Earth Science Study Guide The age of the Earth Lord Kelvin Earth estimated to be 4 6 Ba because of recycling of rock material due to plate tectonics no rocks remaining on earth that are that old 9 most common minerals in the crust all silicates mostly made up of oxygen silicon and aluminum Ma c Minerals 1 Biotite 2 Amphibole 3 Pyroxene 4 Olivine 5 Calcium plagioclase feldspar Felsic Minerals 1 Quartz 2 Muscovite 3 Orthoclase Feldspar 4 Sodium plagioclase feldspar Physical Properties of minerals and how they are used to identify minerals Physical Properties Color Streak Luster Hardness Cleavage Fracture magnetism acid reactivity Color easiest property to identify most unreliable property many minerals can show a variety of colors Examples Amethyst purple Rose quartz pink Streak The color of mineral when powdered commonly streak is the same as color but not always Example hematite Luster How light re ects off of a mineral gives the mineral an appearance of being metal example chrome Most commonly light re ected off the mineral is similar to when is re ected off glass example car window Hardness scratchibility resistance to being scratched Gympsum calcite Finger nail Fluorite Apatite copper coin Feldspar knife glass Quartz Diamond steel Cleavage The ability of the mineral to predictively break along planes of weakness in the crystal structure Classi ed by number of pairs of at parallel sides Further classi ed by the angle of planes whether they are at 90 or not at 90 usually at 60 or 120 Example Halite Fracture Tendency of a mineral to break in irregular unpredictable ways that are different each time silica quartz and glass and garnet commonly display conchoidal fracture Example Quartz An example of a mineral from each non silicate mineral group Carbonates Malachite green Sulfates Gypsum clear Oxides Hematite dark shiny Sul des cinnabar pink Chlorides Fluorite Halite Native Elements Copper Polymorphs Mineral with the same chemical composition but different structures Ex diamonds and graphite are all carbon calcium carbonate Solid Solution Series and How they Work When you have ions of similar size and charge they can be substituted with each other in a crystal structure thats why minerals can have a variation in their chemical composition Silicate groups Isolated Tetrahegan triangle base pyramid Single chain Double chain Sheet silicate bound by water molecules tension is not strong holding it together biotite muscovite Application build roads on clay minerals the minerals compress so clay will start to swell on the road Because of the chemical structure Igneous Rocks Extrusive Rocks formed outside of the earth mid ocean ridges outside of volcanoes Intrusive Rocks formed inside the earth underneath the crust Texture Has to do with crystal size Bigger the crystals longer time that had to cool and form smaller the crystal less time is had to cool and form ex Obsidian Intrusive Texture Pegmatitic has the very large crystals sub type grain course grain textures also called phaneritic minerals are visible slow cooling Example Granite Pegmatitic Large crystals Quartz Feldspar Micas Extrusive texture Fine grain texture also called aphanitic vesicular is lled with holes caused by trapped gas pumice scoria glassy rocks cool so quickly there are no crystals Pyroclastic volcano eruptions not distinguishable rapid cooling Example Basalt do not need to know Intrusive or Extrusive Porphyritic either or 2 simni cally different grain sized More Silica lighter felsic Lower Temps Less Silica Darker Ma c Ultrama c Higher temps Faster to weather Bowens Reaction Series mineral reacts with residual leftover magma to form new mineral Magma Temperature Discontinuous Continuous series Felsic Granitic rocks are most stable at earth surface temp Intrusive Igneous Bodies Certain rock phases more buoyant liquid rocks tend to rise up Dikes magma squeezes up into cracks magma cutting across bedding planes not parallel Sills Parallel to layering Laccolith Mushroom shape top forming between layers Diapar Blob of magma rising through crust Pluton the forming of Diapar Sedimentary Rocks Rocks formed by the deposition of sediments on the Earths Surface Formation 1 Erosion removal of rock from place of origin called the source area occurred by wind or 2 Transported Eroded sediment transported by gravity wind water ice 3 Preservation Mostly easily happens on sea oor not all is preserved in layers basins are good for preservation because covered quickly 4 Lithi cation Three steps 1 Deposition deposited 2 Compaction start compacting 3 Cementation particles ll in gaps and compact even more water Crystallization Growth of crystals out of a solution sea water make things like rocks Classi cation of Sedimentary Rocks 3 main groups classi ed by the process that formed them and materials that makes them up 1 Detrital clastic rock made up of tiny pieces of other rocks eroded material from igneous 2 Biochemical Made up of material created by biological activity but can be created by plants 3 and metaphoric rocks classi ed by grain size Example Iimestone chert coal Coquina Inorganic Chemical Formed by inorganic precipitation of supersaturated minerals such as salt commonly from sea water Example Rock Gympsum salt Rounding Rounder the edges longer the distance the rock has traveled shorter distance more angular the edges Sorting Grains are selected throughout transportation process Asymmetrical river Maturitiy Combination of Rounding and Sorting longer distance more mature Shorter distance less mature reference back to rounding and sorter Sedimentary Structures 1 Bedding Layering of rock usually horizontal each layer represents a different rock time period environment 2 Graded Bedding Larger grains are at the bottom of the layer smaller at the top ooding event 3 Cross Bedding Water and Wind movement with inclined layers of bedding 4 Ripple Marks Form on top of bedding from wind and water Symmetrical ocean vs 5 Mud Cracks When ne grain sediment dries Sedimentary Environments 1 Glacial able to carry really big pieces of rock angular poorly sorted 2 Alluvial Fan when sediments fan out at the base of a mountain and stops at base 3 River Channel Moderately well sorted rounded longer travel distance is better for mature rocks 4 Lake low energy bigger grains deposit at the edges ne grain go towards center 5 Lake Varves Annual layers of sediment deposition 6 Swamp slow moving low energy mud a lot of organic material and low oxygen 7