G131 HOME
INFORMATION
SCHEDULE
RESOURCES
EXERCISES
NOTES
Links to summaries of key issues for each topic
PREAMBLE
Introduction
PART I
Ocean World
Plate Tectonics
Margins/Basins
Review 1
Sediments
Chemistry
PART II
Atmosphere
Ocean Circuln.
Waves
Tides
PART III
Coasts
Ocean Life
Primary Prodn.
Mar. Animals
Communities
Mar. Resources
Env. Concerns
VISUALS
Links to images employed in lectures
TEXT
Link to chapter outlines at online learning center
NOTES
Links to summaries of key issues for each topic
 
Plate Tectonics

Notes on Topic:

  • The notes identify the learning objectives within dominant themes
  • They present summaries of key issues for each topic
  • They emphasize the terminology used to describe the various phenomena.
1. Internal Structure of the Earth:
Learning Objectives:
  • Recognition of the internal, layered structure of the Earth and its composition.
  • Understanding the nature of seismicity, seismic waves and earthquakes.
Earth's Layered Structure:
  • A series of concentric spheres
  • Core: 
    • dense, composed of metals Fe, Ni 
    • inner core, solid (1070km), outer core, liquid (2400km) 
  • Mantle: 
    • 2855km thick made of Mg-Fe silicates
    • lower mantle is solid
    • upper mantle is partly molten or plastic (asthenosphere),
  • Crust: 
    • rigid, two types; 
    • less dense continental crust, thick, ~45km, rich in Mg, Al silicates 
    • denser oceanic crust, thin, ~7km, rich in Mg, Fe silicates
  • Hydrosphere: envelope of water
  • Atmosphere: gaseous envelope
Clues to Earth's Structure :
  • Seismic waves from earthquakes and underground explosions
    • P waves (primary), fast compression waves
    • S waves (secondary), slow shear waves, do not travel in liquid
  • Seismic waves travel through Earth's interior
    • waces are bent (refracted) by changes in rock density
    • waves are refracted as they pass from one layer to another
    • wave shadows are created where waves cannot travel
    • S wave shadow defines outer core. P wave shadow defines size of core
  • Seismic tomography: 
    • identifies presence of hotter/cooler areas of mantle
Lithosphere: Earth's Outer Rigid Shell:
  • Crustal types: 
    • Continents are granitic, and oceans are basaltic. 
    • Lower boundary of crust is the Moho (Mohorovicic discontinuity)
    • Lithosphere consists of crust plus the uppermost rigid mantle 
  • Asthenosphere: 
    • upper mantle below the lithosphere, which is partially molten/plastic
  • Isostasy: 
    • crust 'floats' on asthenosphere, based on density and thickness
    • can be loaded by glacial ice, or by an accumulation of volcanic rocks

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