What do rocks tell us about the Earth?

 Formed from the cooling and crystallization of magma  Magma – Molten rock beneath the Earth’s surface ( °C to melt rock)  Lava – Magma that flows out onto Earth’s surface

 Very similar to elements found in Earth’s crust  O, Si, Al, Fe, Mg, Ca, K and Na  Silica - Most abundant What is wrong with this picture?

 Extrusive Igneous Rocks Fine grained igneous rocks that cool quickly on Earth’s surface Obsidian Extrusive Small Crystals Cooled Fast

Granite Intrusive Large Crystals Cooled Slow Intrusive Igneous Rocks –Coarse grained igneous rocks that cool slowly beneath Earth’s surface

 Felsic (Granitic) Light colored, High silica content, contain quartz and feldspars Felsic Igneous Rock

Mafic Igneous Rock Mafic (Basaltic) –Dark colored, rich in iron and magnesium Ultra Mafic –Low silica content, very high levels of Fe and Mg

 Porphyritic Rocks Rocks characterized by large well-formed crystals surrounded by fine grained crystals of the same mineral  Vesicular Rocks Spongy looking rock whose gas bubbles have broken

 Fractional Crystallization Process where different minerals form at different temperatures  Bowen’s Reaction Series Predictable, dual branched pattern in which minerals crystallize from cooling magma

 Veins Igneous rock intrusions that contain ores (Au and Quartz)  Pegmatites Vein deposits of extremely large grained minerals (Li and Be)  Kimberlites Rare, ultramafic rock that can contain diamonds and other minerals formed only under very high pressures

 Compare and Contrast magma and lava.  What two types of igneous rocks are formed as each cools?  Describe the three major mineral groups of igneous rocks. What minerals are found in each?