CH 6 SmartBook Questions

steeper

A composite cone has slopes that are ______ than those of a shield volcano.

a hazardous flood

A volcanic eruption occurring beneath an ice sheet is likely to cause ______.

composite volcano

Almost 40,000 people were killed by the 1883 eruption of Krakatau, Indonesia. Krakatau was a ______ that formed a caldera.

more soil and plants

An older scoria cone would have ______ compared to a younger scoria cone.

volcanic eruptions

Changes in topography, water chemistry, heat flow, and gas output all are used to help predict ______.

the formation of gas bubbles

Decreasing the pressure on a liquid that contains dissolved gases will result in ______.

magma rising in the volcano

Earthquakes at Mount St. Helens prior to the major eruption in 1980 were caused by

hot spots

Flood basalts are believed to erupt at ______ directly over rising mantle plumes.

long fissures/dikes

Flood-basalt eruptions are fed by ______.

hazards; risks

Flowing lava and volcanic flooding are considered ______, whereas the likelihood of fatalities and building damage from these two events are considered ______.

-what rock types it will form -what landforms it will create

Gas in basaltic magma is the major controlling factor that determines ______.

high

Gases more easily remain dissolved in liquids at ______ pressures.

calderas; fissures

Huge circular depressions from which volcanoes erupt are ______; magma also can erupt from cracks, or ______.

Flat-topped mesa with eroded volcanic rock cliffs at the top

In trying to determine whether a landform is a volcano or not, which of the following would not be used to describe a volcano?

caldera

Krakatau (1883) and Thera (3,500 years ago) were both disastrous______eruptions that blew apart islands.

less gas

Lava flows are produced by basaltic magmas that contain ______ than those that produce scoria cones.

seismic shaking

Magma rising through the crust fractures rocks, producing rhythmic, repeating ______.

- Felsic magma = gas bubbles cannot escape easily; high pressures build up in the magma; typically explosive eruptions; magma is high viscosity - Basaltic magma = gas bubbles escape easily; little pressure builds in the magma; typically nonexplosive eruptions; magma is low viscosity

Match the magma type with its gas bubble behavior. Instructions

- Scoria cone: > falling volcanic cinders and bombs > volcanic ash and gases - Lava flow: > burial of roads > bulldozing and crashing of houses and other structures

Match the volcanic feature with the hazard.

convergent

Most composite volcanoes are found along ______ plate boundaries.

pyroclastic flows

Mount Pelée, a composite volcano on Martinique, destroyed the town of St. Pierre in 1902, killing about 30,000 people with

composite

Mount Pelée, which erupted and killed about 30,000 people with pyroclastic flows in 1902, is a

lava flows

Nonexplosive eruptions of basaltic magmas produce ______.

pyroclastic flows

Over 25,000 people perished at Pompeii and Herculaneum in A.D. 79 as a result of ______ from Mount Vesuvius.

injected magma inflating the mountain

Prior to an eruption, the surface of a volcano may rise centimeters to hundreds of meters as a result of ______.

plate

Proximity to certain types of ______ boundaries is the major factor making some places more prone to volcanic hazards than others.

precede and accompany

Rhythmic seismic activity tends to ______ volcanic eruptions.

satellites

Scientists can monitor volcanic activity in remote locations by using___equipped to measure the heat energy emitted by them.

ejected fragments of vesicular lava

Scoria cones are composed primarily of ______.

- mudflow deposits - lava flows - pyroclastic flows

Select from below the typical components of a composite volcano.

nonexplosive outpourings of lava

Shield volcanoes are built up primarily by relatively ______.

basaltic

Shield volcanoes are composed primarily of ______ lava flows.

gentler

Shield volcanoes typically have ______ slopes than composite or scoria cone volcanoes.

measuring and detecting changes in temperatures and heat emitted by the volcano

Spaced-based satellites can be used to remotely monitor volcanoes by ______.

volcanic domes

Steep-sided hills of viscous lava that pile up over volcanic vents are known as ______.

pyroclastic flows

The A.D. 79 eruption at Mount Vesuvius in Italy, which killed about 25,000 people in Pompeii and Herculaneum, consisted mainly of ______ that roared down the slopes of the composite volcano.

composite

The deadly volcanic disasters at Pompeii, St. Pierre, and Mount St. Helens occurred at ______ volcanoes.

Minoan

The downfall of which ancient civilization in the Mediterranean closely followed the caldera-forming eruption at Santorini?

hazard; risk

The existence of a potentially dangerous situation or event is known as a(n) _____, whereas the likelihood and magnitude of its impact on society is known as its _____.

basaltic

The largest eruptions on Earth are floods of ______ magma.

fissures

The massive amount of basaltic magma in flood basalts comes to the surface from the mantle via

volcanic hazards

The type of volcano uniquely determines the ______ likely to be experienced by local populations.

pyroclastic flows

The typical form for a composite volcano is a ______.

steep-sided cone

The typical form for a composite volcano is a ______.

andesite

The volcanic rocks associated with domes are felsic to intermediate in composition, and hence are classified as rhyolite and _____.

False

True or false: All hills made of volcanic rocks are volcanoes.

False

True or false: Nearly all volcanic domes are highly symmetrical in shape.

True

True or false: Proximity to certain types of plate boundaries is the major factor making some places more prone to volcanic hazards than others.

True

True or false: The volcanic hazards associated with a volcano are dependent upon the type of volcano.

viscous

Volcanic domes form from the accumulation of ______ lava over a volcanic vent.

viscous

Volcanic domes grow from lava being injected into the interior of mounds of cooled lava and from the breaking out and moving down the flanks of _____ lava flows.

melting ice sheets

Volcanic eruptions can produce huge floods by ______.

characteristic rumbling produced as they rush down valleys

Volcanic mudflows can be detected remotely by monitoring ______.

Yellow Stone

Which U.S. national park has a "supervolcano" evidenced by hydrothermal activity, frequent earthquakes, and historical ash beds that reach as far as Canada to Mexico?

The characteristics and behavior of the gas in the magma

Which factor below largely controls what rock types and landforms develop from basaltic magma?

- composed of a pile of loose, vesicular lava fragments - steep-sided hill - formed from lava fountains

Which of the following accurately describe a scoria cone?

- broad and gently sloping form - composed of a succession of lava flows

Which of the following accurately describe most shield volcanoes?

- glowing orange lava flowing downhill - fragments of molten rock blasting into the air - billowing clouds of ash rising into the air

Which of the following are characteristics of actively erupting volcanoes?

- often occur in clusters - rubble-covered surface - steep-sided

Which of the following are characteristics typical of volcanic domes? Assume a relatively young dome.

- pumice - lava - ash

Which of the following are erupted by volcanoes?

- melted asthenosphere from around the plume in the shallow mantle - melted lithosphere over a mantle plume - plume material from deep in the mantle that melts at shallow depths

Which of the following are hypothesized sources of the magma that produce flood eruptions?

- form from collapse of overlying ground into emptied magma chamber - bounded by steep escarpments - large, basin-shaped volcanic depression

Which of the following are properties characteristic of calderas?

- large (long and wide) fissures from which the lava spews - multiple eruption events in the same area - low viscosity of the basaltic magma

Which of the following are responsible for the huge size of flood basalts?

-Volatile content of the magma -Magma composition

Which of the following are the two main factors controlling volcanic eruption style?

-Thick flows of lava break out and flow down the steep surface of the dome. -Magma injected into the interior expands and breaks up the overlying cooled lava.

Which of the following are the two ways in which volcanic domes grow?

-High gas pressures commonly lead to highly explosive eruptions. -They tend to have high viscosities. -They do not allow gas bubbles to escape easily.

Which of the following are true of felsic magmas?

- toxic volcanic gases - falling cinders and volcanic bombs - volcanic ash

Which of the following are typical hazards associated with scoria cones?

-Mudflows; -Lava flows; -Small pyroclastic flows;

Which of the following are volcanic hazards made worse by being located along a river valley directly downhill from a volcano?

-Disruption by faulting -Burial by younger rocks -Erosion

Which of the following are ways in which older calderas typically become harder to recognize?

- little soil buildup on slopes - dark, fresh-looking lava - central crater at top of a conical hill

Which of the following best describe a young scoria cone?

- increased heat flow from the volcano - steam eruption from the volcanic crater - increased gas flow from a volcano

Which of the following commonly precede a volcanic eruption?

-Eruption of lava flows -Pyroclastic flows -Ash column eruptions

Which of the following contribute to the growth of composite volcanoes?

-Most of a large island collapses into a caldera -Tsunami waves strike ships and nearby coastline -Largest and loudest explosion in recorded hisotry occurs -HIgh eruption column and pyroclastic flows form

Which of the following events accompanied the 1883 eruption at Krakatau, Indonesia?

- huge ash column forms - pyroclastic flows occur - caldera collapse drops island beneath the sea surface - tsunami travels south and hits Crete

Which of the following events accompanied the caldera-forming eruption at Santorini, Greece, about 3,500 years ago?

steep-sided, basin-shaped depression

Which of the following is a recognizable characteristic of recent calderas?

Totally covered in a fresh blanket of clean, white snow

Which of the following is not a characteristic of an actively erupting volcano?

Mesa

Which of the following is not a common type of volcano?

Bulldozing of houses from their foundations

Which of the following is not a hazard typically associated with scoria cones?

Fast-moving lava flows

Which of the following is not a hazard typically associated with scoria cones?

Age of the volcano

Which of the following is not a major controlling factor on volcanic eruption style?

Melting of snow caps dissolves large amounts of water into the magma.

Which of the following is not a reason why heat flow and gas output from a volcano tend to increase before eruptions?

High winds

Which of the following is not a typical hazard posed to human-made structures by lava flows?

They are cone-shaped.

Which of the following is not true of calderas?

Sandstone

Which of the following materials is not produced by erupting volcanoes?

- heat flow changes - changes in gas output - ground shaking - changes in topography

Which of the following phenomena are monitored to predict volcanic eruptions?

Continent-continent convergent boundary with a high mountain range (Himalaya)

Which of the following plate boundaries is least likely to produce composite volcanoes?

-Santorini -Krakatau

Which of the following represent deadly historical caldera-forming eruptions?

-Volcanic breccia -Obsidian

Which of the following rocks are associated with volcanic domes?

- town located along a river drainage directly downhill from a volcano - town located very near to a volcano

Which of the following situations would represent the highest level of volcanic hazard to a population?

- tiltmeter usage to determine changes in slope - radar imaging to detect small changes in topography - GPS station monitoring

Which of the following techniques are used to monitor changes in the shape of volcanoes that may indicate magma movement and imminent danger of eruption?

-Earthquakes -Formation of a bulge on its flanks

Which of the following were warning signs prior to the catastrophic eruption of Mount St. Helens in May 1980?

-Burning buildings -Crushing/bulldozing buildings -Covering roads

Which of these are ways in which lava flows destroy human-made structures?

-There were three caldera-forming eruptions. -Currently, it is dominated by hydrothermal activity.

Which of these describe volcanic activity in Yellowstone over the past 2 million years?

Volcanic mudflows

______ can be detected remotely from the characteristic shaking produced as they rush down valleys around a volcano.

Flood-basalt

______ eruptions are fed by a series of large fissures.

Caldera-forming

______ eruptions can emit more than 1,000 cubic kilometers of magma, resulting in the collapse of the overlying ground into a large crater.

Caldera-

______ forming eruptions are the largest and most violent volcanic phenomena.

Flood basalts

______ represent the largest igneous eruptions on Earth, with some covering tens of thousands of square kilometers.

Composite

______ volcanoes produced pyroclastic flows that killed tens of thousands of people at Pompeii and St. Pierre.