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Introduction to Rocks Rock: a naturally occurring aggregate of minerals or mineraloids Three Rock Classes… http://www.physicalgeography.net/fundamentals/images/20011005-0039_DAS_large.jpg IGNEOUS ROCKS form from the solidification of molten rock General Classification of Igneous Rocks Extrusive Rocks (Volcanic) Intrusive Rocks (Plutonic) General Classification of Igneous Rocks Felsic Intermediate Mafic Increasing Fe & Mg Increasing Si & Al Igneous Rock Environments Felsic: Continental Intermediate: Volcanic Coasts and Islands Mafic: Oceanic Common Igneous Rocks Felsic Intermediate Mafic Rhyolite Andesite Basalt Fine Grained (Extrusive) Coarse Grained (Intrusive) Granite Diorite Gabbro Three Rock Classes… http://digital-desert.com/mojave-preserve/geology/conglomerate.gif SEDIMENTARY ROCKS form from deposits of weathered pre-existing rock Physical/Mechanical Weathering Abrasion Physical/Mechanical Weathering Root Wedging Physical/Mechanical Weathering Frost Wedging Physical/Mechanical Weathering Salt Wedging Physical/Mechanical Weathering Exfoliation (Pressure Release) Chemical Weathering • Solution – H2CO3 + CaCO3 → Ca2+(aq) + 2HCO3- (aq) • Dissolution of calcite in carbonic acid – NaCl → Na+ (aq) + Cl- (aq) • Dissolution of halite in water Chemical Weathering • Hydrolysis – In hydrolysis a molecule is split into two parts by reacting with water. One product includes an OH- from the water molecule, whereas H+ is added to another Silicic Acid (Dissolved Silica) – Mg2SiO4 + 4H+ + 4OH- ⇌ 2Mg2+(aq) + 4OH- + 4H4SiO4 (aq) • Hydrolysis of olivine results in all products in solution – 2KAlSi3O8 + 2H2CO3 + 9H2O ⇌ Al2Si2O5(OH)4 + 4H4SiO4 (aq) + 2K+ + 2HCO3• Hydrolysis of feldspar produces clay Chemical Weathering • Oxidation – 4FeS2 + 15O2 + 22H2O → 4FeO(OH) + 8SO42- + 16H+ • Oxidation of pyrite to form limonite General Classification of Sedimentary Rocks Clastic (Broken Pieces) Chemical (Precipitated) Classification of Clastic Sedimentary Rocks Conglomerate Sandstone Siltstone Mudstone/Shale Classification of Chemical Sedimentary Rocks Mineral Rock Calcite… Limestone Silica… Chert Gypsum… Halite… Evaporite Hematite… Iron Formation Sedimentary Rock Environments Breccia Sandstone Evaporite Conglomerate Limestone Shale Three Rock Classes… http://farm4.static.flickr.com/3227/2897260233_24897666ba.jpg METAMORPHIC ROCKS form from pre-existing rocks that have been subjected to heat and pressure Classification of Metamorphic Rocks Foliated (Banded) Non-Foliated (Massive) Classification of Foliated Metamorphic Rocks Slate Schist Gneiss Increasing Temperature Microscope Hand Sample Formation of Foliated Metamorphic Rocks Shale Schist Gneiss Classification of Non-Foliated Metamorphic Rocks Sandstone Quartzite Limestone Peridotite Marble Serpentinite Microscope Hand Sample Formation of Non-Foliated Metamorphic Rocks Quartz Sandstone Quartzite The Rock Cycle Identifying Rocks Foliated/Layered Sedimentary Non-Foliated/Non-Layered Metamorphic Igneous Identifying Rocks Grains Sedimentary Crystals Metamorphic Igneous