Quiz Reading comprehenshion Chapter 4 Rocks PDF

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guide question and answer to defining rocks and mineral...

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Review Test Submission: Ch 4 Reading Comprehension Quiz User

Mary Villarreal

Course

GEOL-1403-91L-Spring2021

Test

Ch 4 Reading Comprehension Quiz

Started

3/5/21 6:05 AM

Submitted

3/5/21 6:17 AM

Status

Completed

Attempt Score Grade not available. Time Elapsed

12 minutes

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Feedback, Incorrectly Answered Questions

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Question 1 (Q001) Magmas can have a variety of chemical compositions for which of the following reasons? Response Feedback:

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Question 2 (Q002) Volatiles that come out of the Earth as volcanic products Response Feedback:

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FEEDBACK: The factors affecting magma composition are melt source, degree of partial melting, assimilation, and magma mixing. Three of these are listed in this problem.

FEEDBACK: Volcanic gases usually consist mostly of water vapor and constitute up to 15% of a magma. Dry melts contain no volatiles, while wet melts do.

Question 3 (Q003) Felsic (or silicic) magma Response FEEDBACK: Felsic magma crystallizes at low (not high) Feedback: temperatures, contains about 66% to 76% silica (not 40%), forms

light-colored (not dark-colored) igneous rocks, and is more viscous than mafic magma because the silicon tetrahedrons link up in chains that, at the microscopic level, tangle and impede smooth flow.

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Question 4

(Q004) In this diagram, Point A represents rock that fits which of the following descriptions?

Click to view larger image. Response Feedback:

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FEEDBACK: The rock's temperature is more than 1,500°C. Since Point A is left of the solidus line, the rock is solid. The region to the right of the liquidus line represents molten rock, and between the two lines, the rock is a mixture of solid and melts.

Question 5 (Q005) As a sample moves from Point A to Point B in this diagram, what happens?

Click to view larger image. Response Feedback:

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FEEDBACK: At Point B, the sample is at a shallower depth within the Earth, which has changed its pressure but not its temperature. At Point B, the sample is on the solidus line, so it will begin to melt as a result of decompression, even though its temperature remains the same.

Question 6 (Q006) Hot, solid rock in the Earth's crust Response FEEDBACK: Rocks within the Earth are hotter than those at the Feedback: Earth’s surface because of the geothermal gradient. The addition

of volatiles lowers the melting temperature, which means rocks will melt at lower temperatures if water or carbon dioxide is present. Magma composition evolves as rock melts because of partial melting and assimilation processes.

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Question 7 (Q007) The dramatic scenery of the Sierra Nevada mountain range in California, shown here,

Click to view larger image. Response Feedback:

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Question 8 (Q008) Bowen's reaction series Response Feedback:

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FEEDBACK: This is not a hot-spot location. The batholith (an intrusive igneous feature) is light-colored granite, an intrusive, coarse-grained igneous rock. Dark-colored, finegrained basalt would be an extrusive igneous rock.

FEEDBACK: Bowen's reaction series was deduced through laboratory procedures that cooled molten rock. The crystal formation in the resulting igneous rocks followed a predictable order because as a magma crystallizes, the remaining melt becomes more enriched (not depleted) in silica.

Question 9 (Q009) Magma may cool and crystallize to become solid igneous rock Response FEEDBACK: Magma will cool and freeze when its volatile content Feedback: decreases, not increases. It will cool faster (not slower) in the

presence of circulating groundwater, and it will cool faster if the surface area of the intrusion is high, not low. The deeper the magma (such as a deep pluton), the longer the cooling time.

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Question 10 (Q010) Magma moves upward toward the Earth's surface Response Feedback:

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FEEDBACK: Magma moves upward slowly toward the Earth’s surface. The hotter (not cooler) the magma, the less viscous it is and the faster it flows. The weight of the crust does not affect whether magma can rise.

Question 11 (Q011) The black, fine-grained tabular intrusions between layers of horizontal sedimentary rock shown in this picture are

Click to view larger image. Response Feedback:

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Question 12 (Q012) Mafic minerals Response Feedback:

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FEEDBACK: Mafic minerals are rich in iron and magnesium (not aluminum and sodium), typically crystallize first out of a cooling melt (not last), and form rocks like basalt and gabbro (not rhyolite and granite).

Question 13 (Q013) Which of the following terms has to do with extrusive igneous activity? Response Feedback:

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FEEDBACK: Granite is light-colored, and a dike cuts across existing layers.

FEEDBACK: Pyroclastic rocks are igneous rocks with a fragmental texture formed by explosive volcanic eruptions. The other terms describe intrusive bodies or their components.

Question 14 (Q014) An igneous rock that has a medium-gray, fine-grained groundmass with large crystals of plagioclase Response FEEDBACK: A pegmatite is a very coarse-grained rock without Feedback: any groundmass. Rapid cooling forms glass, not crystals. Diorite

is a plagioclase-rich phaneritic rock, and does not contain groundmass. An aphanitic porphyry like this one, containing large crystals of plagioclase set in a fine-grained groundmass, must have crystallized slowly for a period of time before being erupted and cooling quickly.

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Question 15

(Q015) Which of the following words could be used to describe portions of a rock with a porphyritic texture? Response Feedback:

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Question 16 (Q016) Granite Response Feedback:

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FEEDBACK: In a porphyritic rock, the fine-grained, aphanitic material making up the majority of the rock is called groundmass, and the larger crystals are called phenocrysts.

FEEDBACK: Granite is a felsic, intrusive (and therefore coarsegrained) igneous rock. It is often found as plutons rather than lava flows, which are extrusive. The coarse-grained equivalent of andesite is diorite, not granite.

Question 17 (Q017) After an explosive volcanic eruption on an island, the surrounding sea is full of light-gray, floating rock. What must it be? Response FEEDBACK: Obsidian is a dense, glassy igneous rock; basalt is a Feedback: dense, fine-grained igneous rock; and rhyolite is a light-colored,

felsic igneous rock. All of these are denser than water and, therefore, would not float. Pumice is a felsic, vesicular rock that, because of its abundant vesicles, is less dense than water.

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Question 18 (Q018) Intrusive igneous rocks Response Feedback:

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FEEDBACK: Extrusive (not intrusive) igneous rocks are finegrained but cooled quickly. Intrusive igneous rocks do solidify in the Earth but eventually are exposed by uplift and erosion. Basalt, andesite, and rhyolite are extrusive (not intrusive) igneous rocks.

Question 19 (Q019) In which tectonic setting would you most expect to find igneous activity? Response FEEDBACK: Passive margins occur when continental boundaries Feedback: are far from plate boundaries; they are (as the name implies)

quiet and do not have volcanoes, rifts, or trenches. The same is true for continental interiors, which are far from plate boundaries. Transform motion involves plates sliding past each other; the heat from friction is not enough to melt rock. Oceanic trenches are associated with subduction and volcanic arcs.

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Question 20

(Q020) Volcanic arcs Response FEEDBACK: Volcanic arcs form on continental or oceanic crust Feedback: above (not on) a subducted plate, and are long, curving chains of

volcanoes that lie adjacent to trenches, not mid-ocean ridges. Melt beneath a volcanic arc is produced by flux melting when volatiles are released into the mantle from the subducting slab.

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Question 21 (Q021) Pillow basalts Response Feedback:

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Question 22 (Q022) Large igneous provinces (LIPs) Response Feedback:

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FEEDBACK: Pillow basalts are bulbous (not tabular) flows of molten basalt, a mafic (not felsic) magma. They cool very quickly and harden as they are expelled into seawater.

FEEDBACK: LIPs usually erupt mafic (not felsic) magma, which is low (not high) in viscosity. They occur on the seafloor or on land, along margins or in the interiors of oceanic plates or continents. LIPs may be the result of plume activity.

Question 23 (Q023) How does subduction trigger melting? Response Feedback:

FEEDBACK: Flux melting (the addition of volatiles) occurs as the downgoing slab adds water to the surrounding asthenosphere; the water acts as a catalyst for melting. The subducted slab itself usually does not melt.

Friday, March 5, 2021 6:17:47 AM CST

QUESTION 1

1. (Q001) Magmas can have a variety of chemical compositions for which of the following reasons? a All of the possible answers are correct. . b Melts may come from different source rocks. . c Two magmas may mix together to form a third .

of differing composition. d Source rocks undergo varying degrees of partial melting, . producing magmas of a different composition than the rock. 1 points

Q UEST I O N 2

1. (Q002) Volatiles that come out of the Earth as volcanic products

a often contain little . b are brought to the .

water vapor.

surface in "dry" melts. c were mixed with the molten rock. . d constitute .

50% of most magma. 1 points

Q UEST I O N 3

1. (Q003) Felsic (or silicic) magma a is likely to form dark-colored igneous rocks.

. b crystallizes at the highest temperatures. . c is more viscous than mafic magma. . d has approximately 40% silica and little magnesium .

and iron.

1 points

Q UEST I O N 4 1. (Q004) In this diagram, Point A represents rock that fits which of the

following descriptions?

Click to view larger image. a Its temperature is about 1,000°C.

. b It . c It .

is crustal rock.

has a pressure of approximately 100,000 bars (100 kbar). d Its physical state is molten. .

1 points

Q UEST I O N 5 1. (Q005) As a sample moves from Point A to Point B in this diagram,

what happens?

Click to view larger image. a It heats up. . b It . c It . d It .

begins to melt as a result of decompression. stays at the same depth within the Earth.

does not change its physical state because its temperature has not changed. 1 points

Q UEST I O N 6

1. (Q006) Hot, solid rock in the Earth's crust a is cooler than surface lava because of the pressure of overlying . rock.

b melts .

at a higher temperature if volatiles such as water and carbon dioxide are added. c may melt if heat is transferred to it from hot mantle rock rising up . into the crust. d maintains uniform composition as it melts and becomes magma. .

1 points

Q UEST I O N 7 1. (Q007) The dramatic scenery of the Sierra Nevada mountain range in

California, shown here,

Click to view larger image. a owes its existence to erosion of a batholith. . b is . c is .

the result of a continental hot spot.

especially impressive because of its dark-colored basalt rock. d is composed of fine-grained volcanic rock. .

1 points

Q UEST I O N 8

1. (Q008) Bowen's reaction series a shows that as magma crystallizes, the remaining melt is depleted . in silica. b explains why some compounds use ionic bonds, and others have . covalent bonding. c explains why some igneous rocks are phaneritic, and others . aphanitic. d shows that minerals in a cooling magma crystallize in a . predictable order. 1 points

Q UEST I O N 9

1. (Q009) Magma may cool and crystallize to become solid igneous rock

a when its volatile content increases. . b faster if the surface area of the intrusion is low. . c more slowly in a deep pluton than in a shallow .

sill.

d more .

slowly in the presence of circulating groundwater. 1 points

Q U E S T I O N 10

1. (Q010) Magma moves upward toward the Earth's surface a quickly, working its way up through cracks and narrow . conduits. b because it is less dense than the surrounding rock. . c .

because the crust is not heavy enough to keep it in the mantle. d more quickly as it cools, and therefore becomes less . viscous. 1 points

Q U E S T I O N 11 1. (Q011) The black, fine-grained tabular intrusions between layers of

horizontal sedimentary rock shown in this picture are

Click to view larger image. a basaltic . sills. b granitic . sills. c basaltic . dikes. d granitic

.

dikes. 1 points

Q U E S T I O N 12

1. (Q012) Mafic minerals a typically crystallize last out of a melt. . b are rich in aluminum and sodium. . c form rhyolite and granite. . d crystallize at a higher temperature .

than do silicic

minerals.

1 points

Q U E S T I O N 13

1. (Q013) Which of the following terms has to do with extrusive igneous activity? a batholith . b laccolith . c pyroclast .

ic

d pluton . 1 points

Q U E S T I O N 14

1. (Q014) An igneous rock that has a medium-gray, fine-grained groundmass with large crystals of plagioclase a is called pegmatite. . b is called diorite. . c indicates that the .

lava flow that produced it cooled very quickly, forming the crystals. d crystallized at depth from intermediate-composition magma, and . then rose to the surface and became a lava flow. 1 points

Q U E S T I O N 15

1. (Q015) Which of the following words could be used to describe portions of a rock with a porphyritic texture? a groundmass . b aphanitic . c all of the possible .

correct.

answers are

d phenocryst . 1 points

Q U E S T I O N 16

1. (Q016) Granite a logically could be found in a lava . flow. b is felsic in composition. . c .

is the coarse-grained equivalent of andesite. d is an extrusive igneous rock. .

1 points

Q U E S T I O N 17

1. (Q017) After an explosive volcanic eruption on an island, the surrounding sea is full of light-gray, floating rock. What must it be? a rhyolit . e b pumic . e c basalt . d obsidia .

n

1 points

Q U E S T I O N 18

1. (Q018) Intrusive igneous rocks a are rocks like basalt, andesite, and rhyolite. . b cool slowly and . c are never seen .

are coarse-grained.

by humans because they form deep in the Earth and are never exposed at the surface. d are fine-grained because they cooled slowly. .

1 points

Q U E S T I O N 19

1. (Q019) In which tectonic setting would you most expect to find igneous activity? a passive margins . b continental .

transform fault zones c landward of oceanic

.

trenches

d continental .

interiors 1 points

Q U E S T I O N 20

1. (Q020) Volcanic arcs a are long, curving chains of volcanoes adjacent to mid. ocean ridges. b are fed magma from flux melting. . c form on plates that are subducting. . d occur only on continental crust. .

1 points

Q U E S T I O N 21

1. (Q021) Pillow basalts a are formed in a submarine . environment. b are composed of felsic lava.

. c occur in tabular intrusions called dikes. . d contain large, bulbous crystals that cool .

slowly.

1 points

Q U E S T I O N 22

1. (Q022) Large igneous provinces (LIPs) a occur only along continental margins. . b erupt .

only high-viscosity magma and are therefore localized but very thick. c are places where huge amounts of felsic magma have been . erupted or intruded. d represent special events in the Earth's history that may have . been caused by plume activity. 1 points

Q U E S T I O N 23

1. (Q023) How does subduction trigger melting? a Flux melting of the asthenosphere above the subducting slab . creates a rising melt. b The overriding slab insulates the subducting slab, increasing . temperature and causing melting. c The subducting slab is made of felsic minerals, and therefore .

melts at lower temperatures. downgoing slab melts as it reaches hotter temperatures deep in the Earth.

d The .

1 points

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