Igneous RocksIgneous Rocks

RockRock- material made up of one or more minerals

3 groups of rocks classified by HOW they are formed

Igneous rock- form from melted rock when hardened

Extrusive igneous rocksExtrusive igneous rocks Formed from lava “exiting” the volcano Formed from lava “exiting” the volcano

and cooling quicklyand cooling quickly Forms fine-grain crystalsForms fine-grain crystals

Andesite Basalt Obsidian Pumice

Rhyolite

Intrusive igneous rocksIntrusive igneous rocks Formed when magma “inside” the Formed when magma “inside” the

volcano cools s-l-o-w-l-yvolcano cools s-l-o-w-l-y Forms large grain crystals

Peridotite Gabbro Granite Pegmatitie

Diorite

FormationFormation

Igneous rocks form from cooling magma.Igneous rocks form from cooling magma. If they cool inside the Earth, they are If they cool inside the Earth, they are

called __________ igneous rocks and called __________ igneous rocks and have _______ crystals.have _______ crystals.

If they cool on the surface, they are If they cool on the surface, they are called __________ igneous rocks and called __________ igneous rocks and have _______ crystals.have _______ crystals.

Crystal SizeCrystal Size

This piece of This piece of obsidian cooled so obsidian cooled so _____ on the surface _____ on the surface that it did not have that it did not have time to form any time to form any crystals.crystals.

Crystal SizeCrystal Size

This piece of rhyolite This piece of rhyolite also cooled on the also cooled on the surface very fast and surface very fast and has ______ crystals. has ______ crystals.

Crystal SizeCrystal Size

This piece of granite This piece of granite cooled _______ cooled _______ inside the Earth and inside the Earth and has ______ crystals.has ______ crystals.

Classification is based on Classification is based on crystal size and crystal size and composition.composition.