Volcanoes

The viscosity of magma is its resistance to flow and is controlled by the silica content. Which is more viscous: mafic or felsic magma?

Felsic

What volcanic hazard killed nearly every person in the town of St. Pierre on the island of Martinique when Mont Pelée erupted in 1902?

Pyroclastic flow

What are the limitations of volcanic eruption predictions?

Exact times and eruptive styles are difficult to achieve in predictions.

Match the volcanic (fine-grained) rock to its plutonic (coarse-grained) equivalent. Instructions

Rhyolite: Granite Andesite: Diorite Basalt: Gabbro

The volcanic activity in Iceland is the result of both the island's location on a spreading center and being over a(n) ______________ ______________.

Blank 1: hot or mantle Blank 2: spot or plume

Scientists are still uncertain the reason for ___________ _________, but the leading explanations suggest a locally warm area at the boundary between the outer core and the mantle.

Blank 1: hot or mantle Blank 2: spots or plumes

What mafic volcanic rock is formed at seafloor spreading ridges?

Basalt

A relatively small and steep volcano, a __________ ________is made of pieces of basaltic magma thrown into the air near the vent due to the escape of dissolved gases.

Blank 1: cinder or scoria Blank 2: cone

Match the igneous rock to its basic chemical (mineral) composition. Instructions

Granite: Dominated by quartz and feldspars (felsic) Andesite: Dominated by feldspars and ferromagnesians, with some quartz (intermediate) Basalt: Dominated by ferromagnesians and feldspars (mafic)

Choose all of the hazards associated with volcanic ash.

It causes mechanical failures. It is dangerous to breathe since it is composed of microscopic glass. It can bury entire cities.

Which of the following best describes the eruptive history of the Yellowstone caldera?

It has had three major explosive eruptions in recent geologic history.

Which of the following describe a pyroclastic flow? (Choose all that apply.)

It is a very dangerous volcanic hazard. It is also known as a nuée ardente.

What is the composition of the magma and rocks formed at seafloor spreading ridges?

Mafic

What type of magma allows gas to escape more easily?

Mafic

How does silica content affect the escape of gas in magma?

Magma high in silica content does not allow gas to escape easily.

The largest volcano on earth, ____________ _____________is a type of shield volcanoes, those are created from hundreds to thousands of runny basalt flows.

Mauna Loa

Which of these volcanoes in the Cascades is the most recently active?

Mount St. Helens

Where does the majority of volcanic activity occur?

Seafloor spreading ridges

Which of the following commonly precede a volcanic eruption? (Choose all that apply.)

Seismic activity Changes in the volcano's shape Changes in gas emissions

What type of volcano is produced from fluid basalt flows that create a large, broad, gently sloping structure?

Shield

What causes the earthquakes that precede volcanic eruptions?

The movement of magma and gas

The creation of magma in subduction zones is accomplished through the introduction of water into the asthenosphere. What is the source of this water?

The ocean floor rocks that are subducted

Which of the following describe the volcanoes of the Cascade Range? (Choose all that apply.)

They are created through the process of subduction. They are composite volcanoes.

Which of the following describe stratovolcanoes? (Choose all that apply.)

They are known to erupt explosively. They are also known as composite volcanoes. They are made up of both pyroclastic and lava flow layers.

Which of the following describe lahars? (Choose all that apply.)

They move quickly. They are made of ash and water.

True or False: The evacuations associated with active volcanic activity are often inconvenient for the nearby residents and business owners, as it can be difficult to predict how long the activity will last.

Ture

What is the acronym for the scale used to rank the size of volcanic eruptions based on the volume and height of pyroclastics released, as well as the length of the eruption?

VEI

What is pyroclastic material?

Volcanic fragments of all sizes

Of all the gases listed below that are emitted by volcanoes, which is the primary?

Water vapor

The caldera underlying ______________ National Park has erupted 3 times in the last 2 million years, with ash fall reaching from Canada to Mexico.

Yellowstone

Most of the world's active volcanoes are located ______.

along plate boundaries

Volcanic ________ can bury cities, it is slippery, it can cause roofs to collapse, is bad for people's lungs, and is damaging to engines and other mechanical equipment.

ash

Hot spot activity under ocean crust is associated with _______________ magma, whereas hot spot activity under continental crust can create more felsic magma

basaltic or mafic

A very large volcanic crater is known as a(n) _____________.

caldera

Formed by either the collapse of a volcano into an emptied magma chamber or the enlargement of an existing crater, a ______ represents a very large volcanic eruption.

caldera

This symmetric volcano made of pieces of magma thrown into the air by the escape of dissolved gases is called a ______.

cinder cone

Moving magma and gas within the lithosphere create _____________ that are common precursors to volcanic eruptions.

earthquakes

Mafic magmas flow much more easily, or are less viscous, than __________ magmas

felsic or silicic

Eruptions of lava from cracks in the earth's surface, as opposed to from single vents, are called ____________ eruptions.

fissure

Carbon monoxide, carbon dioxide, fluorine, sulfur compounds, and water vapor are all ___________ emitted by volcanoes.

gases or volatiles

A fast-moving volcanic mudflow created through the combination of ash and water is called a _________.

lahar

Rhyolitic and andesitic lavas can erupt rather quietly, piling up to form somewhat small and steep ______.

lava domes

Hot spots underneath ocean crust result in ______ magma, whereas continental hot spots may produce more ______ magma.

mafic; felsic

Magma generated in subduction zones is initially ______ in composition but can change as it makes its way to the surface. If this magma encounters continental crust, which it is hot enough to melt, the composition will change to intermediate or ______.

mafic; felsic

Fissure eruptions occur ______ and can result in massive outpourings of basalt.

on continents or on the seafloor

A very hot, very fast-moving flow of hot gases and ash from a volcano is known as a(n) ______ flow.

pyroclastic

The entire town of St. Pierre, save for one person, died in a(n) ___________ flow when Mont Pelée erupted in 1902.

pyroclastic

The Volcanic Explosivity Index is a way to categorize the size of eruptions based on three categories which include the volume of ______ produced.

pyroclastics

Rock fragments of any kinds ejected from a volcano are called

pyroclastics or pyroclasts

The felsic rock granite is rich in ______________ and feldspars, whereas the mafic rock basalt is rich in ________________ and feldspars

quartz; ferromagnesians

Harmonic tremors associated with volcanic activity create a ______ pattern.

rhythmic, continuous

Lava domes are made of ______ lava.

thick, viscous

True or false: The mafic magma created at a subduction usually makes its way to the surface unchanged in composition.

False

True or false: Volcanic eruption predictions accurately include the time of the eruption within a few hours.

False

Many of the world's active volcanoes are located along the rim of the ______.

Pacific Ocean

Evacuations necessitated by impending volcanic eruptions have saved significant numbers of lives, yet they can be seen as inconvenient and disruptive because ______.

volcanoes don't always erupt in the time and fashion they are expected to

The majority of magma at subduction zones is created ______.

when water from the subducting plate moves upward into the overlying asthenosphere

Earthquakes, harmonic tremors, and changes in topography and gas emissions are all precursor to volcanic _____________.

eruptions, explosions, or activity

The plutonic equivalent of rhyolite is ______.

granite

Scientists are trying to understand how continuous, rhythmic ______________ tremors are associated with volcanic activity.

harmonic

The volcanic activity in both Hawaii and Yellowstone is the result of ______.

hot spots

Explanations for hot spots include that they lie above regions in the mantle or in the outer core that are hotter due to a higher percentage of ______.

radioactive materials

What type of volcano is composed of both pyroclastic and lava flow layers?

stratovolcano

Seafloor spreading ridges are the most volcanically active areas on earth's surface because ______.

they are so widespread