chapter 6 volcanoes 2 reading assignment

The most significant hazard associated with ____-type volcanism is the flowing lava alters the landscape and destroys buildings and roads.

hawaiian

Pyroclastic debris can be deposited by ______. lava domes high-speed, gas-charged flows air-fall from an ash cloud the breakup of lava flows as they cool

high-speed, gas-charged flows air-fall from an ash cloud

The solubility of gases in a magma _____ with increasing pressure. increases decreases remains constant

increases

The viscosity of magma ____with silica content because the tetrahedra link up in different configurations and hinder flow.

increases

A volcanic mudflow, produced by the mixing of water with volcanic ash, is also known as a _____. pyroclastic flow debris avalanche lava flow lahar

lahar

Herculaneum was destroyed by ______, which is a landslide of volcanic debris. lahars pyroclastic flows ash fall earthquakes

lahars

____ melting occurs when mantle rocks rise upward and experience lower pressure.

decompression

Increasing the temperature of a lava will tend to ______ its viscosity. decrease have no effect on increase

decrease

Increasing the temperature of a lava will tend to ______ its viscosity. have no effect on decrease increase

decrease

Volcanism at subduction zones is typically _______. rare peaceful very high volume explosive

explosive

True or false? A Plinian eruption is followed by a Vulcanian eruption rather than the other way around.

false

The word pyroclastic comes from the Greek pyro, meaning ____, and clastic, meaning ____.

fire, fragments

Vast outpourings of basaltic lava from fissures that cover very large areas of the Earth's surface are called ____________. shield volcanoes pillow basalts flood basalts blanket basalts

flood basalts

The basalt flows that compose a shield volcano typically ______, which results in gentle slopes. flow just a short distance, forming small mounds flow for a long distance, forming thin flows erupt explosively, forming spatter cones

flow for a long distance, forming thin flows

Which of the following best describes a stratovolcano? A broad, gently sloping volcano constructed of solidified lava flows A volcano constructed of pyroclastic fragments ejected from a central vent A steep-sided, dome-shaped mass of solidified viscous lava A large volcano composed of alternating layers of pyroclastic fragments and solidified lava flows

A large volcano composed of alternating layers of pyroclastic fragments and solidified lava flows

The less viscous a fluid, the more ______ it is. dense fluid sticky resistant to flow

fluid

Which of the following statements explain why basalt is typically a low-viscosity magma? Basaltic magmas typically have high volatile contents. Basaltic magmas have high densities. Basaltic magmas have higher temperatures. Basaltic magmas have lower SiO2 contents. Basaltic magmas generally contain more crystals.

Basaltic magmas have higher temperatures. Basaltic magmas have lower SiO2 contents.

Match the labels on this figure to the roles of volatiles in generating an explosive eruption. A B C D Hot gases create a buoyant plume Expansion of gases produce a powerful gas jet Gas bubbles form as magma rises Expanding gas bubbles causes fragmentation of magma

D B A C

Which of these eruptive styles are most closely associated with stratovolcanoes? Strombolian Hawaiian Vulcanian Plinian

Vulcanian Plinian

What is the most abundant volatile in magma? Sulfur dioxide Carbon dioxide Water Methane

Water

Which of the following factors is usually the most important in determining whether a volcanic eruption will be peaceful or explosive? Water content of magma Density of magma Depth of magma Volume of magma

Water content of magma

A(n) ______ basalt lava flow, such as the one shown in this image, has a rubbly and jagged surface. pahoehoe rubbly plateau aa Hawaiian

aa

When very high-viscosity lava piles up over a volcanic vent, it typically forms a ______. volcanic crater cinder cone lava dome volcanic neck

lava dome

Volcanic glass can form when ______. magma cools slowly within a magma chamber magma is extremely fluid magma cools too rapidly for minerals to crystallize magma is too hot for minerals to form

magma cools too rapidly for minerals to crystallize

Basaltic magmas are most commonly associated with ______. violently explosive eruptions nonviolent lava flow eruptions moderately explosive eruptions

nonviolent lava flow eruptions

A high-viscosity rhyolite magma with low water content will produce a(n) _______. pyroclastic flow explosive eruption slow-moving lava flow highly fluid lava flow

slow-moving lava flow

A typical shield volcano is composed primarily of __________. cinders and volcanic bombs layers of volcanic ash solidified basalt lava flows alternating layers of lava and ash

solidified basalt lava flows

An air-fall deposit of pyroclastic debris can be distinguished from a pyroclastic flow deposit by the _______. thickness of the layer composition of the deposited material distance from the vent sorting of pyroclasts by size

sorting of pyroclasts by size

Plinian and Vulcanian eruptive styles are associated with ____ volcanoes.

strato

The volcano shown here is an example of a _______. shield volcano scoria cone lava dome stratovolcano

stratovolcano

Mount Vesuvius is a product of the ____ of the Mediterranean seafloor (African plate) beneath Europe (the Eurasian plate).

subduction

Magma viscosity is affected by its ____, the silicon and ____content, and how much of the magma has already crystallized into ____.

temperature, oxygen, minerals

Plinian eruptions are characterized by _______. the generation of a sustained, gas-powered eruption column that carries pyroclastic material high into the atmosphere eruption of large volumes of low-viscosity basaltic lava short-lived eruptions of pyroclastic debris that pile up around the vent to form a scoria cone short, explosive blasts of ash and dust interspersed by eruption of thick, viscous lava

the generation of a sustained, gas-powered eruption column that carries pyroclastic material high into the atmosphere

At what approximate depth is magma generated below subduction zones? 1,000 km 100 km 5 km 50 km

100 km

Approximately ____ Plinian eruptions occur each century.

2

How many Plinean eruptions typically occur each century? 0-1 5-8 2-3 9-10

2-3

Seismic surveys at Vesuvius have shown that a magma body lies at a depth of ____ below the surface, suggesting a future eruption is probable. 1 km 8 km 20 km

8 km

Which of the following best describes a cinder cone? A relatively small cone constructed of pyroclastic debris piled up next to a central vent A large cone composed of alternating layers of pyroclastic fragments and solidified lava flows A large, broad, gently sloping volcano constructed of solidified lava flows

A relatively small cone constructed of pyroclastic debris piled up next to a central vent

Which of these descriptions best characterizes a Vulcanian eruption? Alternating flows of thick, highly viscous lava and explosive blasts of pyroclastic material A sustained eruption column of hot gases and pyroclastic material that climbs to several kilometers in the atmosphere High volumes of low-viscosity basaltic magma spreading out over large areas Slow eruption of very viscous lava, leading to the buildup of a lava dome

Alternating flows of thick, highly viscous lava and explosive blasts of pyroclastic material

What role do gas bubbles play in generating eruptions? Increasing the volume of gas bubbles increases the magma's viscosity, and thereby decreases the likelihood of an eruption. Gas bubbles do not play an important role in eruption of magma. As gas bubble volume increases, it helps propel magma out of the volcano.

As gas bubble volume increases, it helps propel magma out of the volcano.

Arrange the following pyroclastic fragments in order from smallest to largest in size. Put the term for the smallest pyroclasts at the top. Blocks and bombs Ash Cinders

Ash Cinders Blocks and bombs

Why is the viscosity of a magma lower at higher temperatures? Atoms vibrate more vigorously at higher temperatures, breaking bonds and increasing fluidity. Water turns to gas at higher temperatures, increasing the fluidity of the remaining liquid. More crystals form at higher temperatures, thus lowering the fluid content. The viscosity of a magma is not lower at higher temperatures.

Atoms vibrate more vigorously at higher temperatures, breaking bonds and increasing fluidity.

Which of these images shows a Vulcanian eruption? E A D B C

D

Which of these is the main hazard associated with Hawaiian volcanism? Failure of airplane jet engines due to interaction with ash plumes Loss of life due to pyroclastic bombs and blocks Destruction of property and infrastructure by lava flows Tsunamis caused by slope failure events at the shore

Destruction of property and infrastructure by lava flows

This eruption at Surtsey, an island off the coast of Iceland, is typical of a _____ eruption. Flood basalt Plinian-type Strombolian-type Hawaiian-type

Hawaiian-type

Which of these best describe the nature of magma that forms a lava dome? High volatiles High viscosity Low volatiles Low viscosity

High viscosity Low volatiles

Which of the following explain why rhyolitic eruptions are commonly violent and explosive? High pressure High temperature High water content High silica content High viscosity

High water content High silica content High viscosity

Which of these statements explain the explosive nature of eruptions at subduction zones? High water content of magma High temperature of magma High pressure of magma Basaltic composition of magma High silica content of magma High viscosity of magma

High water content of magma High silica content of magma High viscosity of magma

Which of the following are common features of Hawaiian-type eruptions? Lava fountains along fissures Pyroclastic flows Buildup of a low cone with fountain eruptions Lava dome formation Lava flows

Lava fountains along fissures Buildup of a low cone with fountain eruptions Lava flows

Which of these statements explain the peaceful nature of eruptions at spreading centers? Low volatile content of the magma Highly fluid magma High viscosity of the magma Low volume of magma Low silica content of the magma High temperature of the magma

Low volatile content of the magma Highly fluid magma Low silica content of the magma High temperature of the magma

Which of the following explain why basaltic eruptions are commonly peaceful? (Select all that apply.) Multiple select question. Low pressure Low water content Low viscosity Low temperature Low silica content

Low water content Low viscosity Low silica content

Which of these are the three ways in which rock may melt? Lowering the pressure Increasing the silica content Increasing the temperature Increasing the viscosity Addition of water

Lowering the pressure Increasing the temperature Addition of water

Which of these is an example of a shield volcano? Mount Rainier, Washington Paricutin, Mexico Mount Vesuvius, Italy Mauna Loa, Hawaii

Mauna Loa, Hawaii

Which of these is not an example of a stratovolcano? Mount Fuji, Japan Mount Wrangell Mount Shasta, California Mount Rainier, Washington Mount Kilimanjaro, Tanzania

Mount Wrangell

The eruption of Mount Pinatubo in the Philippines, shown in this image, is an example of a _______ eruption. Strombolian Vulcanian Hawaiian Plinian

Plinian

Which of these magmas would typically be the most viscous? Andesite Rhyolite Basalt

Rhyolite

______ magmas are associated with the most violent and explosive volcanic eruptions. Rhyolitic Andesitic Basaltic

Rhyolitic

Which of the following statements explain why rhyolite is typically a high-viscosity magma? Rhyolitic magmas have high densities. Rhyolitic magmas have higher SiO2 contents. Rhyolitic magmas have lower temperatures. Rhyolitic magmas generally contain very few crystals. Rhyolitic magmas typically have high volatile contents.

Rhyolitic magmas have higher SiO2 contents. Rhyolitic magmas have lower temperatures.

Which of the following best describes the appearance of the surface of an aa basalt flow? Rubbly and jagged Ropy or billowy Perfectly smooth Sandy

Rubbly and jagged

Match the 3 Vs to each of these volcano landforms. Shield volcano Scoria cone Stratovolcano Lava dome ___Low/medium viscosity, medium/high volatiles, small volume ___ low viscosity, low volatiles, large volume ___high viscosity, low volatiles, small volume ___medium/high viscosity, medium/high volatiles, large volume

Scoria cone Shield volcano Lava dome Stratovolcano

Match each of the 3 Vs of volcanology with its effect on an eruption. Viscosity Volatiles Volume ____Controls the intensity of an eruption ____ Controls whether magma flows away or piles up ____ Controls the explosivity of an eruption

Volume Viscosity Volatiles

Which of the following best explains why silica (SiO2) increases the viscosity of a magma? Silicon and oxygen bond to form silicon-oxygen tetrahedra, which bond to each other, making flow more difficult. Silicon and oxygen are nonreactive elements and thus prevent the formation of crystals, which increases viscosity. Silicon and oxygen atoms are very large, which decreases the fluidity of the magma. Silicon and oxygen prevent the formation of bubbles, thus increasing the fluidity of the magma.

Silicon and oxygen bond to form silicon-oxygen tetrahedra, which bond to each other, making flow more difficult.

Pyroclastic debris is classified as dust, ash, cinders, blocks, or bombs according to what feature? Size Bubble content Density Composition

Size

Which of the following best describes the appearance of the surface of a pahoehoe basalt flow? Sandy Smooth and ropy Rough and blocky

Smooth and ropy

Which of the following statements explain why spreading centers are the ideal locations for volcanism? The asthenosphere below spreading centers has a high water content. Spreading centers are associated with high-temperature hot spots. The asthenosphere below spreading centers has a very low viscosity. Spreading centers lie above the high-temperature asthenosphere. The upward motion of the asthenosphere below spreading centers causes a decrease in pressure.

Spreading centers lie above the high-temperature asthenosphere. The upward motion of the asthenosphere below spreading centers causes a decrease in pressure.

This image shows a _______ eruption, which is distinguished by discrete explosive bursts that throw pyroclasts tens to hundreds of meters into the air. Hawaiian Strombolian Plinian Vulcanian

Strombolian

What style of eruption is typically associated with scoria cones? Hawaiian Strombolian Vulcanian Plinian

Strombolian

What is the plate tectonic setting of Mount Vesuvius in Italy? Subduction zone Transform fault Continental collision zone Continental rift Spreading center

Subduction zone

What happens to volatiles in a magma as it rises toward the surface? The volatiles come out of solution and form bubbles. The volatiles dissolve into the magma. The volatiles become more concentrated in the magma. The volatiles react with silica in the magma to form chains of silicon-oxygen tetrahedra.

The volatiles come out of solution and form bubbles.

True or False? Magma at great depths does not contain gas bubbles.

True

Which of the following best describes flood basalts? Vast outpourings of basaltic lava from fissures that do not build a central volcano Broad, gently sloping volcanoes made up of thin basaltic lava flows HIghly explosive eruptions of basaltic magma that cover the land in pumice and ash

Vast outpourings of basaltic lava from fissures that do not build a central volcano

_____ is a measure of the internal resistance of a fluid to flow. Permeability Temperature Viscosity Density

Viscosity

In 1790, an eruption of Kilauea led to the death of over 80 members of King Keoua's army. The majority were killed by ______. pyroclastic blocks and bombs thrown from the volcanic vent a fast-moving lava flow a base surge of hot ash and gas from an explosive eruption suffocation by thick falling ash and dust

a base surge of hot ash and gas from an explosive eruption

Decompression melting requires ________. a decrease in pressure the addition of water both a decrease in pressure and an increase in temperature an increase in temperature

a decrease in pressure

The two most important factors in the melting of mantle rock are ______ and _______. the addition of water; an increase in temperature a decrease in pressure; the addition of water a decrease in volume; an increase in viscosity an increase in temperature; the addition of water

a decrease in pressure; the addition of water

The people who remained in Pompeii during the eruption of Vesuvius in 79 CE were killed by ______. scalding hot water that flowed down from the summit ash and pumice that fell on the town volcanic mudflows fast-moving lava flows

ash and pumice that fell on the town

The magma composition with the lowest viscosity is ______ because it is both the hottest and has the lowest silicate content. andesite basalt rhyolite

basalt

Another name for a stratovolcano is a _________. shield composite volcano volcanic dome cinder cone

composite volcano

____ is the name for the cooled volcanic glass shown here.

obsidian

A(n) ______ basalt lava flow, such as the one shown in this image, has a billowy or ropy surface. pahoehoe pillow aa

pahoehoe

Vulcanian eruptions are commonly "throat-clearing" events that precede ____ eruptions.

plinian

The frothy, glassy, volcanic rock shown here is called ______. scoria pumice basalt obsidian

pumice

Fragments of magma formed by an explosive eruption are called ______. pyroclastic debris pahoehoe clasts lahar fragmental material

pyroclastic debris

People near the sea during the 79 CE eruption of Vesuvius were mostly killed by _______. pyroclastic flows a tsunami pyroclastic blocks and bombs lava flows

pyroclastic flows

A relatively small volcano that is composed of loose, dark colored pieces of pyroclastic debris and has a single, circular vent is a ____ cone.

scoria

The name for this basaltic rock, which is full of holes made by expanding gas bubbles, is ____.

scoria

A ____ ____ is a relatively small volcano constructed of pyroclastic debris piled up around a central vent.

scoria cone

This image shows an erupting ______. caldera shield volcano scoria cone stratovolcano

scoria cone

Mount Kilauea in Hawaii is a ____ volcano.

shield

This diagram shows a broad, gently sloping volcano made up of low viscosity lava flows, which is called a ______. lava dome scoria cone shield volcano stratovolcano caldera

shield volcano

A large volume of low viscosity and low volatile magma will produce a ____ volcano, while a large volume of high viscosity and high volatile magma will produce a ____ volcano.

shield, caldera

The deadly, explosive eruption of Kilauea in 1790 was caused by _______. the incorporation of water into basalt and heating of the groundwater the presence of high-silica, high-viscosity magma the breaking apart of a lava cap that had blocked the vent, leading to a pressure buildup an exceptionally large volume of magma

the incorporation of water into basalt and heating of the groundwater

Shield volcanoes typically have gentle slopes because _________. they are formed from overlapping ash layers they are the result of the collapse of the ground into magma chambers they are subject to intense erosion in tropical environments they are formed from eruptions of low-viscosity basaltic lava

they are formed from eruptions of low-viscosity basaltic lava

Flood basalt eruptions can affect global climate because _______. they heat the surface of the Earth over a vast area, which can affect weather patterns they emit large volumes of the greenhouse gas carbon dioxide and sulfur dioxide they thrust vast amounts of ash into the atmosphere, which can block sunlight for many years

they emit large volumes of the greenhouse gas carbon dioxide and sulfur dioxide

Although there has not been a flood basalt eruption in historic time, we know that they can have a devastating global effect because ________. two major flood basalt eruptions correlate in time with two mass extinctions the beginning of the most recent ice age correlates with the most recent flood basalt eruption ash deposits from a single flood basalt eruption can be found around the globe a flood basalt eruption occurred in Siberia at the same time as the collapse of the Roman Empire

two major flood basalt eruptions correlate in time with two mass extinctions

The term for gases, such as water and carbon dioxide, that are dissolved in a magma is ____.

volatiles

Magma viscosity is directly affected by all of the following except ______. Multiple choice question. volume silica content mineral crystal content temperature

volume

The "three Vs" of volcanology are ____, ____, and ____.

volume, viscosity, volatiles

Typically, the most abundant dissolved gas in a magma is ____.

water

Melting of the mantle at subduction zones occurs because _______. rising mantle material experiences lower pressures friction along the surface of the subducting plate heats the overlying mantle water carried into the mantle by the subducting plate significantly reduces the melting temperature of the rock mantle rocks are dragged down by the subducting plate into regions of high temperature

water carried into the mantle by the subducting plate significantly reduces the melting temperature of the rock