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Transcript
Formation of Earth Earth forms 4.65 Byrs ago through accretion process Molten rock/metal leads to differentiation Structure of Earth Crust (3 g/cm3) - made of continental (granites) and oceanic (basalts) Mantle (3 - 5 g/cm3) - 2900 km thick layer; location of lithosphere & asthenosphere Core (10.5 g/cm3) - liquid Fe/Ni shell surrounding solid Fe/Ni center Hadean Eon Leftover planetesimals crash into Earth regularly for the first 500 million years (Heavy Bombardment Period) Origin of Atmosphere/Oceans Atmospheric gases produced through outgassing during volcanic eruptions and impact events Early atmosphere dominated by CO2 Today: Nitrogen (78 %), Oxygen (21 %), trace CO2 (< 0.1 %) Origin of Atmosphere/Oceans Water vapor condenses and rains collect to form the oceans Water source still unclear; suspect a combination of outgassing and vaporized comets Formation of Life After .5 Byrs, chemical reactions produce self-replicating molecules Miller-Urey Experiment Miller Panspermia Life on Earth appeared such a short time (500 Myrs) after Earth’s formation that it might make more sense that it came from elsewhere. But where? Impact Sterilizations Heavy Bombardment Period of Earth makes for impact sterilization Impactors with D = 350 - 400 km will raise surface temperature to 2000 °C Origin of Continents All rock is originally basaltic; some is remelted through plate tectonics and low density granites form continents Types of Rocks Igneous Rocks: made from molten rock that cools underground (intrusive) or above ground (extrusive) Extrusive rock (lava) will form dark, dense basalts at plate boundaries or above hot spots Santiago Island, Galapagos Queen’s Bath, Kaua’i Types of Rocks Intrusive rock (magma) will form low density, granites that form the basis of mountains Granite with minerals of quartz & feldspar Types of Rocks Sedimentary Rocks: formed by gradual compression of sediments - Covers 75% of the land area - Fossils are most commonly found in sedimentary rocks Clastic rock forms from sediments that are the result of weathering and erosion Breccia Types of Rocks Organic sedimentary rock is formed by gradual compression of organic material Coal Types of Rocks Metamorphic Rocks: igneous/sedimentary rocks that have been transformed under intense heat and/or pressure Schist Slate Minerals are the crystals found in rocks that tell what the rock is made of Geologic Activity Convergent boundary: continental vs. continental Geologic Activity Mt. Everest Convergent boundary: continental vs. continental Geologic Activity Convergent boundary: continental vs. oceanic Geologic Activity Mt. St. Helens (1980) Mt. St. Helens (1982) Convergent boundary: continental vs. oceanic Geologic Activity Divergent boundary: seafloor spreading (ridge) Mid-Atlantic Ridge Continental Drift Over time, plate motions cause continents to drift apart and come together (forming super continents, like Pangaea) Surface Features Mantle plumes: isolated pockets of hot magma in the mantle that give rise to volcanic island chains and geysers Hawaiian Islands Climate Regulation Without an atmosphere, the global average temperature would be -17 °C; the greenhouse effect raises that temperature to 15 °C Greenhouse gases (CO2, CH4) slow the release of IR back into space Initial CO2 levels were 170,000 times present levels and raised global surface temperature to 85 °C Hydrosphere The collective mass of water on any world (oceans, rivers, ice caps, clouds) ~ 70% of Earth’s surface covered by water Climate Regulation The CO2 Cycle - Atmospheric CO2 dissolves into rain water, ends up in oceans - Silicate rocks are eroded and sediments end up in the oceans - Minerals from rocks mix with CO2 in ocean to form carbonate minerals - Carbonate minerals sink to ocean floor to make carbonate rock - Plate tectonics force carbonate rock into mantle along subduction zones - Carbonate rock melts & CO2 is released through outgassing Climate Regulation The CO2 Cycle as a Thermostat If the global average temperature increases, ocean H2O evaporation increases Increases cloud formation & rainfall Increases weathering of silicates & more CO2 dissolved out of atmosphere CO2 in oceans forms carbonate rocks faster More CO2 able to be stored in oceans Global average temperature lowers Ice Ages When the global average temperature is a few degrees cooler than normal, snowfall reaches lower latitudes. Most recent ice age peaked about 10,000 years ago Other Influences on Climate The Sun’s brightness has slowly increased since its formation Rotation period of Earth has slowed down due to tidal forces of the Moon Precession & nutation of Earth’s rotational axis