AnswersEarth and Space ScienceIgneous Rock

Igneous Rock — Quiz Answers

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1
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Which explanation best accounts for the mineral and structural features observed in this sample?

A
The crystal structure suggests growth under stable pressure conditions that disrupted the alignment of mineral grains.
B
The uneven crystal distribution indicates rapid magma ascent, where heat loss prevented uniform crystallization across the rock.
C
The rock likely formed at the surface during explosive lava cooling, producing vesicles and trapping volcanic gases.
D
The rock likely formed in a deep setting, where unusual chemical conditions enabled selective crystal growth within a finer matrix.
2
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During a follow-up trip, the geology team revisited one of their volcanic study sites to collect new samples near the base of an ancient lava dome. Nearby mapping showed several narrow igneous dikes that had intruded through older rock layers. Two samples collected only a few meters apart showed clear differences: Sample E contained large, interlocking crystals of feldspar and quartz and was very dense. Sample F displayed tiny, intergrown crystals with a few scattered gas cavities (vesicles) and a dull gray surface. The team noted that both rocks likely originated from the same magma source but cooled under different conditions. Choose the correct answer from each drop-down menu to complete the statements.

Answer:

Sample E|coarse, dense texture|environment

3

Classify each sample based on its likely formation environment. Drag each to the correct box.

Answer:

Sample B|Sample C,Sample A,Sample D

4

Choose the correct answer from each drop-down menu to complete the statement.

Answer:

Arden|supported slow, continuous cooling

5

Choose the correct answer from each drop-down menu to complete the statement.

Answer:

Solen|was in contact with seawater

6

Which interpretation most accurately explains the rock’s formation process?

A
The magma cooled steadily within the shallow crust, forming an intermediate crystalline texture without glassy material.
B
The magma solidified during repeated eruptions, creating alternating layers of crystalline and volcanic rock.
C
The magma cooled slowly at considerable depth, allowing coarse interlocking crystals to develop.
D
The magma experienced rapid quenching near the surface, stopping crystal growth before minerals could form.
7

Which statement best explains why no measurable cavities were recorded in the seafront sample open paren cap k minus 4 close paren ?

A
Gas was completely lost through venting before eruption.
B
High pressure prevented gas release from the magma.
C
The magma cooled so rapidly that bubbles could not expand before solidifying.
D
The magma contained unusually high silica, blocking vesicle formation.
8

Which eruption environment likely produced rock with a texture closest to pumice, a highly vesicular volcanic glass?

A
ventflow
B
midflow
C
seafront
D
intrusive setting
9

How does the transition from a midflow environment to a ventflow environment illustrate the effect of heat-loss rate on igneous textures?

A
The higher cooling rate at ventflow caused fewer vesicles but larger cavities.
B
Samples at both environments cooled slowly, so textures are nearly identical.
C
Differences in gas content were caused only by magma chemistry, not cooling rate.
D
The higher cooling rate at ventflow produced more vesicles and slightly smaller average cavity diameters.
10

Which statement best explains why no measurable cavities were recorded in the seafront sample open paren cap k minus 4 close paren ?

A
The magma cooled so rapidly that bubbles could not expand before solidifying.
B
Gas was completely lost through venting before eruption.
C
High pressure prevented gas release from the magma.
D
The magma contained unusually high silica, blocking vesicle formation.

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