Eosc 114 Volcanoes

What correctly describes volcanism at a continental volcanic arc?

High Viscosity dacitic lavas and explosive volcanism

During the 1986 lake Nyos eruption, the most dangerous areas to be in were_____because the gas was______?

In valleys,denser than air

what magma type is produced by partial melting of the Earth's mantle?

Mafic

Fatalities from volcanic eruptions have increased steadily over the past 200 years because _________.

the world's population has increased and people are living closer to 100% volcanoes.

True or False:Mount St. Helens is a composite volcano that can erupt magmas with the entire possible range of silica contents.

True

What type of volcanic landform is MOST commonly associated with Hawaiian mafic volcanism?

Shield Volcano

The type of magma most likely to cause a violent volcanic eruption is________.

high viscosity and relatively cool

True or False:All minerals have Si and O.

False

What is NOT measured in volcano monitoring programs

temperature of the magma body at depth

What was the volcanic hazard that caused the tragedy at Lake Nyos in Cameroon?

Co2 gas

Pyroclastic flows don't originate in _______.

fall of ballistic debris

A common example of a mafic volcanic landform is a ________.

Shield Volcano

A hazard NOT caused by volcanic ash and ash clouds is:

causing a tsunami when ash falls into the ocean

Most magma is generated by melting of pre-existing rock through _________.

decompression melting

The majority of the world's explosive volcanoes are found at:

Convergent plate boundaries

Which volcanic hazards is the LEAST hazardous to humans?

Lava

What is NOT a product of a volcanic eruption?

intrusive igneous rocks

The MOST LIKELY place to find an active subaerial volcano is ______.

Above a subduction zone

A magma erupting at a temperature of 600-800°C, with high silica content, high gas content, and high viscosity will erupt as a/an _________.

rhyolite pyroclastic flow in a caldera

he explosivity of hot spot volcanism is dictated by ?

the composition of the overlying plate

True or False: about volcanism in an ocean-ocean convergence setting? Mafic-intermediate lavas are common.

True

How does a cinder cone form?

Relatively short-lived eruptions of pyroclastic material build up a small volcano.

Which volcanic hazard does hydrothermal alteration promote?

Landslides

True or False: A Lava flow is is not typical of cinder cone eruptions

False

Immediately after an eruption at Kilauea in Hawaii, the surface of the volcano ______.

subsides, making the slopes of the volcano less steep

Which of the following volcanic hazards is typically the DEADLIEST for people?

pyroclastic flows from stratovolcanoes

Which of the following eruptions had the highest Volcanic Explosivity Index (VEI)?

Yellowstone caldera, 600,000 years ago

Which volcano poses the GREATEST risk to life and property in Vancouver and southern British Columbia?

Mount Baker

Which magma composition will produce the most explosive volcanoes?

Rhyolite

What magma has the highest viscosity ?

Rhyolite

Which of the following poses the GREATEST hazard to the Metro Vancouver area from a nearby volcanic eruption?

Ash Fall

Large eruptions from stratovolcanoes typically affect climate by ______.

ejecting ash particles that block sunlight and cause global cooling

How did the residents of Vestmannaeyjar, Iceland, save their harbor from a lava flow?

They chilled the lava flow with water, making the flow solidify before it blocked the harbor.

Which of the following is the most common volcanic rock on Earth?

Basalt

Aircraft flying at high altitudes between North America and Asia can be very susceptible to ______ erupted from volcanoes in Cascadia and Alaska.

Volcanic Ash

Which of the following volcanic hazards can occur without an accompanying eruption?

sector collapse / volcanic landslide / Lahars

If you are hiking in Garibaldi Provincial Park and your map identifies a feature near your trail as "The Cinder Cone", what rock type would you be most likely to encounter as you walk near this feature?

Basalt

Why are stratovolcanoes the most common type of volcano around the Pacific Rim?

they are typical of continent-ocean subduction zones

Two volcanic gas products are ______.

carbon dioxide and water vapour

The Hawaiian volcanic chain extends from southeast to northwest, growing progressively older to the northwest. This age progression implies that movement of the Pacific Plate in this region has been towards the ______.

Northwest

How can studying the geologic history of a volcano help most in eruption forecasting?

Mapping previous volcanic deposits from a volcano is helpful for developing hazard maps for land-use planning and disaster preparedness

Good news! You have just been informed that your annual charity bicycle-ride is up to the top of a volcano. But it is next week and you have an injured knee. If you could choose the EASIEST ride up, which type of volcano would it be?

Shield volcano

Jokulhlaups are ______.

floods induced by volcanic eruptions underneath glaciers

Maars are ______.

craters formed by the interaction of magma with groundwater

Which of the following correctly describes volcanism at a continental volcanic arc?

high viscosity dacitic lavas and explosive volcanism

The Volcanic Explosivity Index (VEI) is based on all of the following EXCEPT ________.

the recurrence interval of eruptions

What are the two basic requirements for lahars?

Tephra and water

Which of the following volcanic HAZARDS is the most likely to kill people, plants, and animals?

pyroclastic flow

True or False:Lava is the extrusive equivalent of magma.

True

Which of the following describe hot spot volcanism in Hawaii?

dark-colored, high-temperature basalt, non-explosive volcanism

______ is another name for extrusive igneous rocks and _______ is another name for intrusive igneous rocks.

olcanic; plutonic

Which of the following does NOT influence a volcano's explosivity?

Ash content

The explosivity of hot spot volcanism is dictated by which of the following?

the composition of the overlying plate

True or False:

Predicting eruptions can be very costly because many times equipment is completely destroyed.

When considering all the predictive tools you could use to predict an impending eruption, which is considered to be the SINGLE MOST USEFUL?

seismic monitoring

Ture of false: magma/lava colour effects volcano explosively

False

Molten material beneath the Earth's surface is called _________.

Magma

The Cascade arc sits adjacent to a plate boundary where the ______ plate is ______ the ______

Juan de Fuca; subducting beneath; North American plate

What type of volcanic landform is MOST commonly associated with Hawaiian mafic volcanism?

Shield Volcano

Magma is molten rock material ________.

beneath the surface of the Earth

Mafic lavas have ______.

low silica content and temperature between 1200-1400 °C

The high viscosity of some lavas results from:

high SiO2 content

Compared to pyroclastic flow deposits, air-fall deposits are recognized by _________.

the presence of layers, each of a specific grain size

Highly viscous lavas (m = 7) with high gas content will generally yield ______ volcanism

explosive

An igneous rock with a coarse-grained interlocking texture of crystals is called ______.

Intrusive

Which of the following Cascade Arc volcanoes have had a recent (in the last 500 years) eruption history?

Mount St. Helens

Acoustic Flow Monitors _____________.

respond to higher frequency vibrations than those produced by earthquakes

Which of the following is NOT used to predict volcanic eruptions?

air density

Carbon dioxide CO2 gas is a MAJOR hazard at active volcanoes because it ______.

causes death by asphyxiation

Take 3 pieces of uncooked spaghetti of different lengths and put raisins on each end. Now, hold the sticks (make sure the ends with the raisins are on top) and shake the sticks vigorously back and forth. WHICH ONE will break first and WHY?

The shortest one because short objects resonate more during high frequency shaking.

True or false:The absence of seismic activity is characteristic of the magma chamber.

True

Immediately after an eruption at Kilauea in Hawaii, the surface of the volcano ______.

subsides, making the slopes of the volcano less steep

Which of the following volcanic hazards is typically the DEADLIEST for people?

pyroclastic flows from stratovolcanoes

During the 1986 Lake Nyos eruption, the most dangerous areas to be in were ____ because the gas was _____.

in valleys, denser than air

Which of the following magma types is produced by partial melting of the Earth's mantle?

Mafic

Which of the statements about composite volcanoes are TRUE?

Mount St. Helens is a composite volcano that can erupt magmas with the entire possible range of silica contents.

A high volcano explosivity index (VEI) generally corresponds with _________.

long recurrence intervals

Which of the following is FALSE about a mineral?

All minerals have Si and O.

Which of the following are NOT measured in volcano monitoring programs?

temperature of the magma body at depth

Pyroclastic flows originate in all of the following ways EXCEPT _______.

fall of ballistic debris

The majority of the world's explosive volcanoes are found at:

convergent plate margins

Which of the following volcanic hazards is the LEAST hazardous to humans?

lava

Which of the following is NOT a product of a volcanic eruption?

intrusive igneous rocks 100%

Which of the following statements would be TRUE about volcanism in an ocean-ocean convergence setting?

Mafic-intermediate lavas are common

Which is FALSE? A lava flow ______.

is not typical of cinder cone eruptions

Why did you choose your answer for Question 5? That magma composition ______.

has the highest viscosity

Which of the following can be fount at a plate boundary where shear stress is taking place?

felt intensity

Grain size in igneous rocks is a function of ______ over time.

cooling

What does satellite radar interferometry (InSAR) measure?

ground deformation of a volcano or volcanic area over time

A volcano that is likely to erupt will MOST LIKELY show which of the following combination of precursors?

abundant 'fringes' on InSAR images; increased COSPEC measurements; unseasonal melting of snow

The explosivity of magmatic eruptions is most dependent on ______.

the ease with which dissolved gases can escape from the magma

What is the primary volcanic hazard to communities built along rivers near Mount Rainier?

lahars

The occurrence of a lahar is difficult to predict because ______.

lahars can occur long after an eruption ceases

Compared to shield volcanoes, composite volcanoes are ______.

smaller, with steeper slopes and more felsic lavas

Which of the following properties of extrusive igneous rock/magma does NOT depend on its chemical composition?

crystal size

Which of the following monitoring techniques would BEST indicate year-to-year uplift of the ground in a volcanic area and hence the possibility of a potential future eruption?

InSAR imagery

The "resistance to flow" of any liquid is known as its ______.

viscosity

Volcanic landslides can be triggered by all of the following EXCEPT ________.

lahars

Which of the following is an important difference between a pyroclastic flow and a lahar?

pyroclastic flows only occur during eruptions

Which of these Cascade Range volcanoes do geologists believe has the ability to greatly affect (i.e. be very hazardous) the largest area around it?

Mount Rainier