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
http://www.lib.utexas.edu/maps/colorado.html Headward Erosion
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
http://wiseman.brandonu.ca/earthscience/newpage35.htm Alluvial Fan
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.flickr.com/photos/snogun/191723596/ http://www.paintersflat.net/saltflat.html 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