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Geol 11 > Lecture 5: Igneous Processes > Flashcards

Lecture 5: Igneous Processes Flashcards

1
Q

completely/partially molten rock beneath the earth’s surface composed of:
s -
l -
g -

A

magma

solid: minerals, unmelted rock fragment
liquid: melt, ions of (Mg, Ca, Al, Na, K, O, Si, Fe
gas: volatiles (H2O, CO2, SO2)

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2
Q

Types of Magma

A

felsic, intermediate, mafic, ultramafic

granitic, andesitic, basaltic, picritic

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3
Q 
Based on SiO2 and Fe, Mg content
Felsic
Intermediate
Mafic
Ultramafic
A

Felsic highest SiO2 content (>63%), lowest Fe, Mg content (~2%)
Ultramafic lowest SiO2 content (<45%), highest Fe, Mg content (>8-32%)

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4
Q 
Based on Temperature and Viscosity
Felsic
Intermediate
Mafic
Ultramafic
A

Felsic - lowest temperature, high viscosity
Ultramafic - highest temperature, low viscosity
Felsic - high
Intermediate - intermediate
Mafic - low
Ultramafic - low to very low

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5
Q 
Based on eruptive behavior and where it is commonly found
Felsic
Intermediate
Mafic
Ultramafic
A

Felsic : explosive, continental crust
Intermediate: explosive, continental crust
Mafic: gentle, oceanic crust
Ultramafic: gentle, upper mantle

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6
Q

How to melt rocks? (generate magma)

A
  1. Increase temperature (hot spots)
  2. Decrease pressure (rift zones)
  3. Addition of volatiles (subduction zones)
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7
Q

Temperature is * proportional to viscosity

A

inversely

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8
Q

decrease in pressure with no heat transfer

A

Adiabatic decompression

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9
Q

‘any process which cause magma composition to change’

A

Magmatic Differentiation: (How magma evolves)

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10
Q

Magmatic DIfferentiation

A
  1. Assimilation of host rock
  2. Magma mixing
  3. Fractional crystallization
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11
Q

Explain:

  1. Assimilation of host rock
  2. Magma mixing
  3. Fractional crystallization
A

pass

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12
Q

phenomenon by which magma is erupted to the surface through volcanoes as lava

A

Volcanism

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13
Q

Geomorphic (landform) feature where magma is exhumed to the surface (not always conical)

A

Volcanoe

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14
Q

Why do volcanoes erupt?

A
  1. Influx of new magma

2. Degassing magma

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15
Q

What is VEI

A

Volcano Explosivity Index

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16
Q

Relative measure of explosiveness of volcanic eruptions based on volume of products, height of eruption cloud, frequency

A

Volcano Explosivity Index

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17
Q

VEI is based on

A

volume of products, height of eruption cloud, frequency

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18
Q

Parts of a volcano

A

Conduit (pipe), vent, crater, parasitic cone, lava, bombs, pyroclastic material

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19
Q

VEI of Mt. Pinatubo

A

6

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20
Q

degassed form of magma

A

Lava flows

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21
Q

aa vs pahoehoe

A
  • Aa – more viscous, composed of clinker (broken lava)

* Pahoehoe – smooth, billowy, undulating, ropy surface

22
Q

Columnal joints/basalts

A

Lava flow:

cooling joints refecting the high temperature during its emplacement

23
Q
  • Fragmented crystals or rocks that are either from the crystallizing magma or from the volcano edifice itself
A

Pyroclasts

24
Q

Pyroclasts examples

A

pass

25
Q

Volcanic Gases

A

SO2, CO2, CO, H2O

26
Q

Form of Volcanic gas (type)

A

juvenile (from magma), heated meteoric (ground or surface)

27
Q

Types of Volcanic Eruptions based on degree of explosivity

A

a. Explosive – pyroclastic rocks, ash fall, pyroclastic flows, debris avalanches, pyroclastic surges
b. Non-explosive/Effusive – lava flows, lava fountains

28
Q

Types of Volcanic Eruptions based on Type of Material

A
  • Magmatic (magma)
  • Phreatomagmatic (magma + H2O)
  • Phreatic (mostly gaseous)
29
Q

Magmatic volcanic eruptions

A
  1. Hawaiian and Kelandic type
  2. Vulcanism type
  3. Strombolian type
  4. Palean type
  5. Plinian type
30
Q

Phreatomagnetic volcanic eruptions

A
  1. Surtseyan

2. Subglacial

31
Q

Phreatic volcanic eruptions

A

Geysers and fumaroles

32
Q

*highly viscous lava
*volcanic bombs and blocks
MVE

A

Vulcanism

33
Q
  • short-lived eruptions of lavas; lava fountains
A

Strombolian

34
Q
  • creates large eruptive columns

* glowing gases

A

Palean type

35
Q

pumice, pyroclastic flows, calderagenic collapse

A

Plinian type

36
Q

Gentle, very little amount of ash (gentle/effusive)

A

Hawaiian and Icelandic Type

37
Q

Hawaiian

A

vent

38
Q

Icelandic

A

(more linear or fissure)

39
Q

involves basaltic magma interacting with water in a shallow sea or lake
PmER

A

Surtseyan

40
Q

involves basaltic magma interacting with ice

PmER

A

Subglacial

41
Q

Erupts steam or hot fluids (no magma)

A

Geysers and Fumaroles

42
Q

Types of Volcanoes (Age of Activity)

A
  1. Active
    - Erupted for last 10,000 years
    - Erupted with historical times (human record within 600 years)
  2. Potentially Active
    - Volcanic activity between 1.65 Ma to Ka
  3. Inactive
    - No historical records of eruption (morphologically young-looking)
43
Q

Types of Volcanoes (Architecture)

A
  1. Shield
  2. Composite/Stratovolcano
  3. Pyroclastic cones
  4. Caldera
  5. Plug domes
44
Q
  • Composed mostly of fluid lava flows

- Resembles warrior shield

A

Shield volcano

45
Q
  • Alternating layers of lava flows and pyroclastic deposit

- Steep; periodic, explosive eruptions

A
  1. Composite/Stratovolcano
46
Q
  • Short lived explosive activity

- Collection of airborne ash, lapilli and blocks as they fall around a central vent

A
  1. Pyroclastic cones
47
Q
  • Mound-shaped protrusion resulting from slow extrusion of viscous lava from a volcano
A
  1. Plug domes
48
Q

Types of pyroclastic cones

A

Scoria cone, Maar, Tuff ring, Tuff cone

49
Q

Caldera formation process

A

Plinian eruption - faulting - collapse

50
Q

melt field and start of crystallization; demarcates the start of crystallization

A

Liquidus

51
Q 
complete solidification (melt + crystals)
boundary
A

Solidus

52
Q

temperature gradient of Earth with depth

A

geotherm

Geol 11 (20 decks)

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