Igneous Rocks

How are Igneous Rocks Made Most rock melts around 750 C – 1250 C Temperatures in the mantle are at least this high When molten rock hardens it forms Igneous Rock

Intrusive Igneous Rock Made from Magma Inside the Earth’s crust Due to high temperatures Cools slowly Large Crystal size

Examples of Intrusive Igneous Rock Granite Most common Continental Used in countertops, paving stones, floor tiles, ext Found at the surface – Mt. Rushmore, Stone Mt. Made up mostly of Feldspar (pink), Quartz or Muscovite (clear or smoky gray), Biotite or Hornblende (Black)

Examples of Intrusive Igneous Rock Diorite Coarse-grained Usually continental Contains Feldspar, pyroxene, hornblende and sometimes quartz

Examples of Intrusive Igneous Rock Gabbro Usually black or dark green Most abundant rock deep in oceanic crust Usually contains Feldspar Clinopyroxene Very little quartz (unlike most other igneous rocks)

Extrusive Igneous Rock Formed on the surface Formed when lava cools Due to cooler temperatures Cools quickly so small crystal structure

Examples of Extrusive Igneous Rock Basalt Dark-colored Fine-grained Made mostly of plagioclase and pyroxene minerals Makes up most of the ocean floor

Examples of Extrusive Igneous Rock Pumice Usally Light-colored Vesicular Gas trapped in

Examples of Extrusive Igneous Rock Rhyolite Light-colored Fine-grained Usually continental Typically made of Quartz Feldspar

Examples of Extrusive Igneous Rock Obsidian Has no crystals – Cools to quickly Usually black in color Forms Along the edges of a lava flow Where lava contacts water When lava cools while airborn