Notes 5 – Igneous Rocks Mrs. Gordon Earth Science Monday, June 27, 2022
Dec 13, 2015
Notes 5 – Igneous Rocks
Mrs. GordonEarth Science
Tuesday, April 18, 2023
1. Igneous Rocks• A. Forms when molten material
cools and hardens.
2. LocationA. Extrusive - formed
from lava on Earth's surface, cools quickly
• Examples: Basalt (dark colored, Snake River Plain, ocean floors)
• B. Intrusive - formed from magma below Earth's surface, cools slowly• Examples: Granite (light/dark
color, Rocky Mountains, Sawtooth Mts.)
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
Other Textures:• Vesicular –
spongy, many small holes or pores = pumice
• Glassy – no grains, smooth feel, sharp edges = obsidian
•4. Mineral Composition• A. High SILICA (quartz) = light color
• B. Low SILICA (quartz) =dark color
5. USES• A. BasaltA. Basalt - crushed to make roads• B. Obsidian - sharp tools• C. Granite - building materials• D. Pumice - cleaning materials, face wash