Deck 9: Crustal Deformation

Question 1

During mountain building episodes, originally flat lying sedimentary and volcanic rocks are often bent into a series of ________.

A)heaves and sags
B)horsts and grabens
C)folded anticlines and synclines
D)box pleats

Answer 1

C

Question 2

When an overturned fold lies on its side it is called ________.

A)lazy
B)reclining
C)recumbent
D)wasted

Answer 2

C

Question 3

Brittle deformation would be favoured over plastic deformation in which of the following conditions?

A)high confining pressures
B)warmer temperatures and high confining pressures
C)cooler temperatures and low confining pressures
D)great depths

Answer 3

C

Question 4

When measuring the orientation of a planar structure in rocks the dip direction is measured ________ to the strike.

A)at 90 degrees
B)parallel
C)backwards
D)sideways

Question 5

When does permanent rock deformation occur?

A)once its elastic limit is surpassed
B)only after it comes to be located on a plate margin
C)once it is completely lithified and becomes inflexible
D)when it goes on a real bender

Question 6

Which is not evidence of former structural deformation or major tectonic forces that affected rocks of continental interiors?

A)massively folded metamorphic rock units with structures that resemble putty
B)faults which juxtapose vastly different rock types like deep lower crustal granites and fluvial deposits containing coal beds
C)extensive, flat lying younger beds disconformably overlying older strata
D)extinct marine fossils found thousands of metres above sea level in tilted strata in the mountains

Question 7

Belts of ________ in layered sedimentary rocks are evidence for horizontal compression and shortening.

A)normal faults
B)strike-slip faults
C)horsts and grabens
D)tight folds

Question 8

A syncline is ________.

A)a fold in which the older central strata dip away from the axis
B)a fold with only one limb
C)a fold in which older flanking strata dip toward the axis
D)a paralytic drunken fold characterized by recumbent limbs

Question 9

Most crustal deformation occurs in active tectonic zones ________.

A)at the base of sedimentary basins
B)along plate margins
C)deep within old plate interiors
D)in thick piles of unconsolidated sedimentary strata

Question 10

The outer flanks of the Colorado Plateau are marked by a series of ________ displaying a narrow zone of steeply inclined beds that flatten out to form elevated upland areas.

A)overturned anticlines
B)monoclines
C)recumbent synclines
D)imbricate thrust faults

Question 11

Which one of the following stress situations results in folding of flat-lying, sedimentary strata?

A)horizontally directed, compressive stresses
B)vertically directed, extensional or stretching stresses
C)horizontally directed, extensional stresses
D)vertically oriented digital stresses

Question 12

Which one of the following is true for anticlines but not for synclines?

A)The limbs dip or are inclined towards the fold axis.
B)Some may be asymmetric and some may have plunging axes.
C)The deeper strata are buckled upward along the fold axis.
D)After erosion, the younger strata are exposed along the axial region of the fold.

Question 13

Which one of the following statements regarding rock deformation and strength is correct?

A)Rupture and plastic deformation occur when stresses and strain rates exceed the elastic limit of a material.
B)Rocks undergo plastic deformation less readily as temperatures and pressures increase.
C)Elastic deformation is accomplished through internal flow of material.
D)When rocks are subjected to stress for long time spans, very small, plastic deformations accumulate to produce large, permanent, elastic deformations.

Question 14

Which one of the following is consistent with deformation by folding?

A)Horizontal distance is shortened perpendicular to fold axes.
B)The crust is thinned.
C)The crust is stretched and elongated.
D)Horizontal distance perpendicular to fold axes is lengthened.

Question 15

When do rocks deform?

A)after their bonds weaken when they get really old
B)only during major earthquakes
C)whenever they are subjected to stresses or strain rates which exceed their own strength
D)when they are quarried or mined, otherwise they are too strong to break under natural conditions

Question 16

When do rocks succumb to ductile deformation?

A)at shallow depth, at low confining pressure, and low temperature
B)at great depth under active mountain belts with high confining pressure and low strain rates or prolonged strain
C)in fault zones with intermittent high strain rates
D)on the rims of meteorite impact craters

Question 17

In detail, the elegant fold and flow patterns developed in deformed rock are achieved by ________.

A)a single application of a complex set of stresses
B)Earth's "Great Laundress"
C)an ongoing combined effect of: distortion, sliding, and rotation of individual mineral grains
D)very rapid application of two or more strains

Question 18

What are the three types of differential stress in the Earth's lithosphere?

A)compression, shear, and tension
B)confined, unconfined, and directed
C)hydrostatic, lithostatic, and vibratory
D)upwards, downwards, and sideways

Question 19

How does elastic deformation of rocks differ from brittle or plastic deformation?

A)It only occurs are very fast or high strain rates.
B)It is reversible or recoverable and when the stress is removed, the rocks snap back to their original shape or position.
C)It only happens to rocks that can bounce.
D)It can only occur once and never happens in cycles.

Question 20

What kind of stress creates most fold belts?

A)compressional
B)decompressional
C)shear
D)tensile

Question 21

What is the cause of most earthquakes?

A)folding deep under active mountain belts
B)nuclear weapons tests in secret underground locations
C)sudden movements from elastic strain release and rupture along pre-existing faults on or near to plate boundaries
D)volcanic eruptions

Question 22

How wide is the San Andreas Fault Zone at its northern and southern ends?

A)<1 kilometre
B)5 kilometres
C)10 kilometres
D)>100 kilometres

Question 23

A ________ is a planar fracture in rock along which there has been no displacement.

A)joint
B)shear zone
C)monocline
D)transformed crack

Question 24

________ joints form when igneous rocks cool and develop pillar-like columns.

A)Reverse
B)Columnar
C)Offset
D)Backward

Question 25

A deeply eroded, structural basin would exhibit ________.

A)outcrops of the oldest strata in the centre of the basin
B)inward dipping strata oriented in roughly circular, outcrop patterns
C)strata dipping outward away from the centre of the basin
D)older strata at the edges of a basin dip away from a central, horizontal, fold axis

Question 26

Name two landforms or distinctive landscape features that mark the trace of the San Andreas Fault.

A)chevron folds with a northwesterly plunge on the eastern side of the fault
B)artichoke fields that have been stretched to 10 times their initial width perpendicular to the fault
C)long straight escarpments, narrow ridges, and sag ponds
D)hot springs and active geyser fields in central California

Question 27

A ________ is a prominent angular ridge formed by the differential erosion of tilted, alternating hard and soft strata.

A)mesa
B)wadi
C)hogback
D)scarp face

Question 28

The two different sides of a dip-slip fault are called ________.

A)the boothill and the hanging valley
B)the dingwall and the dongwall
C)the footwall and the hanging wall
D)the nose banger and the toe stubber

Question 29

When folding occurs, rocks situated in the hinges (on the axes)of the folds are ________.

A)crushed and compressed to make them atypically dense and tight
B)elongated and pulled apart to produce tensional joints and greater fracture porosity
C)plastically deformed and extruded down the flanks of the folds
D)sheared out parallel to the fold limbs

Question 30

Which one of the following best describes the geology of the Black Hills region in South Dakota?

A)an eroded syncline with Cretaceous and Tertiary younger, sedimentary strata in the axial region, and older, metamorphic rocks around the margins
B)a basin filled with folded, sedimentary rocks and thick Precambrian coal beds
C)a large graben deeply eroded by Pleistocene glaciers
D)an elongate upwarped dome between the Cheyenne and Belle Fourche Rivers, flanked by hogbacks of the Dakota Sandstone and cored by older crystalline igneous and metamorphic rocks

Question 31

Broad downwarps in the basement rock may deform the overlying sedimentary cover strata to generate large elliptical to circular folds called ________.

A)basins
B)doubly plunging anticlines
C)domes
D)monoclines

Question 32

There were 11 earthquakes M>6.9 on the San Andreas Fault between 1812 and 1994.On average, how many years pass between earthquakes of this size, somewhere along the fault?

A)16.5 years
B)1)65 years
C)165 years
D)1650 years

Question 33

Which statement is not true about joints?

A)can result from igneous cooling
B)can result from unloading of exposed batholiths
C)can result from ductile deformation
D)can result from tension near fold axes

Question 34

Joints in rocks are characterized by ________.

A)closely spaced, parallel faults along which the blocks have moved in opposite directions
B)structures formed where normal and reverse faults intersect
C)roughly parallel fractures separating blocks that show no appreciable displacement
D)small cylindrical Cannabis fossils found in the Doobie-doo sandstone

Question 35

The Michigan geologic map shows older Precambrian crystalline metamorphic rocks, surrounding Paleozoic marine strata (in roughly circular patterns), surrounding a central core area of Carboniferous rocks.What is this structure?

A)a dome
B)a recumbent horst
C)a klippe
D)a basin

Question 36

Considering the largest earthquakes to occur along the San Andreas Fault, which was the most damaging?

A)1906 San Francisco
B)1857 Fort Tejon
C)1952 Kern County
D)1994 Northridge

Question 37

Normal and reverse faults are characterized mainly by ________.

A)strike slip
B)horizontal slip
C)dip slip
D)camisole slip

Question 38

Vertical displacements along dip-slip faults can produce long low breaks in the landscape or cliffs called ________, that can show the relative sense of motion across the fault.

A)dipsy-doodles
B)fault scarps
C)hanging walls
D)strike hurdles

Question 39

Broad upwarps in the basement rock may deform the overlying sedimentary cover strata to generate large elliptical to circular folds called ________.

A)anticlines
B)domes
C)doubly plunging synclines
D)monoclines

Question 40

When rock is broken and pulverized as the sides of a fault grind past each other, this generates a loosely coherent, easily moved and easily eroded material called fault ________.

A)breccia
B)gouge
C)grot
D)slickensides

Question 41

Which one of the following would not be a characteristic of the San Andreas fault zone?

A)steep, near vertical, dip-slip, fault scarps
B)sag ponds
C)deformed, broken, and pulverized bedrock
D)laterally offset stream channels

Question 42

________ are planar extensional structures which thin the crust in response to horizontally directed, tensional stresses.

A)Normal faults
B)Anticlines
C)Reverse faults
D)Thrust faults

Question 43

In thrust faulting, ________.

A)grabens develop on the footwall block
B)the crust is shortened and thickened
C)horizontal, tensional stresses drive the deformation
D)the hanging wall block slips downward along the thrust fault

Question 44

The Great Rift Valley of East Africa is characterized by ________.

A)mainly thrust faulting as Africa collides with Arabia
B)a belt of anticlinal and synclinal folding formed by Africa's collision with Madagascar
C)a valley formed from a series of grabens, nearly 6000 kilometres long and flanked by tilted horsts, formed mainly by normal faulting as East Africa begins to split apart
D)mainly transform faulting along zones connecting the rift with the Red Sea

Question 45

In a ________ fault, the hanging wall block moves up over the footwall block.

A)normal
B)detachment
C)reverse or thrust
D)strike slip

Question 46

Crowsnest Mountain on the Lewis thrust in Alberta is an eroded thrust-outlier called a ________.

A)fenster
B)inselberg
C)klippe
D)soul thrust

Question 47

A transform fault is ________.

A)a lithospheric scale, strike-slip fault that forms the boundary between tectonic plates in shear, such as at oceanic ridge offsets
B)a dip-slip fault connecting an anticline with a syncline
C)a reverse fault that steepens into a thrust fault
D)the rift-bounding faults parallel to the axial valley on a mid-ocean ridge

Question 48

What kind of faults occur where the crust is being compressed?

A)normal
B)reverse and thrust
C)strike slip
D)chronic

Question 49

A horst is ________.

A)an uplifted block bounded by two normal faults
B)a downdropped block bounded by two reverse faults
C)an uplifted block bounded by two reverse faults
D)an inflexible square head surrounded by immovable faults

Question 50

In a normal fault ________.

A)the hanging wall block, below an inclined fault plane, moves downward relative to the other block
B)the footwall block, below an inclined fault plane, moves downward relative to the other block
C)the hanging wall block, above an inclined fault plane, moves downward relative to the other block
D)the footwall block, above an inclined fault plane, moves upward relative to the other block

Question 51

________ are the products of horizontally directed, tensional stresses.

A)Normal faults
B)Crustal thickening
C)Reverse faults
D)Thrust faults

Question 52

A reverse fault is one in which ________.

A)the hanging wall block has moved up relative to the footwall block along an inclined fault
B)the block above the fault plane has moved backwards with respect to the other block
C)one block has moved downward and the other moved horizontally along a vertical fault
D)both blocks have moved horizontally in opposite directions along an inclined fault

Question 53

A ________ fault has little or no vertical movements of the two blocks.

A)oblique-slip
B)strike-slip
C)dip-slip
D)stick-shift

Question 54

Since the San Andreas fault started moving about 29 million years ago it has moved a total distance of 560 kilometres.How many centimetres does it move per year on average?

A)0)193 cm/yr
B)0)518 cm/yr
C)1)93 cm/yr
D)5)18 cm/yr

Question 55

A thrust fault has ________.

A)slickensides parallel to its strike
B)a shallow inclination less than 45° and a hanging wall that slid down relative to the footwall
C)a shallow inclination less than 45° and a hanging wall that rode up over the footwall
D)a steep inclination more than 45° and a hanging wall that rode up over the footwall

Question 56

A thrust fault is best described as ________.

A)a steeply inclined, oblique-slip fault
B)a low-angle, reverse fault
C)a vertical, normal fault
D)a near vertical, strike-slip fault

Question 57

A graben is characterized by ________.

A)a hanging wall block that has moved up between two reverse faults
B)a footwall block that has moved up between two normal faults
C)a hanging wall block that has moved down between two normal faults
D)a footwall block that has moved down between two reverse faults

Question 58

Most high angle reverse faults ________ in regions dominated by other types of faulting.

A)are small and accommodate local displacements of a few metres
B)exist at the very largest scales and delineate the edges of most major mountain belts
C)occur in local zones of crustal extension
D)occur where tectonic stresses frequently switch back an forth

Question 59

The ________ in California is the boundary between the North American and Pacific lithospheric plates.

A)San Andreas strike-slip fault
B)Garlock left-lateral strike-slip fault
C)Moine thrust fault
D)Queen Charlotte-Fairweather right-lateral strike-slip fault

Question 60

Igneous and metamorphic rocks exposed in the "stable" interiors of continents have necessarily been uplifted from much deeper levels in the Earth's crust.

Question 61

As long as it is not in a region of active faulting, the structures in the bedrock are not of major concern for buildings or engineers designing construction projects like dams or nuclear power plants.

Question 62

Many oil and gas deposits and artesian bedrock aquifers occur in geologic reservoirs within structural traps.

Question 63

The oldest, sedimentary rock strata are exposed along the axial parts of deeply eroded anticlines.

Question 64

The two sides of a fold are called its lobes.

Question 65

Fractures which appear in unloaded rock, yet do not involve any fault slippage, are called joints.

Question 66

Rocks resist deformation and maintain their rigid shapes until they fault or fracture.

Question 67

A dip measurement includes both the angle of inclination and the compass direction from which the rock is inclined (uphill direction).

Question 68

Downwarped regions of the crust with closed elliptical or circular outcrop patterns that preserve sedimentary strata are called basins.

Question 69

Weak differential stresses which are unable to deform solid rock initially, may still cause rock to flow like putty if applied for a sufficiently extended period of time.

Question 70

When stress is applied gradually, rocks first respond by deforming elastically.

Question 71

Horizontal, compressive deformation involves shortening and thickening of the crust.

Question 72

Rocks that display contorted folds and other evidence of ductile flow usually were deformed at great depth.

Question 73

Strike, the geologic trend line, is the intersection of a dipping surface of rock with the horizontal, and its direction is measured by the compass away from true north.

Question 74

The cause of most monoclines is crustal convergence or compression.

Question 75

Most earthquakes involve the release of brittle energy that was stored up gradually between earthquake cycles.

Question 76

Rock salt forms ductile diapir "intrusions" up through overlying shales because it it gets hot enough to melt at great depths below the sedimentary basin.

Question 77

The 1976 failure of the Teton (clay-earthfill)Dam in Idaho was due water flow in fractured and jointed volcanic bedrock beneath the dam.

Question 78

While weaker rocks like shale or rock salt will fracture or flow when subjected to stresses, harder rocks like granite, quartzite and peridotite rarely deform.

Question 79

Plastic (ductile)deformation occurs more readily in warm rock than in cool rock.

Question 80

Most earthquakes form a new fault where one did not exist before.