Week 5 Reading

In 1991, Mt. Pinatubo erupted so much ——— that global temperatures dropped for about 2 years.

Ash

What particular pyroclastic material can bury cities, is slippery, can cause roofs to collapse, is bad for people's lungs, and is damaging to engines and other mechanical equipment? Volcanic ——-

Ash

What hazard associated with an Icelandic volcano eruption in 2010 caused the shutdown of air travel across northern Europe for 9 days?

Ash plumes

Magma compositions can change when they incoperate supporting rocks through the process of _________; where minerals form and come out of melt through fractional _ _____; and through mixing with a different type of magma

Assimilation crystallization

A magma travels through existing rock on the way to the surface, some of the rock melts changing the composition of the magma. This process is called

Assimiliation ( Reason: As magma travels through exisiting rock on the way to the surface some of the rock melts changing the composition of the magma. This process is called Assimilation)

What mafic volcanic rock is formed at seafloor spreading ridges?

Basalt

What type of gas, which had accumulated in the bottom of Lake Nyos and then leaked out when the lake overturned, was responsible for suffocating 1700 people in Cameroon in 1986?

Carbon dioxide Reason: Lake Nyos is located along a rift valley with volcanic activity.

This relatively small, symmetrical volcano made of pieces of basaltic lava is a(n).

Cinder cone

A relatively small and steep volcano, a ———-,————is made of pieces of magma thrown In the air near the vent due to the escape of dissolved gases

Cinder or scoria Cone

The mafic magma created at a subduction zone usually makes its way to the surface unchanged in composition.

False

Most rocks undergo partial melting becuase ___________ minerals melt at lower temperatures than other types

Felsic

What is the key element in understanding the potential for a volcano to erupt in the future?

Its eruptive history

A rare success story in diverting a lava flow occurred in the early 1970s, when residents on the island of Heimaey in Iceland pumped ocean water cool the lava in order to

Keep their fishing harbor open

*Mt. Rainier is a tall, steep, snow-covered stratovolcano that is at high risk of producing ——— this map shows the extent of deposits from some recent such events.

Lahars

Select all the factors that work together to make lahars on Mt. Rainier a serious risk.

Lahars have occurred there in the recent geologic past. Heat from the volcano can alter feldspars into slippery clays It has glaciers and snow year-round.

What is Partial melting?

The incomplete melting of a source rock to create magma of a different composition ( Reason: The new magma is always higher in silica content than the source rock)

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

Following the 1991 Mt. Pinatubo volcanic eruption, the world experienced a 1°C drop in global temperatures. Why did this occur?

The production of sulfuric acid interfered with solar radiation, leading to a short-term period of global cooling. Reason:. Following the 1991 Mt. Pinatubo volcanic eruption, the world experienced a 1°C drop in global temperatures because the production of sulfuric acid interfered with solar radiation, leading to a short-term period of global cooling.

How do sulfur gases emitted during volcanic activity affect climate?

They are long-lasting and get moved around in the atmosphere, affecting climate in areas far removed from the source. Sulfuric-acid aerosols block sunlight and lead to cooling.

Which of the following describe lahars?

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

Which of the following describe stratovolcanoes?

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

How did the residents of Heimaey in Iceland deter erupting lava from closing off their harbor?

They pumped seawater on it to cool and harden it.

Melting of the astheonsphere can occur due to a(n) _____ in pressure which is how magma is fromed at spreading ridges and hot spots

decrease or drop or lowering or reduction

How is magma behavior related to plate setting and volcanic hazards?

each tectonic produces distinct types of magma which erupt in ways directed by their compstitions

Magma taht has a relatively high silica content is __________ magma

felsic

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

gases or volatiles

What type of image, as shown here, records the deformation of a volcano over a certain time period?

interferogram

A fast-moving volcanic mudflow created through the combination of ash and water is called a(n)

lahar

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

lava domes Reason: However, when gas builds up under these viscous lavas, domes can explosively erupt.

Magma that contains 45% t0 50% silica are called ____; they are relatively rich in iron and magnesium

mafic

Rock fragments of any type or size ejected from a volcano are called

pyroclastics or pyroclasts

Harmonic tremors associated with volcanic activity create a(n) ———— pattern.

rhythmic, continuous

Where does the majority of volcanic activity occur?

seafloor spreading ridges

What causes the dissolved gas within magma to escape as the magma erupts at the surface?

A reduction in pressure

Most of the world's active volcanoes are located

along plate boundaries

As magma travels through existing rock on the way to the surface, some of the rock melts, changing the composition of the magma. This process is called:

assimilation Reason:. As magma travels through existing rock on the way to the surface, some of the rock melts, changing the composition of the magma. This process is called assimilation.

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

What volcanic gas is so dangerous because it is both odorless and denser than air?

carbon dioxide

Most magma originates in the ______.

upper mantle reason ( here the combination of tempeature and pressure is just right to either partially or wholly melt rock

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

water vapor

The majority of magma at subduction zones is created ____

when wtaer from the subducting plates move upward into the overlying asthenosphere

Which of the following describe mafic magma?

- Contains 45% to 50% silica Reason ( Mafic magma 45% to 50% silica) - has a relativley high amount of iron and magnesium reason ( Mafic magma has a relativly high amount of iron and magnesium )

Match the volcanic ( fine-grained) rock to its plutonic (coarse-grained) equivalent Rhyolite Andesite Basalt

- Granite - Diorite - Gabbro

Which of the following commonly precede a volcanic eruption?

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

How is volcanic activity associated with landslides?

- Steep and/or coastal volcanoes may have materials that are weakened and fail suddenly. - Earthquakes associated with moving magma may cause landslides. - Landslides may allow volcanic gases to escape.

chose all the statements that correctly describe the releationship between plate setting, magama behavior, and hazards

- The composition of the magma controls how much the magma erupts - each plate setting creates certain magma compositions - the way a magma erupts determines the type of hazards associated with it

Rank these igneous rocks by their silica content, with the felsic rock on the top ( most silica) and the mafic rock on the bottom

1) Granite 2) Andesite 3) Basalt

Lava is typically ______ or hotter.

850∘C

The cloud of carbon dioxide that suffocated 1700 people and many livestock in Cameroon in 1986 emanated from

A volcanic lake

Volcanoes that are labeled ——- have erupted in recent history whereas ——- volcanoes have not erupted during recent history but have the potential to do so.

Active Dormant

Match the igneous rock to its basic chemical ( minera) composition Granite Andesite Basalt

Dominated by quartz and feldspar ( felsic) Dominated by feldspar and ferromagnesian with some quartz ( intermediate) Dominated by ferromagnesian and feldspar (mafic)

Match the different activity levels of volcanoes to their descriptions. Active Dormant Extinct

Erupted within recent history Potential to erupt again Unlikely to erupt again

Earthquakes, harmonic tremors, and changes in topography and gas emissions are all precursors to volcanic

Eruptions

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

Felsic reason ( because mafic magma has less silica so it is less viscous and flows more easily)

Mafic Magma flows much more easily or are less viscous than ________ magmas

Felsic or silicic

Eruptions of lava from cracks in Earth's surface, as opposed to from single vents, are called ————eruptions.

Fissure

Scoria is created when the dissolved ——- in magma is released during an eruption, flinging bits of lava into the air that solidifies before or as it reaches the surface.

Gas or gases

Besides monitoring for different types of precursors, what other information is used to determine danger zones for impending volcanic eruptions?

Geologic maps showing volcanic debris from previous eruptions

The Plutonic equivalent of Rhyolite is _____________

Granite

While lava usually is not life threatening, it is——— enough to burn and destroy any property it encounters.

Hot

How does volcanic ash and dust cause cooling of the climate?

It blocks sunlight from reaching earth.

Which of the following describe a pyroclastic flow?

It is a very dangerous volcanic hazard. It results from the collapse of a dense cloud of ash and gas.

Choose all of the hazards associated with volcanic ash.

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

Why is carbon dioxide emitted during volcanic activity so dangerous?

It is denser than oxygen and can accumulate in low-lying areas. Reason: People and animals suffocate when CO, takes the place of oxygen gas.

How important is it to understand a volcano's eruptive history in order to understand its potential for eruption in the future?

It is essential knowledge.

Which of the following describe a pyroclastic flow?

It results from the collapse of a dense cloud of ash and gas. It is a very dangerous volcanic hazard.

How will a large amount of volcanic ash and dust from a single large eruption affect global climate?

It will cause regional or global cooling for months up to a few years.

What will a decrease in pressure do to a rock that is already hot enough to melt?

It will cause the rock to start melting

Select all the factors that work together to make lahars on Mt. Rainier a serious risk.

Lahars have occurred there in the recent geologic past. Heat from the volcano can alter feldspars into slippery clays. It has glaciers and snow vear-round

The partial melting of the ultramfic mantle creates magma that is _______ in composition

Mafic

The asthenosphere is untramafic in compostion meaning that is is very rich in ferromagnesian minerals. When it melts it usally forms _________magma

Mafic (Reason: Applying the rule of partial melting to the asthenosphere results in mafic magma)

What type of magma allows gas to escape more easily?

Mafic reason: (Mafic magma is silica poor and less viscous)

Hot spots underneath ocean curst result in _______ magma, whereas continental hot spots may produce more __________ magma

Mafic; Felsic

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

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

Which of these best describes the current state of worldwide volcano monitoring?

Many active volcanoes are actively monitored.

Magma composition is controlled by the type of ________ that is being melted and the extent to which it is melted

Material or rock or materials

What is allowing scientists to monitor closely more of Earth's active and dormant volcanoes?

Remote sensing

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

Pacific Ocean This is known as the Ring of Fire and is marked by subduction zones.

Mauna Loa is the largest volcano on Earth. It is a(n) ——— volcano, created from hundreds to thousands of runny basalts flow

Shield

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

Stratovolcano

Most Magma originates in the upper mantle becuase the __ __ is hig enough and the ______ low enough to at least partially melth the rock there

Tempeature; pressure

What are the reasons that lava flows from Nyiragongo are so dangerous?

The city of Goma, with over 1.5 million people, is directly below the volcano The lava is very hot and moves very quickly.

What is pyroclastic material?

Volcanic fragments of all sizes

Magma generated in subduction zones is initially ——— 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

When the Icelandic volcano Eyjafjallajökull erupted in 2010, it created an enormous ash cloud that

moved to Europe and caused a nine-day shutdown of air traffic Reason: Subsequently, the airline industry lost over $1.5 billion.

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

on continents or on the seafloor

The eruption of Krakatoa in 1883 was so forceful that it blew the island apart; it resulted from a ———- explosion.

phreatic

What volcanic hazard is associated with the eruption of Krakatoa in 1883? This event is famous for blowing the island apart, creating a tsunami, and allegedly creating the loudest noise ever heard.

phreatic explosion

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

pyroclastic

The entire town of St. Pierre, save for two people, died in a(n) ———flow when Mont Pelée erupted in 1902.

pyroclastic

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

shield

A felsic magma is rich in the minerals feldspar and quartz and so has a high _______ content

silica

Which of the following volcanic emissions are associated with both global cooling and the formation of acid rain?

sulfur gases

What are two primary controls on magma compositions?

the extrend of melting the parent material

The eruption of Nyiragongo in 2002 was particularly dangerous because:

the lava flows moved very quickly.

Landslides may lead to volcanic eruptions when ______.

the removal of material allows gases to escape

Seafloor spreading ridges are the most volcanically active areas on Earth's surface because

there is an extensive network of ridges (Reason:. There is about 30,000 miles of seafloor spreading ridges.)

Lava domes are made of ______ lava.

thick, viscous