Ch. 4 Questions

Question 1

1. All igneous rocks have _________.

carbon and oxygen
interlocking crystals of silicate minerals
a vesicular texture
a felsic composition

Answer 1

interlocking crystals of silicate minerals

Question 2

2. A ________ is an open cavity in a volcanic rock that was filled by a gas bubble when the lava was still mainly liquid.

porphyrocryst
vesicle
phenocryst
xenocryst

Answer 2

vesicle

Question 3

3. Coarse grained igneous rocks are_________.

intrusive
felsic
extrusive
porphyritic

Answer 3

intrusive

Question 4

4. ________ is a volcanic rock that is extremely vesicular and glassy.

Obsidian 
Pegmatite 
Tuff 
Pumice 
none of the above

Answer 4

pumice

Question 5

5. Igneous rocks containing both large and small mineral crystals are referred to as _________.

vesicular
aphanitic
phaneritic
glassy
none of the above

Answer 5

none of the above

Question 6

6. Generally speaking, _________.

mafic rocks are light-colored
ultramafic rocks are low density
felsic rocks are light-colored
felsic rocks are high density

Answer 6

felsic rocks are light-colored

Question 7

7. Basalt is ________.

intrusive and felsic
extrusive and felsic
extrusive and mafic
intrusive and mafic

Answer 7

extrusive and mafic

Question 8

8. Consider the Bowen’s reaction series. Which mineral would you expect to see as a phenocryst in a porphyritic basalt?
Olivine
Quartz
Biotite
Sodium-rich plagioclase

Answer 8

olivine

Question 9

9. ________ is the dominant feldspar in basalt.

Plagioclase
Quartz
Muscovite
Pyroxene

Answer 9

plagioclase

Question 10

10. A batholith is ________.

an eroded volcanic cone
a large mass of intrusive igneous rockmade of plutons
a large lava flow
a large volcanic crater

Answer 10

a large mass of intrusive igneous rockmade of plutons

Question 11

11. ________ is characterized by very coarse mineral grains.

Obsidian
Pumice
Pegmatite
Granite

Answer 11

pegmatite