Deck 7: Metamorphism: a Process of Change

Question 1

A buried body of aragonitic limestone is recrystallized at low temperatures and pressures,producing calcite; this is an example of ____________.

A) diagenesis
B) erosion
C) metamorphism
D) weathering

Answer 1

A

Question 2

All metamorphic rocks are formed within a fairly narrow range of temperature,approximately 400 to 600°C.

Answer 2

False

Question 3

Net chemical change in metamorphic rock induced by reaction with hot groundwater is termed ____________.

A) foliation
B) metasomatism
C) anachronism

Answer 3

B

Question 4

Consult the figure below.Compared to low-grade metamorphic rocks,high-grade rocks ____________.

A) only occur at depths of 30 km
B) are produced closer to the surface, high in the stratigraphic column
C) are produced at greater temperatures and pressures
D) are produced at cooler temperatures, but greater pressures

Question 5

Consult the figure below.Spreading peanut butter on bread is an application of ____________.

A) normal stress
B) shear stress

Question 6

If someone were to put a rock on the table in front of you,how might you determine that it was a metamorphic rock?

A) by looking for one specific mineral that is formed during metamorphism
B) by examining its specific gravity
C) by examining it for minerals typically found in other rock types, such as quartz
D) by looking for distinctive arrangements of mineral grains not found in other rock types

Question 7

Squashing a fly with a flyswatter is an application of ____________.

A) normal stress
B) shear stress

Question 8

Why,when you heat a rock,do its components transform into new material?

A) The heat causes the minerals to melt and rearrange.
B) The heat causes the atoms to vibrate rapidly and rearrange.
C) As a liquid, the minerals are free to change composition.
D) As a liquid, the atoms can more easily flow throughout the rock.

Question 9

Differential stress will cause crystals to align in a preferred orientation unless the crystals are ____________.

A) primarily mica
B) platy
C) equant
D) elongate

Question 10

Metamorphism may be induced by ____________.

A) contact with a hot pluton
B) contact with hot groundwater
C) heat and pressure associated with deep burial
D) All of the above are correct.

Question 11

A buried body of shale is subjected to differential stress,causing clay minerals to realign and produce slate; this is an example of ____________.

A) diagenesis
B) erosion
C) metamorphism
D) weathering

Question 12

Metamorphism,in broadest terms,involves ____________.

A) the settling of crystals in a melt as it cools
B) the sorting of grains by size, as is accomplished by rivers and beach waves
C) cementation of loose grains and precipitation of new minerals into pore spaces
D) changes in mineralogy and texture in response to heat and stress

Question 13

The development of a preferred orientation of large,flaky mica crystals within metamorphic rock is termed ____________.

A) slaty cleavage
B) phyllitic luster
C) schistosity
D) compositional banding

Question 14

Metamorphism brings changes in mineral arrangement and the texture of rocks,but it never leads to new mineral assemblages.

Question 15

Which of the following processes CANNOT occur in the formation of metamorphic rock?

A) realignment of minerals so that they develop a preferred orientation
B) segregation of minerals into layers of different compositions
C) solid-state rearrangement of atoms or ions to create a new assemblage of minerals
D) complete remelting of the rock, followed by solidification to form a new rock

Question 16

A body of gneiss is subjected to heat and forms a melt.Later the melt cools and crystallizes to form a(n)____________.

A) metamorphic rock
B) igneous rock
C) sedimentary rock

Question 17

The protolith subjected to metamorphism ____________.

A) is always metamorphic rock
B) is always igneous rock
C) is always sedimentary rock
D) may belong to any of the three primary rock types

Question 18

Which of the following is an adequate analogy for the pressure a metamorphic rock experiences?

A) A pile of frosting is sheared with a side-to-side motion.
B) When a pile of frosting is pushed down on, it spreads out evenly.
C) An air-filled balloon swells as it experiences less pressure.
D) An air-filled balloon becomes much smaller at 10-m depth in a lake.

Question 19

Clay minerals within a buried body of slate are recrystallized at high temperatures and pressures to form mica,producing a rock called phyllite; this is an example of ____________.

A) diagenesis
B) erosion
C) metamorphism
D) weathering

Question 20

At the Earth's surface,potassium feldspar reacts with water to form clay; this is an example of ____________.

A) diagenesis
B) erosion
C) metamorphism
D) weathering

Question 21

In the formation of gneiss from granite,the distinctive compositional bands form due to ____________.

A) crystals migrating within the rock
B) crystals dissolving, and atoms and ions migrating and reorganizing as new crystals
C) crystals melting, with new crystals solidifying in color bands
D) the bizarre and seemingly unknowable nature of the blueschist metamorphic facies

Question 22

The mineral assemblage within metamorphic rock is ____________.

A) always identical to that found within the protolith
B) dependent only on the mineral assemblage of the protolith
C) dependent only on the temperature and pressure of formation
D) dependent on both the mineral assemblage of the protolith and the temperature and pressure of formation

Question 23

What does the lack of foliation mean in a metamorphic rock?

A) that the rock formed in an environment free of compression or shear
B) that most of the new crystals in the rock could only form in inequant form
C) that only high temperature was involved in the rock's creation
D) that both low temperature and pressure were involved in the rock's creation

Question 24

Two common metamorphic rocks that typically lack foliation are ____________ and ____________.

A) slate; phyllite
B) gneiss; migmatite
C) quartzite; marble
D) schist; metaconglomerate

Question 25

A primary difference between phyllite and schist is that ____________.

A) schist contains mica, whereas phyllite contains only clay
B) phyllite contains mica, whereas schist contains only clay
C) mica crystals within schist are larger than those within phyllite
D) mica crystals within phyllite are larger than those within schist

Question 26

How does the banding in gneiss form?

A) by the well-understood process of metamorphic differentiation
B) from the evolution of bedding in the protolith
C) from compressional stress on the protolith
D) from fluids running through the rock during creation

Question 27

Gneiss typically forms under higher pressures than hornfels.

Question 28

The blueschist facies is a metamorphic realm of ____________.

A) high temperature and pressure
B) low temperature and pressure
C) high temperature but relatively low pressure
D) high pressure but relatively low temperature

Question 29

Marble and quartzite are nonfoliated rocks because ____________.

A) they are never found beneath fault zones or collisional mountain ranges
B) both are dominated by minerals that produce equant grains
C) both are dominated by minerals with crystalline structures that cannot be dissolved
D) dynamothermal metamorphism can break down the structures of their constituent minerals, but neither of these minerals is stable in that metamorphic environment

Question 30

____________ commonly serves as a protolith in the formation of quartzite.

A) Limestone
B) Sandstone
C) Shale
D) Slate

Question 31

The preexisting rock that is subsequently altered to form a metamorphic rock is termed a ____________.

A) parent rock
B) source rock
C) protolith
D) premetarock

Question 32

Slaty cleavage,schistosity,and compositional banding are all examples of ____________.

A) mineral cleavage
B) foliation
C) recrystallization
D) sedimentary structures

Question 33

Consult the figure below.A mineral within a metamorphic rock that can be used to provide a narrow constraint on the temperature and pressure of formation of the rock is termed a(n)____________.

A) thermineral
B) index mineral
C) mafic mineral
D) halide mineral

Question 34

____________ commonly serves as a protolith in the formation of slate.

A) Limestone
B) Sandstone
C) Shale
D) Slate

Question 35

____________ commonly serves as a protolith in the formation of marble.

A) Limestone
B) Sandstone
C) Shale
D) Slate

Question 36

Foliated metamorphic rocks possess ____________.

A) leafy plant fossils (ancient foliage)
B) a homogeneous texture resulting from randomly oriented grains
C) a planar fabric consisting of mineral grains in preferred orientations or preferred patterns of association (banding)
D) minerals precipitated directly from seawater

Question 37

Consult the figure below.As compared to the amphibolite metamorphic facies,the greenschist facies ____________.

A) consist of lower-grade rocks
B) consist of higher-grade rocks
C) are an identical temperature and pressure regime; greenschists and amphibolites bear different mineral assemblages only because of differences in protolith chemistry

Question 38

____________ commonly serves as a protolith in the formation of phyllite.

A) Limestone
B) Sandstone
C) Shale
D) Slate

Question 39

Why do sculptors love to work with marble?

A) It comes only in a creamy white variety that is perfect for statues.
B) Its distinction between grains and cement produces an excellent texture.
C) Its interlocking halite crystals provide uniformity.
D) It is relatively soft.

Question 40

Where does the water in hydrothermal fluids come from?

A) Some of it may seep into the protolith from nearby metamorphic units.
B) Some of it may seep into the protolith from nearby sedimentary units.
C) Some of it was originally bonded to minerals in the protolith.
D) Some of it may come from underlying groundwater.

Question 41

Thermal (contact)metamorphism produces ____________.

A) foliated rocks only
B) nonfoliated rocks only
C) both foliated and nonfoliated rocks

Question 42

Regional metamorphism ____________.

A) takes place at cool temperatures and low pressure
B) takes place at cool temperatures but high pressure
C) is another name for thermal metamorphism
D) is another name for dynamothermal metamorphism

Question 43

Which type of metamorphism affects the greatest volumes of rock?

A) thermal metamorphism
B) dynamothermal metamorphism
C) dynamic metamorphism

Question 44

Dynamothermal (regional)metamorphism occurs when ____________.

A) rock becomes buried deeply during continental collision and mountain building
B) regression of the sea leads to erosion of sedimentary cover atop a body of rock
C) the upper surface of a body of rock develops a thick soil profile
D) a pluton causes metamorphism in a small surrounding region

Question 45

Dynamothermal (regional)metamorphism produces ____________.

A) foliated rocks only
B) nonfoliated rocks only
C) both foliated and nonfoliated rocks

Question 46

Which list properly orders metamorphic rocks from lowest to highest grade?

A) conglomerate, sandstone, siltstone, shale
B) shale, slate, phyllite, quartzite
C) slate, phyllite, schist, gneiss
D) gneiss, phyllite, schist, slate

Question 47

Where should you look today to find metamorphic rocks that are currently exposed?

A) subduction zones
B) the United States shield
C) mountain ranges
D) the Alaskan shield

Question 48

Rapid,deep burial of sediments in an accretionary prism leads to the formation of a metamorphic rock termed ____________.

A) blueschist
B) greenschist
C) migmatite
D) gneiss

Question 49

Flattened-clast conglomerate would most likely be found ____________.

A) in an aureole around a cooled igneous intrusion
B) at the eroding base of an ancient collisional mountain range
C) at a depth within the mid-ocean ridge system
D) within a meteorite impact crater

Question 50

Consult the figure below.Hot water reacting with crustal rock is the basis for what type of metamorphism?

A) contact
B) hydrothermal
C) regional
D) shock

Question 51

Thermal (contact)metamorphism occurs ____________.

A) in areas surrounding igneous intrusions
B) only where gneiss is in contact with schist
C) as a consequence of the sinking of a broad region to great depth
D) only at Earth's surface, where rock is in contact with the atmosphere

Question 52

Rocks resulting from thermal (contact)metamorphism will not possess ____________.

A) a new mineral assemblage distinct from that found prior to intrusion
B) larger crystals than those characterizing the country rock prior to intrusion
C) foliation
D) silicate minerals

Question 53

Why is dynamic metamorphism different from the other types of metamorphism?

A) It only requires high temperatures.
B) It only requires high pressures.
C) It is the result of only compressional stress.
D) It is the result of only shear stress.

Question 54

Mylonites,formed from dynamic metamorphism,typically display ___________.

A) foliation roughly parallel to a fault
B) very fine grains
C) shear zones
D) All of the above are correct.

Question 55

Consult the figure below.The region of thermally metamorphosed rock surrounding a cooled pluton is called a(n)____________.

A) shear zone
B) aureole
C) oriole
D) fire ring

Question 56

Burial metamorphism produces ____________.

A) foliated rocks only
B) nonfoliated rocks only
C) both foliated and nonfoliated rocks

Question 57

Which of the following is part of the process that leads to the exhumation of metamorphic rocks?

A) continents squeezing together
B) mountain belts collapsing
C) erosion
D) All of the above are correct.

Question 58

Precambrian metamorphic rocks are exposed at the surface ____________.

A) on Mars and Venus, but nowhere on Earth
B) at places in continental interiors termed platforms
C) at places in continental interiors termed shields
D) at the bottom of the deep sea

Question 59

Meteorite impacts have been known to induce metamorphism of sediments and rocks.

Question 60

Which of the following is analogous to all of the metamorphic grades creating an aureole as one moves toward the source pluton?

A) the transition from clay to porcelain
B) the transition from brick to pottery
C) the transition from porcelain to clay
D) the transition from pottery to brick

Question 61

Within a single mountain range,____________.

A) only low-grade metamorphic rocks are likely to be found
B) only high-grade metamorphic rocks are likely to be found
C) it is possible to find a variety of metamorphic rocks produced in distinct facies, including high-, low-, and intermediate-grade rocks