Subdisciplines of Earth Science Geology; study of the earth



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CHAPTER 8





  1. Plate Tectonics

    1. Definition

    2. Importance




  1. Continental Drift

    1. Alfred Wegener

    2. Pangaea

    3. Evidence

      1. Similarities in shorelines of South America and Africa

      2. Fossils

        1. Mesosaurus

        2. Australian marsupials

      3. Rock types and structural similarities

        1. Mountain ranges

        2. Similar rock types

      4. Paleoclimates

        1. Fossil ferns near poles

        2. Glacial deposits near equator

      5. Problems

        1. No mechanism

        2. Not accepted by American geologists




  1. Plate Tectonic Theory

    1. Earth composed of lithospheric plates

    2. Move on plastic asthenosphere

    3. Composition of plates

      1. Oceanic crust only

      2. Continental crust only

      3. Both oceanic and continental crust

    4. Seven major plates

    5. Plate boundaries




  1. Three Types of Plate Boundaries

    1. Divergent boundaries

      1. Rift zones

      2. Sea floor spreading

      3. New ocean crust forms

      4. Examples

      5. Magnetic reversals

        1. Normal polarity

        2. Reverse polarity



    1. Convergent boundaries

      1. Subduction

      2. Oceanic-continental convergence

        1. Examples


      1. Oceanic-oceanic convergence

        1. Examples




      1. Continental-continental convergence

        1. Examples



    1. Transform plate boundaries

      1. San Andreas fault



  1. Testing the Model

    1. Ocean drilling

      1. Deep Sea Drilling Project (1968-83)

        1. Glomar Challenger

        2. Discoveries

          1. Composition of ocean crust

          2. Sediment age increases away from ridges

    2. Hot spots

      1. Mantle Plumes

      2. Hawaii

      3. Yellowstone

    3. Paleomagnetism

      1. Apparent polar wandering

      2. Magnetic striping

        1. Magnetic reversals

        2. Magnetic time scale

        3. Vine and Matthew’s research

    4. Earthquakes

      1. Convergent plate boundaries

        1. Shallow, intermediate, deep foci

      2. Divergent margins

        1. Shallow foci only



  1. Driving forces of Plate Motion

    1. Convective flow is driving force

    2. Unequal distribution of heat

    3. Forces

      1. Slab pull

      2. Ridge push

      3. Slab suction

    4. Models of plate-mantle convection

      1. Layering at 660km

      2. Whole-mantle convection

      3. Deep layer model




  1. Plate Tectonics into the Future

    1. Potential locations 500 my

    2. Potential locations 250my

CHAPTER 9


I. 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

i. Hawaiian volcanoes

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

  1. Fumaroles; vents that emit only gas

b. Three types of volcanoes

i. Shield


  1. Broad, domed structure

  2. Mauna Loa

  3. Kilauea

ii. Cinder cones

  1. Ejected lava fragments

  2. Paricutin, Mexico

iii. Composite or Stratovolcanos

  1. Most on Pacific rim

  2. Most explosive

  3. Mt. St. Helens

  4. St. Pierre

  5. Vesuvius

  6. Lahars

    1. Mudflows

    2. Nevado del Ruiz 1985

    3. 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
VII. Igneous Activity and Plate Tectonics

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

c. Divergent plate boundaries

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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