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CEGEOLO EV > (MODULE 7.2) GEOLOGICAL HAZARDS - VOLCANIC ERUPTIONS > Flashcards

(MODULE 7.2) GEOLOGICAL HAZARDS - VOLCANIC ERUPTIONS Flashcards

1
Q

a mountain that forms when molten rock (magma) reaches the surface of the earth

A

volcano

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2
Q

volcanoes are formed when ___.

A

magma forces its way through a crack in the earth’s crust.

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3
Q

a volcano is classified as ___ if it erupts lava, rock, gas, or ash, or if it shows seismic activity.

A

active

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4
Q

a volcano is ___ if it hasn’t erupted for a long time (less than 1 million years) but could erupt again one day.

A

dormant

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5
Q

an ___ volcano will never erupt again.

A

extinct

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6
Q

indicate the parts of a volcano

A
  1. crater
  2. vent
  3. cone
  4. conduit
  5. magma chamber
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7
Q

the opening from which lava flows. dust, ash, and rock particles can also be thrown out of it.

A

vent

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8
Q

the pile of lava, dust, ashes, and rock around the vent; can be found in different shapes

A

cone

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9
Q

the top of the volcano; it is a funnel shaped pit formed when the material explodes out of the vent.

A

crater

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10
Q

some volcanoes have very large circular depressions called ___, that have diameters greater than 1 kilometer.

A

calderas

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11
Q

a passageway followed by magma in a volcano.

A

conduit

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12
Q

the subterranean cavity containing the gas-rich liquid magma which feeds a volcano

A

magma chamber

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13
Q

volcanoes are classified by ___.

A

how they are formed

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14
Q

this type of volcano is wide and somewhat flat, between 2 to 10 degrees.

A

shield volcano

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15
Q

what are the characteristics of a shield volcano?
1.
2.
3.
4.

A
  1. it is wide and flat
  2. it is constructed of solidified lava flows
  3. it forms from a quiet eruption
  4. lava flows out quietly and for great distances because the shield volcano doesn’t have a long conduit
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16
Q

this type of volcano has a tall, very sleep slope

A

cinder cone volcano

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17
Q

what are the characteristics of a cinder cone volcano?
1.
2.
3.
4.

A
  1. it has a tall, very steep slope
  2. it is constructed of ejected pyroclastic fragments
  3. it has explosive eruptions due to its long conduit
  4. eruptions from cinder cone volcanoes produce a lot of cinder and ash
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18
Q

this volcano is of intermediate steepness and constructed of alternating layers of pyroclastic fragments and solidified lava flows

A

composite volcano

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19
Q

what are the characteristics of a composite volcano?
1.
2.
3.

A
  1. it is constructed of alternating layers of pyroclastic fragments and solidified lava flows
  2. it is built over long spans of time because eruption is intermittent
  3. it has intermediate steepness; slope is less than 33 degrees
20
Q

why does a volcano erupt?

A

a volcano erupts when magma and gases find a way to escape and burst to the surface through a vent.

since magma is buoyant, it rises up through the curst to erupt on the surface.

21
Q

there are two factors that determine eruption patterns:
1.
2.

A
  1. the amount of gas in the lava or magma
  2. the ease or difficulty with which the gas can escape into the atmosphere (viscosity)
22
Q

___ is how thick and gloopy a material is. an example of such material is honey in room temperature.

A

viscosity

23
Q

the ___ viscous the lava and the ___ the volume of gas trying to escape, the ___ the eruption.

A
  1. more
  2. greater
  3. more violent
24
Q

the three factors that influence viscosity of lava or magma are:
1.
2.
3.

A
  1. the silica content
  2. the temperature
  3. gas dissolved in magma
25
Q

the silica content of lava ranges from ___ to ___ by weight.

A

45% to 75%

26
Q

___ rocks are silica-rich (>65% silica)

A

felsic

27
Q

___ rocks are silica-deficient (~50%)

A

mafic

28
Q

mafic lavas which are silica-deficient tend to ___.

A

flow easily

29
Q

felsic lavas which are silica-rich are ___ and tend to ___.

A

much more viscous; flow sluggishly

30
Q

temperatures at which lavas solidify range from about ___ for felsic rocks to ___ for mafic rocks.

A
  1. 700 C
  2. 1,200 C
31
Q

if the lava being extruded is considerably hotter than its solidification temperature, the lava is ___ than when its temperature is near its solidification point.

A

less viscous (more fluid)

32
Q

water vapor dissolved in magma tends to increase fluidity because ___.

A

it reduces formation of long silicate chains by breaking silicon-oxygen (silicate) bonds.

33
Q

the loss of gases renders magma ___.

A

more viscous

34
Q

there are two types of eruption patterns, namely:
1.
2.

A
  1. explosive eruption
  2. effusive eruption
35
Q

caused by large amounts of gas and high viscosity magma, this is the most violent eruption of all due to the gases and magma trapped in the volcano.

A

explosive eruption

36
Q

this eruption pattern is characterized by outpourings of lava onto the ground.

described as quiet and gentle, the eruptions contain small amounts of gas and/or low viscosity magma.

the lava is very runny and can move fast.

A

effusive eruption

37
Q

most of the gas released during eruptions is ___, which condenses as steam.

A

water vapor

38
Q

collectively regarded as extrusive igneous rock or surface rock resulting from volcanic activity.

A

tephra

39
Q

when magma solidified quickly as it was blasted explosively by gases into the air, it produces rock fragments known as ___.

A

pyroclasts

40
Q

types of volcanic hazards:
1.
2.
3.
4.

A
  1. pyroclastic fall
  2. pyroclastic flow
  3. volcanic mudflows
  4. volcanic lightning
41
Q

the fallout of rock, debris and ash from an explosive eruption column

A

pyroclastic fall

42
Q

most of the deaths due to pyroclastic fall are caused by ___ or ___.

A
  1. collapse of ash-covered roof
  2. being hit by falling rock fragments
43
Q

a mixture of hot gas and pyroclastic debris that rapidly flows down a volcano’s flanks

A

pyroclastic flow

44
Q

characteristics of pyroclastic flows
1.
2.
3.

A
  1. they can reach over 100 km distances from a volcano
  2. they can travel 100 km/h
  3. temperature is > 400C
45
Q

pyroclastic flows can happen ___ or ___ the eruption

A

before or after

46
Q

a flowing mixture of soil, fine pyroclastic debris, and water from heavy rains

A

volcanic mudflows or lahars

47
Q

this volcanic hazard is generated by tiny particles of rocks thrown out by the volcano. the ash causes friction that generates an electrical charge.

A

volcanic lightning

CEGEOLO EV (14 decks)

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