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College Geology > Lesson 4 > Flashcards

Lesson 4 Flashcards

1
Q

What are the primary factors of magma that determine the nature/violence of volcanic eruptions?

A

temperature
composition
amount of dissolved gas

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2
Q

What is viscosity?

A

A measure of a materials resistance to flow

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3
Q

As viscosity increases, the mobility _____.

A

decreases

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4
Q

What are the factors that affect viscosity?

A

temperature
composition
volatiles (dissolved gasses)

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5
Q

If the temperature of the magma is hotter, then it is _____ viscous.

A

less

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6
Q

If the magma’s composition has a high silica content, the magma will have a _____ viscosity.

A

high

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7
Q

If the magma’s composition has a low silica content, the magma will have a _____ viscosity because it has more ___..

A

low

fluid

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8
Q

What is an example of a magma composition with a high silica content?

A

rhyolitic lava

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9
Q

What is an example of a magma composition with a low silica content?

A

basaltic lava

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10
Q

What is the most abundant volatile or gas in magma?

A

water vapor

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11
Q

What are the main gasses in magma?

A

water vapor

carbon dioxide

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12
Q

What provides the force to extrude lava?

A

gases expanding near the surface

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13
Q

What is the violence of a eruption related to?

A

how easy gas escapes form magma

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14
Q

When gases have a hard time to escape, they have a ____silica content, ____viscosity, and _____eruptions

A

high
high
violent

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15
Q

What is congealing?

A

solidify by cooling

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16
Q

When gases have an easy escape, they have a ____silica content, ____viscosity, and _____eruptions

A

low
low
non-violent

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17
Q

What are the materials associated with volcanic eruptions?

A

lava flows
gases
pyroclastic materials

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18
Q

Are basaltic lavas more or less fluid?

A

more

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19
Q

What are the types of basaltic lava?

A

Pahoehoe lava

Aa lava

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20
Q

What does Pahoehoe lava look like?

A

resembles braids in ropes

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21
Q

What does Aa lava look like?

A

rough, jagged blocks

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22
Q

Pahoehoe lava is _____ viscous than AA lava.

A

less

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23
Q

What kind of flows does rhyolitic lava create?

A

short and thick flows

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24
Q

What kind of flows does basaltic lava create?

A

fluid flows that travel long before congealing

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25
Q

How much percent of magma by weight is gases?

A

1-5

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26
Q

What are pyroclastic materials also called?

A

“fire fragments”

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27
Q

What are the types of pyroclastic materials?

A

Ash and dust
Pumice
Lapalli
Cinders

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28
Q

Give a description of ash and dust (pyroclastic material).

A

fine, glassy fragments

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29
Q

Give a description of pumice (pyroclastic material).

A

from “frothy” lava

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30
Q

Give a description of lapilli (pyroclastic material).

A

“walnut” size

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31
Q

Give a description of Cinders (pyroclastic material).

A

“pea-sized”

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32
Q

What are particles larger than lapilli?

A

blocks

bombs

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33
Q

What are blocks?

A

hardened lava

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34
Q

What are bombs?

A

ejected as hot lava

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35
Q

What is pulverized rock and lava fragments blown from the volcanos vent?

A

pyroclastic material

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36
Q

Successive eruptions of lava from a central vent results in a montainous accumulation of material called a ____

A

volcano

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37
Q

What is a volcanoes surface opening called?

A

vent

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38
Q

What is a steep-walled depression located at the summit called?

A

crater

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39
Q

The vent is connected to the ______ through a pipe.

A

magma chamber

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40
Q

What is the pipe that carries gas rich magma to the surface?

A

conduit

41
Q

What is a caldera?

A

a crater that is greater than 1 km diameter

42
Q

What is the cone shaped material formed from volcanic material not part of the central vet of a volcano.

A

Parasitic cones

43
Q

What is the opening called where gases emerge?

A

fumaroles

44
Q

What are the three types of volcanos?

A

shield
cinder
composite

45
Q

What is a shield cone volcano shape?

A

broad, slightly domed

46
Q

What are shield cones primarily built of?

A

fluid- basaltic lava

47
Q

Shield volcanoes are generally sized ____ and produce a _____ of lava

A

large

large volume

48
Q

What is an example of a shield volcano?

A

Mauna Loa in Hawaii

49
Q

What type of volcano frequently occurs in groups?

A

Cinder cones

50
Q

What is the shape of cinder cone volcanoes?

A

very steep slopes and rather small

51
Q

What are cinder cones composed of?

A

pyroclastic material- ejected lava fragments

52
Q

What are composite cones built of ?

A

interbedded lavas

pyroclastic deposits.

53
Q

Where are most composite cones located?

A

adjacent to the pacific ocean

54
Q

What is an example of a composite cone volcano?

A

Mt Rainer

55
Q

What is another name for composite cones?

A

stratovolcanoes

56
Q

What is the shape of composite cones?

A

large

nearly symmetrical

57
Q

What volcano has the most violent type of activity?

A

composite cone

58
Q

What do composite volcanoes often produce?

A

nuea ardente

59
Q

What is a nuea ardente?

A

fiery cloud of hot gases infused with incandescent ash

60
Q

Nuea ardente flows down the side of a volcano at speeds up to ____per hour?

A

200km (125 miles) per hour

61
Q

Composite cones may generate mudflow called _____.

A

lahar

62
Q

What is lahar?

A

a type of mudflow

63
Q

What are most volcanoes are fed by?

A

conduits or pipes

64
Q

What are resistant vents left standing after erosion has removed the volcanic cone?

A

volcanic neck

65
Q

Volcanic eruptions from a central vent are the most familiar, but the largest amounts of volcanic material are extruded from ______

A

fissures

66
Q

The term flood basalts describes the fluid, waterline, basaltic lava flows that cover an extensive region in the northwestern United States known as the __________

A

Columbia Plateau

67
Q

When silica-rich magma is extruded, pyroclastic flows consisting largely of _______ fragments.

A

ash and pumice

68
Q

How are calderas formed?

A

by collapse

69
Q

What is the shape of calderas?

A

nearly circular

70
Q

What is fluid basaltic lava extruded from crustal fractures?

A

fissures

71
Q

What are short conduits that connect a magma chamber to the surface?

A

pipes

72
Q

Example of a volcanic pipe and neck?

A

Ship Rock, New Mexico

73
Q

Magma is created from a rock located where?

A

crust and upper mantle

74
Q

How can a rocks temperature raise?

A

from hot mantle plume “ponds” beneath crustal rocks

75
Q

What can happen when there is a decrease in pressure?

A

decompression melting

76
Q

What can volatiles (water) do to a rock to generate magma?

A

lower a rock’s melting point

77
Q

What end of the compositional spectrum is the partial melting magma

A

granitic (felsic) end

78
Q

What factors influence the generation of magma from solid rock

A

heat
pressure
volatiles
partial melting

79
Q

Earth’s natural temperature increases with depth is called a ______

A

geothermal gradient

80
Q

What three ways is heat created to melt magma?

A

Friction in subduction zones
Crustal rocks heated during subduction
Rising, hot mantle rocks

81
Q

What happens to the temperature if the confining pressure increases?

A

melting temp increases

82
Q

What plays an important role in subducting ocean plates?

A

volatiles

83
Q

What kind of minerals is partial melting made of?

A

lowest-melting-temperature minerals

84
Q

What is different from the low melting temp minerals and original rock?

A

they have a high silica content

85
Q

What are most active volcanoes are associated with?

A

plate boundaries

86
Q

Plate boundry found along mid-ocean ridges where seafloor spreading is occurring?

A

divergent plate boundaries

87
Q

Rising plumes of hot mantle rock are the source of most ______

A

intraplate volcanism

88
Q

what are the three plate motions providing help to create magma?

A

Convergent
Divergent
intraplate igneous activity

89
Q

Name the plate motion.

  1. Deep-ocean trenches are generated
  2. Descending plate partially melts
  3. Magma slowly rises upward forming a structure
A

convergent plate boundaries

90
Q

What two structures can form from convergent plate boundaries?

A

Volcanic island arcs in an ocean

Continental volcanic arcs

91
Q

What is the composition of Volcanic island arcs in an ocean?

A

Basaltic composition

92
Q

What is the composition of Continental volcanic arcs?

A

Andesitic or rhyolitic composition

93
Q

What is an example of a volcanic island arc in an ocean?

A

the Aleutians

94
Q

What is an example of continental volcanic arcs?

A

Andes mountains

95
Q

Name the plate motion.

a. Activity within a rigid plate
b. Plumes of hot mantle material rise
c. Form localized volcanic regions called hot spots

A

Intraplate igneous activity

96
Q

Where is the greatest volume of volcanic rock produced along

A

the oceanic ridge system

97
Q

Name the plate motion.

  1. Lithosphere pulls apart
  2. Less pressure on underlying rocks
  3. Partial melting occurs
  4. Large quantities of fluid basaltic magma are produced
A

Divergent plate boundaries

98
Q

Plate boundary in the vicinity of ocean trenches where one plate is being subducted beneath another?

A

convergent plate boundaries

99
Q

Plate boundary in the interiors of plates themselves?

A

intraplate volcanism

College Geology (14 decks)

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