EESA06H3 Lecture : The last 4.5 billion
Document Summary
Canada"s geological journey: the last 4. 5 billion years (chapter 20) Paradigm revolutionary idea that changes people"s views. Craton each continent has one, inner core of old crystalline rocks (igneous, metamorphic) all precambrian aged (~600 million years) They are underneath large areas of cover rocks. Continents have grown from micro-continents, small crusts, and grow in size, rocks get younger as you go towards the margins of large continents. (ie. yummy swiss rolls and snowballs) We can destroy ocean floors/crust cause they are made of basalt, they get recycled back as continental crust, added to other continents. Obduction continents grow through time; the accretionary process that builds continents from smaller crustal blocks, adding blocks to another one to make a bigger continent - called cratinization. Box 2. 5 peneplained craton and enlarged continent > early rifting > full ocean basin > subduction zone > closing ocean basin > collision orogeny (process of building mountains)
