Geology 101 Lab 3 Monday September 15 2014 Rocks and The Rock Cycle Chapter 4 and Chapter 5 The Rock Cycle rocky planets Rocks are the solid materials that comprise nearly all of the earth moon and These earth materials are changed both on surface and inside the earth The rock cycle is a conceptual model that explains how the various types of rocks are formed deformed and transformed Three types of rocks o Igneous Form as molten lava or magma rock cools and solidifies Basalt flow in Hawaii Form from loose weathered sediment that is compacted and or cemented together or by precipitation out of a solution Sandstone in Wyoming o Sedimentary o Metamorphic Formed as a result of intense heat and pressure Gneiss in Canadian Rockies Igneous Rocks Rocks that are formed when molten rock called magma cools Magma is melted rock that can form in the earth s crust and upper mantle As magma cools and solidifies it forms Texture describes the size shape and arrangement of the crystals Igneous rocks are described by their texture and composition comprising the rock In general a slower cooling magma results in coarser grained igneous rock Igneous Rock Textures Phaneritic Aphanitic eye Porphorytic o Igneous rocks are coarse grained consisting of a mass of intergrown crystals of roughly equivalent size that can be identified without the aid of a hand lens or microscope o Igneous rocks are very fine grained o The crystals that comprise them cannot be distinguished by the naked o Igneous rocks have two distinct sized of crystals Pegmatitic Vesicular Glassy Pyroclastic The larger crystals are termed phenocrysts and the surrounding smaller ones called groundmass o Igneous rocks are very coarse grained Individual crystals of pegmatitic rocks exceed 1cm o Texture results from gas bubbles trapped within the magma o Very volatile and rich mixed with the cooling forms the cavities o Texture results when unordered ions are frozen before they can unite into an ordered crystal structure o Igneous rocks are composed of particles or fragments rather than interlocking crystals They are produced by explosive volcanism Igneous Rock Composition Felsic o Rocks have a high portion of light colored silicates Quartz and feldspars Granite and rhyolite only texture different Coarse grain vs Intermediate fine grain o Rocks have moderate portions of light and dark silicate Diorite and andesite Magic Ultramafic o Have a higher proportion of dark colored silicates Amphiboles pyroxenes and calcium rich plagioclase feldspars o Very high proportions of Fe Mg rich silicated and are green because of high amounts of olivine Insert Chart from picture Bowen s Reaction Series Bowen s Reaction Series provides visual representation of the order in which minerals crystallize from a magma of average composition