Earth s dynamic environment 01 19 2018 Scientific method Empirical knowledge knowledge arises from experience and evidence gathered specifically using the senses Science knowledge in the form of testable explanations and predictions about the universe Earth Places that provide us with material needs o Everything that we can exploit Geographic pole Where the spin axis of the earth intersects the planet surface Magnetic pole Ends where the compass points upwards or downwards Layers of atmosphere Exosphere thermosphere mesosphere stratosphere troposphere o Troposphere where we live and breath holds most mass o Strat where the airplane flies ozone layer resides to prtect against UV rays Earth s Materials Organic chemicals carbon containing compounds Minerals a solid natural substance in which atoms are arranged in an orderly pattern Glass Rocks Sedimentary Metamorphic rocks pre exsisting rocks undergo changes in response to heat and pressure Igneous rocks hot molten rocks cools and freezes solid Grain Individual crystals embedded in an igneous or metamorphic rocks Individual fragments originally derived from a oce larger mineral Melts Once solid material becomes hot and transform into liquid magma from volcanic eruption Volatiles Matierals that can transform into gas at the relatively low temperatures found at the Earth s surface Jan 26 2018 Rocks Silicate rocks o Rocks composed of silicate material Igneous Rocks o Cooling and solidify magma or lava Igneous Silicate rocks o Increasing r felsic intermediate mafic ultramafic o Granite felsic rock w large grains o Gabbaro mafic rock w large gain o Basalt mafic rock with small grains o Peridotite an ultramafic rock with large grains FELSIC LESS DENSE MAFIC DENSE Basic Concepts Gravitational attraction o All things with mass are brought towards each other a low of physics o F gravitational attraction o G gravitational constant o R distance between M1 AND M2 o M1 and m2 The amount of deflection of plumb line from the gravitational pull tells the mass of the mountain relative to the entire earth Seismic wave Propagating vibrations that carry energy from the source of the earthquake landslide volcanic eruption etc Hypothesis for earth s different layers Plump line measurement o Earths interior is much denser than crust Deduction o The metal must of concentrated near the center centrifugal force o The interior of the earth cannot be fluid not land tides o A very dense core immense pressure Observation for earth s different layers Seismeic waves Layers of earth Moho crust mantle boundary seismic wave velocity starts to increase Oceanic vs continental crust Crust o Upper mantle above 410 km o Outer core 2900 5155 km o Inner core Below 5155 Rigid vs Plastic Rigid o Bend or break but not flow Lithosphere Rigid crust plus the upper part of the mantle the cool and rigid part Plate boundaries Seismic wave propagating vibrations that carry energy from the source of the earthquake landslide volcanic eruption etc Seismic belt suggests that our continents and ocean floors are fragmented Lithosphere is fragmented into 20 tectonic plates Plates moe at 1 15 cm per year Consumption of lithosphere at the subduction zone Old oceanic lithospehere is more dense than mantle Once bent downward however the leading edge sinks downward like an achor rope Key features in the subduction zone Wadati benioff zone Volcanic arc a chain of volcanoes on overriding plate The descending plate partially melts at 150 km depth Magmas burn through the overriding plates Arc type depends upon the overriding plates Continental crust continental arc Oceanic crust island arc Transform boundaries Lithosphere slides past not created or destroyed o Many transforms offset spreading ridge segments o Some transforms cut through continental crust Characterized by o Earth quakes and absences of volcanoism Feb 12 01 19 2018 Geological definition of a rock Rock holds together Is a coherent Can be used to build structures Rock must be naturally occurring Must be formed by natural process Manufactured products are not rocks A rock can be an aggregate of minerals or body of glass Collection of many mineral grains or crystals Classic rocks are held together by cement composed of minerals precipitated between mineral grains Crystalline rocks are held together by interlocking crystals Physical characteristics of rocks Grain size and shape Composition Texture Layering Equant same dimensions in all directions Inequant dimensions not in the same direction all the time Rocks can contain one to a variety of chemicals Texture Configurations of grains in a rock Whether inequant grains are parallel to each other Distinctive layer reflects different compositions grain sizes or textures in bedding of rock Modern classification of rock uses a genetic scheme based upon origin of the rock Igneous rocks o Formed by freezing molten rock Sedimentary rocks o Form by the cementation of grains o Precipitation of minerals from a water solution Metamorphic rock o Pre existing rock change character due to a change in temperature and or pressure conditions o Squashing stretching sharing of rocks without cracking or breaking original rock o All changes occur in solid state Ophiolites A section of the earth s oceanic crust Documentation of former ocean basin being consumed by subduction The underlying upper mantle has been uplifted above the sea level and often emplaced onto the continental crust Thin section Create a very thin slice of rock Mount on a small glass plate Polarized light revels different minerals photomicrographs Scanning electron microscope provides ultra high magnification image of rock sample Electron microphobe defines chemical compositions of rock sample mass spectrometer analyzes isotopes of elements in rock sample X ray defractometer Indicators of Sedimentary Environments Sedimentary rocks form in horizontal layers Identified by composition thickness and characteristics Thick beds stable environments 01 19 2018