STUDY GUIDE Unit conversion self explanatory Convert to Metric system Written like 1 8 x 10 8 mm Plate Tectonic Theory theory in which the plates that make up earth s crust move slowly over time Alfred Wegener Theory came up with idea of continental drift and Pangea Lacked sufficient evidence at the time to show what could possibly be the driving force of huge solid rock Types of Plate Boundary Convergent ocean ocean island arcs and ocean trenches ocean continent mountains and ocean trenches continent continent mountains Divergent ocean ocean mid atlantic ridge and continent continent rift valley Transform ocean ocean major offset of mid oceanic ridge axis continent continent San Andres fault Mechanisms of plate movement pushed away from spreading centers pulled down into trenches or dragged along by the friction of convection on their undersides Definition of mineral naturally occurring solid formed by geological processes crystalline structure and clear chemical compositon Mohs Hardness Scale list of minerals in a sequence of relative hardness Helps to identify minerals Talc is softest diamond is hardest Mineral Properties luster streak cleavage fracture etc Color is least reliable Luster sheen or shine of the rock Streak scratching the surface with another rock Cleavage the way a rock breaks along a plane Fracture breakage that is not flat Rock Cycle 1 magma 2 crystallization freezing of rock 3 igneous rocks 4 erosion 5 sedimentation 6 sediments sedimentary rocks 7 tectonic burial and metamorphism 8 metamorphic rocks 9 melting Types of Igneous Rocks Felsic high silica Intermediate intermediate silica Mafic low silica Ultramafic very low silica Texture of Igneous Rocks Phaneritic crystals visible with naked eye Aphanitic crystal too small for naked eye Porphyritic two different dominant grain sizes Fragmental composed of disagregated igneous material Pegmatitic very large xtals cm to 10s of cm i e slowly cooled Glassy non crystalline cools very fast e g obsidian Vesicular vesicles holes pores cavities form as gases expand Bowen reaction series explain why certain types of minerals tend to be found together while others are almost never associated with one another Two types Continuous and Discontinuous Minerals at the top are first to crystallize so the temperature gradient is read from highest to lowest shows the stability of minerals with the ones at bottom being most stable and the ones at top being quickest to weather Lava and magma lava is on the surface and volcanic magma is beneath the surface and plutonic Types of sedimentary rocks intrusive slowly cooled off magma granite gabbro coarse grainm interlocking Extrusive rapidly cooling magma extruded on surface of Earth as lava Rhyolite basalt scoria pumice fine grained discrete crystals ejected and cooled in the air Weathering and its types Lithic Rock Fragments granite basalt schist etc Dissolved Ions Calcium Potassium Sodium etc Rust Minerals Hematite Goertite etc Clay Minerals Bentonite Montmorillonite etc Residual Minerals Quartz Orthoclase Muscovite etc Erosion process in which rocks and soil are removed from the surface by natural processes like wind water and air then transported and deposited elsewhere Lithification compaction and cementation process where rocks compact under pressure and loose water gradually becoming solid rock It is a process of porosity destruction through compaction and cementation Textures of sedimentary rocks Clastic made up of rock clasts Shape size orientation how the clasts are sorted Detrital or chemical Types of metamorphic rocks Detrital clastic texture Chemical crystalline Textures of metamorphic rocks size shape and arrangement of mineral grains Foliation any planar arrangement of mineral grains or structural features within a rock Examples of foliation Parallel alignment of platy and or elongated minerals Closely spaced planar surfaces along which Can develop in a number of ways depending on metamorphic conditions and parent rock rocks split Schistosity Gneissic Platy minerals are discernible with the unaided eye and exhibit a planar or layered structure Rocks having this texture are referred to as schist During higher grades of metamorphism ion migration results in the segregation of minerals exhibit a distinctive banded appearance nonfoliated metamorphic rocks that lack foliation Develop in environments where deformation is minimal Typically composed of minerals that exhibit equidimensional crystals Porphyroblastic textures Large grains called porphyroblasts Types of metamorphism Heat surrounded by a fine grained matrix of other minerals o Most important agent o Recrystallization results in new stable minerals Two sources of heat o Contact metamorphism heat from magma o An increase in temperature with depth due to the geothermal gradient Confining pressure o As depth increases pressure increases o Confining pressure is similar to water pressure forces are equal in all directions o Causes spaces between mineral grains to close producing a more compact rock with a greater density o Can cause minerals to re crystallize into new minerals that display a more compact crystalline form Differential stress forces are unequal in different directions Mainly acts along one plane Shortened in the direction that pressure is applied and elongated in the direction perpendicular to the force At low temperatures rocks are brittle and tend to fracture At high temperatures rocks are ductile Mineral grains tend to flatten and elongate when subjected to differential stress Chemically active fluids o Mainly water with other volatile components o Enhances migration of ions o Aids in recrystallization of existing minerals What is meant by Geologic Dating The method to find the age of rocks How can geologic dating be done methods Absolute Dating Relative Dating Radioactivity Difference between Relative and Absolute dating Absolute is based upon the fact that atoms of radioactive elements decay to form stable isotopes Relative can only determine the sequence of which rocks formed not the exact date Principles of geology Stratigraphic Principles Law of Superposition Developed by Nicolaus Steno in 1669 In an undeformed sequence of sedimentary or volcanic rocks oldest rocks at base youngest at top Principle of original horizontality Layers of sediment are originally deposited horizontally flat strata have not been disturbed by folding faulting Principle of cross cutting relationships Younger features cut