Deck 6: Metamorphism: Alteration of Rocks by Temperature and Pressure

Question 1

What is the average rate at which temperature increases with depth in Earth's crust?

A)10°C/km
B)30°C/km
C)100°C/km
D)300°C/km

Answer 1

B

Question 2

What is metasomatism?

A)a change in the bulk composition of a rock during metamorphism
B)metamorphism caused by nearby magmatic intrusions
C)metamorphism caused by tectonic movements along faults
D)the parallel alignment of minerals in a metamorphic rock

Answer 2

A

Question 3

Which of the following rocks represents the highest metamorphic grade?

A)gneiss
B)phyllite
C)schist
D)slate

Answer 3

A

Question 4

Which of the following is not used to classify foliated rocks?

A)the metamorphic grade
B)the size of the crystals
C)the nature of the foliation
D)the texture of the parent rock

Question 5

Which of the following is a general pressure in all directions,such as the pressure that the atmosphere exerts?

A)confining pressure
B)pore pressure
C)directional pressure
D)stress pressure

Question 6

Marble is a metamorphic rock that forms from

A)granite.
B)limestone.
C)sandstone.
D)shale.

Question 7

Where does seafloor metamorphism take place?

A)continent collision zones
B)subduction zones
C)divergent plate boundaries
D)transform plate boundaries

Question 8

During metamorphism,changes in the bulk composition of a rock occur primarily as a result of

A)increases in pressure.
B)reaction with hydrothermal fluids.
C)increases in temperature.
D)decreases in temperature.

Question 9

Which of the following processes will cause metamorphism?

A)an increase in pressure
B)interaction with hydrothermal fluids
C)an increase in temperature
D)all of the above

Question 10

The parallel alignment of mica in a metamorphic rock is an example of

A)bedding.
B)foliation.
C)metasomatism.
D)porphyroblasts.

Question 11

What type of metamorphism is caused by igneous intrusions?

A)burial metamorphism
B)regional metamorphism
C)contact metamorphism
D)shock metamorphism

Question 12

What is the relationship between metamorphic foliation and sedimentary bedding?

A)Sedimentary bedding is generally perpendicular to metamorphic foliation.
B)Sedimentary bedding is generally at a 45° angle to metamorphic foliation.
C)Sedimentary bedding is generally parallel to metamorphic foliation.
D)There is no general angular relationship between sedimentary bedding and metamorphic foliation.

Question 13

A geothermometer is

A)a device that measures current rock temperatures.
B)a device that measures temperature when lowered into deep drill holes.
C)a mineral assemblage that reveals the maximum temperature attained by a rock.
D)the range of temperatures encountered by a rock in its geologic history.

Question 14

Which of the following tectonic settings will be coolest at 30 km depth?

A)regions of continental extension
B)stable continental lithosphere
C)volcanic arcs
D)The temperature in all three tectonic settings above will be the same at 30 km depth.

Question 15

What type of metamorphic rock was once used to make blackboards because of its ability to split easily into thin sheets along smooth,parallel surfaces?

A)hornfels
B)quartzite
C)schist
D)slate

Question 16

At what depth does low-grade metamorphism begin?

A)1 to 2 km
B)6 to 10 km
C)20 to 50 km
D)100 to 200 km

Question 17

What type of metamorphism is caused by high temperature and high pressure imposed over a large volume of crust?

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

Question 18

Approximately what is the pressure on a rock at 15 km depth in Earth's crust? (Note: 1 bar is approximately 1 atmosphere and 1000 bars equals 1 kbar.)

A)4 bars
B)40 bars
C)400 bars
D)4 kbars

Question 19

What is the primary source of the carbon dioxide in metamorphic fluids?

A)atmospheric carbon
B)carbon dioxide released from Earth's core
C)sedimentary carbonates
D)weathered cement and other man-made materials

Question 20

Which of the following minerals is diagnostic of metamorphism?

A)calcite
B)feldspar
C)staurolite
D)quartz

Question 21

Which metamorphic mineral commonly forms porphyroblasts?

A)amphibole
B)calcite
C)chlorite
D)garnet

Question 22

Which of the following rocks represents the highest grade of metamorphosed mafic volcanic rocks?

A)amphibolite
B)blueschist
C)greenschist
D)granulite

Question 23

Which of the following metamorphic rocks cannot form from a shale?

A)hornfels
B)marble
C)schist
D)slate

Question 24

What type of metamorphic rock has undergone partial melting?

A)hornfels
B)migmatite
C)schist
D)slate

Question 25

Granoblastic metamorphic rocks generally contain minerals that are _______ in shape.

A)linear
B)platy
C)equant
D)bladed

Question 26

What is the most likely parent rock of a metamorphic rock containing muscovite,biotite,garnet,and quartz?

A)basalt
B)limestone
C)sandstone
D)shale

Question 27

Which of the following tectonic settings may be characterized by regional,high-pressure,and ultra-high-pressure metamorphism?

A)convergent plate boundaries
B)plate interiors
C)divergent plate boundaries
D)transform plate boundaries

Question 28

What metamorphic facies occurs at temperatures of 400°C and pressures of 6 kilobars?

A)granulite
B)greenschist
C)hornfels
D)zeolite

Question 29

What is a porphyroblast?

A)a common type of copper ore deposit
B)an igneous rock with two distinct crystal sizes
C)a relatively large metamorphic mineral
D)a strongly foliated metamorphic rock

Question 30

Which of the following sequences describes the metamorphic changes in a shale with increasing metamorphic grade?

A)schist,gneiss,slate
B)slate,schist,gneiss
C)gneiss,slate,schist
D)gneiss,schist,slate

Question 31

Under what conditions does zeolite-facies metamorphism occur?

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

Question 32

Which of the following metamorphic rocks forms from mafic volcanic rocks?

A)greenstone
B)marble
C)quartzite
D)all of the above

Question 33

Which of the following metamorphic facies represents the highest temperature?

A)amphibolite
B)blueschist
C)granulite
D)greenschist

Question 34

A nonfoliated contact metamorphic rock is called a

A)gneiss.
B)hornfels.
C)phyllite.
D)schist.

Question 35

Which of the following metamorphic rocks is always foliated?

A)hornfels
B)marbles
C)quartzites
D)schists

Question 36

Which of the following rocks can be considered gradational between an igneous and a metamorphic rock?

A)amphibolite
B)gneiss
C)migmatite
D)zeolite

Question 37

Which of the following metamorphic rocks is incorrectly paired with its parent rock?

A)greenstone - basalt
B)quartzite - granite
C)marble - limestone
D)schist - shale

Question 38

Light-colored rocks with coarse bands of segregated light and dark minerals are called

A)gneisses.
B)quartzites.
C)schists.
D)slates.

Question 39

Which of the following statements about the metamorphism of a shale is false?

A)With increasing metamorphism,clay minerals break down to form micas.
B)With increasing metamorphism,the grain size of the rock gets smaller.
C)With increasing metamorphism,foliation develops.
D)With increasing metamorphism,the amount of water in the rock decreases.

Question 40

Which of the following rocks has a granular texture?

A)gneiss
B)hornfels
C)schist
D)slate

Question 41

Mélanges and blueschists are characteristic of which tectonic setting?

A)continent collisions
B)subduction zones
C)mid-ocean ridges
D)transform faults

Question 42

What metamorphic rock could also be considered a transitional rock between igneous and metamorphic?

A)schist
B)hornfels
C)gneiss
D)migmatite

Question 43

The flow of metamorphic rocks back to Earth's surface is controlled by tectonics and

A)erosion.
B)hydrothermal circulation.
C)magmatism.
D)retrograde metamorphism.

Question 44

Metamorphic rocks may form from

A)igneous rocks.
B)sedimentary rocks.
C)other metamorphic rocks.
D)any of the major rock types.

Question 45

A metamorphic rock that is described as porphyroblastic has

A)original igneous rock textures.
B)abundant equant minerals.
C)large crystals in a fine-grained matrix.
D)no preferred alignment of minerals.

Question 46

Which metamorphic rock forms in the forearc of a subduction zone?

A)amphibolite
B)blueschist
C)hornfels
D)granulite

Question 47

Metamorphic mineral assemblages that can be used as pressure gauges are referred to as

A)kilobarometers.
B)geothermometers.
C)geobarometers.
D)kilothermometers.

Question 48

The parent rock of quartzite is

A)granite.
B)limestone.
C)shale.
D)sandstone.

Question 49

The prograde part of a metamorphic P-T path occurs during

A)burial and cooling.
B)exhumation and cooling.
C)burial and heating.
D)exhumation and heating.

Question 50

What kind of metamorphism(s)would you expect to find at a convergent plate margin?

A)regional
B)high-pressure
C)contact
D)all of the above

Question 51

Which mineral is commonly used to determine a metamorphic P-T path?

A)calcite
B)garnet
C)muscovite
D)quartz

Question 52

Which mineral is commonly found as a porphyroblast?

A)quartz
B)biotite
C)mica
D)staurolite

Question 53

Different pressure-temperature zones within a belt of regionally metamorphosed rock are defined by the presence of

A)porphyroblasts.
B)index minerals.
C)migmatite.
D)sillimanite.

Question 54

What kind of metamorphism would you expect to see in the rocks at a meteorite impact site?

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

Question 55

The parent rock(s)of granofels is(are)

A)shale.
B)impure sandstone.
C)granite.
D)shale,impure sandstone,and granite.

Question 56

Eclogite rocks form during ___________ metamorphism.

A)high-pressure
B)ultra-high-pressure
C)burial
D)seafloor

Question 57

The process whereby metamorphic rocks rise to Earth's surface is called

A)exhumation.
B)orogeny.
C)subduction.
D)progradation.

Question 58

What type of metamorphic rock is granofels?

A)a granulite
B)a schist
C)a gneiss
D)a marble

Question 59

Which of the following metamorphic rocks is most likely to contain visible fossils?

A)gneiss
B)hornfels
C)marble
D)quartzite

Question 60

Epidote is a common metamorphic mineral found in metamorphosed

A)shale.
B)limestone.
C)basalt.
D)sandstone.

Question 61

Metasomatism does not involve a change in

A)bulk rock chemistry.
B)mineral composition.
C)fluid composition.
D)rock texture.

Question 62

During metamorphism a rock will not

A)loose its solid form.
B)change shape.
C)change its texture.
D)experience metasomatism.

Question 63

At temperatures of approximately 600˚C and pressure of approximately 5 kbar,the minerals muscovite and quartz react with each other and produce orthoclase feldspar,sillimanite,and water.Which mineral is the source of the water?

A)orthoclase feldspar
B)muscovite
C)sillimanite
D)quartz

Question 64

In which of the following tectonic settings is the depth to the 1300˚C isotherm greatest?

A)volcanic mountain belt
B)subduction zone
C)zone of plate extension
D)stable continental lithosphere

Question 65

Which of the following factors remains constant and does not vary depending on tectonic setting?

A)the geothermal gradient
B)the thickness of the lithosphere
C)the rate of pressure increase with depth
D)the depth to the 1300˚C isotherm

Question 66

Carbon dioxide is one of the fluids consumed during metasomatism.What is the likely source of this fluid?

A)silicate minerals
B)the atmosphere
C)the core
D)carbonate rocks

Question 67

One would expect shock metamorphism to be less common on Earth than on the Moon.This is because the moon has

A)a smaller diameter.
B)lower gravity.
C)softer crust.
D)virtually no atmosphere.

Question 68

What kind of metamorphism would you expect to be pervasive on the lunar surface?

A)regional metamorphism
B)burial metamorphism
C)contact metamorphism
D)shock metamorphism

Question 69

One might expect shock metamorphism to be more common on the lunar than terrestrial surface because the Moon has __________ than Earth.

A)a thicker atmosphere
B)a denser atmosphere
C)a less dense atmosphere
D)higher atmospheric pressures

Question 70

During metamorphism,hydrothermal fluids can remove all _____ from an affected rock.

A)solids
B)minerals
C)water-soluble chemical elements
D)chemical elements

Question 71

Under what P and T conditions does zeolite-facies metamorphism occur?

A)less than 5 kbars and 200°C
B)5 to 10 kbars and 200 to 400°C
C)less than 5 kbars and greater than 400°C
D)greater than 5 kbars and less than 400°C

Question 72

Directed pressure is also sometimes called

A)confining pressure.
B)differential stress.
C)differential pressure.
D)confining stress.

Question 73

During metamorphism pressure will ____ the rocks in the direction a force is applied and ____ in the direction perpendicular to that same force.

A)elongate; flatten
B)elongate; elongate
C)flatten; elongate
D)flatten; flatten

Question 74

Geologists have recently linked rapid rates of uplift and exhumantion to

A)tectonic setting.
B)rock type.
C)climate.
D)isograds.

Question 75

In a thickened lithosphere you expect to see

A)thinner crust.
B)shallower geothermal gradients.
C)steeper geothermal gradients.
D)constant temperature increase with depth.

Question 76

Which of the following metamorphic rocks can be either foliated or phorphyroblatstic,but not granoblastic?

A)hornfels
B)marble
C)granulite
D)gneiss

Question 77

Which metamorphic facies would be highly unlikely to occur in a subduction zone?

A)zeolite
B)blueschist
C)eclogite
D)granulite

Question 78

Oil companies rarely drill deeper than the _____ isotherm.

A)100˚C
B)150˚C
C)200˚C
D)250˚C

Question 79

Metamorphism happens when rocks are subjected to

A)new temperatures and pressures.
B)fluids.
C)whole-scale melting.
D)atmospheric gases.

Question 80

During metamorphism,the process called metasomatism does not change the ______ of the affected rock.

A)chemical composition
B)mineral chemistry
C)mineral content
D)texture