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Lecture 9

Lecture 9 Notes

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Department
Environmental Science
Course Code
EESA06H3
Professor
Nick Eyles

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Lecture 9
Alpine-himalayan orogeny: the building of the next supercontinent (Pangea II)
Obduction: the process whereby we collide continents together. Theres no subduction
(destroying crust) involved so theres not volcanoes, but theres lots of earthquakes.
Most of the continents originated as small crustal pieces about the size of a province
in Canada then the obducted together into larger masses.
Relationship between tectonics and climate: tectonic processes can change climate on
much larger time scales. The geology of Canada would be much different if it wasnt
for the major orogenic belt, its formation changed global climates and led to the
cooling over the climate. It was climate changes in east Africa which promoted
human development, and allowed humans to leave Africa, this climate change was
caused by alpine Himalayan orogeny.
History doesnt repeat itself but it often rhymes: earths history is a succession of
super continents. We are just about in the maximum extent of that process, the
atlantic ocean will start to close, the pacific is already closing.
Slide 4: Plate map red arrows show which direction the plates are moving in and the
length shows the velocity. Parts of the pacific plate are moving quite fast headed
right for Japan. Everything is headed towards south east Asia.
Slide 5: Figure 2.29 in text book: it does into obduction and shows cross sections.
Before india collided with asia there was an ocean the Himalayas were created from
this obduction. Earthquake in Burma was the result of India being driven north. Its
pushing into the Asian continent and spreading it as well, so youll see the little
ladders, this is where the spreading is going on, there is also rift basins. The most
important thing to get out of this diagram is that the effects of India being driven up
are felt over a very large area; we can see that Afghanistan and Pakistan as well as
southeast Asia are escaping.
Slide 6: the collision started about 24 million years ago, this diagram shows a
timeline, we can see the other Asian crust trying to escape, there is a subduction
zone down by Indonesia. The mediteranian is a remnant of the ocean that lay
between Africa and Europe, near India the ocean is completely gone, the
Mediterranean is still there but it will be gone once Africa continues to collide with
Europe, resulting mountain range is the Swiss/French/Austrian alps.
Slide 7: the most common type of rock will be high grade metamorphic rocks, gneiss,
high temperature. If you drive up north in Ontario you will see the roots of an old
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mountain chain, a north of barrie, drive through gneiss rocks that are very deeply
buried. Granite has a high content of silica (very acidic opposite of basalt) melt large
area of gneiss produce granite, may get what we call rhyolite produced, highly
explosive volcanism, but by and large you arent melting crust on a large scale
because theres no subduction. We do not see volcanoes in obduction zones, no
volcanoes in the Himalayas. On either side of the Himalayas we get fold and thrust
belts, this is where the cover rocks sitting on top of the continental rocks
(dominantly sedimentary) have been shoved, they’ve been put in a huge vice and
squeezed. There will be a lot of oil and gas in these belts, because youve got the right
structures to trap hydro carbon. This process welds to formally separate pieces of
continental crust together. Just beyond this weld youll see ophiolite (remnants of
oceanic crust; green rocks result from metamorphism of basalts) basalt that has
erupted under water pillows (pillow basalts).
Slide 9: People can actually build pieces of equipment and model what happens
during obduction, you can see the initial indent and the chinese southeast Asian
area trying to escape from that. Eathquakes in china are the result of India moving
north.
Slide 10: shows complete Alp Himalayan orogeny, some people argue that it
continues down through the arc down to new guinea. Orogeny describes the process
of mountain building. Orogen is the name given to the rocks that result, this
diagram shows the orogen. Alpine-himalayan orogeny.
Slide 11: closure of the Tethys ocean as Pangea breaks up, this is basically the end of
Pangea, it had a crudely C-shaped mass, southern continents called gondwana.
Right in the heart of the C is the Tethys ocean, there is a long history before this are
blocks rifting off of Australia being carried north and then colliding with laurasia.
India and Antarctica are separated by a mid ocean ridge, pushes india was to the
north, then Australia also moves away and the ocean is destroyed.
Slide 12: fig 229: subduction on the far right (top figure) this is the simarian
orogeny (sp?) its subduction because were subducting the ocean floor, ocean crust
subducts below continents (more dense). And then top left india finally collides and
we get the obduction phase. Foreland basin: when we have high mountains its a
considerable load on the softer rocks that we call the asthenosphere (means weak
sphere in greek) its the softer plastic rocks over which the plates move, without this
we would be fixed. When we have these huge mountains (think of it as a giant
iceberg) it depresses more than india and we get these broad foreland basins, this is
important when we look at the Appalachians or rocky mountains (next week) very
important because we have shallow sea waves sometimes invade, we get deltas down
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Description
Lecture 9 Alpine-himalayan orogeny: the building of the next supercontinent (Pangea II) Obduction: the process whereby we collide continents together. Theres no subduction (destroying crust) involved so theres not volcanoes, but theres lots of earthquakes. Most of the continents originated as small crustal pieces about the size of a province in Canada then the obducted together into larger masses. Relationship between tectonics and climate: tectonic processes can change climate on much larger time scales. The geology of Canada would be much different if it wasnt for the major orogenic belt, its formation changed global climates and led to the cooling over the climate. It was climate changes in east Africa which promoted human development, and allowed humans to leave Africa, this climate change was caused by alpine Himalayan orogeny. History doesnt repeat itself but it often rhymes: earths history is a succession of super continents. We are just about in the maximum extent of that process, the atlantic ocean will start to close, the pacific is already closing. Slide 4: Plate map red arrows show which direction the plates are moving in and the length shows the velocity. Parts of the pacific plate are moving quite fast headed right for Japan. Everything is headed towards south east Asia. Slide 5: Figure 2.29 in text book: it does into obduction and shows cross sections. Before india collided with asia there was an ocean the Himalayas were created from this obduction. Earthquake in Burma was the result of India being driven north. Its pushing into the Asian continent and spreading it as well, so youll see the little ladders, this is where the spreading is going on, there is also rift basins. The most important thing to get out of this diagram is that the effects of India being driven up are felt over a very large area; we can see that Afghanistan and Pakistan as well as southeast Asia are escaping. Slide 6: the collision started about 24 million years ago, this diagram shows a timeline, we can see the other Asian crust trying to escape, there is a subduction zone down by Indonesia. The mediteranian is a remnant of the ocean that lay between Africa and Europe, near India the ocean is completely gone, the Mediterranean is still there but it will be gone once Africa continues to collide with Europe, resulting mountain range is the SwissFrenchAustrian alps. Slide 7: the most common type of rock will be high grade metamorphic rocks, gneiss, high temperature. If you drive up north in Ontario you will see the roots of an old www.notesolution.com
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