Class Notes (839,394)
Canada (511,324)
EESA06H3 (570)
Nick Eyles (502)
Lecture

Lecture2b

2 Pages
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Department
Environmental Science
Course Code
EESA06H3
Professor
Nick Eyles

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• Sea  floor  created  at  MOR’s  recycled  into  mantle  at  trenches  at  about  the  same   rate   o Subduction   o Plates  go  down  600  km,  melt,  and  get  recycled  back  into  mantle   o This  is  the  way  the  planet  is  cooling   • Finite  radioactive  source  of  heat  that  drives  this  process   o We  are  about  halfway  through  this  evolution   o Another  4  billion  years  left   o At  that  point  no  more  plate  tectonics;  dead  planet  like  Mars     Continuous  volcanic  activity  along  mid-­‐ocean  ridges   • Smokers  and  mineral  deposits   o Superheated  water  is  released  and  when  cooled  cannot  hold  as  much   material  in  solution   o Contains  a  lot  of  metal   o Form  chimney-­‐like  structures   o Unique  ecosystems  surviving  down  here  with  limited  light   § Chemotrophic  bacteria  use  smokers  for  food   o Mineral  deposits  =  massive  sulphides   § Copper,  zinc     Magnetic  stripes  (1965)   • Magnetometer  –  instrument  that  measures  the  direction  and  strength  of   magnetic  fields  in  rocks   • Magnetometer  surveys  of  ocean  floor  identified  patterns  of  anomalies  on   each  side  of  MORs   • Gives  information  about  deep  buried  structures   • In  north  America,  there  are  old  buried  faults  that  may  still  be  slightly  active   o One  goes  below  Pickering   • There  are  arromagnetic  maps  of  southern  Ontario   o Give  us  magnetic  anomalies   • In  northern  Canada  used  to  search  for  oil  reservoirs,  by  finding  porous  rocks   o Gas  migrating  from  other  sources  get  trapped   o Reservoirs  are  often  bounded  by  faults   • Mineralized  rock  is  hidden  under  glacial  sediments   o Diamonds  occur  in  Kimberlite  pipes   § Highly  magnetic   § Iron-­‐rich  minerals   • Magnetic  stripes  on  ocean  floor  are  made  up  of  negative  and  positive   magnetic  anomalies     Paleomagnetism  and  magnetic  stripes  on  the  ocean  floors   • The  earth’s  magnetic  field  is  unstable   • Episodically  the  earth’s  magnetic  field  flips   • North  magnetic  pole  changes  to  south   o Negative  anomaly   • We  live  in  era  with  positive  magnetic  field     The  earth’s  magnetic  field:  our
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