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 (contd.)   

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.
4. Plate Motion :
Learning Objectives:
  • Recognition of significance of hot spots and evidence for plate motion. 
  • Understanding of positions of tectonic features and their changes over time. 
  • How Volcanoes form: island and volcanic arcs, mid-ocean ridges and hot spots.
Spreading Rates: 
  • Mechanism of spreading:
    • mantle convection or "slab pull" of subducting crust (or both?)
  • Overall range of rates: 1 - 17cm/a. 
    • Mid-Atlantic ~3cm/a, East Pacific Rise 6 - 17 cm/a. 
    • Vary through time.
Volcanic Activity at Hot Spots:
  • Fixed sites of volcanic activity, broad, shield volcanoes 
    • thermal plumes deep-seated at core/mantle boundary?
      • Iceland, Hawai'i
    • form volcanic islands as plate moves that verify sea-floor spreading
      • chain of Hawai'ian islands and Emperor seamounts
    • Older Hawai'ian islands eroded, newest Loihi (submarine). 
    • Can produce transverse ridge 
      • Tristan da Cunha, Walvis Ridge 
    • Also form oceanic plateaus
      • Kerguelen, Ontong-Java
4. History of the Continents:
Learning Objectives: 
  • Appreciation of the ancient positions of continents and oceans. 
  • Understanding how continent are built and the assembly of terranes. 
  • The significance of the occurrence of hydrothermal vents.
Breakup of Pangaea:
  • ~225Ma with Pangaea (supercontinent) and Panthalassa (superocean); 
  • Pangaea is split by Tethys into Laurasia and Gondwanaland
    • later separated by Atlantic. 
  • Series of reconstructions based on geological data have been compiled
  • Plate reconstructions reveal principal landmasses before Pangaea: 
    • Laurussia, Baltica, Siberia, Gondwana, Kazakhstania, China
Formation/Destruction:
  • Sequence of events
    • rifting (E. Africa), expansion (Red Sea), maturity (Atlantic), 
    • subduction (S. Sandwich), basin closure (Mediterranean)
    • continental collision (India/Asia, Himalayas)
  • Continents are built from cratons and terranes 
    • terranes are land packages added to continent during subduction
Hydrothermal Vents:
  • Water infiltrates new crust, heated and expelled at vents:
    • hot water plumes emanate from sea floor 
    • black smokers, hot (300-400°C), S-bearing, point sources 
    • white smokers, cooler (25-250°C), point sources
  • Occur at cracks, fissures in volcanically active areas, rifts. 
    • communities of organisms exist at these locations
    • vent fluids provide energy for (chemosynthetic) bacteria
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Phone: (812) 855-5582  Last updated: 26 September 2002
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