Question 1

Concordant plutons cut across existing structures while discordant plutons are parallel to existing features.

Accepted Answer

Concordant plutons are parallel to existing structures, while discordant plutons cut across existing features.

Question 2

Dikes tend to form as solitary structures.

Accepted Answer

Dikes tend to form as part of a network of other igneous structures, such as sills and volcanic necks.

Question 3

Mineral crystals that form early in the crystallization process will have better-developed crystal faces than later crystals.

Accepted Answer

As the crystal grows, it competes with other crystals for space and resources, resulting in less well-formed faces. Early crystals have less competition and therefore have the opportunity to develop more defined crystal faces.

Question 4

Refer to the scenario above.Assuming a temperature of 20°C at the ground surface, what is the temperature at a depth of 2 miles?

Accepted Answer

The answer of Refer to the scenario above.Assuming a temperature...

Question 5

How will mantle-derived magma change when it ponds against crustal rocks?

Accepted Answer

The answer of How will mantle-derived magma change when it...

Question 6

Magmas in the magma chamber of a volcano are often compared to soda to explain how the magma is erupted.How is magma like a bottle of soda? What happens to both substances when the pressure changes?

Accepted Answer

The answer of Magmas in the magma chamber of a...

Question 7

In the process of a magma cooling and crystallizing, if the original melt contained large amounts of iron, why isn't quartz a ferromagnesian mineral?

Accepted Answer

The answer of In the process of a magma cooling...

Question 8

What is the definition of magma mixing?

Accepted Answer

Magma mixing occurs when one body of magma interacts and blends with another, resulting in a mixture that has characteristics of both original magmas. This can happen when magmas of different compositions, temperatures, or viscosities come into contact with each other as they move within the Earth's crust.

Question 9

Temperatures will decrease with increasing depth into the Earth.

Accepted Answer

Temperature generally increases with depth into the Earth due to the geothermal gradient, where heat from the Earth's inner layers makes its way to the surface.

Question 10

What is the role that depth can play on cooling and crystallization of igneous rocks?

Accepted Answer

The answer of What is the role that depth can...

Question 11

When teaching about igneous rocks, one trick instructors often implement to help students determine the igneous composition of the samples is to use the color of the rocks as a guide.Explain how the color of an igneous rock can often be used as an indicator of its igneous composition.Be sure to reference specific minerals for each composition.

Accepted Answer

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Question 12

How could a researcher use magmatic differentiation to determine if a batholith is the result of one body of magma cooling and crystallizing or multiple bodies of magma?

Accepted Answer

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Question 13

Peridotite that undergoes partial melting will create a melt enriched in ________.

Accepted Answer

The answer of Peridotite that undergoes partial melting will create...

Question 14

Plutonic bodies that have a surface exposure less than 100 km² are called ________.

Accepted Answer

Plutonic bodies with a surface exposure less than 100 km2 are called stocks. Dikes are igneous intrusions that cut across layers of rock, swarms are groups of dikes or sills that occur together, and batholiths are large bodies of intrusive igneous rock that cover an area greater than 100 km2.

Question 15

Refer to the scenario above.How would you expect the geothermal gradient to change if this borehole were drilled near Yellowstone National Park? Why?

Accepted Answer

The answer of Refer to the scenario above.How would you...

Question 16

Most sills are intrusive igneous structures that display a fine-grained texture.

Accepted Answer

Sills are formed from magma that intrudes and solidifies between layers of existing rock, cooling relatively quickly and resulting in a fine-grained texture.

Question 17

The two branches of Bowen's reaction series are the continuous series and the discontinuous series.In what ways do the minerals in the discontinuous series differ from each other? And the minerals in the continuous series?

Accepted Answer

The answer of The two branches of Bowen's reaction series...

Question 18

Refer to the scenario above.How does this gradient compare to the average geothermal gradient?

Accepted Answer

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Question 19

Which of the following regions will primarily erupt silica-rich lavas?

Accepted Answer

Continental margins are associated with convergent plate boundaries where subduction occurs. This results in the melting of the crust and the production of magma that is rich in silica.

Question 20

Igneous rocks with an andesitic composition are found along volcanic island arcs.

Accepted Answer

Andesitic composition is associated with intermediate volcanism, which is typically found at subduction zones where oceanic crust is melting and mixing with continental crust. This process occurs along volcanic island arcs, making the statement true.

Quiz 4: Magma, Igneous Rocks, and Intrusive Activity