geology ch.4 hw

What is the term for a tabular igneous pluton that occurs in an orientation that is discordant with the bedding surfaces of adjacent sedimentary rocks? dike sill stock batholith laccolith

dike

What is the term for a tabular igneous pluton that occurs in an orientation that is concordant with the bedding surfaces of adjacent sedimentary rocks? batholith sill dike laccolith stock

sill

When lava erupts at Earth's surface, what type of rock is produced? intrusive extrusive sedimentary limestone metamorphic

extrusive

What is an accessory mineral? A mineral that you cannot see with the naked eye A mineral crystal that forms in violent volcanic eruptions A mineral that makes up a relatively small portion of the total rock composition A large mineral crystal in a porphyritic texture A mineral that is used in conjunction with texture to classify igneous rocks

A mineral that makes up a relatively small portion of the total rock composition

Which of the following is true about mafic igneous rocks? Mafic igneous rocks are dominantly composed of muscovite and quartz. Mafic igneous rocks are rich in Si, K, and Na. Mafic igneous rocks are rich in Fe, Mg, and Ca. Mafic igneous rocks have a melting temperature around 650° C. Mafic igneous rock examples include diorite and andesite.

Mafic igneous rocks are rich in Fe, Mg, and Ca

What do pumice and scoria have in common? They both are formed in intrusive settings. They both show crystals larger than 2 cm in diameter. They both have a similar composition. They both exhibit a vesicular texture. They both are primarily composed of volcanic rock fragments.

They both exhibit a vesicular texture.

Most igneous rocks never reach the surface. However, igneous rocks other than those formed in volcanoes are found exposed on many parts of Earth. How do you account for this phenomenon? They are composed of lava flows. They formed at the surface and sank due to their greater density. They are the result of meteorite impact. They have been glaciated. They formed at depth and have been exposed by uplift and erosion.

They formed at depth and have been exposed by uplift and erosion.

Which of the following describes a texture containing bubble-shaped cavities? Porphyritic Aphanitic Vesicular Pegmatitic Pyroclastic

Vesicular

Pyroclastic debris from a volcanic eruption can include _____. cross-bedding ash and cinders coarse-grained crystals very well-rounded particles fossils

ash and cinders

What is the term used to describe a very large, widespread, and deep intrusive body of igneous rock? lava flow sill volcano batholith laccolith

batholith

Which of the following terms is best described as a massive pluton? batholith dike sill nuée ardente laccolith

batholith

Which of the choices below lists the four basic compositional groups of igneous rocks, ranging from the highest silica content to the lowest silica content? granitic, andesitic, basaltic, ultramafic basaltic, granitic, andesitic, ultramafic ultramafic, mafic, intermediate, felsic ultramafic, basaltic, andesitic, granitic intermediate, mafic, ultramafic, felsic

granitic, andesitic, basaltic, ultramafic

Igneous rocks of felsic composition have __________ and __________ relative to mafic igneous rocks. greater Ca; lower melting temperature darker color; lower melting temperature greater silica; lower melting temperature greater K and Na; higher melting temperature lighter color; higher melting temperature

greater silica; lower melting temperature

A phaneritic texture is characteristic of a(n) __________ igneous rock that cooled __________. extrusive; over a long period of time extrusive; below the surface extrusive; at Earth's surface intrusive; very quickly intrusive; below the surface

intrusive; below the surface

Which of the following igneous rocks contains no mineral crystals? gneiss limestone granite obsidian basalt

obsidian

What is required to generate an igneous rock with a fine-grained texture? A fine-grained texture requires an environment where heat is lost slowly over a long period of time. A fine-grained texture results from cooling far below the crust. A fine-grained texture is the product of very slow cooling and crystallization of magma. A fine-grained texture is the product of rapid cooling and crystallization of lava. A fine-grained texture results from large grains that recrystallize to smaller grains with increased heat and pressure.

A fine-grained texture is the product of rapid cooling and crystallization of lava.

How do the crystallization and settling of the earliest formed minerals affect the composition of the remaining magma? -After the earliest formed minerals have settled, the resulting magma will be denser than the original magma. -After the earliest formed minerals have settled, the resulting magma will be more felsic than the original magma. -After the earliest formed minerals have settled, the resulting magma will become richer in iron and magnesium than the original magma. -After the earliest formed minerals have settled, the resulting magma will be less felsic than the original magma.

After the earliest formed minerals have settled, the resulting magma will be more felsic than the original magma.

How is basaltic magma transformed into felsic magma? Basaltic magma partially melts the continental crust, which is more felsic in composition. Fe- and Mg-rich minerals are added to the magma during partial melting. By a change in pressure and temperature. An elevated geothermal gradient causes olivine and pyroxene to be the first minerals to melt. By the partial melting of mantle peridotite.

Basaltic magma partially melts the continental crust, which is more felsic in composition.

Why does partial melting result in a magma having a composition different from the rock from which it was derived? -Because different minerals solidify at different temperatures, minerals that solidify at higher temperatures will be removed from the melt first, leaving behind only the minerals that solidify at lower temperatures. -Because different minerals melt at different temperatures, minerals that melt at lower temperatures will melt from the rock first, creating a magma formed from the minerals that melted first. -Because different minerals melt at different temperatures, minerals that melt at higher temperatures will melt from the rock first, creating a magma formed from the minerals that melted first. -Because different minerals all melt at the same temperature, minerals that are closer to the Earth's surface will melt first, creating a magma composed of minerals that are closer to the Earth's surface. -Because different minerals solidify at different temperatures, minerals that solidify at lower temperatures will be removed from the melt first, leaving behind only the minerals that solidify at higher temperatures.

Because different minerals melt at different temperatures, minerals that melt at lower temperatures will melt from the rock first, creating a magma formed from the minerals that melted first.

How do light-colored igneous rocks differ from dark-colored rocks? Dark-colored igneous rocks have a higher silica content than light-colored rocks. Light-colored rocks are called mafic, whereas dark-colored rocks are called felsic. Light-colored igneous rocks begin melting at a much higher temperature than dark-colored rocks. Dark-colored igneous rocks have a higher iron and magnesium content than light-colored rocks. Light-colored igneous rocks have a higher iron and magnesium content than dark-colored rocks.

Dark-colored igneous rocks have a higher iron and magnesium content than light-colored rocks.

What causes an elevated geothermal gradient in a divergent plate setting? An increase in pressure Partial melting of continental crust Decompression melting of the mantle A decrease in temperature Plate subduction

Decompression melting of the mantle

Once a source rock partially melts, what does it produce? Felsic lava Mafic magma and felsic residue Granite and rhyolite Mafic lava Felsic magma and mafic residue

Felsic magma and mafic residue

Intrusive and extrusive igneous rocks are classified based on what criteria? The composition of the molten rock and how quickly it cools and crystallizes How quickly the molten rock cools and crystallizes, and where this occurs with respect to Earth's surface The linked framework of the silicon-oxygen tetrahedra, and where the molten rock cools with respect to Earth's surface The composition of the molten rock, and where it cools with respect to Earth's surface

How quickly the molten rock cools and crystallizes, and where this occurs with respect to Earth's surface

Why does magma have a tendency to rise after its formation? The rocks below can't melt. It is denser than the surrounding rock. It contains significant amounts of volatile gases. It is less dense than the surrounding rock. It has less volume when it is a liquid.

It is less dense than the surrounding rock.

What is one way a glassy texture forms? Lava slowly degasses. Lava cools rapidly. Lava decompresses during eruption. Lava cools slowly. Magma cools slowly.

Lava cools rapidly.

Which of the following textures indicates two stages of cooling and crystallization? Porphyritic Frothy Phaneritic Pyroclastic Glassy

Porphyritic

What is the geothermal gradient, and how does it relate to the melting curve of peridotite? View Available Hint(s) -The geothermal gradient is the increase in temperature with depth under the Earth's surface. The melting curve of peridotite is at first higher than the geothermal gradient, but cross to lower than the gradient at about 300km below the Earth's surface. -The geothermal gradient is the increase in temperature with depth under the Earth's surface. The melting curve of peridotite is consistently lower than the geothermal gradient. -The geothermal gradient is the decrease in temperature with depth under the Earth's surface. The melting curve of peridotite is consistently lower than the geothermal gradient. -The geothermal gradient is the decrease in temperature with depth under the Earth's surface. The melting curve of peridotite is consistently higher than the geothermal gradient. -The geothermal gradient is the increase in temperature with depth under the Earth's surface. The melting curve of peridotite is consistently higher than the geothermal gradient.

The geothermal gradient is the increase in temperature with depth under the Earth's surface. The melting curve of peridotite is consistently higher than the geothermal gradient.

What does it mean if an igneous rock has an aphanitic texture? This igneous rock texture can be described by a variety of both large and small mineral crystals. The igneous rock exhibits a texture that results from the slow cooling of molten rock. The igneous rock displays mineral crystals easily seen with the naked eye. The igneous rock exhibits mineral crystals too small to see with the naked eye. An igneous texture that results from the cooling of magma below the surface of the Earth.

The igneous rock exhibits mineral crystals too small to see with the naked eye.

What does an igneous rock with a pyroclastic texture tell a geologist? The rock was filled with gas and decompressed upon eruption. The rock was likely formed by a violent volcanic eruption. The rock was formed from two distinct cooling episodes. The rock was formed in an intrusive setting. The rock was formed by rapid crystallization after eruption.

The rock was likely formed by a violent volcanic eruption.

How does decompression melting occur? -When hot, liquid mantle rock ascends, it moves to areas of lower pressure. This reduction in pressure allows the hot material to melt into a less viscous liquid phase. -When hot, solid mantle rock ascends, it moves to areas of higher pressure. This increase in pressure allows the hot material to melt into a less compressed liquid phase. -When hot, solid mantle rock descends, it moves to areas of lower pressure. This reduction in pressure allows the hot material to melt into a less compressed liquid phase. -When hot, solid mantle rock ascends, it moves to areas of lower pressure. This reduction in pressure allows the hot material to melt into a less compressed liquid phase. -When hot, liquid mantle rock descends, it moves to areas of higher pressure. This increase in pressure allows the hot material to melt into a solid phase.

When hot, solid mantle rock ascends, it moves to areas of lower pressure. This reduction in pressure allows the hot material to melt into a less compressed liquid phase.

According to Bowen's Reaction Series, __________ is one of the first minerals to melt, but last to crystallize. amphibole quartz potassium feldspar calcium plagioclase olivine

quartz

At a subduction zone, melting is triggered by _____. stretching the continental crust a decrease in pressure the introduction of water heating the crustal rocks the presence of volcanism

the introduction of water

As a result of partial melting, magma originates in __________. the outer core and the inner core the crust and the inner core the mantle and crust the outer core and the mantle the atmosphere

the mantle and crust

In a subduction zone, water driven from subducted oceanic crust causes __________. the melting temperature of mantle rocks to increase a melt of felsic composition a decrease in pressure the melting temperature of mantle rocks to decrease decompression melting

the melting temperature of mantle rocks to decrease

In what type of igneous feature would you find rocks with a vesicular texture? laccolith the surface of a lava flow batholith at the base of a lava flow sill

the surface of a lava flow