How Are Igneous Rock Formed?

• Igneous rocks are called fire rocks and are formed either underground or above ground

• Underground, they are formed when the melted rock, called magma, deep within the earth becomes trapped in small pockets

• Magma - cools slow….ly

underground forming Large grains or crystals. The atoms

have Time to make orderly arrangements

• Igneous rocks can also form above ground when volcanoes erupt, causing the magma to rise above the earth's surface. It will now be called Lava

• As the lava cools above ground it cools Quickly. The grains or crystals do not have time to form and arrange themselves

• Quick cooling causes small grain sizes and sometimes no grain sizes at all. When grains do not take any shape at all the term used is called

• non-crystalline(no grains) or glassy

• Intrusive – refers to magma that cooled slowly underground forming large grains or crystals

• Extrusive – refers to Lava that cooled quickly above the ground it forms small-tiny grain sizes or no crystals

( ) in the rock

• Lets look at some picturesand compare what you see to your reference table

Lets look at some picturesand compare what you see to

your reference table

• http://volcano.und.edu/vwdocs/vwlessons/lessons/Slideshow/Igrocks/Igindex.html

Granite

Gabbro

Rhyolite

Basalt

Scoria (vesicular – holes in it)

Vesicular Basalt

Obsidian (non-crystalline)

Pumice

Basaltic Glass