Ch 2 geologic history and processes


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Ch 2 geologic history and processes

  1. 1. Chapter Two Geologic History and Processes
  2. 2. Plate Tectonics <ul><ul><li>Divergent Boundary </li></ul></ul><ul><ul><ul><li>East Pacific Rise </li></ul></ul></ul><ul><ul><ul><li>Salton Trough </li></ul></ul></ul><ul><ul><ul><li>Cape Mendocino </li></ul></ul></ul><ul><ul><li>Convergent Boundary </li></ul></ul><ul><ul><ul><li>Cascades: Mt Shasta and Mt Lassen </li></ul></ul></ul><ul><ul><ul><li>Historically: Sierra Nevada, Coast Ranges, Klamath Mtns. </li></ul></ul></ul><ul><ul><li>Transform Boundary (“Sliding”) </li></ul></ul><ul><ul><ul><li>San Andreas </li></ul></ul></ul>
  3. 3. California Through the Ages <ul><ul><li>Precambrian Era ends 540 mya </li></ul></ul><ul><ul><li>California’s oldest rocks 1.8 billion years old </li></ul></ul><ul><ul><ul><li>Crust under us 1.8 billion years old </li></ul></ul></ul><ul><ul><ul><ul><li>Basin and Range, Transverse Range, and deserts </li></ul></ul></ul></ul><ul><ul><ul><li>Many younger intrusions </li></ul></ul></ul>A nearly 3,000 meter-thick section of Paleozoic-age sedimentary rocks are exposed in the mountain ranges of the eastern Mojave Desert region. This view shows Paleozoic-age rocks exposed on the eastern flank of the Panamint Mountains in Death Valley National Park.
  4. 4. California Through the Ages <ul><ul><li>San Gabriel Mountains </li></ul></ul><ul><ul><ul><li>Metamorphic and igneous rocks </li></ul></ul></ul><ul><ul><ul><li>Complex geologic past </li></ul></ul></ul>
  5. 5. California Through the Ages <ul><ul><li>Proterozoic (late precambrian) </li></ul></ul><ul><ul><ul><li>A sea covered California </li></ul></ul></ul><ul><ul><ul><li>Sediments were deposited </li></ul></ul></ul><ul><ul><ul><ul><li>Later igneous material intrudes </li></ul></ul></ul></ul>
  6. 6. California Through the Ages <ul><ul><li>Roof Pendants abundant in California </li></ul></ul><ul><ul><ul><li>Sierra Nevada’s, Inyo-White Mtns. </li></ul></ul></ul><ul><ul><ul><ul><li>Hornfels, cherts, marbles, slates, and quartzites </li></ul></ul></ul></ul>
  7. 7. California Through the Ages <ul><ul><li>Northern California </li></ul></ul><ul><ul><ul><li>More volcanic material mixed with ocean sediments </li></ul></ul></ul><ul><ul><ul><li>Continental crust crushed together with ocean crust </li></ul></ul></ul>
  8. 8. California Through the Ages <ul><ul><li>Southern California </li></ul></ul><ul><ul><ul><li>Paleozoic rocks not as common </li></ul></ul></ul><ul><ul><ul><li>Some in the Ord Mountains, Eastern Transverse Range, Peninsular Ranges </li></ul></ul></ul><ul><ul><ul><ul><li>Some gneiss and schist, Riverside limestone quarried for cement </li></ul></ul></ul></ul>http://
  9. 9. California Through the Ages <ul><ul><li>Mesozoic Period </li></ul></ul><ul><ul><ul><li>Lots of subduction going on </li></ul></ul></ul><ul><ul><ul><li>Results in mountain building </li></ul></ul></ul><ul><ul><ul><li>Nevadan Orogeny </li></ul></ul></ul><ul><ul><ul><li>When the sea began to disappear </li></ul></ul></ul>
  10. 10. California Through the Ages <ul><ul><li>Mesozoic Rocks Important </li></ul></ul><ul><ul><ul><li>Pre-Nevadan roof pendants </li></ul></ul></ul><ul><ul><ul><li>Limestone, slate </li></ul></ul></ul><ul><ul><li>Cenozoic Basins </li></ul></ul><ul><ul><ul><li>Filled with sediments and eroded mesozoic rocks </li></ul></ul></ul>
  11. 11. California Through the Ages <ul><ul><li>Mesozoic period </li></ul></ul><ul><ul><ul><li>Granite plutons: Sierra Nevadas and Cascades </li></ul></ul></ul><ul><ul><ul><li>Franciscan Complex (Coast Ranges) </li></ul></ul></ul><ul><ul><ul><ul><li>When sedimentary material was brought to and crushed against the continent </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Chert, serpentine, sandstone, shale </li></ul></ul></ul></ul><ul><ul><ul><li>Klamath Mountains: </li></ul></ul></ul><ul><ul><ul><ul><li>both plutons and schist from being pushed against and onto the continental plate </li></ul></ul></ul></ul>
  12. 12. California Through the Ages <ul><ul><li>California: 1.8 billion years of rocks </li></ul></ul><ul><ul><ul><li>Impressive quantities of valuable minerals, ores, and other earth resources. </li></ul></ul></ul><ul><ul><ul><ul><li>Shaped history and still an import part of the economy </li></ul></ul></ul></ul>
  13. 13. Gold, Silver, and Other Ores <ul><ul><li>In and near subduction zones, ocean and continental crust materials incorporate into magmas. </li></ul></ul><ul><ul><li>This magma becomes granitic plutons. </li></ul></ul><ul><ul><li>As the magma is pushed towards the surface it comes in contact with older sedimentary or metamorphic rocks. </li></ul></ul><ul><ul><li>As the magma cools, it squeezes into cracks and joints forming veins. </li></ul></ul><ul><ul><li>Often it is the most felsic magma with the most minerals that forms the veins. </li></ul></ul><ul><ul><li>High feldspar veins then cool and crystallize with precious mineral deposits. </li></ul></ul>
  14. 14. Gold <ul><ul><li>Placer Deposits </li></ul></ul><ul><ul><ul><li>Where veins have eroded into streams, rivers, lakes, etc. </li></ul></ul></ul><ul><ul><li>Mother Lode </li></ul></ul><ul><ul><ul><li>Principal zone of veins of gold or silver </li></ul></ul></ul><ul><ul><ul><li>Usually refers to California’s Sierra Nevada .7 mi wide, 120 mile long zone </li></ul></ul></ul><ul><ul><li>Hydraulic Placer Mining </li></ul></ul><ul><ul><ul><li>Way of mining with high powered water spray </li></ul></ul></ul>
  15. 15. Mix of Valuable Resources in the North <ul><ul><li>Klamaths </li></ul></ul><ul><ul><ul><li>Chromium, cobalt, nickel, zinc, copper, gravel, clay, limestone </li></ul></ul></ul><ul><ul><li>Shasta </li></ul></ul><ul><ul><ul><li>Pyrite, chalcopyrite, sphalerite, magnetite, mercury </li></ul></ul></ul>
  16. 16. Mines in Transmontane California <ul><ul><li>Basin and Range </li></ul></ul><ul><ul><ul><li>Today: talc, saline minerals </li></ul></ul></ul><ul><ul><ul><li>Cerro Gordo </li></ul></ul></ul><ul><ul><ul><ul><li>Silver, lead, zinc </li></ul></ul></ul></ul><ul><ul><ul><li>Bodie </li></ul></ul></ul><ul><ul><ul><ul><li>gold </li></ul></ul></ul></ul>
  17. 17. Mining in the Mojave and Southern Deserts <ul><ul><li>Rand Mining District </li></ul></ul><ul><ul><ul><li>Gold, silver, tungsten, boron </li></ul></ul></ul><ul><ul><li>Further South </li></ul></ul><ul><ul><ul><li>Gold, rare earth minerals, iron, limestone, magnetite, hematite, boron </li></ul></ul></ul>