Created by the solidification (crystallization) of magma or lava

1. EXTRUSIVE (volcanic)Formed on surface of earth from

crystallization of lava

2. INTRUSIVE (Plutonic)Formed

underground from

crystallization of magma

Intrusive Rocks

Cooled Slowly

Medium/Large Crystals

Extrusive Rocks

Cooled Quickly

Small/No Crystals

The chemical

composition of a

magma/lava determines

which minerals will

form

8 most common elements in crust

% of Crust by weight

Oxygen 46.6

Silicon 27.7

Aluminum 8.1

Iron 5.0

Calcium 3.6

Sodium 2.8

Potassium 2.6

Magnesium 2.1

All Others 1.5

Types of Magma/LavaType Chemical

CompositionRocks from this

typeE=Extrusive; I=Intrusive

Mafic Fe, Mg, Ca E = BasaltI = Gabbro

Felsic Si, O, Al, Na E = RhyoliteI = Granite

Intermediate In between mafic and

felsic -- some of everything

E = AndesiteI = Diorite

*4

FELSIC ROCK Light ColorsHigh in Al &

SiO2

LESS DENSE

MAFIC ROCK Dark Colors

High in Fe & Mg

MORE DENSE

Since every mineral has a unique freezing temperature, minerals crystallize out of a magma in a very specific order.

Temperature Discontinuous Series

Continuous Series Rock Type (E/I)

UltramaficPeridotite

MaficBasalt/Gabbro

Intermediate

Andesite/

Diorite

FelsicRhyolite/

Granite

1400 C

1200 C

1050 C

800 C

600 C

Orthoclase Feldspar+

Muscovite Mica+

Quartz

Olivine

Pyroxene

Amphibole

Biotite

Pla

gioc

lase

Fel

dspa

r

Ca-rich

Na-rich

MAFIC

Ocean crust, mantle rock, more dense and will sink

• Divergent Plate Boundaries

• Hot Spots

FELSIC

Continental Crust, less

dense so will float

• Collision Zones

• Sliding Plate Boundaries

INTER-MEDIATE

Where mafic and felsic rock

mixes

• Subduction Zones