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EESA06H3 (570)
Nick Eyles (502)
Lecture

Lecture3a

2 Pages
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Department
Environmental Science
Course Code
EESA06H3
Professor
Nick Eyles

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LECTURE  3     • Supercontinent  cycle  is  500-­‐600  million  years   • Has  been  happening  for  3  billion  years   o We  can  recognize  at  least  5  of  these  break  ups  and  assemblies   • Uniformitarianism  –  the  theory  that  changes  in  the  earth's  crust  during   geological  history  have  resulted  from  the  action  of  continuous  and  uniform   processes   o The  same  processes  happening  today  also  occurred  in  the  ancient  past   o We  look  at  how  volcanoes  work  today  and  use  that  knowledge  to   study  ancient  rocks   o This  concept  doesn’t  always  work  (see  below)   § Its  weakness  is  that  we  haven’t  been  on  this  planet  for  very   long  and  so  haven’t  been  observing  geological  processes  very   long   • Catastrophism  –  the  theory  that  changes  in  the  earth's  crust  during   geological  history  have  resulted  chiefly  from  sudden  violent  and  unusual   events     o Big,  rare  events   o Like  the  Big  Bang,  major  meteorite  strikes,  supernova,  super   volcanoes   o Examples  of  super  volcanoes:  Yellowstone,  Taupo   § In  North  America  we  can  find  ash  layers  in  limestone  as   evidence  of  past  super  volcanoes   § 15  m  thick  –  capable  of  burying  North  America   • Vertical  tectonics  –  huge  amounts  of  magma  come  up  from  the  mantle  and   erupt  from  the  earth’s  surface   • Create  large  igneous  provinces  (LIPs)   o Cannot  be  explained  in  terms  of  plate  tectonic  theory   • Very  important  economically  –  contain  a  lot  of  gold  and  diamonds   • Ash,  water  vapor,  and  sulfur  gases  also  come  up   o Volcanic  gases  are  very  toxic  and  may  be  linked  to  extinctions   • All  the  modern  oceans  formed  from  very  narrow  cracks  called  rifts   o Widened  and  filled  with  water     Triple  Junctions  and  Aulacogens  (Failed  Rifts)  [Fig.  2.40]   • Continental  slab  (part  of  a  supercontinent)  trapping  heat  from  the  mantle   • Slowly  rises  in  elevation  –  process  called  inflation   • This  is  why  interiors  of  supercontinents  are  very  dry   o Inimical  to  life   o Supercontinents  are  not  favorable  with  respect  to  diversity  of  life   forms   o No  great  range  of  environments   o Surrounded  by  old  deep  ocean  not  under  influence  of  light   • Then  the  cont
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