Igneous Rock

Question 1

Magma formation (2)

Answer 1

1) Solitus

2) Liquidus

Question 2

Solitus

Answer 2

at which the matter starts to melt

Question 3

Liquidus

Answer 3

at which the last solid disappears

Question 4

decompressional melting (3)

Answer 4

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

Question 5

Volatiles

Answer 5

Help break chemical bonds

lowers melting T of hot rocks

Question 6

What temperature does continental crust melt at?

Answer 6

650-850 C

Question 7

components of all magma

Answer 7

solid, liquid, gas

Question 8

Example of volatiles (5)

Answer 8

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

Question 9

Factors in types of melts: (4)

Answer 9

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

Question 10

Initial source rock composition

Answer 10

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

Question 11

Partial melting

Answer 11

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

Question 12

Assimilation

Answer 12

Magma melts the wall rock it passes through

Question 13

magma mixing

Answer 13

Different magmas may blend in a magma chamber

Question 14

viscosity

Answer 14

measures resistance to flow

Question 15

Aspects that affect viscosity (3)

Answer 15

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

Question 16

Cooling rate (3)

Answer 16

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

Question 17

Fractional crystallization

Answer 17

Sequential crystal formation and settling by gravity

Question 18

Bowen’s reaction series (2)

Answer 18

1) continuous

2) discontinuous

Question 19

Continuous Bowens series

Answer 19

plagioclase changed from Ca-rich to Na-rich.

Question 20

Discontinuous bowerns series

Answer 20

minerals start and stop crystallizing.

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

Question 21

Xenolith

Answer 21

Country rock fragment in magma

Thermally altered

Question 22

Tabular Intrusions (2)

Answer 22

1) Dike

2) Sill

Question 23

Dike

Answer 23

Crosscuts rock fabric

spread rock sideways

Question 24

Sill

Answer 24

Parallels rock fabric (look like bedding)

lift up entire landscape

Question 25

Pluton

Answer 25

a large, deep, igneous body

Question 26

Where are plutons created?

Answer 26

subduction zones | may form large batholiths

Question 27

Describing igneous rocks (3)

Answer 27

1) interlocking 2) fragmental 3) glassy

Question 28

interlocking igneous rock

Answer 28

mineral crystals fit like jigsaw puzzle pieces

Question 29

Fragmental igneous rock

Answer 29

pieces of preexisting rock, usually shattered

Question 30

Glassy igneous rock

Answer 30

made of solid glass or glass shards

Question 31

how are glassy rocks formed?

Answer 31

very quick cooling of magma in water or air

Question 32

Types of igneous "interlocking" (2)

Answer 32

1) Aphanitic | 2) Phaneritic

Question 33

Aphanitic

Answer 33

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

Question 34

Phaneritic

Answer 34

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

Question 35

Porphyritic Texture

Answer 35

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

Question 36

Extrusive magma Characteristics (2)

Answer 36

1) Lava flows | 2) Explosive ash eruptions

Question 37

Lava flows

Answer 37

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)

Question 38

Explosive Ash Eruptions

Answer 38

high viscosity felsic magma = increased P | violent eruptions with associated ash

Question 39

Tephra

Answer 39

Deposits of pyroclastic debris

Question 40

Lapilli

Answer 40

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

Question 41

Pyroclastic flows

Answer 41

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

Question 42

Characteristics of Volcanos (4)

Answer 42

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

Question 43

Volcanic vents

Answer 43

outlets for magma | can form anywhere on volcano

Question 44

Volcanic crater

Answer 44

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

Question 45

Caldera

Answer 45

A major depression (up to 10km) | magma chamber empties --> volcano collapses into it

Question 46

Types of Volcanos (3)

Answer 46

1) shield volcano 2) cinder cone 3) stratovolcano

Question 47

Shield volcano

Answer 47

broad lateral flow low slope;large geographic areas Hawaii

Question 48

Cinder cone volcano

Answer 48

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

Question 49

Stratovolcano

Answer 49

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

Question 50

Recurrance interval

Answer 50

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

Question 51

Predicting Volcanic Eruptions

Answer 51

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

Question 52

Igneous activity (4 settings)

Answer 52

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