EROSION DEPOSITION AND SEDIMENTARY ROCKS Reading Earth Science Tarbuck and Lutgens Chapter 5 pages 124 133 Chapter 3 pages 52 54 61 69 Base Level Resistant bed Resistant bed creates a local base level Local Base Level Niagara Falls Base Level local and ultimate Over time the resistant bed is eroded Local base level becomes closer to ultimate base level Base Level ultimate Eventually resistant rock is eroded to ultimate base level Base Level Erode to BASE LEVEL Cannot erode below base level Local base level temporary Gradual decrease in gradient from head to mouth Ultimate profile is idealized graded stream Base Level Lower base level allows more erosion Raise base level reduces erosion Incised meanders Stream Erosion Cut their own channels Cut three main ways 1 Deepening 2 Widening 3 Headward erosion Deepening Yellowstone River Stream Processes and Floodplain Development Widening Headward Erosion Pecos in NM http www lib utexas edu maps new mexico html http www lib utexas edu maps national atlas 1970 ca000043 large jpg Headward Erosion http www lib utexas edu maps colorado html Stream Valleys V shaped in headwaters Wide with flat floors nearer to mouth Broad flat bottomed Valley Low gradient Stream cuts into valley walls Mass wasting delivers sediment to stream Deposition SLOWING OF VELOCITY Decrease in gradient Decrease in discharge Evaporation Infiltration Loss of channelization Flood stage Body of water Deposition Flows into a body of water Creates delta Delta Formation Deposition decreases gradient Flood stage gets out of its deposit Delta Formation Flood stage gets out of its deposit Forms set of DISTRIBUTARIES Delta Formation Forms set of DISTRIBUTARIES Mississippi Delta Deposition SLOWING OF VELOCITY Loss of channelization Enters body of water Flood stage out of banks Stream Processes and Floodplain Development Natural Levee Formation Natural Levee Creation Competence lost when stream leaves its channel Deposits largest particles first http www ucpress edu books pages 6664 6664 ch04 html Natural Levees floodstage Natural Levees sediment deposits Yazoo River http www mvk usace army mil offices pp yazoobackwater basics asp category basics Alluvial Fan Badwater Fan Death Valley California http www windows ucar edu earth geology images alluvial fan lg jpeg Alluvial Fan http wiseman brandonu ca earthscience newpage35 htm Drainage Patterns Channel layout within a drainage basin Described by overall shape formed Dentritic Radial Rectangular Trellis Drainage patterns Dendritic Radial Rectangular and trellis Rock Types Igneous Sedimentary Metamorphic Rock cycle diagram Sedimentary rocks Features of sedimentary rocks Strata or beds most characteristic Bedding planes separate strata May have important characteristics Size shape and distribution of grain sizes Fossils Bedding and bedding planes http www birdandhike com Hike General Info Glossary Gloss4 htm Fossils Traces or remains of prehistoric life Are the most important inclusions Help determine past environments Used as time indicators Used for matching rocks from different places Features of sedimentary rocks Porosity Permeability Sedimentary rocks Sediment is derived from weathering Carried by fluid Formed at Earth s surface Important to reconstruct much of Earth s history Sedimentary rocks Economic importance Coal Petroleum and natural gas Precipitation of iron and aluminum Deposition of gold and tin Sand gravel clay Sedimentary rocks Two main types Rocks formed by deposition of sediment Detrital Rocks formed by precipitation from water Chemical includes rocks formed by organisms Sediment grains Particle loosened from pre existing rock Transported to place of deposition Shape size and sorting of grains can tell about the environment of deposition Lithification Process of becoming stone Burial and compaction Precipitation of cement Each reduces pore space Cement Brought in by water Mineral material between grains Fills in pore spaces Commonly calcite silica and sometimes iron oxide Types of Detrital Rocks Shale most abundant Sandstone Conglomerate Shale with plant fossils Shale Composed of very fine grained sediment Shows obvious tendency to split along planes fissile Usually gray Most common type of sedimentary outcrop Sandstone Sandstone Composed of sand size particles Between 1 16 mm and 2 mm diameter Particles may be individual mineral grains or rock fragments Quartz most common type of grain Environments include Beach river shallow sea sand dunes Conglomerate Conglomerate Composed of particles larger than 2 mm Usually particles are rock fragments Detrital clastic rocks Shale is the most common one Made from solid particles Classified by particle size Chemical rocks Material was once in solution and precipitates to form sediment Directly precipitated as the result of physical processes or Through life processes biochemical origin Fossiliferous limestone Chemical rocks Limestone Composed of the mineral calcite calcium carbonate Much of this calcite was precipitated by organisms Considered an organic chemical sediment if from organisms Most common type of chemical rock second most common type of sedimentary rock Coquina Close up of coquina Chalk Rock salt Chemical rocks Direct mineral precipitation from water Evaporites such as rock salt or gypsum Microcrystalline quartz precipitated quartz known as chert flint jasper opal or agate Travertine calcite and sinter silica from hotspring deposits Evaporites http www bonnevillehealeyclub org http www img uni karlsruhe de 925 php http www pitt edu cejones GeoImages 1Mi nerals 2SedimentaryMineralz Gypsum html http www paintersflat net saltflat html http www flickr com photos snogun 191723596 http www nv blm gov Winnemucca blackrock BRHR Planning htm http www mii org Minerals photochert html http geomaps wr usgs gov sfgeo geologic stories marin sedimentary html Chert http homestake sdsmt edu Photos Surface geology photos htm Travertine http njminerals org travertine html http www cis nctu edu tw whtsai World 20Highlig hts New 20Side 20Sho w 20Webpages imagepa ges Turkey 202001 Travertine 20stones 20 and 20water 20in 20P amukale html http www gonomad com destinations 0409 hot springs of the sierras html Classification of sedimentary rocks
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