Class Notes Unit 6 Part 2 Flashcards
What 4 things do convergent P.B result in the formation of?
1) earthquake zones
2) most of Earth’s volcanism that is visible
3) oceanic trenches
4) tectonic / orogenic Mountain belts
What is the difference between mountains at CPB and DPB?
CPB are not the same that form at divergent plate boundaries–they are not tectonic / orogenic at DPB
What are the 3 possible types of CPB collisions?
1) oceanic crust –> cont. crust
2) o.c. –> o.c.
3) c.c. –> c.c.
What are the two types of volcanic arcs?
- volcanic continental arcs (on land)
2) volcanic island arcs (sea)
What are the 3 Earthquake benioff zones?
1-50 km…shallow
50-300 km…intermediate
300-670 km…deep
Why is isostatic sinking important at CPB?
Because it makes more room for more stuff to be deposited
What forms tectonic mountains–mountain belts we call orogens?
10-30 km thick piles of sediments and volcanics and intrusions are compressed and deformed.
How long does the orogen deformation phase last?
~ 100 my
___transformed into orogens.
Geosynclines
What is the evolutionary sequence of orogeny?
1) Erosion of pre-existing land mass and volcanism
2) deposition of sediment
- plate collision
5) uplift
6) orogeny
7) erosion of uplifted rocks
8) deposition
etc. …….
What is the continent building process?
Sedimentary re-cycling plus additional volume through volcanic and intrusive rocks, partly derived from the mantle.
Structural___causes mountains.___carves out individual structures.
- structural
- erosion
When did most tectonic mountain building take place?
end of the Palaeozoic
What is the key to the origin of continents?
plate tectonics is the key
What are the 3 steps to the origin of the continents?
1) Continental breakup and continental growth
2) Continental accretion
3) Cratons and orogens
What are the archean microcontinents?
S-R-H (Slave-Rae-Hearne Cratons)
N- Nain Craton
SC- Superior Craton
How old are the rocks of areas microcontinents?
older than 2.5 Ga
When was the orogeny of the THO (Trans-Hudson Orogen)?
Began in 1.9 and finished in 1.8 Ga
What did the S-R-H, N, and SC collide to form?
THO
What are the rock ages of the THO?
2.9 (uncommon)-1.8 (1.9-1.85, mostly) Ga
What is an example of a stitching orogen?
the THO because all three microcontinents of the Archean formed North America 1.8 billion years ago.
What created North America?
The collision of S-H-R, N, and SC to form THO
What is the name of the ocean between S-H-R and SC?
Manikewan Ocean
-seperates Archean continents
What are the other proterozoic orogens?
WO - Wopmay Orogen 1.9-1.8 Ga
YO - Yavapai O. 1.8-1.7 Ga
MO - Mazatzal O. 1.7-1.6 Ga
GO - Grenville O. 1.2-1.0 Ga
Briefly describe the building of WO, YO, MO, and GO.
After the 3 microcontinents collided, erosion dropped sediment off to the south side they formed orogenic belt (YO) followed by MO. This as a kind of accretion. Then, through erosion, deposition, geosynclines formed and Rodina came to be. Collision of these continents produced GO. Rodina then broke up.
What happened 700 million years after the break up of Rodina and after erosion dumped stuff into the ocean?
Pangea assembled and formed Appalachian Orogen.
When did Appalachian Orogen (AO) form?
450-250 Ma
When did Cordilleran Orogen form?
150-50 Ma
How did Cordilleran O. become tectonic mountain belt?
More accretion to North America. Erosion dumping sediment to western region of continent until cordilleran became tectonic mountain belt.
The entire mantle is___.
convecting
What causes divergence and subduction to occur?
Don’t even try to answer–just click it and read it several times
-Uplift of plume –> creates too slope
-Gravity takes over and if cracks and faults form gravity can pull them down the slope –> plate sliding
-As it is being arched up, cracks fill with magma which helps to widen cracks –> will push rocks away from divergent plat boundary –
Ridge push
- Lithosphere now unstable
-drag between lithosphere and stuff above
-Sheet may detach from continent
-As it cools –> dense and will sink (involves cool lithosphere and asthenosphere)
-Ends up going down and finish convective sell.
What happens with convecting CPB and DPB? (how are they related, what causes mantle plumes, what are mantle plumes)?
CONVECTION CELL
-More than heat flowing, rock is flowing which forms the orogens called mantle plumes which causes Divergent Plate Boundary. When they go down again, they form Convergent Plate Boundary.
What distance does a plume advance each year?
several cm/yr
What does the processes involved inflate tectonics create?
Most of the important physical features that occur at the earths’ surface, and the affects humans.
What happens as each plate moves?
The continents on it change their location, thus their climate and other environmental factors that affect organic life–and is a factor in organic evolution
What is cratoniztion?
geosynclines –> orogens –> carton
What is volume added to the continental crust from? What is this due to?
Volume added to continual crust (sial) through volcanism and intrusion due to melting of mantle and subjecting slab.
___of sialic material with cont. crust / oceanic crust.
recycling
What is the supercontinent cycle?
- All of many contents collide forming large (or a single) continents – break up later on – cont. crust/cont. crust.
- “stitching” and “accretion”
- Really just a plate-tectonic driven megascale recycling – no volume added
Pangea = ~\_\_\_Ma Rodina = ~\_\_\_Ga Ur = ~ \_\_\_Ga
200-300 Ma
- 0 Ga
- 0 Ga
How deep are most ocean trenches
8-12 km deep
How deep will subduction go?
600 km max
