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Canada’s Geological Journey: The last 4.5 billion

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Environmental Science
Course Code
Nick Eyles

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EESA06 Lecture 10 Canadas Geological Journey The last 45 billion years Chapter 20Paradigmrevolutionary idea that changes peoples viewsCratoneach continent has one inner core of old crystalline rocks igneous metamorphic all Precambrian aged 600 million yearsSurrounded by cover rocks They are underneath large areas of cover rocksContinents have grown from microcontinents small crusts and grow in size rocks get younger as you go towards the margins of large continents ie yummy Swiss rolls and snowballsWe can destroy ocean floorscrust cause they are made of basalt they get recycled back as continental crust added to other continents Cannot subduct continental crust cause low density Obductioncontinents grow through time The accretionary process that builds continents from smaller crustal blocks adding blocks to another one to make a bigger continentcalled CratinizationBox 25Peneplained craton and enlarged continentearly riftingfull ocean basinsubduction zoneclosing ocean basincollision orogeny process of building mountainsFigure 204Decontructing North America NA How NA became what it is nowo Made of 5 piecesTerraneo Failed rift mid ocean ridge under Greenland o Cratonfrom Mexico to Greenland o Last piece added to NA is the left coast continental crust that arrived fairly recently o Slave Provinceoldest crust in NA original NA continent o Orogensthe deformed rocks that result from orogeny o South American crust left behind when Rhodinia was forming o African crust that got left behind At time of Pangea o NA gets pushed to the west pushing younger rocks to the east o Cordilera Orogenybuilt western part of NA o Forms by repeated collisions o LaClochevalley ranges made up white quartzite folded into ridges o Penokean Orogenynarrow o Not finished due to sacadia subduction zone on west recycling of continental crust Geological Provinces through Geologic TimeAcasta Gneiss NWTfamous rock oldest continental crust formed by metamorphic rock zercons inside rock are called DETRITAL something derived from something else by weathering of rocks deposited into a basin like quartz zircon etc Older than the rock they are part ofEvidence that craton is result of obduction processes GREENSTONE BELTS with minerals like gold
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