock that is old plutonic and metamorphic rock
D) All of these choices are correct.

D) All of these choices are correct

The Precambrian shield
A) contains geologically young rocks
B) occurs only in mountainous regions
C) is a complex of Precambrian metamorphic and plutonic rocks exposed over a large area
D) All of these choices are correct.

C) is a complex of Precambrian metamorphic and plutonic rocks exposed over a large area

Folds and reverse faults in a mountain belt suggest
A) crustal shortening
B) tensional stress
C) deep-water deposition of the sediment
D) All of these choices are correct.

A) crustal shortening

The likely reason that the Himalaya is much higher than the adjoining Tibetan Plateau is:
A) Heavy precipitation results in rapid erosion in the Himalaya.
B) The crust of the Himalaya is less dense than that of the Tibetan Plateau.
C) The Tibetan Plateau is being subducted.
D) The mantle beneath the Himalaya is hotter than that beneath the Tibetan Plateau.

A) Heavy precipitation results in rapid erosion in the Himalaya

To explain fold and thrust belts, simultaneous normal faulting, and how once deep-seated
metamorphic rocks rise to an upper level in a mountain belt, geologists use a model called
A) tectonism
B) gravitational collapse and spreading
C) orogeny
D) faulting

B) gravitational collapse and spreading

76) The Wilson Cycle describes
A) the cycle of uplift and erosion of mountains
B) the movement of asthenosphere
C) the block-faulting that occurs at mountains
D) the cycle of splitting of a supercontinent, opening of an ocean basin, followed by closing of
the basin and collision of continents

D) the cycle of splitting of a supercontinent, opening of an ocean basin, followed by closing of
the basin and collision of continents

The detachment of part of the mantle portion of the lithosphere beneath a mountain belt is
called
A) gravitational collapse
B) rifting
C) lithospheric delamination
D) None of these choices are correct.

C) lithospheric delamination

Which is not a type of terrane?
A) accumulated
B) exotic
C) suspect
D) accreted

A) accumulated

Which is a source for terranes?
A) microcontinents
B) fragments of distant continents
C) island arcs
D) All of these choices are correct.

D) All of these choices are correct.