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1st Semester > GHC Ch 6: Volcanism > Flashcards

GHC Ch 6: Volcanism Flashcards

1
Q

We locate volcanoes in the context of what?

A

plate tectonics

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2
Q

What four factors determine whether eruptions are peaceful or explosive?

A

chemical composition, viscosity, gas content, and volume

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3
Q

What are the 3 V’s of volcanology

A

Volatiles, Viscosity, and Volume

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4
Q

90% of volcanism is associated with how many plate boundaries?

A

Two

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5
Q

80% of volcanoes are at what kind of plate boundary?

A

spreading centers

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6
Q

About 10% of volcanoes are at what plate boundary? And the rest of the 10%?

A

at subduction zones. above hot spots

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7
Q

No volcanism associated with which to types of faults?

A

transform faults and continent-continent collisions

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8
Q

Oceanic volcanoes are peaceful or explosive?

A

peaceful

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9
Q

Subduction-zone volcanoes are peaceful or explosive?

A

explosive

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10
Q

Which of the 92 elements are by far most abundant naturally occurring element of Earth’s crust?

A

Oxygen and silicon

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11
Q

Oxygen and silicon typically join up as what?

A

SiO4 tetrahedron

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12
Q

Minerals form in magma by what process?

A

crystallization

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13
Q

Order of crystallization of different minerals in magma is known from what?

A

observation and experiment

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14
Q

Elements combine to form…?

A

minerals

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15
Q

Minerals combine to form…?

A

rocks

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16
Q

Different compositions of magma result in different (…) rocks?

A

ingeneous

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17
Q

If magma cools slowly and solidifies beneath surface, what type of rock results?

A

plutonic rocks

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18
Q

If magma erupts and cools quickly at surface, what type of rock results?

A

volcanic rocks

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19
Q

What is viscosity?

A

internal resistance to flow

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20
Q

Water is high or low viscosity? Honey?

A

Low, high

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21
Q

Viscosity determined by what three factors?

A

temperature, more silicon and oxygen tetrahedra, amount of crystals

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22
Q

More silicon and oxygen tetrahedra results in higher or lower viscosity?

A

higher

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23
Q

Solubility increases as pressure (…) and temperature (…)

A

increases, decreases

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24
Q

What is the most abundant dissolved gas in magma?

A

Water

25
Q

As magma rises, pressure (…), water becomes (…)

A

decreases, gas bubbles

26
Q

Lower water content results in more or less peaceful eruptions.

A

more peacefull

27
Q

Rhyolitic magma has higher (…) and (…)

A

water content and viscosity

28
Q

In rhyolitic magma, many (…) form and can not escape through thick magma, so explode and result in violent, dangerous eruptions

A

steam bubbles

29
Q

At spreading centers, Plates pull apart so asthenosphere (…) and (…) under low pressure.

A

rises, melts

30
Q

At spreading centers, eruptions are peaceful or violent?

A

peaceful

31
Q

Subduction zones have violent eruptions because…?

A

Magma is generated by partial melting of mantle above the subducting plate with water in it, and melts overlying crust to produce magmas of variable composition

32
Q

Three things will cause rock to melt:

A

Lowering pressure
Raising temperature
Increasing water content

33
Q

What is the most common way to melt rock?

A

decompression melting: lowering pressure

34
Q

Magma at depth is under too much pressure for (…) to form

A

gas bubbles

35
Q

Eventually gas bubble volume may overwhelm magma,(…) that explode out as a (…)

A

fragmenting it into pieces, gas jet

36
Q

Concentration of water in magma largely determines (…) eruption.

A

peaceful or explosive

37
Q

Rhyolitic magma usually erupts violently because of high (…) and high (…).

A

water content, viscosity

38
Q

Low-water content, low-viscosity magma leads to…?

A

lava flows

39
Q

High-water content, high-viscosity magma leads to…?

A

pyroclastic debris

40
Q

What were some non-explosive eruptions?

A

Pahoehoe, Aa

41
Q

What are pyroclastic debris?

A

broken up fragments of magma and rock from violent gaseous explosions, classified by size

42
Q

Viscosity controls what about magma?

A

whether magma flows easily or piles up

43
Q

Volatile abundance controls whether magma…?

A

may ooze out harmlessly or explode

44
Q

Greater volume of magma leads to…?

A

more intense eruption

45
Q

Three V’s of Shield Volcanoes? What does a shield volcano look like?

A

Low Viscosity, Low Volatiles, Large Volume. Great width compared to height.

46
Q

What is the Volcanic Explosivity Index?

A

Provides a means of evaluating eruptions according to volume of material erupted, height of eruption column and duration of major eruptive blast. Scale from 0 to 8.

47
Q

Three V’s of Flood Basalts?

A

Low Viscosity, Low Volatiles, Very Large Volume

48
Q

Some flood basalts coincide with mass…?

A

extinctions

49
Q

Three V’s of Stratovolcanoes? What does a Stratovolcano look like? What are they composed of?

A

High Viscosity, High Volatiles, Large Volume. Steep-sided, symmetrical volcanic peaks. alternating layers of pyroclastic debris and andesitic to rhyolitic lava flows.

50
Q

Plinian-type Eruptions? Water content and viscosity?

A

Gas-powered vertical columns of pyroclastic debris up to 50 km into the atmosphere. High water content and high viscosity.

51
Q

Vesuvius, 79 CE

A

Most of 4,000 people who remained in Pompeii killed by thick layers of hot pumice or pyroclastic flows

52
Q

Three V’s of Calderas? What does a Calderas look like?

A

High Viscosity, High Volatiles, Very Large Volume. Large volcanic depressions formed by inward roof collapse into partially emptied magma reservoirs

53
Q

Where do Calderas occur?

A

Occur where large volumes of basaltic magma intrude to shallow depths and melt surrounding continental rock, to form high-viscosity, high-volatiles magma

54
Q

Yellowstone National Park has had how many recent catastrophic (ultra-Plinian) eruptions?

A

3

55
Q

The 3 mechanisms by which rocks melt? Which is most common?

A

Heating, Pressure decrease , Addition of water. Pressure decrease

56
Q

where volcanism is focused?

A

At the subduction zone

57
Q

What are the three types of magma?

A

Basaltic, Andesitic, and Rhyolitic

58
Q

Describe the anatomy of an eruption.

A

Magma rises from areas of high pressure to low pressure. Gas comes out of solution. Bubbles form. Bubbles overwhelm magma. Gas jet is created leading to a buoyant plume.

1st Semester (27 decks)

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