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Download 6.3 Sedimentary Rocks
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Sedimentary Rx pages 135-140 • For thousands, even millions of years, little pieces of our earth have been eroded-broken down and worn away by wind and water. These little bits of our earth are washed downstream where they settle to the bottom of the rivers, lakes, and oceans. Layer after layer of eroded earth is deposited on top of each. These layers are pressed down more and more through time, until the bottom layers slowly turn into rock. • Most common rock at Earth's surface • Thin blanket over ____________ of the surface covering igneous and metamorphic rocks _________________are often found in sedimentary rock. • Volcanism builds new rocks-----_____________________breaks them down into sediments WED: Weathering, Erosion, and Deposition Two types of weathering: ________________and ____________________ I. Mechanical weathering breaks rock into smaller pieces Three ways 1. 2. 3. 1. Mechanical weathering increases the ______________ _____________ of the rock exposed to chemical weathering 2. Chemical Weathering Chemical Reactions with water ______________ rock Write the equation for chemical weathering Water and carbon dioxide yields carbonic acid This is what dissolves limestone and makes __________________ Erosion • Erosion--___________________________ of seds • What can move it? Or, what are the ______________ of _______________? 1. 2. 3. The ______________________ the sediment the _____________ it is to move Deposition—seds are _____________________________ •When deposited sediment accumulates, it begins to transform into sedimentary rock Two types of sedimentary rocks 1. ___________________________ – Made of bits and pieces of _________________ rock Transformation of Clastic rocks occurs in two ways: • ____________________________ – seds are pressed together – grains ________________________________ • ____________________ Seds are _______________________ together like glue The most common cements are – 1. – 2. – 3. Clastic sediments bits and ________________of old __________________/_____________________/__________________ • Clastic sedimentary rocks are classified by their sediment _____________________ and __________________ Size – Most common is _______________--very fine particles – Sandstone—___________ sized particles – Siltstone—____________sized particles And by shape of seds _________________ means longer ____________________ – ______________________--rounded seds ______________________—angular seds 2. Chemical Sediments • Chemical sediments precipitate from water – Two types 1. 2. Carbonates Made of mostly calcite CaCO3 or CaMgCO3 • Limestone is _____________________ – Very common here • Dolomite is _______________________________ – Some of the carbonate is replaced by magnesium Evaporites • Evaporites ____________________ from water when a basin dries up ___________________ Ca SO4. H2O ________________ (Rock Salt) NaCl • • Sedimentary Rock Lab Name the rocks you find in your sample bag. Choices – – – – Sandstone Coal Conglomerate Coquina – – – Gypsum Rock salt Oolitic limestone Sedimentary environments • Sedimentary rocks provide information about events that occurred on Earth's surface • Their color, grain size, and composition give us information about what was happening when they formed Crossbedding and Ripple Marks • Crossbedding gives us an indication of wind or water direction – Symmetrical-oscillating – Asymmetrical- current ripple marks • Ripple marks may be Caves form in sedimentary rock Depositional Environments • Delta-a fan-shaped body formed when water flows from a stream into a standing body of water • Example: the Mississippi River Delta ,The Nile River Delta River—Fluvial-- Unconsolidated gravels, sand, and clay Desert—aeolian—sand Sandstone would indicate a beach or desert • • • Shoreline Alluvial Fan • Forms when sediment flows from a steep incline onto a flat floored valley and looses velocity rapidly • Seds are laid down the largest first, followed by progressively smaller and smaller as the velocity slows Oxbow lake formation— occurs when a mature river is cut off at flood state • An oxbow lake occurs between here and Oxford
