Volcanic Hazards

Question 1

lava is…

Answer 1

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

Question 2

magma is…

Answer 2

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

Question 3

intrusive rocks…

Answer 3

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

Question 4

extrusive rocks…

Answer 4

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

Question 5

mafic rocks are

Answer 5

rich in iron and magnesium

Question 6

ultramafic rocks are

Answer 6

very rich in iron and magnesium

Question 7

felsic rocks are

Answer 7

rich in silica and feldspar

Question 8

intermediate rocks are

Answer 8

somewhere in the middle

Question 9

rocks are

Answer 9

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

Question 10

minerals are

Answer 10

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

Question 11

coarse- Phaneritic crystal size

Answer 11

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

Question 12

medium crystal size

Answer 12

2-6mm

Question 13

fine -aphanitic crystal size

Answer 13

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

Question 14

glassy crystal size

Answer 14

no crystals

Question 15

mafic rocks are shown to be

Answer 15

a dark colour

Question 16

intermediate rocks are shown to be

Answer 16

a grey colour

Question 17

felsic rocks are shown to be

Answer 17

a white/pink colour

Question 18

what structure are igneous rocks

Answer 18

crystalline

Question 19

crystalline rocks have

Answer 19

no pore space -holes between grains

Question 20

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

Answer 20

phenocrysts

Question 21

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

Answer 21

matrix

Question 22

porphyritic texture with 2 crystal sizes show

Answer 22

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

Question 23

vesicular texture is due to

Answer 23

gas escaping and expanding during an eruption forming a vesicle

Question 24

more vesicles in the rock show

Answer 24

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

Question 25

stretching bubbles show

Answer 25

the direction the rock was magma

Question 26

in amygaloidal texture what are the vesicles filled with

Answer 26

new crystals

Question 27

in amygaloidal texture- new crystals form as

Answer 27

precipitation of minerals dissolved in the water eg. calcite

Question 28

amygaloidal texture shows that

Answer 28

the rock has been affected by fluids after emplacement

Question 29

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

Answer 29

Gd=GxsinB

Question 30

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

Answer 30

G=mg

Question 31

in G=mg what value is g

Answer 31

9.8 constant

Question 32

in G=mg what unit is m in

Answer 32

kg

Question 33

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

Answer 33

sub our G into Gd=GxsinB

Question 34

if Gd-shear stress = F-friction means...

Answer 34

that it is just about to slide called precarious equilibrium

Question 35

if Gd-shear stress >F-friction means...

Answer 35

unstable

Question 36

if F-friction > Gd-shear stress means...

Answer 36

stable

Question 37

to analyse the slope stability use the safety factor equation

Answer 37

SF=F/Gd

Question 38

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

Answer 38

is the number calculated in newtons N from Gd=GxsinB

Question 39

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

Answer 39

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

Question 40

if SF-safety factor >1.3 this means..

Answer 40

stable

Question 41

if SF-safety factor <1 means..

Answer 41

actively unstable

Question 42

SF-safety factor >1 but <1.3 means...

Answer 42

conditionally unstable

Question 43

the melting point of a rock depends on

Answer 43

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

Question 44

how do we find the weathering rate on a graph

Answer 44

x1000 of the value following the + ending in x

Question 45

what are effusive eruptions

Answer 45

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

Question 46

what are explosive eruptions

Answer 46

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