Subdisciplines of Earth Science Geology; study of the earth
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CHAPTER 8Plate Tectonics Definition Importance Continental Drift Alfred Wegener Pangaea Evidence Similarities in shorelines of South America and Africa Fossils Mesosaurus Australian marsupials Rock types and structural similarities Mountain ranges Similar rock types Paleoclimates Fossil ferns near poles Glacial deposits near equator Problems No mechanism Not accepted by American geologists Plate Tectonic Theory Earth composed of lithospheric plates Move on plastic asthenosphere Composition of plates Oceanic crust only Continental crust only Both oceanic and continental crust Seven major plates Plate boundaries Three Types of Plate Boundaries Divergent boundaries Rift zones Sea floor spreading New ocean crust forms Examples Magnetic reversals Normal polarity Reverse polarity Convergent boundaries Subduction Oceanic-continental convergence Examples Oceanic-oceanic convergence Examples Continental-continental convergence Examples Transform plate boundaries San Andreas fault Testing the Model Ocean drilling Deep Sea Drilling Project (1968-83) Glomar Challenger Discoveries Composition of ocean crust Sediment age increases away from ridges Hot spots Mantle Plumes Hawaii Yellowstone Paleomagnetism Apparent polar wandering Magnetic striping Magnetic reversals Magnetic time scale Vine and Matthew’s research Earthquakes Convergent plate boundaries Shallow, intermediate, deep foci Divergent margins Shallow foci only Driving forces of Plate Motion Convective flow is driving force Unequal distribution of heat Forces Slab pull Ridge push Slab suction Models of plate-mantle convection Layering at 660km Whole-mantle convection Deep layer model Plate Tectonics into the Future Potential locations 500 my Potential locations 250my CHAPTER 9I. General Information on Mt. St. Helen’s volcano II. Nature of Volcanic Activity a. Viscosity; resistance to flow b. Gas content; dissolved gases increase fluidity c. Magma Types i. Basaltic; low silica; low viscosity; no pyroclastics ii. Andesitic; intermediate silica; intermediate viscosity; some pyroclastics iii. Granitic; high silica; high viscosity; pyroclastics III. Material Extruded From Volcano a. Lava; magma at surface 1. Pahoehoe; twisted braids 2. Aa; rough edges b. Gases i. Water vapor; 70%; most abundant ii Carbon dioxide iii. Nitrogen iv. Sulfur c. Pyroclastics; usually granitic magmas; ash, lapilli, cinders, blocks, bombs IV. Volcanic Structures and Volcanic Eruptions a. Anatomy of a volcano i. Central vent ii. Crater; steep-walled depression at top of volcano iii. Pipe; pathway that connects volcano to magma chamber iv. Calderas; large collapse structures v. Fissures; cracks near volcano Fumaroles; vents that emit only gas 
b. Three types of volcanoes i. Shield
Broad, domed structure Mauna Loa Kilauea ii. Cinder cones Ejected lava fragments Paricutin, Mexico iii. Composite or Stratovolcanos Most on Pacific rim Most explosive Mt. St. Helens St. Pierre Vesuvius Lahars Mudflows Nevado del Ruiz 1985 Mt. Rainier, WA risk for lahar V. Other Volcanic Landforms a. Calderas i. Crater Lake ii. Hawaii iii. Yellowstone b. Fissure eruptions and lava plateaus i. Flood basalts ii. Columbia Plateau c. Volcanic pipes and necks VI. Intrusive Igneous Activity a. Dike; discordant; magma injected into fractures b. Sill; tabular; concordant; magma injected along bedding planes c. Laccolith; sediments pushed up by high silica magma; discordant d. Batholith; most massive; discordant; granite; associated with large mountain ranges
a. Origin of Magma i. Generating magma from solid rock ii. Heat
1. Geothermal gradient iii. Pressure VIII. Plate Tectonics and Igneous Activity a. Distribution of Igneous Activity i. Circum-Pacific belt ii. Basaltic lavas in deep ocean basins iii. Interiors of continents b. Convergent plate boundaries i. Continental island arcs ii. Examples d. Intraplate volcanism i. Mantle plumes ii. Hot spots IX. Volcanoes and Climate a. Ash blocks sunlight b. Cold summer 1816 c. Extinction of dinosaurs d. Modern examples
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