Deck 5: Volcanoes and Volcanism

Question 1

Briefly explain how magma can originate at spreading zones if temperatures at such shallow depths cannot produce melting alone.

Answer 1

The material is kept from melting because the lithostatic pressure of the overlying rock raises its melting temperature.The divergence of the plates and the fracturing that accompanies it reduces the pressure and lowers the material's melting temperature,which allows the rock to melt and become magma.

Question 2

How did the recent eruptions of Mt.Pinatubo,in the Philippines,and Kilauea,in Hawaii,differ?

Answer 2

Mt.Pinatubo's eruption was explosive,while Kilauea had quiet lava flows.

Question 3

How do pillow lavas form?

Answer 3

A lava is erupted into water and rapidly chilled.

Question 4

Why are there volcanoes on the west coast of North America but not on the east coast?

Question 5

Would you rather be chased by a pahoehoe flow or an aa flow? Explain.

Question 6

What is the difference between an active volcano and a dormant volcano?

Question 7

Distinguish aa from pahoehoe flows.

Question 8

What type of eruption is mainly responsible for producing plateau basalts?

Question 9

Why are some places (e.g.,northern California)more likely to experience volcanic eruptions than others (e.g.,New York)?

Question 10

What other bodies in the solar system are thought to possess active volcanoes?

Question 11

Mauna Loa volcano in Hawaii is huge and has gentle slopes.Mt.Rainier in Washington is tall,with much steeper slopes.Paricutin in Mexico is smaller and has very steep slopes composed of loose pyroclastic material.What type of volcano does each one represent,and what kind of volcanic activity produced it?

Question 12

How could you distinguish a volcanic crater from a caldera?

Question 13

Discuss what volcanologists look for in trying to determine if a volcano is about to erupt.

Question 14

Why is Crater Lake in Oregon considered to be misnamed?

Question 15

What produces columnar jointing in lava flows?

Question 16

How could carbon dioxide gas cause so many deaths in Cameroon?

Question 17

How is volcanism destructive? What are two reasons that it is primarily a constructive process?

Question 18

What causes the configuration of the islands that make up Santorini? How has volcanism at Santorini affected the people who live there?

Question 19

Which type of volcano is Mt.St.Helens?

Question 20

Briefly explain why volcanism occurs at subduction zones.

Question 21

Besides monitoring,what other knowledge helps geologists determine what to expect for eruptions from a given volcano?

Question 22

Pyroclastic material that is less than 2 mm in diameter is called ____________________.Particles ranging from 2 to 64 mm in diameter are known as ____________________,while ____________________ are pieces larger than 64 mm in diameter.

Question 23

Pahoehoe is lava erupted by Hawaiian volcanoes that has a(n)____________________ viscosity and a(n)____________________ appearance.

Question 24

What does harmonic tremor indicate is happening beneath the surface of a volcano?

Question 25

Composite volcanoes are also known as ____________________ and are composed of both ____________________ flows and ____________________ material.

Question 26

Lavas of ____________________ composition are more likely to produce lava domes.

Question 27

The one place on earth where mid-ocean ridge volcanism occurs above sea level is ____________________.

Question 28

Volcanic activity that takes place away from plate boundaries is the result of volcanism at a(n)____________________.In the U.S.,an example of this type of volcanism in the ocean is ____________________; an example on land is ____________________.

Question 29

Why does most volcanism at spreading ridges go undetected?

Question 30

The type of volcano that is the most common in the two major volcanic belts on Earth is ____________________.

Question 31

An extinct volcano is one that ____.

A) existed during a past geological period or epoch
B) has not erupted during recorded history
C) has shown no evidence of activity over recorded history
D) has not erupted during recorded history and has shown no evidence of activity over recorded history
E) all of these

Question 32

Sometimes the pyroclastic material that flows from a volcano is so hot that it fuses together to form a deposit known as ____________________.

Question 33

Columnar joints caused by the contraction of lava as it cools form typically in a(n)____________________ shape.

Question 34

One common but dangerous gas emitted from volcanoes,which is responsible for many deaths in Cameroon,is ____________________.

Question 35

The eruption that buried the city of Pompeii,Italy in 79 A.D.was that of Mount ____________________,which prior to the eruption had been quiet for at least ______ years.

Question 36

Shield volcanoes are composed largely of lavas of ____________________ composition; they commonly have slopes that are ____________________,and their eruptions tend to be ____________________ in explosivity.

Question 37

Mount Vesuvius is part of a chain of volcanoes along Italy's south coast where the ____________________ plate is being subducted beneath the ____________________ plate.

Question 38

The dominant gas emitted from volcanoes is ____________________.

Question 39

Cinder cones rarely reach heights greater than ____________________; they are composed of ____________________ material of ____________________ composition.

Question 40

At Laki fissure in Iceland,the eruption of the gas ____________________ caused about 75 percent of the nation's livestock to die,25 percent of the population to die,and crops to fail.

Question 41

Which is the correct ranking of regions with the most active volcanoes and volcanic activity?
1)Circum-Pacific belt
2)Mid-oceanic ridges
3)Mediterranean Belt
4)isolated sites like the Hawaiian Islands

A) 2, 1, 3, 4
B) 1, 3, 2, 4
C) 2, 3, 4, 1
D) 1, 2, 3, 4
E) 3, 2, 1, 4

Question 42

Earth is the only body in our solar system that is volcanically active.

Question 43

Crater Lake in Oregon is an example of a caldera.

Question 44

The chemical composition of all lavas is the same.

Question 45

A nuée ardente is composed of fiery hot gases and dust.

Question 46

Basalt plateaus erupt from ____.

A) supervolcanoes
B) shield volcanoes
C) fissures
D) lava domes
E) cinder cones

Question 47

Alaska's volcanoes are

A) composite with huge calderas.
B) fissure with large lava flows.
C) the result of seafloor spreading.
D) all dormant or extinct.

Question 48

The volcanic explosivity index (VEI)can be correlated with the number of deaths caused by an eruption.

Question 49

Give an example of a caldera.

A) Mount St. Helens, Washington
B) Paricutin, Mexico
C) El Chichon, Mexico
D) Krakatau, Java
E) Crater Lake, Oregon

Question 50

What do lava domes form from?

A) mafic magma
B) intermediate magma
C) viscous magma
D) pyroclastic materials
E) basalt

Question 51

What are the three main types of volcanoes?

A) cinder cones, clastic cones, and stratocones
B) cinder cones, composite cones, and shield volcanoes
C) shield volcanoes, composite volcanoes, and Hawaiian-style volcanoes
D) clastic cones, stratocones, and Hawaiian-style volcanoes
E) none of these

Question 52

Nuee ardentes erupt from ____.

A) supervolcanoes
B) shield volcanoes
C) fissures
D) lava domes
E) cinder cones

Question 53

Andesite is the type of lava most likely to erupt in a fissure eruption.

Question 54

Supervolcanoes ____.

A) are enormous peaky volcanic cones
B) produce enormous volcanic eruptions
C) erupt about once a century
D) are enormous peaky volcanic cones that produce enormous volcanic eruptions
E) all of these

Question 55

The volcanic explosivity index (VEI)is intended to do what?

A) describe the frequency of volcanoes
B) be used to forecast eruptions
C) prevent fatalities and property damage
D) document the size of eruptions
E) encourage people not to live near active volcanoes

Question 56

Ozone depletion in the stratosphere is caused by

A) CFCs and other manmade compounds.
B) carbon dioxide from fossil fuel burning.
C) volcanic gases like HCl.
D) all of these.

Question 57

Most of the approximately 3,300 historic eruptions lasted how long?

A) less than one month
B) one to six months
C) one to two years
D) more than two years
E) none of these

Question 58

Name an example of a cinder cone volcano.

A) Mount St. Helens, Washington
B) Mayon, Philippines
C) Eldfell, Iceland
D) Vesuvius, Italy
E) Mazama, Oregon

Question 59

What is an example of a composite volcano?

A) Fujiyama, Japan
B) Nevado del Ruiz, Columbia
C) Mount Vesuvius, Italy
D) Mount St. Helens, Washington
E) All of these

Question 60

Where are most volcanoes located?

A) the Mediterranean belt
B) the mid-oceanic ridges
C) the circum-Pacific belt
D) the East African Rift Zone
E) Indonesia

Question 61

The ozone hole is the region of depleted stratospheric ozone that is found over the equatorial region.

Question 62

The eruption of Mount St.Helens was one of the largest and deadliest in the world in historic times.

Question 63

Lava flows are the greatest hazard of volcanoes.

Question 64

The lateral blast associated with the 1980 Mount St.Helens eruption traveled at speeds possibly greater than 1000 km/hr.

Question 65

A lahar is a volcanic mud flow.

Question 66

Pyroclastic sheet deposits were formed by enormous ash falls.