ROCKS ARE IDENTIFIED AND GROUPED BASED ON 3 THINGS: 1. COMPOSITION: which minerals make up the rocks 2. TEXTURE: what rocks look like and feel like 3. ORIGIN: the way rocks are formed

IGNEOUS ROCKS cools and hardens either below or on the earth’s surface Igneous rocks are formed when molten rock cools and hardens either below or on the earth’s surface. Igneous rocks are classified into 2 groups based on the location where they formed: extrusive (outside earth) or intrusive (inside earth)

All igneous rocks are classified as either extrusive or intrusive

EXTRUSIVE IGNEOUS ROCKS The crystals are very small and cannot be seen without a magnifying glass. The texture or crystal size is described as fine-grained or glassy (no crystals) Extrusive igneous rocks include basalt, obsidian and pumice Formed from lava (molten rock outside of earth) that has cooled quickly or solidified causing the crystals to stop growing

BASALT Basalt is fine-grained and makes up most of the ocean floor Where and how did this rock cool? EXTRUSIVE IGNEOUS ROCK Outside of the earth & quickly

EXTRUSIVE IGNEOUS ROCKS OBSIDIAN Obsidian has a glassy texture because it cooled extremely fast when it hit water

PUMICE Pumice floats on water because gas bubbles were trapped in it forming air pockets when it was cooling Most volcanic rock is extrusive EXTRUSIVE IGNEOUS ROCKS

INTRUSIVE IGNEOUS ROCKS Intrusive igneous rocks include granite Formed from magma (molten rock inside of earth) that has cooled slowly before the magma solidified allowing the crystals to grow The crystals are very large and can be seen without using a magnifying glass. The texture or crystal size is described as coarse-grained.

INTRUSIVE IGNEOUS ROCK Where and how did this rock cool? Intrusively and slowly ….inside the earth GRANITE

Granite is formed from 4 minerals: Mica Quartz Feldspar Hornblende

Devil’s Tower

Mt. Rushmore is made of granite…which means the rock cooled slowly 100’s of miles below earth’s surface

Crazy Horse First blast removed 10 ton of rock; today's blasts average about 700 tons It is being carved in the round and when completed it will be 641 feet long and 563 feet high.

AMAZING EARTH SCIENCE FACTS 1. _________ rocks are produced by the cooling of magma or lava. 2.Igneous rocks are classified by __________________________. 3. Texture or crystal size in igneous rocks is determined based on ______________. 4.Fast cooling = __________ ----texture includes fine-grained or small crystals, examples are basalt, obsidian (glassy), pumice (air holes) 5. Slow cooling = _________ ----texture includes coarse- grained or large crystals, example includes granite Igneous composition and texture rate of cooling extrusive intrusive