Geology 101 Outline of Last Lecture After Big Bang Solar System Components Outline of Current Lecture Age of Solar System Earth Unique Planet Geology History Geologic Time Earth s Sphere Earth s Layered Structure Rocks and Rock Cycle Geology 101 Chapter 1 22 Lecture 3 Age of Solar System o Based on dating meterorites Left over planetesimals o 4 6 billion years ago o Younger than universe Earth Unique Planet o Only place we know that can support life o Right Size Larger Too thick of an atmosphere gravity would be too great and create a hostile atmosphere o ammonia methane hydrogen Smaller Lack an atmosphere o oxygen water vapor would escape o No rigid lithosphere over asthenosphere Plate tectonics wouldn t operate Planet would be covered in ocean o No molten metallic core Most life wouldn t exist Magnetic fields prevent lethal cosmic rays o Right Location Closer 10 Geology 101 o Like Venus o Too hot greenhouse gases Mostly CO2 Farther too cold No water cycle Near modest size star Right Time Atmosphere Developed over time o Primitive atmosphere composed mostly of methane water vapor ammonia CO2 NO OXYGEN Microorganisms released oxygen in photosynthesis o Cyanobacteria o Initially captured by chemical reactions with organic matter iron Iron released submarine volcanism hydrotherma l vents Banded in iron formations More oxygen generating oxygen Great Oxygenation Event 2 5 billion spike end of Pennsylvanian period Good for aerobic life forms bad for anaerobic Birth of Geology o James Hutton Theory of the Earth Fundamental pillar Uniformitarianism physical chemical and biological laws that operate today have operated in past o Present is key to past Geology Today o Rock record o Radioactivity o Dinosaurs died 65 million years ago Geology 101 o Earth was created 4 6 billion years ago Formation Earth s Layered Structure o Early period of heating Chemical differentiation Molten masses rose solidified to form crust o Gradually formed past 4 billion years primitive one eroded away o Enriched in oxygen calcium sodium silicon and aluminum Iron rich core Differentiation allowed gases to escape and forming primitive atmosphere Geology History o Catastrophism Earth s landscapes developed by catastrophes o Uniformitarianism present key to past Geological Time o Relative dating by some principles Superposition rock layers Fossil succession o Numerical Dates Radioactive dating Started 100 yrs ago Earth System 4 spheres o Water Hydro 71 Hydrolic cycle o Gas Atmo Protects from UV Allows life Surface and atmosphere energy exchanges cause weather and climate Strong influence on external processes o Land Geo Soil Supports plant growth weathered rocks debris air water o Living Bio All life Ocean has most life More life where there are more extreme conditions Life forms help form and change physical Earth System Science o Land water air and life forms are all interconnected o Carbon cycle o Hydrolic Cycle Water enter atmosphere through evaporation condenses and forms clouds and then precipitation o Rock Cycle o Earth system is powered by the sun earth s interior Geology 101 o Atmosphere hydrosphere Weather climate Ocean circulation Erosion Also powered by humans Earth s Layers o Crust o o o Low density Thin rocky Oceanic 7 km thick on average Homogenous Basalt Less dense Continental Granite Varies place to place Mantle Largest in volume Upper Lithosphere o Cool rigid o 100 km thick Asthenosphere o Weak detached o Top part temperature and pressure cause small amount of melting Transition zone o Increase in density o 410 600 km Lower Increase in pressure Strengthens with depth D Special layer between mantle and core Core Iron nickel Outer Liquid iron Movement causes magnetic field Inner Solid Geology 101 Immense pressure Nature of Rocks o Influences Texture Size Arrangement of minerals Reflects geologic processes Rock Cycle o Allows us to view interrelationships o Origin Magma Molten forms deep underground Cools and solidifies Crystallization Igneous Weathering creates sediment Sedimentary Sediment deposited Litihfication when compacted by layers Metamorphic Pressure Higher temperatures Melt and turns back into magma turns into to igneous then erosion and deposition leads sedimentary and heat and pressure back to metamorphic Igneous can go straight to metamorphic due to its close proximity to heat and pressure Metamorphic can turn straight into sedimentary due to erosion