Igneous Rocks Objective: Understanding the different ways igneous rocks form and their characteristics and locations.

Minerals IN Rocks Monominerallic Polyminerallic Rocks made up of only one mineral Ex. Rock Salt = Halite; Limestone = Calcite Polyminerallic Rocks made up of more than one mineral Ex. Granite, Andesite

Rock Classification Three Groups Igneous: from fire Sedimentary Metamorphic

Igneous Rocks Igneous Rock Rocks formed from molten rock material that cools and solidifies Magma: molten rock material below the Earth’s surface; forced upward towards the surface by density differences in the magma Lava: molten rock material above the Earth’s surface

Magma vs. Lava Insert video here

Classification of Igneous Rocks Classification – texture and composition

Igneous Textures Coarse Grained Slow cooling; thousands to millions of years large crystals Intrusive: below ground Minerals can be seen with the naked eye

Igneous Textures Fine Grained Fast cooling; days to weeks Small crystals Extrusive: above ground Ex: rhyolite

Igneous Textures Glassy No crystals; hours to days Ex. obsidian

Types of Igneous Rocks Intrusive Igneous Rocks Formed inside the Earth from cooled magma Pressure and temperature in the Earth are high, causing a slow rate of cooling Slow cooling causes large crystals or a coarse texture Example: Granite Intrusion Magma works its way up through rock layers as it cools

Types of Igneous Rocks Extrusive Igneous Rocks Forms on the surface of the Earth from cooled lava Rapid cooling causes small crystals (glassy texture or fine grained) Example: Basalt Extrusion Lava makes its way down through rock layers as it cools

Igneous Rock Identification Granitic/Felsic Igneous Rocks high in aluminum Light in color Low density Continental crust

Igneous Rock Identification Basaltic/Mafic Igneous Rocks High in iron and magnesium Dark in color High density Oceanic crust

Igneous Rock Identification Vesicular Igneous Rocks Gas pockets Cooled rapidly and gas could not escape Example: Pumice

Igneous Rock Identification Andesitic Rocks Composed of both basaltic and granitic rocks Found in the Pacific Ocean and near volcanoes

Continental vs. Oceanic Continental Igneous Rocks Composition: silicon and aluminum Density: low Thickness: very thick Example: granite, light in color, felsic

Continental vs. Oceanic Oceanic Igneous Rocks Composition: silicon, iron, magnesium Density: high Thickness: very thin Example: basalt, dark in color, mafic