Chapter 4 quiz & hw

q23: How does subduction trigger melting?

Flux melting of the asthenosphere above the sub-ducting slab creates a rising melt.

q20: Volcanic arcs

are fed magma from flux melting.

q21: Pillow basalts

are formed in a submarine environment.

q12:Mafic minerals

crystallize at a higher temperature than do silicic minerals.

h2: Choose the most likely product of partially melting a rock of intermediate composition.

felsic magma

h4: Order the steps that lead to assimilation.

first: -a magma forms and begins to migrate through the crust -blocks of the surrounding silica-rich crust break off and become incorporated into the magma -incorporated crustal blocks within the magma melt, mixing with the magma -the amount of silica increases and the magma composition changes accordingly last:

q2: Volatiles that come out of the Earth as volcanic products

were mixed with the molten rock

h10: This is a coarsely crystalline igneous rock, so to identify the rock you only need to estimate its composition. Select the option that gives the closest approximation of the proportion of the minerals.

15% mafic (dark) minerals, 85% felsic (light) minerals

q1: Magmas can have a variety of chemical compositions for which of the following reasons? A. Two magmas may mix together to form a third of differing composition. B. Source rocks undergo varying degrees of partial melting, producing magmas of a different composition than the rock. C. All of the possible answers are correct. D. Melts may come from different source rocks.

All of the possible answers are correct.

h5: Using the phase diagram shown below, determine which statement best describes what happens as a rock is moved from point A to point B.

As a rock is moved up in the Earth, it is subjected to slightly lower temperatures and much lower pressures, and it begins to melt.

q11: The black, fine-grained tabular intrusions between layers of horizontal sedimentary rock shown in this picture are

basaltic sills.

q10: Magma moves upward toward the Earth's surface

because it is less dense than the surrounding rock

q18: Intrusive igneous rocks

cool slowly and are coarse-grained.

q14: An igneous rock that has a medium-gray, fine-grained groundmass with large crystals of plagioclase

crystallized at depth from intermediate-composition magma, and then rose to the surface and became a lava flow

h9: Determine whether the rock is felsic, intermediate, mafic, or ultramafic. (Note the relatively high proportions of grey, white, and pink minerals in the sample.)

felsic

h11: Sort the images below into either the intrusive or extrusive categories based on how they cooled.

intrusive: -split rock -penny extrusive: -lava flow label -man -rocks

q16: Granite

is felsic in composition.

q3: Felsic (or silicic) magma

is more viscous than mafic magma

q19: In which tectonic setting would you most expect to find igneous activity?

landward of oceanic trenches

h1: Order the compositions of magmas produced via melting from lowest temperature to highest. To do this, you will need to use the green slider bar for the temperature control on the far left of the simulation. Slide the green bar to various temperatures, and then migrate the magma to see the composition of the magma that will result. What composition of magma is produced by melting at lower temperatures? At higher temperatures?

lower: - felsic - intermediate - mafic - ultramafic higher:

q6: Hot, solid rock in the Earth's crust

may melt if heat is transferred to it from hot mantle rock rising up into the crust.

q9: Magma may cool and crystallize to become solid igneous rock

more slowly in a deep pluton than in a shallow sill.

q7: The dramatic scenery of the Sierra Nevada range in California, shown here,

owes its existence to erosion of a batholith.

q5: As a sample moves from Point A to Point B in this diagram, what happens?

It begins to melt as a result of decompression.

q4: In this diagram, Point A represents rock that fits which of the following descriptions? A. Its physical state is molten. B. It has a pressure of approximately 100,000 bars (100 kbar). C. It is crustal rock. D. Its temperature is about 1,000°C.

It has a pressure of approximately 100,000 bars (100 kbar).

h6: Order the steps involved in fractional crystallization.

- magma, after entering through the bottom of the magma chamber, reaches the top of the chamber where temperatures are lower - magnesium-and iron rich minerals begin to crystallize - mineral crystals, having a higher density than liquid magma, sink to the bottom of the magma chamber - the magma shifts toward a more intermediate composition

h3: Which of the following statements are true about partial melting? A.Mafic components of the parent rock tend to go into the liquid state first during partial melting. B.Partial melting results in magmas that are more felsic in composition than the parent rock. C.Felsic components of the parent rock tend to go into the liquid state first during partial melting. D.As more of the rock melts during partial melting, the magma becomes more mafic than the original melt that formed.

-Felsic components of the parent rock tend to go into the liquid state first during partial melting. -Partial melting results in magmas that are more felsic in composition than the parent rock. -As more of the rock melts during partial melting, the magma becomes more mafic than the original melt that formed.

h12: Identify the four tectonic settings of igneous activity.

-top left: contential rift -top right: subduction zone -bottom left: hot spot volcano -bottom right: mid-ocean ridge

h8: Coarse-grained igneous rocks, such as the granite shown below, contain crystals that are large enough to identify. The crystals are interlocking, so the boundaries of crystals can be difficult to recognize. Here, minerals have been outlined and shaded to emphasize individual grains. Using your knowledge of mineral properties such as color and luster, identify the minerals by dragging and dropping the labels to the correct location.

White: plagioclase feldspar Pink: potassium feldspar Gray: quartz Black: biotite

q15: Which of the following words could be used to describe portions of a rock with a porphyritic texture? A. phenocryst B. All of the possible answers are correct. C. groundmass D. aphanitic

all of the possible answers are correct.

q17: After an explosive volcanic eruption on an island, the surrounding sea is full of light-gray, floating rock. What must it be?

pumice

q13: Which of the following terms has to do with extrusive igneous activity? A. batholith B. pluton C. pyroclastic D. laccolith

pyroclastic

q22: Large igneous provinces (LIPs)

represent special events in the Earth's history that may have been caused by plume activity.

q8: Bowen's reaction series

shows that minerals in a cooling magma crystallize in a predictable order.

h7: What a Geologist Sees. A geology student sits beside an outcrop on Mont Royal, the namesake of Montreal. This exposure shows the intrusion of molten basalt into preexisting limestone.

top to bottom: -pointing to line: depositional contact -in between lines:bed of limestone -pointing to root: intrusive contact -in root: igneous dike -first scale: correct scale -second scale: