7 n 8: Igneous Rocks

Question 1

Intrusive characteristics

Answer 1

Form inside the earth and are coarse grained (big crystals), spend along time crystallizing

Question 2

What causes rock to be mafic or felsic

Answer 2

Amount of Mg and temperature cooling. More mg= more mafic

more Si= felsic

Question 3

Extrusive characteristics

Answer 3

erupted magma formed rock on surface; fine grained; cools rapidly

Question 4

What is fractionation

Answer 4

removal of higher temp. materials from rock to allow lower temp. to cool at and consecutive formation of diff. composition rocks

Question 5

What is a dike

Answer 5

Igneous rock that cuts across a stratigraphy (UP)

Question 6

What is a Sill

Answer 6

Rock that is parallel to the stratigraphy

Question 7

What affects the MP of magma?

Answer 7

Amount of Mg in it as it has an extremely high MP (very hard to melt)

Question 8

What are felsic melts composition?

Answer 8

Na, K, Si

Question 9

Why don’t mafic magmas fractionate much?

Answer 9

Dry and quench rapidly into basalts of crystallise to a gabbro

Question 10

Why are arc magmas explosive?

Answer 10

Water keep magma molten for long time, fractionates all the way up to a high Si content and end up viscous and explosive