Chapter 6, Section 1 Igneous Rocks • Igneous Rock • A rock that forms from the cooling and hardening of molten rock • Magma • Lava • Molten rock found under the Earth’s Surface • Molten Rock found on the Earth’s surface • Felsic magma • Mafic magma • Light in color, very thick; has a high silica content • Dark in color and very thin; low silica content • Intrusive igneous rocks • Rocks that form underground from magma • Take a long time to cool because underground (holds the heat in) • Extrusive igneous rock • Forms on the Earth’s surface from lava • Cools and hardens very quickly b/c on the Earth’s surface • Crystal size • Porphyry • Intrusive igneous rocks tend to have LARGE crystals • The longer it takes the rock to cool, the larger the crystals will be • VERY large crystals • Granite family • • • • • Felsic magmas Granite Rhyolite Pumice Obsidian • Gabbro family • • • • • Mafic magmas Gabbro Basalt Scoria Diabase • Diorite family • Intermediate magma • Diorite and andesite