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Earth Science > Volcanic Hazards > Flashcards

Volcanic Hazards Flashcards

1
Q

lava is…

A

the molten rock on or above the earth’s surface and forms extrusive igneous rocks

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2
Q

magma is…

A

molten rock below the earth’s surface and forms intrusive igneous rocks

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3
Q

intrusive rocks…

A

-cool slow
-more insulated in the earth
-produce coarser larger crystals

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4
Q

extrusive rocks…

A

-cool fast
-on the surface of the earth
-produce fine or smaller or glass tend to be smoother

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5
Q

mafic rocks are

A

rich in iron and magnesium

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6
Q

ultramafic rocks are

A

very rich in iron and magnesium

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7
Q

felsic rocks are

A

rich in silica and feldspar

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8
Q

intermediate rocks are

A

somewhere in the middle

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9
Q

rocks are

A

-solid
-naturally occurring
-made of at least one mineral

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10
Q

minerals are

A

-have a crystalline structure
-solid
-inorganic
-have a chemical composition
-naturally occurring

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11
Q

coarse- Phaneritic crystal size

A

6-22mm this means that the cooling rate is slow

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12
Q

medium crystal size

A

2-6mm

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13
Q

fine -aphanitic crystal size

A

0.06-2mm this means that the cooling rate is fast

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14
Q

glassy crystal size

A

no crystals

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15
Q

mafic rocks are shown to be

A

a dark colour

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16
Q

intermediate rocks are shown to be

A

a grey colour

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17
Q

felsic rocks are shown to be

A

a white/pink colour

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18
Q

what structure are igneous rocks

A

crystalline

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19
Q

crystalline rocks have

A

no pore space -holes between grains

20
Q

porphyritic texture with 2 crystal sizes - large crystals called..

A

phenocrysts

21
Q

porphyritic texture with 2 crystal sizes - small crystals between large crystals called…

A

matrix

22
Q

porphyritic texture with 2 crystal sizes show

A

that the igneous rock has went through 2 stages of cooling one slow then one fast

23
Q

vesicular texture is due to

A

gas escaping and expanding during an eruption forming a vesicle

24
Q

more vesicles in the rock show

A

the magma was very gas rich and the more vesicle the more explosive the eruption was likely to be

25
Q

stretching bubbles show

A

the direction the rock was magma

26
Q

in amygaloidal texture what are the vesicles filled with

A

new crystals

27
Q

in amygaloidal texture- new crystals form as

A

precipitation of minerals dissolved in the water eg. calcite

28
Q

amygaloidal texture shows that

A

the rock has been affected by fluids after emplacement

29
Q

to calculate the shear stress of a slope what equation do you use

A

Gd=GxsinB

30
Q

to find the force (G) in shear stress equation what equation do we use

A

G=mg

31
Q

in G=mg what value is g

A

9.8 constant

32
Q

in G=mg what unit is m in

A

kg

33
Q

once calculate the G in G=mg then what do we do

A

sub our G into Gd=GxsinB

34
Q

if Gd-shear stress = F-friction means…

A

that it is just about to slide called precarious equilibrium

35
Q

if Gd-shear stress >F-friction means…

A

unstable

36
Q

if F-friction > Gd-shear stress means…

A

stable

37
Q

to analyse the slope stability use the safety factor equation

A

SF=F/Gd

38
Q

in the equation SF=F/Gd where is Gd found

A

is the number calculated in newtons N from Gd=GxsinB

39
Q

in the equation SF=F/Gd where is F found

A

will be given in as a strength of also in newtons N

40
Q

if SF-safety factor >1.3 this means..

A

stable

41
Q

if SF-safety factor <1 means..

A

actively unstable

42
Q

SF-safety factor >1 but <1.3 means…

A

conditionally unstable

43
Q

the melting point of a rock depends on

A

-pressure-decrease
-temperature-increase
-volatiles like water

44
Q

how do we find the weathering rate on a graph

A

x1000 of the value following the + ending in x

45
Q

what are effusive eruptions

A

-low viscosity lava
-low gas and water
-hotter
-rich in magnesium and iron

46
Q

what are explosive eruptions

A

-produces tephra and ash into the air
-high viscosity lava
-high gas and water
-cooler
-magma is fragmented into pyroclastic rocks

Earth Science (5 decks)

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