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13-4 Types of rocks Some PowerPoint resources taken from Prentice Hall Earth Science Tarbucks & Lutgens Rocks • Made of 1 or more minerals • Usually from one of the 8 naturally occurring minerals Igneous Metamorphic Sedimentary 3 types of rock Igneous- formed from the crystallization of molten magma Metamorphic- preexisting rock that has been transformed physically and chemically by heat/pressure from within the earth Sedimentary- formed from weathered products of preexisting rocks that have been transported, deposited, compacted, and then cemented The Rock cycle weathered pieces of earths elements Sediment molten material deep within the earths surface Magma Rock cycle- the continuous changing of rocks over long periods of time Weathering process in which rocks are broken down by water, air, or other living things Lava magma that reaches the earths surface Igneous Rocks review • Igneous rock begins as magma. • Formation: When rock is heated When pressure is released When rock changes composition • A mixture of many minerals Classified by composition & texture 95% of earths crust are igneous http://www.fi.edu/fellows/payton/rocks/create/igneous.htm Igneous rock Texture Glassy a.k.a Volcanic glass Fine Grainedmicroscopic crystals (cools quickly) Course Grainedcrystals visible to the eye (long time to cool, thus larger) Igneous Rocks Coarse-Grained Fine-Grained Felsic Light Granite Rhyolite Mafic dark Gabbro Basalt Extrusive Intrusive Forms when magma erupts onto the surface, cooling quickly Magma pushes upward into preexisting rock below earth’s surface, then hardens No crystals Plutons- large masses of intrusive rock that can form domes thru the surface Igneous Rocks Is this rock Felsic or Mafic? Is it fine-grained or coarse-grained? Is this rock Intrusive or Extrusive? Mafic, fine grained, extrusive 13-6 Sedimentary Rocks 3 Types Clastic Organic Chemical Recall: • Formation due to weathering, erosion and deposition • Compaction (squeezing of the sediment) • Cementation (dissolved minerals cement the sediment together) ¾ of earths surface rocks are sedimentary Stream Granite Sea 1. Sediment builds up 2. Bottom layers feel pressure 3. Temperature increases 5. Dissolved minerals cement the sediment together in layers Clastic • Rocks made from preexisting rocks • Ex. Conglomerate- a rock full of pebbles • Sandstone (sand-size fragments) • Shale (most abundant, dust sized fragments) Organic Rocks Come from organisms that were once living Ex. Limestone (most abundant organic rock) Reefs, built by oysters or coral coal CHEMICAL Rocks Form when dissolved substances precipitate, or separate from water usually by evaporation Mono Lake Ca, formations of salt, and calcium carbonate are left behind as the sun beats down evaporation leaves these standing rocks Metamorphic • Formation – Pre-existing buried rock melts and remolds under extreme heat and pressure – Chemical change due to atoms rearranging into new minerals During the change the rock does not melt, but it does become flexible Foliated • Has a banded or layered appearance Nonfoliated • Does not have a banded texture
