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Lecture 10

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Environmental Science
Nick Eyles

Lecture 10 Canadas Geologic Journey The last 45 billion years This weeks lecture is based on Chapter 20 Geology of North America known for 100 years but what put it together So heres the geologic map and we known this for more than 100 years Geologist had found out across continents looked at rocks most are driven by fine and economic minerals This map has been here for a long time but it didnt make a lot of sense There was no model and no pyridine which means a big idea Its a revolutionary idea that changes peoples views on day of things that had been around for many years We talk about plate tectonic pyridine nanotechnology pyridine and all these sort of things We are looking at previous date that previously didnt make sense Plate tectonic revolution came along in the 70s and then people started looking at this map and realized how it worked Canadian Shield deals with ancient rocks so theres a problem with having no fossils We didnt know where all the rocks where Plate tectonic revolution came along and we can now make much more sense of this map The inner part which is coloured in orange is where we call the craton Thats the same as the Canadian Shield they are not quite the same thing Each continent if you go around the world has a craton It is the inner core of old crystalline igneous metamorphic rocks rocks have a long history rock They are all precambrianated They are all old and roughly 600 million years These craton areas are surround by blue lime coloured rocks We referred to these rocks as cover rocks because they do cover the craton The craton that you see here on this map has a much wider extent because it is underneath these coloured rocks The big picture is continents have grown from small land masses what we call microcontinents and they grow like a snowball The oldest rocks are in the middle of the country and as you go to the margins the continents are getting to younger rocks Continents actually do grow up The general rule is the rocks get younger as you go towards the margins of large continentsWhat kind of crust can we not destroy through subduction What cant we push down through subduction in terms of crustal types continental crust We can destroy ocean floors because they are made of basalt Heavy rock they can go down through subduction and they get recycled as continental crust On the last 4 billion years the Earth has been recycling oceanic crust into continental crust The second point is you cannot subduct continental crust because its relatively low density Obduction is where continents grow through time Ocean basins can be destroyed that crust is recycled as granite continental crust and its faith is to be shuffled around the surface of the Earth and to be added to other continents Canadas most famous geologist J Tuzo WilsonBox 25A grand concept of a paradigm This gives out the basic ordering of earth history and we have large super continents and they are very unstable This could take 5 to 7 million years to accomplish This is one cycle and in fact in Earth history we got previous cycle Tuzo Wilson present this as a pyridine He went to University of Toronto who was a geophysicist which is a geologist who uses physical data On the bottom right is in Alberta and on the circle is mount Tuzo which named after Tuzos mother who was a pioneer mountaineerFig 204
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