igneous rock

Question 1

petrology

Answer 1

study of rocks

Question 2

lava vs magma

Answer 2

lava is magma that has erupted

Question 3

igneous rocks form from….

Answer 3

cooling of magma

Question 4

3 ways of magma formation

Answer 4

• decompression melting (pressure drop)
• flux melting (add volatiles H2O CO2 SO2)
• heat transfer from rising magma

Question 5

_______ magma is the most abundant magma, it is of ________ composition and generated in the ______

Answer 5

mafic magma is the most abundant magma, it is of basaltic composition and generated in the mantle

Question 6

_________ and ______ magmas are of ________ to rhyolitic composition, and are generated in the _____

Answer 6

intermediate and silicic magmas are of andesitic to rhyolitic composition, and are generated in the crust

Question 7

how does addition of volatiles help melt mantle rock? what type of magma is formed

Answer 7

• break molecular bonds
• decreases melt temp
• basaltic magma (mafic) formed

Question 8

magma is _______ (silicic) if melted crust alone rises in Heat transfer

Answer 8

magma is rhyolitic (silicic) if melted crust alone rises in Heat transfer

Question 9

formation of andesitic (intermediate) magma in heat transfer

Answer 9

basaltic magma and melted crust mix

Question 10

BOWEN’s Reaction series

Answer 10

dictates what minerals crystalise at what temperatures

Question 11

according to BOWEN’s reaction series, what crystallises at high T and Low T

Answer 11

high T- Mafic minerals

low T- Felsic minerals

Question 12

three igneous rock textures

Answer 12

1. Aphanitic - fine
2. Phaneritic - coarse
3. Porphyritic - large phenocrysts in fine matrix

Question 13

eg of aphanitic

Answer 13

basalt

Question 14

eg of phaneritic

Answer 14

gabbro

Question 15

eg of porphyritic

Answer 15

andesite

Question 16

magma thats cooled over centuries would form

Answer 16

phaneritic texture

Question 17

main way to classify igneous rock, based on chemical composition

Answer 17

silica content (SiO2)

Question 18

most silica = ,

least silica = , and ,

Answer 18

most silica = silicic,

least silica = mafic, ultramafic and ,

Question 19

3 environments igneous rock forms in

Answer 19

1. Plutonic environment - High P, slow cooling
2. subvolcanic/ hypabyssal - transitional
3. volcanic
   - low P, fast cooling

Question 20

most common plutonic rock in the continental crust

Answer 20

granite

Question 21

gabbro (mafic) forms significant part of what?

Answer 21

oceanic crust

Question 22

how are plutonic rocks found on the surface of the earth?

Answer 22

by uplift and erosion

Question 23

peridotite is what type of mineral?

Answer 23

ultramafic

Question 24

example of intermediate, phaneritic rock

Answer 24

Diorite

Question 25

dyke

Answer 25

cross-cutting, flat sheet cuts across rock layers

Question 26

sill

Answer 26

parallel to local structures

Question 27

effusive volcanic activity

Answer 27

- forms crystalline rock - magma extruded at the ground surface - little gas involved

Question 28

explosive volcanic activity

Answer 28

forms clastic rock

Question 29

2 variances of rhyolite

Answer 29

Pumice and obsidian

Question 30

basalt forms from ___ viscosity lava. Andesite forms from ___ viscosity lava. Dacite forms from ____ viscosity lava.

Answer 30

low, medium, medium-high

Question 31

IGNIMBRITE

Answer 31

pumice-dominated (glassy) pyroclastic flow deposits

Question 32

2 major groups of igneous rocks

Answer 32

1. volcanic - extruded onto the earths surface | 2. plutonic - cooled from magma inside the crust

Question 33

having same chemical composition what are the plutonic equivalents of: Basalt = Andesite & Dacite = Rhyolite =

Answer 33

Basalt = Gabbro Andesite & Dacite = Diorite Rhyolite = Granite

Question 34

Basalt colour and varieties

Answer 34

dark grey. Vesicular variety and Scoria variety

Question 35

some uses of Basalt include...

Answer 35

aggregate, fill in construction, armour rock, scoria for drainage

Question 36

colour of andesite vs basalt

Answer 36

lighter grey

Question 37

Andesite uses

Answer 37

aggregate fill in roading and construction (not good in concrete due to high silica)

Question 38

Rhyolite is light-coloured, name 3 varieties:

Answer 38

1. Obsidian (glassy) 2. pumice (vesicular) 3. Ignimbrite (lithification of ash and pyroclastic flow)

Question 39

Gabbro colour and uses

Answer 39

very dark black. Used as aggregate and as a building stone in foyers etc. ('black granite')

Question 40

what will happen if an aggregate with high silica content or glass is used in cement?

Answer 40

reacts with cement to produce swelling materials which will result in cracking

Question 41

what mineral would be good in an aggregate for cement?

Answer 41

ferromagnesium

Question 42

would granite bind well with bitumen? why/why not?

Answer 42

NO, it has large mineral grains