Igneous Rocks

Question 1

Name some mafic minerals in igneous rocks.

Answer 1

Olivine, pyroxene, amphibole, biotite.

Question 2

How do igneous rocks form?

Answer 2

By cooling and solidification of magma or lava.

Question 3

What is the difference between intrusive and extrusive igneous rocks?

Answer 3

Intrusive (plutonic) form underground, cool slowly, and have large crystals; extrusive (volcanic) form at the surface, cool quickly, and have small crystals.

Question 4

Give an example of an intrusive igneous rock.

Answer 4

Granite

Question 5

Give an example of an extrusive igneous rock.

Answer 5

Basalt

Question 6

What is crystallization in igneous rocks?

Answer 6

The formation of minerals as magma cools.

Question 7

What does Bowen’s Reaction Series show?

Answer 7

The sequence of mineral crystallization as magma cools

Question 8

Name the order of the discontinuous series in Bowen’s Reaction Series.

Answer 8

Olivine → Pyroxene → Amphibole → Biotite → (Muscovite, K-feldspar, Quartz).

Question 9

What is partial melting?

Answer 9

When different minerals melt at different temperatures, creating magmas of different compositions.

Question 10

What is fractional crystallization?

Answer 10

Removal of early-formed crystals from magma, changing the magma’s composition.

Question 11

What is assimilation in igneous processes?

Answer 11

Incorporation of surrounding rock into the magma.

Question 12

Name some felsic minerals in igneous rocks.

Answer 12

Quartz, muscovite, potassium feldspar, sodium-rich plagioclase.

Question 13

Name some intermediate minerals in igneous rocks.

Answer 13

Amphibole, biotite, intermediate plagioclase.