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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

25
Volcanic Gases
SO2, CO2, CO, H2O
26
Form of Volcanic gas (type)
juvenile (from magma), heated meteoric (ground or surface)
27
Types of Volcanic Eruptions based on degree of explosivity
a. Explosive – pyroclastic rocks, ash fall, pyroclastic flows, debris avalanches, pyroclastic surges b. Non-explosive/Effusive – lava flows, lava fountains
28
Types of Volcanic Eruptions based on Type of Material
* Magmatic (magma) * Phreatomagmatic (magma + H2O) * Phreatic (mostly gaseous)
29
Magmatic volcanic eruptions
1. Hawaiian and Kelandic type 2. Vulcanism type 3. Strombolian type 4. Palean type 5. Plinian type
30
Phreatomagnetic volcanic eruptions
1. Surtseyan | 2. Subglacial
31
Phreatic volcanic eruptions
Geysers and fumaroles
32
*highly viscous lava *volcanic bombs and blocks MVE
Vulcanism
33
* short-lived eruptions of lavas; lava fountains
Strombolian
34
* creates large eruptive columns | * glowing gases
Palean type
35
pumice, pyroclastic flows, calderagenic collapse
Plinian type
36
Gentle, very little amount of ash (gentle/effusive)
Hawaiian and Icelandic Type
37
Hawaiian
vent
38
Icelandic
(more linear or fissure)
39
involves basaltic magma interacting with water in a shallow sea or lake PmER
Surtseyan
40
involves basaltic magma interacting with ice | PmER
Subglacial
41
Erupts steam or hot fluids (no magma)
Geysers and Fumaroles
42
Types of Volcanoes (Age of Activity)
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
Types of Volcanoes (Architecture)
1. Shield 2. Composite/Stratovolcano 3. Pyroclastic cones 4. Caldera 5. Plug domes
44
- Composed mostly of fluid lava flows | - Resembles warrior shield
Shield volcano
45
- Alternating layers of lava flows and pyroclastic deposit | - Steep; periodic, explosive eruptions
2. Composite/Stratovolcano
46
- Short lived explosive activity | - Collection of airborne ash, lapilli and blocks as they fall around a central vent
3. Pyroclastic cones
47
- Mound-shaped protrusion resulting from slow extrusion of viscous lava from a volcano
5. Plug domes
48
Types of pyroclastic cones
Scoria cone, Maar, Tuff ring, Tuff cone
49
Caldera formation process
Plinian eruption - faulting - collapse
50
melt field and start of crystallization; demarcates the start of crystallization
Liquidus
51
``` complete solidification (melt + crystals) boundary ```
Solidus
52
temperature gradient of Earth with depth
geotherm

Geol 11 (20 decks)

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