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Fall 2018 > Geology 101 Quiz 5 > Flashcards

Geology 101 Quiz 5 Flashcards

1
Q

in both volcanoes and carbonated beverages

A

gas is dissolved under pressure; when the pressure is released, gases expand and carry part of the liquid out the top with the escaping gas

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2
Q

in a volcano, rising magma does what to overlying rock?

A

stresses, which eventually creates fractures that reach the surface

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3
Q

as gases expand, what gets carried up through the fractures along with the expanding gases?

A

magma

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4
Q

Mt. St. Helens in Washington had a ? eruption in what year?

A

explosive; 1980 - the entire side of the volcano was blasted away

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5
Q

are all volcanic eruptions explosive?

A

no

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6
Q

the explosiveness of a volcano depends on two criteria

A

gas content & magma composition

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7
Q

most of the gas in volcanoes is

A

simple water and carbon dioxide

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8
Q

some of the gases come from ?

A

subducted plates that carry seawater along with the descending crust

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9
Q

if the gas content of the magma is (low/high), the potential for an explosive eruption is much higher

A

high

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10
Q

the composition of magma is important because it affects ?

A

viscosity

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11
Q

viscosity

A

the resistance to flow

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12
Q

something with a (low/high) viscosity does not flow easily (like molasses)

A

high

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13
Q

something with a (low/high) viscosity flows easily (like water)

A

low

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14
Q

if a magma has a low viscosity,

A

gases coming out of the magma can easily rise to the surface and vent

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15
Q

if a magma has a high viscosity,

A

gases will tend to remain trapped within the magma; magma cannot get out of the way easily when gases are rapidly expanding so lots of it will get carried out with the escaping gases

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16
Q

(felsic/mafic) magmas have a higher silica content and thus are (less/more) viscous

A

felsic; more

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17
Q

(felsic/mafic) magmas tend to make more explosive eruptions

A

felsic

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18
Q

Mt. St. Helens if fromed from andesitic lavas/tephra (?)

A

felsic

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19
Q

Kilauea is formed from basaltic lavas (?)

A

mafic

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20
Q

felsic (rhyolitic)

A

higher silica content, more viscous, lower melting temperature

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21
Q

mafic (basaltic)

A

lower silica content, less viscous, higher melting temperature

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22
Q

a lower melting temperature means that

A

felsic magmas can exist when it is not hot enough for mafic rocks to melt

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23
Q

Felsic magma will still be more viscous than mafic magma, however, even if ?

A

the gas content is high

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24
Q

very high explosiveness

A

felsic + high gas content + high viscosity

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25
Q

low explosiveness

A

felsic + low gas content + very high viscosity

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26
Q

intermediate explosiveness

A

mafic + high gas content + very low viscosity

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27
Q

very low explosiveness

A

mafic + low gas content + low viscosity

28
Q

eruptions will not be explosive without

A

dissolved gas

29
Q

80% of volcanoes on Earth are

A

basaltic (most oceanic volcanoes)

30
Q

10% of volcanoes on Earth are ? and the other 10% are ?

A

andesitic & rhyolitic (most continental volcanoes)

31
Q

extrusive igneous rocks are divided into two categories

A

lava and pyroclastic material (tephra)

32
Q

pyroclastic material

A

if magma and solidified fragments spend part of their journey from the volcano hurled through the air

33
Q

pyroclastic material is divided into three categories based on size

A

ash, laphilli, bombs

34
Q

ash

A

dust size tephra up through the size of a BB (< 2 mm)

35
Q

laphilli

A

BB to baseball size (2-64 mm)

36
Q

bombs

A

larger than a baseball (>64 mm)

37
Q

lava

A

magma that flows over the surface of the ground

38
Q

pahoehoe

A

smooth, ropey lava formed from high gas content, low viscosity lava

39
Q

aa

A

rough, jagged lava formed from low gas content, high viscosity lava

40
Q

lava tubes

A

tunnels that lava travels through; form when the upper surface of a lava flow hardens, but the lava beneath continues to flow

41
Q

three different types of volcanoes that result from various combinations of lava and pyroclastic material

A

shield volcano, stratovolcano, cinder cone (or tephra cone)

42
Q

shield volcano

A

formed from lava flows; successive flows builds up a wide, gently sloping volcano with a shield shape

43
Q

examples of shield volcanoes

A

Mauna Loa and Mauna Kea, Hawaii

44
Q

stratovolcano

A

formed from lava and pyroclastic material; forms a more traditionally recognized, steeply sided volcano

45
Q

example of stratovolcano

A

Mt. Fuji, Japan

46
Q

cinder cone (or tephra cone)

A

formed from pyroclastic material; similar shape as stratovolcanoes, but tends to be smaller

47
Q

example of cinder cone (tephra cone) volcano

A

Cerro Negro, Nicaragua

48
Q

caldera

A

large crater formed when a volcano collapses into a massive, partially emptied underlying magma chamber

49
Q

example of a caldera

A

Crater Lake, Oregon

50
Q

when a large crater is left behind after an eruption,

A

the volcano has collapsed into the magma chamber (not blasted away)

51
Q

volcanic hazards

A

lava flows, explosive eruptions, lahars, tsunami, dangerous gas release

52
Q

lava flows

A

mostly a hazard to property since most flows are slow enough, or channeled enough to give time to get out of the way

53
Q

explosive eruptions

A

the primary danger in an explosive eruption is the formation of a pyroclastic flow

54
Q

pyroclastic flow

A

a dense cloud of super-heated tephra and air that flows at high speed down the side of a volcano; these events are also referred to as incandescent avalanches

55
Q

two stories of historic pyroclastic flows

A

Mt. Pelee in Martinique (1902) and Mt. Vesuvius in Italy (79 AD)

56
Q

Martinique is one of the islands in a volcanic arc formed by

A

the convergence of two oceanic plates

57
Q

Mt. Vesuviius is associated with a

A

subduction zone

58
Q

iahars

A

mudflow of tephra and water; similar to flowing, wet cement; they flow with great force down slopes and in stream channels, knocking over structures in their path and burying lowlands in thick deposits of debris

59
Q

tsunami

A

a huge wave caused by a sudden displacement of water in a large body of water (used to be called a “tidal wave”)

60
Q

If a volcano erupts violently under water in the ocean or other large water body, it will displace a large volume of water above it that will trigger

A

a tsunami

61
Q

dangerous gas release

A

volcanic emissions do include noxious sulfur gases, but the most deadly release in recorded history was simply carbon dioxide

62
Q

If a volcano tends to erupt every so many years, this ? may be used to estimate the next time the volcano will erupt, though the estimate is rarely precise

A

recurrence interval

63
Q

early warning signs

A

seismic monitoring, ground deformation (tilt & expansion), water or ground temperature changes, changes in gas emissions (such as SO2 or HCl)

64
Q

seismic monitoring

A

watching for increased number or intensity of earthquakes

65
Q

ground deformation, tilt & expansion

A

as magma rises, the volcano expands and the slope angle increases

66
Q

as signs of volcanic activity increased, the ? got smaller and smaller until it was down to a few days

A

prediction window

Fall 2018 (24 decks)

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