Emily and Megan Earth System Science Elements of Earth Made of atoms Earth is mostly iron by weight Minerals Naturally occurring Not composed of organic molecules Crystalline solid Specific chemical composition Interconnected Rocks and minerals Interior processes Erosion and deposition Water and air Crust Elements Made of atoms Earth is mostly iron by weight Surface is mostly oxygen by weight Crystals Halite crystals NaCl 2 Crystals Amethyst quart Pyrite Rhodochrosite Asbestos Shape reflects internal arrangement of atoms Breaking minerals Hardness Resistance to scratching Compare to glass steel penny fingernail Silicate Structure Strength of bonds within crystals Cleavage Some planes with weak bonding Break along these Breaking minerals Strength of bonds within crystals Fracture No planar arrangement of weak bonds Conchoidal or irregular Mineral Classification Crust is mostly oxygen and silicon Silicon always bonded to oxygen SILICATES 92 of minerals of crust 3 Silicate Minerals Silica bonded to metals Iron magnesium Ferromagnesian silicates ferromags Dense dark Examples of ferromags Amphibole Pyroxene Biotite mica Olivine Non silicates Carbonates Calcite CaCO3 Oxides Fe2O3 Fe3O4 tin chromium uranium Silicate 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 mica Minerals crystallize From liquid usually or gas occasionally Magma molten rock Watery solutions Sulfides Zinc lead mercury Pyrite FeS2 Native elements Au Cu Crystallization of Magma Crystallize from watery solutions 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 proceeds 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 evaporites 4 Rock Types Igneous Sedimentary Metamorphic 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 Two main types Rocks formed by deposition of sediment Clastic Rocks formed by precipitation from water Chemical includes rocks formed by organisms Sedimentary rocks Cover 2 3 of Earth s surface Record conditions at time of deposition Include remains of organisms preserved as fossils 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 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 deposition 5 Lithification Process of becoming stone Burial and compaction Precipitation of cement Each reduces pore space Bedding and bedding planes Cement Brought in by water Mineral material between grains Fills in pore spaces Commonly calcite silica and sometimes iron oxide Types of Clastic Rocks Shale most abundant Sandstone Conglomerate http www birdandhike com Hike General Info Glossary Gloss4 htm Fossils Shale with plant 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 6 Shale Sandstone Composed of very fine grained sediment Shows obvious tendency to split along planes fissile Usually gray Most common type of sedimentary outcrop Sandstone Conglomerate 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 Composed of particles larger than 2 mm Usually particles are rock fragments Clastic rocks Shale is the most common one Made from solid particles Classified by particle size 7 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 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 Chalk Fossiliferous limestone Coquina Close up of coquina 8 Chemical rocks Travertine 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 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 Rock salt http njminerals org travertine html 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 Classification of sedimentary rocks Chert http homestake sdsmt edu Photos Surface geology photos htm 9
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