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EESA06H3 (540)
Nick Eyles (472)
Lecture 10

Lecture 10

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University of Toronto Scarborough
Environmental Science
Nick Eyles

Lecture 10 Dominant themes: plate tectonics Deconstruction- taking something apart, seeing how it works Plate tectonics is the interpretive tool for understanding how North America got built Continents grow through time by obduction, think about India colliding with Asia o Trying to identify how they grew up 5 main stages: o 1. Arctica- oldest land mass- 2.7 Ga o 2. Columbia- 1.8 Ga o 3. Rodina- a billion years ago Abundant life evolves Arctica + Columbia + Rodinia = Canadian Shield (the craton) o 4. Pangea assembly (350 Ma): Maritime Canada is added during Appalachians Orogeny (Appalachian Mountains) o 5. Pangea breakup (<200 Ma): British Columbia is added during Cordileran Orogency (ie. Rockies) The Sheild is sort of the old core of North America (the greens) The blue area on right hand side is Appalachian belt- Maritime Canada Zircons- 2.7 billion year old o Uranium-lead dating o Can do large number of age determination o They are quite precise o Tom Krogh- expert on dating old rocks Measures the amount of lead in the crystal and tells how long lead have been sitting there and the rate at which uranium break down Any continent that has a shield has oldest rocks Acasta gneiss (in Yellow Knife) o Oldest rock- 4 billion years old o It is not technically correct to say that its the oldest rock, because there was a pre-existing rock o Detrital- secondary Earth is 4.5 billion years old, suggesting that forming crust pretty early on Oldest stuff is in middle, and gets younger as you move out Deconstructing North America Superior province- a very old term to identify rocks that extend over large areas which are similar in appearance o Have sharp boundaries Orogen- the rocks that result from orogenic activity- folded, highly deformed rocks o Most common rocks are nice o Provinces are separated from each other by orogens Provinces were micro continents and orogens were folded rocks o Provinces collided with another one and separated by orogens Greenstone belts are metaphoric ocean rocks Slave province is the true core of the shield o Yellowknife area is the oldest part of North America Greenland is part of NA continent, broke off about 80 million years ago, separate by a failed rift
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