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Lecture 10

EESA06H3 Lecture Notes - Lecture 10: The Maritimes, Pangea Corporation, Eurasia

Environmental Science
Course Code
Nick Eyles

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Lecture 10 t v['}o}P]:}µvÇWdZ>ð]oo]}vz
Æu[}u]vvZuÆ Plate tectonics
1. Continents grow through time by obduction
2. North American continent shows 5 growth stages:
a. Arctica (2.7 Ga Æ gigaannum)
b. Columbia (1.8 Ga)
c. Rodina (1.0 Ga)
- Part of human life
a + b + c = Canadian Shield (the craton Æ core of
North America: BROWN AREA)
d. Pangea assembly (350 Ma): Maritime Canada
is added during Appalachians Orogeny
(Appalachian Mountains: BLUE RIGHT AREA)
e. Pangea breakup (<200 Ma): British Columbia
is added during Cordilleran Orogeny (e.g.
Rockies: from Alaska to Mexico on the left)
- Derive from igneous rocks Æ released into water
- Sedimentary rock metamorphosed into a gneiss
- used for uranium, lead age dating Æ 2.7 billion years old
- very small
- put into a mass spectrometer to look at how much lead is in the crystal
Oldest rock on the planet
- Acasta gneiss (North West Territories)
- 4 billion years ld
- Gneiss Æ has been metamorphosed
- Detrital Æ Detritus
o Derived from something else Æ eroded
Continents Grow through Time
- Oldest rocks in the centre t embedded in the
interior of continents
- Begins to get younger as the land disperses

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Deconstructing North America
o Province t identify rocks that extend over very large areas (similar in appearance)
Very sharp boundaries
Can walk from one to the other
Separated by the orogen
o Orogen t the rocks that result from orogeny (activity)
Most common rock found t gneiss
Smaller rocks colliding with others t separated by orogens t green stone belts
(metamorphosed ocean rocks) and gneiss
1. The original North American Continent,
Arctica, which started to form about 2.5 billion
years ago from smaller continents and was
completed by about 1.9 billion years ago when
old Archean cratons (e.g. Slave, Nain
provinces) were welded together by the Trans-
Hudson Orogen and others.
o Earliest North American continent
o Greenland part of it t broke off about
80 million years ago
o Separated by a failed rift
2. Added to the North American continent during
the formation of Nena about 1.8 billion years
ago after the Penokean Orogeny.
3. Added during the formation of Rodinia about
1.3 billion years ago during the Grenville
4. Added during the formation of Pangea about
600 million t 300 million years ago.
5. Added after the breakup of Pangea about 250
million years ago.
o Cordillera orogeny added after the
- Probing rocks
- Zv]vPoZv[t hydraulic plate pushed down onto the ground, subject to strong vibration
o Producing seismic waves that go down to the ground
o Rocks with different hardness, density, types
o Enables us to see what is under the ground about 70km down
- Used to better understand the Canadian Shield
- Transects t cross-sections through the shield
- The earth has cooled down
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