Geography 111 - Principles of Geology
Plate tectonics and the evolution of the continents and ocean basins
(note: the sequence of topics is not necessarily in the same order as the book; topics are covered in chapters 18, 19, and 20. I have given page numbers so that you can locate some topics in the book.)

• Plate tectonics as a unifying theory for explaining observed patterns of geological phenomena
  
 
• Physical features:
• continents (p.558-560; also p.17-18, p.210)
• mountain or orogenic belts: high relief, tectonically active, areas where uplifted rocks are exposed by erosion; aligned paralle to continental margins and plate boundaries
• stable platforms: low relief, sedimentary cover over igneous/metamorphic basement
• continental shields: deeply eroded roots of ancient mountain belts; metamorphic rock exposed at surface, very low relief, earth's oldest exposed rocks
• ocean floors (p.496-511)
• passive continental margins: continental shelf, slope, and rise; ancient normal faults beneath sediment cover at passive margins
• trenches and subduction zones, volcanic island arcs, and tectonically active continental margins with accretionary wedges
• submarine canyons
  
• abyssal plains
• mid-ocean ridges and transform fault/fracture zones; note symmetrical pattern of topography on opposite sides of ridges
• spreading rates (see p.535-536, 548-549)
• seamounts and guyots, coral reefs and atolls (not discussed in class; see p.504-506)
• structure of oceanic crust (see p.511-513)
• global distribution of earthquakes in relation to plate boundaries (p.545-546) and volcanoes in relation to plate boundaries (refer back to p.121-126)
• "fit" of the continents; Wegener's continental drift hypothesis and its rejection (p.519-524)
• additional evidence from fossils and distribution of rock types; correlation between South America and Africa; Appalachian and Caledonian mountain belts; Paleozoic glaciations
  
 
• Other geologic evidence for sea-floor spreading (first proposed by Hess in early 1960's; see p. 524-530)
• Age of rocks:
• continental rocks up to 4 billion years old, oldest rocks in shield areas
• oceanic crust generally < 200 million years old, distributed in symmetrical age bands around mid-ocean ridges
• Paleomagnetism
• Polarity reversals in earth's magnetic field
• Magnetic "stripes" on the ocean floors and Vine and Matthews' hypothesis (p.527-530) of sea-floor as a recording "strip chart" of the earth's changing magnetic field
• stages of rifting and ocean-floor development: East African rift valleys, Red Sea and Gulf of Aden (p.534-538)


• Transform faults and their origins (p.543-544)


• Trenches and subduction zones (p.500-502, 537-543, 560-567):
• spatial distribution of volcanic activity in relation to trenches
• subduction zones and island-arc mountain chains
• accretionary wedge of material scraped off the subducting plate: formation of melange
• suture zones and mountain belts at locations of continent-continent collision


• Paleogeography of Pangaea: a supercontinent and its breakup (p. 519-522, 534-535)
  
 
• Terranes, continental accretion, and orogenic belts (p.567-569)
• importance of crustal fragments: micro-continents or "microplate terranes," rafted together by subduction-zone conveyor belt and sutured together to make "patchwork" continents, e.g. Alaska and Pacific northwest
• history of Appalachians (p.565-567; not illustrated well in book, will discuss in class)
• multiple orogenies over several hundred million years, associated with accretion of terranes followed by final continental collision


• Competing hypotheses about the driving mechanisms of plate tectonics: (p. 550-553, but note comments in class)
  
 
• Continents as remnants of collisions and accretion of terranes: North America as an example (p.569-571, 576-579)
• Stable interior craton (including shields and platforms) flanked by orogenic belts

• Relation of plate-tectonic motion to mountain building (orogeny):
• isostasy, roots of mountains and isostatic adjustment (p.569-574)
• subduction zones and Andes- or Cascade-type mountain chains on land (p.562-564)
• interior California considered as an inactive Andean-type setting (p. 564, 575):
• Coast Ranges as accretionary wedge
• Great Valley as marginal basin
• Sierra Nevada as eroded roots of Andes-type volcanic mountains with batholith exposed after uplift
• continent-continent collisions and Himalayan-type orogeny (p.541-543, 564-565)
• note similar origins for Appalachians, Alps
• subsequent denudation of mountain belts to produce thick wedges of marine sediment deposited along continental margins (look at fig. 18.4, p.498, for example - no mountains shown but that's where the sediment along the passive margin came from)
  
 
• Possible role of hot spots as major upwelling sources: see p.546-548, also p.126-127
• Summing up: driving forces, cycles of supercontinent formation and breakup, and linkage of hot spots with plate tectonics