2Emily and Megan Earth System Science• Interconnected• Rocks and minerals• Interior processes• Erosion and deposition• Water and airElements of Earth• Made of atoms• Earth is mostly iron, by weightCrust Elements• Made of atoms• Earth is mostly iron, by weight• Surface is mostly oxygen, by weightMinerals• Naturally occurring• Not composed of ‘organic’ molecules• Crystalline solid• Specific chemical compositionCrystals• Halite crystals•NaCl3Crystals• Amethyst quart• Pyrite• Rhodochrosite• Asbestos• Shape reflects internal arrangement of atoms Hardness• Resistance to scratching• Compare to glass/steel, penny, fingernailBreaking minerals• Strength of bonds within crystals• Cleavage– Some planes with weak bonding– Break along theseSilicate StructureBreaking minerals• Strength of bonds within crystals• Fracture– No planar arrangement of weak bonds– Conchoidal or irregularMineral Classification• Crust is mostly oxygen and silicon• Silicon always bonded to oxygen• ‘SILICATES’• 92% of minerals of crust4Silicate Minerals• Silica bonded to metals• Iron, magnesium– Ferromagnesian silicates: ‘ferromags’– Dense, dark• Examples of ferromags– Amphibole– Pyroxene– Biotite mica– OlivineSilicate Minerals• Silica bonded to metals• Aluminum, sodium, potassium, calcium– Feldspar: Most abundant mineral– ‘felsic minerals’– Pale, less dense than ferromags• Examples of felsic minerals– Feldspar– Quartz– Muscovite micaNon-silicates• Carbonates– Calcite: CaCO3• Oxides–Fe2O3, Fe3O4– tin, chromium, uranium•Sulfides– Zinc, lead, mercury–Pyrite: FeS2• Native elements: Au, CuMinerals crystallize• From liquid (usually) or gas (occasionally)• Magma: molten rock• Watery solutionsCrystallization of Magma• Cools, atoms attracted to one another• Arrange in orderly crystalline structures• When very hot, low-silica forms• Cooler, greater amounts of silica in them• Composition of magma changes as crystallization proceedsCrystallize from watery solutions• Change solubility by changing physical or chemical conditions in magmatic water left– pH, other ion content– Temperature, pressure• Chemical sedimentary rock– Carbonates: made by organisms, mostly– Increase concentration by evaporation: evaporites5Rock Types• Igneous• Sedimentary• MetamorphicSedimentary rocks• Cover 2/3 of Earth’s surface• Record conditions at time of deposition• Include remains of organisms preserved as fossilsSedimentary rocksSediment is derived from weatheringCarried by fluidFormed at Earth’s surfaceImportant to reconstruct much of Earth's historySedimentary 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•FossilsSedimentary rocksTwo main types • Rocks formed by deposition of sediment—Clastic• Rocks formed by precipitation from water--Chemical(includes rocks formed by organisms)Clastic 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 deposition6LithificationProcess 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 oxideBedding and bedding planes• http://www.birdandhike.com/Hike/General_Info/Glossary/Gloss4.htmTypes of Clastic Rocks• Shale (most abundant)• Sandstone• ConglomerateFossils• 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 Shale with plant fossils7Shale• Composed of very fine grained sediment• Shows obvious tendency to split along planes (fissile)• Usually gray• Most common type of sedimentary outcropSandstoneSandstone• 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 dunesConglomerateConglomerate• Composed of particles larger than 2 mm• Usually particles are rock fragmentsClastic rocks • Shale is the most common one• Made from solid particles• Classified by particle size8Chemical 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) Chemical rocksLimestone• 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 rockChalkFossiliferous limestoneCoquina Close up of coquina9Chemical rocksDirect 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 depositsTravertine• http://njminerals.org/travertine.html• http://www.gonomad.com/destinations/0409/hot_springs_of_the_sierras.html• http://www.cis.nctu.edu.tw/~whtsai/World%20Highlights/New%20Side%20Show%20Webpages/imagepages/Turkey%202001---Travertine%20stones%20and%20water%20in%20Pamukale.htmlEvaporites• http://www.bonnevillehealeyclub.org/• http://www.paintersflat.net/saltflat.html • http://www.nv.blm.gov/Winnemucca/blackrock/BRHR_Planning.htm• http://www.img.uni-karlsruhe.de/925.php• http://www.pitt.edu/~cejones/GeoImages/1Minerals/2SedimentaryMineralz/Gypsum.html• http://www.flickr.com/photos/snogun/191723596/Rock saltCherthttp://geomaps.wr.usgs.gov/sfgeo/geologic/stories/marin_sedimentary.html• http://homestake.sdsmt.edu/Photos/Surface_geology_photos.htm• http://www.mii.org/Minerals/photochert.htmlClassification of sedimentary
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