1. Notes 5 – Igneous Rocks Mrs. Gordon Earth Science Sunday, December 06, 2015

2. 1. Igneous Rocks A. Forms when molten material cools and hardens.

3. 2. Location  A. Extrusive - formed from lava on Earth's surface, cools quickly Examples: Basalt (dark colored, Snake River Plain, ocean floors)

4. B. Intrusive - formed from magma below Earth's surface, cools slowly Examples: Granite (light/dark color, Rocky Mountains, Sawtooth Mts.)

5. 3. Texture A. Fine grained - fast cooling = tiny crystals (basalt) B. Coarse grained - slow cooling = large crystals (granite) C. Porphyritic - TWO textures, due to slow cooling first then fast cooling Magma is underground then an ERUPTION occurs or simply movement closer to the surface

6. Other Textures: Vesicular – spongy, many small holes or pores = pumice Glassy – no grains, smooth feel, sharp edges = obsidian

7. 4. Mineral Composition A. High SILICA (quartz) = light color B. Low SILICA (quartz) =dark color

8. 5. USES A. BasaltA. Basalt - crushed to make roads B. Obsidian - sharp tools C. Granite - building materials D. Pumice - cleaning materials, face wash