Igneous Rocks

Question 1

Igneous facts

Answer 1

over 700 different types
make up 95% of upper part of earths crust
formed by magma,
minerals have large crystals

Question 2

intrusive

Answer 2

igneous rocks below ground

Question 3

extrusive

Answer 3

igneous rocks on the surface

Question 4

melting processes

Answer 4

increase in temp
decrease in pressure
change in composition

Question 5

Igneous classifications

Answer 5

1. intrusive plutonic rocks (5-10 km)
2. extrusive plutonic rocks (1-3 km)
3. volcanic rocks

Question 6

plutonic rocks

Answer 6

rocks formed in the ground

Question 7

Intrusive plutonic rocks

Answer 7

syenite
granit
granodiorite 
diorite
gabbro
peridotite
dunite

Question 8

syenite

Answer 8

intrusive, mostly orthoclase feldspar w/little or no quartz and little bits of mafic minerals

Question 9

granite

Answer 9

from continental crust (from acid magma)
density: 2.7-8
high silica content
=quartz(25%)+mica+feldspars(60%) in solid solution

Question 10

granodiorite

Answer 10

intermediate form between granit and diorite

contains more plagioclase feldspar than granite

Question 11

gabbro

Answer 11

medium silica content
similar to granit in composition
underneath ocean

Question 12

peridotite

Answer 12

dense course grained igneous rock, mostly olivene and pyroxene
rich in magnesium

Question 13

diorite

Answer 13

high silica content (acidic_

common in mountainous rings of pacific ocean

Question 14

Dunite

Answer 14

over 90% olivine

Question 15

Extrusive Plutonic Rock

Answer 15

fast cooling, small crystals
Rhyolite
Dacite
Andesite
Basalt

Question 16

Rhyolite

Answer 16

medium silica content

fine grained

Question 17

dacite

Answer 17

quartz rich extrusive rock

constituent of volcanoes

Question 18

Andesite

Answer 18

forms volcanic arcs
density>2.8
dark/dense

Question 19

Basalt

Answer 19

most abundant rock
forms ocean crust (basic magma
low silica (basic
dark/dense (2.9(

Question 20

Volcanic rocks

Answer 20

aka, pyroclastic rocks
debris ejected by volacnoes
fine granined
sometimes so fast cooling that it becomes glass (obsidian)

Question 21

Tuff

Answer 21

volcanic material consolidate and lithified after deposition
constituents = crystal tuff, rock fragments (lithic tuff), or pumice/glass (vitric tuff
mostly rhyolitic
lots of quartz
high resistance to weathering

Question 22

tuff fabric/foliation

Answer 22

foliation indicates orientation of deposition.

most common fabric in tuff is welding fabric

Question 23

volcanic breccia

Answer 23

composed of angular mineral fragments embedded in a matrix

product of explosive eruptions

Question 24

grain size

Answer 24

coarse (granite) >5 mm slow cool
medium 1-5 mm
fine (rhyolite) <1 mm fast cool
glassy (obsidian) invisible really fast

Question 25

main features (igneous)

Answer 25

mode of occurence
grain size of minerals
total SiO_2 content
other chemical composition
mineral composition
2 sets of data for classification.

Question 26

igneous rocks in HK

Answer 26

mostly acidic intruding magma (light colored, lots of quartz/feldspar)
3 types, granite, granodiorite, quartz monzonite

Question 27

volcanic rocks in HK

Answer 27

occupy about 50% land surface area

came from middle jurassic to early cretaceous period

Question 28

yim tin tsai formation

Answer 28

oldest volcanic rock formationin HK

crystal tuff containing hornblende

Question 29

rock strength

Answer 29

Intrusive Extrusive Volcanic
small————————>Large
ultra-basic Basic Neutral Acid _____________________________________________________________________________________________________

Question 30

Resistance to Weathering

Answer 30

Intrusive Extrusive Volcanic
low————————>high
ultra-basic Basic Neutral Acid ___________________________________________________________________________________________________