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Geology > Igneous Rock > Flashcards

Igneous Rock Flashcards

1
Q

Magma formation (2)

A

1) Solitus

2) Liquidus

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2
Q

Solitus

A

at which the matter starts to melt

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3
Q

Liquidus

A

at which the last solid disappears

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4
Q

decompressional melting (3)

A

1) Mid-ocean ridge
2) Mantle plume
3) Rifts

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5
Q

Volatiles

A

Help break chemical bonds

lowers melting T of hot rocks

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6
Q

What temperature does continental crust melt at?

A

650-850 C

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7
Q

components of all magma

A

solid, liquid, gas

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8
Q

Example of volatiles (5)

A 
Water vapor (H2O)
Carbon dioxide (CO2) 
Sulfur dioxide (SO2) 
Nitrogen (N2) 
Hydrogen (H2)
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9
Q

Factors in types of melts: (4)

A

1) Initial source rock compositions
2) Partial melting
3) Assimilation
4) Magma mixing

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10
Q

Initial source rock composition

A

Mantle: Mafic or ultramafic
Crust: Mafic, intermediate, felsic

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11
Q

Partial melting

A

yields silica-rich magma
partial melting ultramafic –> Mafic magma
partial melting intermediate –> Felsic magma

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12
Q

Assimilation

A

Magma melts the wall rock it passes through

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13
Q

magma mixing

A

Different magmas may blend in a magma chamber

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14
Q

viscosity

A

measures resistance to flow

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15
Q

Aspects that affect viscosity (3)

A

1) temperature
2) volatile content
3) Silica (SiO2) content

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16
Q

Cooling rate (3)

A

1) depth
2) shape
3) Groundwater - circulating water

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17
Q

Fractional crystallization

A

Sequential crystal formation and settling by gravity

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18
Q

Bowen’s reaction series (2)

A

1) continuous

2) discontinuous

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19
Q

Continuous Bowens series

A

plagioclase changed from Ca-rich to Na-rich.

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20
Q

Discontinuous bowerns series

A

minerals start and stop crystallizing.

Highest T) Olivine, Pyroxene, Amphibole, Biotite, K-Feldspar, Muscovite, Quartz

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21
Q

Xenolith

A

Country rock fragment in magma

Thermally altered

22
Q

Tabular Intrusions (2)

A

1) Dike

2) Sill

23
Q

Dike

A

Crosscuts rock fabric

spread rock sideways

24
Q

Sill

A

Parallels rock fabric (look like bedding)

lift up entire landscape

25
Q

Pluton

A

a large, deep, igneous body

26
Q

Where are plutons created?

A

subduction zones

may form large batholiths

27
Q

Describing igneous rocks (3)

A

1) interlocking
2) fragmental
3) glassy

28
Q

interlocking igneous rock

A

mineral crystals fit like jigsaw puzzle pieces

29
Q

Fragmental igneous rock

A

pieces of preexisting rock, usually shattered

30
Q

Glassy igneous rock

A

made of solid glass or glass shards

31
Q

how are glassy rocks formed?

A

very quick cooling of magma in water or air

32
Q

Types of igneous “interlocking” (2)

A

1) Aphanitic

2) Phaneritic

33
Q

Aphanitic

A

finely crystalline
rapid cooling - extrusive
*crystals do not have time to grow

34
Q

Phaneritic

A

coarsely crystalline
slow cooling - intrusive
*crystals have long time to grow

35
Q

Porphyritic Texture

A

A mixture of coarse and fine crystals
2-stage cooling history
- initial slow cooling (large crystals)
- eruption causes quick cooling (small)

36
Q

Extrusive magma Characteristics (2)

A

1) Lava flows

2) Explosive ash eruptions

37
Q

Lava flows

A

Lava cools as it flows
Sheets of cooled lava
Lava flows exit volcanic vents and flow outward.
Low viscosity lava can flow long distances (10-500km)

38
Q

Explosive Ash Eruptions

A

high viscosity felsic magma = increased P

violent eruptions with associated ash

39
Q

Tephra

A

Deposits of pyroclastic debris

40
Q

Lapilli

A

Pea to plum sized material volcanic material that comes from volcanic eruptions

41
Q

Pyroclastic flows

A

Avalanches of hot ash (200-400 C)
300km/h
Kill everything quickly

42
Q

Characteristics of Volcanos (4)

A

1) Magma chamber
2) Fissures and Vents
3) Crater
4) Calderas

43
Q

Volcanic vents

A

outlets for magma

can form anywhere on volcano

44
Q

Volcanic crater

A

bowl shaped depression atop a volcano
form as erupted lava piles around and cools
assentuated by summit collapse

45
Q

Caldera

A

A major depression (up to 10km)

magma chamber empties –> volcano collapses into it

46
Q

Types of Volcanos (3)

A

1) shield volcano
2) cinder cone
3) stratovolcano

47
Q

Shield volcano

A

broad
lateral flow
low slope;large geographic areas
Hawaii

48
Q

Cinder cone volcano

A 
smallest type
built by lapilli sized fragments ontop of vent
slope at angle of repose 
symmetrical 
deep crater
49
Q

Stratovolcano

A

large cone shaped volcano
alternating layers of lava and tephra
often symmetric

50
Q

Recurrance interval

A

Active: erupted or recently erupted
Dormant: capable, but hasn’t in 100’s-1000’s
Extinct: not capable of erupting

51
Q

Predicting Volcanic Eruptions

A

1) earthquake activity
2) heat flows
3) changes in flow
4) emission increase

52
Q

Igneous activity (4 settings)

A

1) Volcanic arcs beside deep ocean trenches
2) isolated hotspots
3) continental rifts
4) mid-ocean ridges

Geology (5 decks)

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