Topic 4B

Question 1

extrusive

Answer 1

fast cooling (small minerals)

Question 2

intrusive

Answer 2

long cooling (large minerals)

Question 3

glassy characteristics

Answer 3

glassy, cools quickly, extrusive

Question 4

aphanitic

Answer 4

small crystals, cools quickly at lower temp, extrusive

Question 5

phaneritic

Answer 5

large crystals, cools slowly at high temp, intrusive

Question 6

porphyrite

Answer 6

two crystal sizes, intrusive

Question 7

pyroclastic

Answer 7

fragments of crystals

Question 8

vesicular

Answer 8

holes, pores

Question 9

Felsic Minerals in general

Answer 9

light in color
light in weight (Fe,Mg poor)
Found in intermediate and felsic rocks

Question 10

mafic minerals in general

Answer 10

dark in color
heavier(Fe,Mg rich)
found in mafic and ultramafic rocks

Question 11

Felsic Rocks

Answer 11

Rhyolite (extrusive)
Granite (Intrusive)

Question 12

Intermediate rocks

Answer 12

Andesite ( extrusive)
Diorite (intrusive)

Question 13

Mafic rocks

Answer 13

basalt (extrusive)
gabbro (intrusive)

Question 14

Ultramafic rocks

Answer 14

Rare (extrusive)
Peridotite (intrusive)

Question 15

intermediate magma can form through

Answer 15

crystal settling in a mafic magma
partial melting of mafic rock
mixing mafic magma with felsic magma
assimilating felsic rocks into mafic magma

Question 16

felsic magma can be formed through

Answer 16

crystal settling in an intermediate magma
partial melting

Question 17

What is a volcano

Answer 17

any landform (earth or ocean) that releases lava, gas or ashes or has done so in the past

Mostly occur at divergent or convergent boundaries

Question 18

Mafic Magma characteristics

Answer 18

thin and flows easily
low silica content
low viscosity
low gas

forms Aa and
Pahoehoe lavas

Question 19

Felsic Magma characteristics

Answer 19

thick
tends to erupt catastrophically
high silica content
more viscous
high gas

Question 20

Pyroclastic debris in ascending mass

Answer 20

ash,lapilli, volcanic bombs, volcanic block, welded tuff, pumice

Question 21

what are the 3 most abundant gases released in an eruption

Answer 21

H20
CO2
SO2

Question 22

central vent volcanoes characteristics

Answer 22

central vent
summit crater
has 4 types
shield volcanoes
cinder cones
stratavolcanoes
rhyolite caldera complexes

Question 23

Large scale volcanic terrains

Answer 23

no central vent
network of source material
extend over large areas

Question 24

Shield volcanoes characteristics

Answer 24

low viscosity creates broad, gentle slops
low silica, low gas, magma comes from mantle

Question 25

Stratovolcanoes characteristics

Answer 25

Alternating layers of mafic to intermediate lava flows with layers of intermediate to felsic explosively pyroclastic fragments (explosions due to gas buildup)

Question 26

Rhyolite caldera complexes characteristics

Answer 26

High silica, high gas magmas massive explosions ( most explosive) withdrawal of magma from magma chamber causes collapse

Question 27

Large scale volcanic terrains characteristics

Answer 27

mid-ocean ridges develop divergent boundaries (spreading centres) basaltic flow creates a global network

Question 28

tectonic environment- divergent boundary

Answer 28

mafic lava flows (efussive) mid ocean ridge

Question 29

tectonic environment- oceanic hot spot

Answer 29

mafic lava flows shield volcanoes

Question 30

tectonic environment- continental hot spot

Answer 30

felsic to mafic lava flows shield volcanoes (rare) stratavolcanoes (common) rhyolite caldera complexes

Question 31

tectonic environment- oceanic/continental subduction zones

Answer 31

felsic to mafic lava flows volcanoes form volcanic arc stratavolcanoes or rhyolite caldera complexes

Question 32

tectonic environment- oceanic/oceanic subduction zones

Answer 32

Intermediate to mafic lava flows volcanoes form and island arc shield volcanoes or stratavolcanoes