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Lecture 10

EESA06 Lecture 10 Notes

Environmental Science
Course Code
Nick Eyles

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Lecture 10
Canadas geologic journey: the last 4 billion years
Dominant theme for exam is plate tectonic, chapter 20
Deconstruction, taking something apart and seeing how its built
How north American got built
Plate tectonic is the tool in understanding how N.A. got built
Other continents are built in a similar way
OUTLINE OF LECTURE (Read Chapter 20 carefully!)
1. Continents grow through time by obduction
Deconstructing continents
2. North American continent shows 5 growth stages:
a) Arctica (2.7 Ga)billion years ago
Oldest one
Zircons used for uranium lead age dating
Tom Crose, lead is given first and then age is determined
Oldest rock on the planet is Acosta gneiss up in the Yellowknife which is 4 billion
years old
That date is not technically correct because we are dating the event that made it
Detrital meaning secondary, coming from the work detritious meaning garbage
The rock had to be derived from something else.
The earth is 4.5 billion years old
Age of rocks on slide 8
Grey represents much younger rocks
This map shows that the oldest rocks are all in the middle, Swiss roll
Province: old term used to identify rocks which are similar in appearance such as
superior province but with sharp boundaries.
Orogen: the rocks that result from orogenic energy. The most common rock are high
deformed, nice
The provinces are separated by orogens
Orogens are all the folded rocks in India, like Himalayas
Provinces are like continents moving around and collide and they form separate
continents and are separated by orogens which we find green stone belts which are
ocean floor rocks
Top left, the true core of the shield because the encastonine is found in the slave
The Yellowknife and slay area are the oldest part of NA
Greenland broke off 80 mya but was part of NA, it was separated by a failed rift
The earliest north American land mass, Arctica @ 2.5/2.7bya
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