Deck 8: Volcanoes and Plutons

Question 1

Explosively erupted rock particles or magma form __________ rock.

Answer 1

pyroclastic

Question 2

Magma with a high water content has a greater tendency to __________ in the crust, compared with magma with a lower water content.

A) solidify
B) remain liquid
C) metamorphose
D) spread out

Answer 2

A

Question 3

Lava and rock fragments commonly erupt from a __________ located in the crater of a volcano.

Answer 3

vent

Question 4

Long chains of silicate tetrahedra form in magma with __________ composition.

Question 5

A granitic pluton that is exposed for less than 100 square kilometers is called a/an __________.

Question 6

A/an __________ __________ is a small volcano composed of pyroclastic fragments.

Question 7

About 75 percent of the Earth's volcanic activity occurs along a circle of subduction zones in the Pacific Ocean called the __________ __________ __________.

Question 8

__________ are pyroclastic volcanic fragments that vary in size from 4 to 32 millimeters.

Question 9

The circular depression left when the roof of a magma chamber collapses is called a/an __________.

Question 10

The Ring of Fire, a zone of concentrated volcanic activity encircling the Pacific Ocean basin, is located adjacent to __________.

A) rift zones
B) subduction zones
C) the Mid-Oceanic Ridge system
D) a lava plateau

Question 11

Granitic magma contains __________ water than basaltic magma.

Question 12

A chaotic mixture of volcanic ash and rock fragments that is left behind when most of the gas escapes into the atmosphere during an ash flow and solidifies is called a/an __________ __________ __________.

Question 13

Typical granitic magma contains __________ silica and __________ water than typical basaltic magma.

A) more, less
B) less, less
C) more, more
D) less, more

Question 14

A/an __________ forms when magma oozes between layers of country rock as a sheet parallel to the layering.

Question 15

Magma production occurs through __________ __________ __________ in a mantle plume.

Question 16

Melting caused by decreased pressure is called __________ melting.

A) pressure-release
B) pressure-decrease
C) pressure-cease
D) pressure-diminish

Question 17

Granitic magma has a __________ melting temperature compared to basaltic magma.

A) lower
B) higher
C) equal
D) much higher

Question 18

The three environments of magma production are __________ __________, __________ __________, and __________ __________.

Question 19

If lava solidifies before the gas in it escapes, the bubbles are preserved as holes called __________.

Question 20

The magma of andesite and diorite contains __________ silica than granite.

Question 21

Continental crust is typically of __________ composition.

A) basaltic
B) granitic
C) peridotitic
D) magnetic

Question 22

When an ash flow comes to a stop, most of the gas escapes into the atmosphere, leaving behind a chaotic mixture of volcanic ash and rock fragments called __________.

A) ash-flow basalt
B) ash-flow tuff
C) shield volcano
D) submarine volcano
Multiple Choice

Question 23

If basaltic magma is too viscous to form a lava plateau, but still quite fluid, it heaps up slightly, forming:

A) cinder cones.
B) calderas.
C) ash-flow tuffs.
D) shield volcanoes.

Question 24

Most basaltic magma erupts at the Earth's surface because it:

A) is more viscous than granitic magma.
B) contains huge amounts of water.
C) contains little water.
D) has a higher silica content than granitic magma.

Question 25

As lava cools and solidifies from the surface down, cracks frequently grow downward through the rock. Such cracks are called:

A) batholiths.
B) columnar joints.
C) sills.
D) stocks.

Question 26

A/an __________ is a crater formed by the collapse of a magma chamber.

A) ash-flow tuff
B) cinder cone
C) caldera
D) impact crater

Question 27

The most catastrophic volcanic explosions occur when __________ reaches the Earth's surface.

A) flood basalt magma
B) granitic magma
C) basaltic magma
D) aa magma

Question 28

Which of the following tectonic environments does not generate large quantities of magma?

A) transform boundaries
B) mantle plumes
C) subduction zones
D) spreading centers

Question 29

Oceanic crust is typically of __________ composition.

A) basaltic
B) granitic
C) peridotitic
D) magnetic

Question 30

Lava with a smooth, ropy surface is:

A) pahoehoe.
B) aa.
C) granitic.
D) plutonic.

Question 31

A __________ is a pluton with an outcrop area of less than 100 square kilometers.

A) batholith
B) volcanic neck
C) dike
D) stock

Question 32

The magma type that most commonly rises to the Earth's surface to erupt from a volcano is:

A) granitic magma.
B) potassium-rich magma.
C) plutonic magma.
D) basaltic magma.

Question 33

The higher silica content of granitic magma causes it to:

A) erupt at the surface.
B) solidify within the crust.
C) become highly viscous.
D) b and c

Question 34

A pluton with an outcrop area of more than 100 square kilometers is a:

A) batholith.
B) volcanic neck.
C) dike.
D) stock.

Question 35

__________ is lava with a jagged, broken surface.

A) Pahoehoe lava
B) Aa lava
C) Cosmic lava
D) Plutonic lava

Question 36

Granitic magma contains up to __________ percent water.

A) 50
B) 40
C) 25
D) 10

Question 37

Which of the following processes causes melting of the asthenosphere and the generation of magma?

A) removal of water
B) increasing pressure
C) decreasing temperature
D) decreasing pressure

Question 38

Gentle eruptions of basaltic lava from long fissures create __________.

A) flood basalts
B) cinder cones
C) shield volcanoes
D) calderas

Question 39

Pyroclastic bombs, cinders, and ash:

A) flow gently from volcanoes.
B) erupt explosively from volcanoes.
C) solidify within the crust as irregularly-shaped plutons.
D) occur as dikes and sills intruded into country rock.

Question 40

Dated rocks and zircon crystals suggest that granitic continental crust had formed by about __________ years ago.

A) 1.6 million
B) 4.4 million
C) 1.6 billion
D) 4.4 billion

Question 41

A shield volcano commonly erupts when:

A) basaltic magma oozes like water over the Earth's surface.
B) fluid basaltic magma builds a gently sloping mountain.
C) water-saturated granitic magma rises.
D) relatively dry granitic magma rises.

Question 42

Volcanic eruptions have no effect on global climate.

Question 43

Basaltic magma forms at the Mid-Oceanic Ridge.

Question 44

Pahoehoe lava cools and stiffens as it flows, forming basalt with smooth, glassy-surfaced, wrinkled, or "ropy" ridges.

Question 45

The gentlest, least catastrophic type of volcanic eruption occurs when magma is so fluid that it simply oozes from cracks as pyroclastic rocks.

Question 46

A composite cone:

A) forms by repeated lava flows and pyroclastic eruptions over a long time.
B) is usually active for only a short time.
C) forms by pyroclastic eruptions only.
D) forms in a single, cataclysmic event.

Question 47

The Columbia River plateau is an example of a lava plateau.

Question 48

A dike is a sheet-like, intrusive rock that forms when magma oozes into a fracture.

Question 49

Granitic magma has longer chains of silicate tetrahedra than basaltic magma.

Question 50

A cinder cone is usually active for only a short period of time because once the gas escapes the driving force behind the eruption is removed.

Question 51

Mount St. Helens in the state of Washington is an example of a stratovolcano.

Question 52

The periodicity of Yellowstone eruptions, the presence of shallow magma, and the well-known tendency of magma of this type to erupt multiple times all suggest that a fourth eruption may occur.

Question 53

Regional predictions can be used to determine exactly when a particular volcano will erupt.

Question 54

Shield volcanoes are relatively small compared to other volcanoes.

Question 55

Yellowstone Park is an example of three overlapping:

A) calderas.
B) mantle plumes.
C) shield volcanoes.
D) lava plateaus.
True/False

Question 56

Which magma type erupts most violently?

A) basaltic
B) Hawaiian
C) Icelandic
D) granitic

Question 57

A sill forms when magma oozes between layers of country rock.

Question 58

If magma contains large amounts of water, the water escapes as the magma rises, and the solidification temperature lowers, causing the magma to erupt.

Question 59

Increased temperature is the most important factor in magma production.

Question 60

A caldera is a:

A) gently sloping mountain formed by low-viscosity magma pouring from a central vent.
B) steep conical mountain formed by repeated lava flows and pyroclastic eruptions.
C) circular depression formed as the roof of a magma chamber collapses after an eruption.
D) broad, flat lava plateau formed by fluid magma.