Igneous rock formation

Question 1

igneous rocks are formed from

Answer 1

the solidification of a melt

Question 2

a melt is

Answer 2

molten rock

Question 3

what’s the difference between lava and magma

Answer 3

magma below ground lava above ground

Question 4

extrusive is

Answer 4

above ground

Question 5

intrusive is

Answer 5

below ground

Question 6

the crust and athenosphere are mostly in what state

Answer 6

solid

Question 7

melts occur in what areas

Answer 7

localized

Question 8

the earth has been cooling by

Answer 8

radiating heat out to space

Question 9

the uppermost layer of the earth froze to form

Answer 9

the crust

Question 10

how thick is the mantle

Answer 10

2800 km

Question 11

temp increases or decreases with depth

Answer 11

increases

Question 12

almost all solid rock is

Answer 12

peridotite

Question 13

lithosphere thickness

Answer 13

100-150km

Question 14

lithosphere is the

Answer 14

crust and upper mantle

Question 15

athenosphere thickness

Answer 15

100-350km

Question 16

athenosphere is a part of the

Answer 16

mantle

Question 17

melts occur because of

Answer 17

decrease in pressure (decompression)

introduction of volatiles’ (flux)

heat transfer (heat transfer)

Question 18

what happens in decompression melting

Answer 18

P decreases but T remains constant

temperature is high enough to melt rock at surface but pressure keeps them solid

Question 19

how does pressure decrease to allow decompression melting

Answer 19

a volume of hot asthenosphere rises by a mantle plume or divergent plate boundaries

Question 20

decompression melting creates M/F material

Answer 20

mafic

Question 21

what kind of melt created hawaii

Answer 21

decompression

Question 22

what happens in flux melting

Answer 22

volatiles help break chemical bonds, creating a melt

h2o or co2 mi with hot dry rock and help break the chemical bonds

this lowers the melting point of the rock

Question 23

where does flux melting happen

Answer 23

subduction zones

Question 24

flux melting creates M/F material

Answer 24

Felsic

Question 25

Heat transfer melting happens when

Answer 25

heat from magma melts adjacent rocks hot mantle rises up and brings heat with it this melts existing crustal rock that has a lower melting point

Question 26

volcanic ars along plate boundaries come from what type of melting

Answer 26

heat transfer melting

Question 27

melt composition is defined by

Answer 27

the proportion of different oxides SILICA SiO2 IRON OXIDE FeO and Fe2O3 MAGNESIUM OXIDE MgO

Question 28

a dry melt has

Answer 28

no volatiles

Question 29

a wet melt has

Answer 29

volatiles

Question 30

What are the four major compositional groups of magma

Answer 30

felsic (silicic). 67-76% silica intermediate. 53-66% silica mafic. 46-52% silica ultramafic. 38-45% silica

Question 31

felsic magma is what percent silica

Answer 31

67-76%

Question 32

intermediate magma is what percent silica

Answer 32

53-66%

Question 33

mafic magma is what percent silica

Answer 33

46-52%

Question 34

ultramafic magma is what percent silica

Answer 34

38-45%

Question 35

the four major compositional groups of magma is the percent

Answer 35

magma weight that is silica

Question 36

the four major compositional groups of solid rock

Answer 36

are dependent on the proportion of silica relative to the combination of magnesium and iron oxide

Question 37

diorite is _ I/S/M and _ F/M

Answer 37

igneous intermediate

Question 38

rhyolite I/S/M and F/M

Answer 38

felsic igneous

Question 39

gabbro I/S/M F/M

Answer 39

igneous mafic

Question 40

why do melts vary

Answer 40

source rock dictates the initial melt composition

Question 41

what is magma mixing

Answer 41

different magmas from different source rocks mix in the magma chamber changing the magma composition

Question 42

what is assimilation / contamination

Answer 42

heat provided by magma partially melts wall rock the new magma the mixes with the original magma blocks of wall rock can dissolve in the original magma and that wall rock may chemically react with the magma changes the melts composition

Question 43

what is partial melting

Answer 43

only a fraction of a source rock will melt at an achievable P and T some minerals melt at lower temps than others

Question 44

in partial melting liquid magma

Answer 44

migrates away from the source rock before the entire rock can melt

Question 45

partial melting produces a rock with

Answer 45

higher silica content

Question 46

how does molten rock flow

Answer 46

melts migrate toward the surface due to their relatively low density

Question 47

viscosity of molten rock depends on

Answer 47

temperature, volatile content, and silica percent content

Question 48

Low viscosity magma is

Answer 48

Hotter more mafic has less volatiles

Question 49

high viscosity magma is

Answer 49

cooler more felsic has more volatiles

Question 50

mafic melts are ___ viscous than felsic melts. why

Answer 50

less more silica tetrahedra in felsic magma. they link together and don’t like to flow

Question 51

how does a melt become a rock

Answer 51

it freezes migrates towards the surface loses heat to surrounding rock or erupts onto surface looses volatiles

Question 52

the time a melt takes to cool depends on how

Answer 52

well insulated it is

Question 53

wall rock is a ____insulator than water or air

Answer 53

better

Question 54

melts cool ___ at the surface than underground

Answer 54

faster

Question 55

the deeper magma is the hotter

Answer 55

the wall rock will be

Question 56

a larger intrusion will cool _____ than a small intrusion at the same depth

Answer 56

slower

Question 57

interaction with ground water can cool a melt _____ as water

Answer 57

faster as water can carry away heat but also introduce volatiles

Question 58

thing lava flows cool ____ than thick ones

Answer 58

faster

Question 59

lava immersed in water cools _____ than water immersed in air

Answer 59

faster

Question 60

what is fractional crystallization

Answer 60

when a melt cools some minerals form earlier than others due to their melting points this results in sequential crystal formation

Question 61

fractional crystallization creates a more

Answer 61

felsic melt

Question 62

in crystal fractionalization the material that solidifies out is

Answer 62

more mafic olivine and calcium rich plagioclase

Question 63

In bowens reaction series Low temperature corresponds to

Answer 63

last minerals to crystallize felsic materials

Question 64

in bowens reaction series high the first minerals to crystallize

Answer 64

do so at high temperatures are ultramafic

Question 65

What are tabular intrusions

Answer 65

Sills and Dikes underground solidified melts

Question 66

Dikes are ___ to rock layers

Answer 66

perpendicular

Question 67

Sills are ___ to rock layers

Answer 67

parralell

Question 68

most sills result in a

Answer 68

change in land elevation of the surface

Question 69

dikes spread in what way

Answer 69

sideways

Question 70

what is a lacolith

Answer 70

when magma that cannot spread accumulates in a blister shaped intrusion

Question 71

what is a pluton

Answer 71

a solid igneous intrusion

Question 72

what is a batholith

Answer 72

a large solid igneous intrusion larger than 100km^2

Question 73

what is a xenolith

Answer 73

a piece of rock in an igneous rock that is not derived from the original magma that showed up from elsewhere

Question 74

what is unroofing

Answer 74

when intrusive igneous features are exposed over a long period of time