Class Notes Unit 6 Part 2

Question 1

What 4 things do convergent P.B result in the formation of?

Answer 1

1) earthquake zones
2) most of Earth’s volcanism that is visible
3) oceanic trenches
4) tectonic / orogenic Mountain belts

Question 2

What is the difference between mountains at CPB and DPB?

Answer 2

CPB are not the same that form at divergent plate boundaries–they are not tectonic / orogenic at DPB

Question 3

What are the 3 possible types of CPB collisions?

Answer 3

1) oceanic crust –> cont. crust
2) o.c. –> o.c.
3) c.c. –> c.c.

Question 4

What are the two types of volcanic arcs?

Answer 4

1. volcanic continental arcs (on land)

2) volcanic island arcs (sea)

Question 5

What are the 3 Earthquake benioff zones?

Answer 5

1-50 km…shallow
50-300 km…intermediate
300-670 km…deep

Question 6

Why is isostatic sinking important at CPB?

Answer 6

Because it makes more room for more stuff to be deposited

Question 7

What forms tectonic mountains–mountain belts we call orogens?

Answer 7

10-30 km thick piles of sediments and volcanics and intrusions are compressed and deformed.

Question 8

How long does the orogen deformation phase last?

Answer 8

~ 100 my

Question 9

___transformed into orogens.

Answer 9

Geosynclines

Question 10

What is the evolutionary sequence of orogeny?

Answer 10

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. …….

Question 11

What is the continent building process?

Answer 11

Sedimentary re-cycling plus additional volume through volcanic and intrusive rocks, partly derived from the mantle.

Question 12

Structural___causes mountains.___carves out individual structures.

Answer 12

• structural

- erosion

Question 13

When did most tectonic mountain building take place?

Answer 13

end of the Palaeozoic

Question 14

What is the key to the origin of continents?

Answer 14

plate tectonics is the key

Question 15

What are the 3 steps to the origin of the continents?

Answer 15

1) Continental breakup and continental growth
2) Continental accretion
3) Cratons and orogens

Question 16

What are the archean microcontinents?

Answer 16

S-R-H (Slave-Rae-Hearne Cratons)
N- Nain Craton
SC- Superior Craton

Question 17

How old are the rocks of areas microcontinents?

Answer 17

older than 2.5 Ga

Question 18

When was the orogeny of the THO (Trans-Hudson Orogen)?

Answer 18

Began in 1.9 and finished in 1.8 Ga

Question 19

What did the S-R-H, N, and SC collide to form?

Answer 19

THO

Question 20

What are the rock ages of the THO?

Answer 20

2.9 (uncommon)-1.8 (1.9-1.85, mostly) Ga

Question 21

What is an example of a stitching orogen?

Answer 21

the THO because all three microcontinents of the Archean formed North America 1.8 billion years ago.

Question 22

What created North America?

Answer 22

The collision of S-H-R, N, and SC to form THO

Question 23

What is the name of the ocean between S-H-R and SC?

Answer 23

Manikewan Ocean

-seperates Archean continents

Question 24

What are the other proterozoic orogens?

Answer 24

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

Question 25

Briefly describe the building of WO, YO, MO, and GO.

Answer 25

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.

Question 26

What happened 700 million years after the break up of Rodina and after erosion dumped stuff into the ocean?

Answer 26

Pangea assembled and formed Appalachian Orogen.

Question 27

When did Appalachian Orogen (AO) form?

Answer 27

450-250 Ma

Question 28

When did Cordilleran Orogen form?

Answer 28

150-50 Ma

Question 29

How did Cordilleran O. become tectonic mountain belt?

Answer 29

More accretion to North America. Erosion dumping sediment to western region of continent until cordilleran became tectonic mountain belt.

Question 30

The entire mantle is___.

Answer 30

convecting

Question 31

What causes divergence and subduction to occur? | *Don't even try to answer--just click it and read it several times*

Answer 31

-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.

Question 32

What happens with convecting CPB and DPB? (how are they related, what causes mantle plumes, what are mantle plumes)?

Answer 32

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.

Question 33

What distance does a plume advance each year?

Answer 33

several cm/yr

Question 34

What does the processes involved inflate tectonics create?

Answer 34

Most of the important physical features that occur at the earths' surface, and the affects humans.

Question 35

What happens as each plate moves?

Answer 35

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

Question 36

What is cratoniztion?

Answer 36

geosynclines --> orogens --> carton

Question 37

What is volume added to the continental crust from? What is this due to?

Answer 37

Volume added to continual crust (sial) through volcanism and intrusion due to melting of mantle and subjecting slab.

Question 38

___of sialic material with cont. crust / oceanic crust.

Answer 38

recycling

Question 39

What is the supercontinent cycle?

Answer 39

- 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

Question 40

``` Pangea = ~___Ma Rodina = ~___Ga Ur = ~ ___Ga ```

Answer 40

200-300 Ma 1. 0 Ga 3. 0 Ga

Question 41

How deep are most ocean trenches

Answer 41

8-12 km deep

Question 42

How deep will subduction go?

Answer 42

600 km max