Class Notes (836,321)
Canada (509,732)
EESA06H3 (563)
Nick Eyles (495)
Lecture

Lecture2c

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Department
Environmental Science
Course
EESA06H3
Professor
Nick Eyles
Semester
Summer

Description
• Was  a  major  paradigm  –  complete  revolution  to  the  way  people  think  about   planet  earth   • All  igneous  rock  contain  isotopes  (usually  of  uranium)   o Unstable  and  break  down  through  time   o Produce  daughter  products  (usually  lead)   o Lead  to  uranium  ratio  determines  age  of  magnetic  stripes     Drilling  the  ocean  floors   • ODP  –  ocean  drilling  program   o First  vessel  called  Resolution   o Can  drill  in  7  km  of  water,  7  km  of  sea  floor   • Riser  drilling  system  of  Chikyu   o Owners  want  drill  down  and  reach  the  earth’s  mantle  to  find   energy/mineral  resources   o Has  BOP  –  blow  out  preventer   § Huge  iron  vessel  surrounding  drill  pipes   § Prevents  high  pressure  fluid  or  gas  from  blowing  out  from   over-­‐pressure  sediments  at  depth   o Open  and  closes  quickly  to  let  off  pressure     Age  of  the  ocean  floor  (Fig.  2.17)   • Older  floor  is  farther  away  from  mid-­‐oceanic  ridges   o On  outer  margins  close  to  the  continents   • Youngest  parts  of  the  ocean  are  right  along  the  mid-­‐oceanic  ridges   • Ocean  spreading  has  only  taken  place  since  the  late  Jurassic   o There  was  no  Atlantic  ocean  before  that   o This  is  when  Pangaea  was  breaking  up   • East  pacific  ocean  floor  has  been  subducted  under  South  America   o Only  young  rock  here   o The  ridge  push  of  the  Atlantic  is  very  strong   o Thus  the  Pacific  is  closing   o This  area  is  called  the  “Pacific  rim”   § Very  dangerous  due  to  earthquakes  and  volcanoes  as  result  of   subduction   • Ocean  floor  thickness  increases  from  the  mid  ocean  ridges  systematically   outwards   • Oldest  ocean  floor  is  thick,  full  of  water,  cold,  high  density   o Allows  it  to  be  sink  under  continents  into  the  mantle   • Creates  cycle  of  ocean  opening  and  closing   • Ridges  are  not  continuously  smooth   o There  are  transform  faults  –  allow  spreading  on  a  sphere   • Ocean  floor  is  mostly  made  out  of  basalt   o Rich  in  magnesium  and  iron   o Dense  minerals   o 2.9  g/cm   o Overlies  plastic  soft  rock  (like  hot  toffee)   o Floor  sinks  back  into  mantle   § This  is  how  ocean  basins  are  formed   • Continents  are  made  out  of  continental  crust   o Not  as  dense   o Act  like  giant  icebergs;  sit  rather  high  on  soft  rocks  underneath   o Contains  quartz,  silica  (glass)   o About  2.7  g/cm  3   Earthquakes  and  what  they  tell  us  of  the  Earth’s  interior   • Produce  enormous
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