Tectonics 1

Question 1

What is the plate tectonic theory? What does it explain?

Answer 1

• Earth 3-layered structure
• Earth’s litosphere broken up, huge pieces (tectonic plates)
• plates alwayz moving
• Plate movements -> landforms phenomena

Question 2

Earth’s structure

Answer 2

Crust, uppermost mantle, mantle, core

Question 3

What does Litosphere contain?

Answer 3

Litosphere = Tectonic Plate
- Crust, uppermost mantle

Uppermost mantle is Solid.

Tectonic Plates
https://docs.google.com/document/d/12rAwkWXiw5RGFDGpRY3RhY_ab2Cs2ZpI7u36Bog2OvM/edit Page 2

Question 4

Two categories of crusts and where they are found

Answer 4

• oceanic (seafloor)
• continental (continents)

Oceanic denser

Question 5

What does the asthenosphere contain?

Answer 5

Semi-solid Upper mantle

Question 6

What causes the athenosphere to be semi-solid?

Answer 6

Heat from core
causes rocks
Athenosphere melt

Semi-solid Upper mantle, Athenosphere same thing

Question 7

Core mantle crust temperature thickness

Answer 7

Core: 4400-6000deg, 3300km
Mantle: 1000-3700deg, 2900km
Crust: Lowest, 6-70km

Question 8

Describe what happens at divergent, convergent and transform boundaries

Answer 8

Divergent -> Plates move away from one another
Convergent -> towards
Transform -> slide past

Question 9

How does convection currents lead to divergent plate movement?

Answer 9

1. Heat from Earth’s core -> mantle material decrease, density
2. Mantle material rises surface
3. Rising convection currents spreads magma under plates, dragging them apart.
4. Mantle loses heat, sinks back towards core
5. material gets heated up again
6. repeat process

Question 10

How does slab-pull force contribute to convergent plate movement?

Answer 10

1. two plates converge, denser crust pulled down, gravity
2. subduct under less dense crust
3. sink under it’s own weight, pull down rest plate with it

Question 11

Subduction
- what is it?
- happens to what crust. why?

Answer 11

Happens to…?
Oceanic crust only.

Continental crust, 2 little density subduct

Descending under another plate

Question 12

Magma VS Lava

Answer 12

same thing except for location
Magma -> In the volcano
Lava -> Outside of volcano

Question 13

How is a Fold Mountain formed?

Answer 13

Two continental plate converges, buckles, folds, forming fold mountains

Question 14

Evidence of Seafloor Spreading. What does it show?

Answer 14

continuous formation, new crust at mid-oceanic ridge push older crust outwards,

pattern where
- Nearest, center mid-oceanic ridge, youngest
- Further away, progressively older

Pattern shows how new oceanic crust is created @ o-o divergence boundary

Question 15

What is Magnetic Striping?

Answer 15

• Zebra-like pattern strips, normal polarity rocks alternate alongside reversed polarity rocks
• symmetrical both sides

Question 16

Explain Normal Polarity in Earth

Answer 16

1. Earth has GN, GS, MN, MS
2. GN, GS does not change
3. Occasionally, Earth magnetic field reversed multiple times, alternating btwn normal, reverse polarity
4. MN points towards GN, MS points towards GS, normal polarity

Question 17

Why/How does Magnetic Striping occur

Answer 17

1. iron-rich lava erupts, center of ridge cools solidifies
2. forms basaltic (rich in iron) rocks, make up seafloor
3. Magnetic materials align towards Earth’s local magnetic field at that time
4. crust is pushed in both directions away from ridge when new lava erupts, solidifies and plates move apart
5. when polarity reverses rocks records it
6. over time, more lava move away from ridge due to divergence, forming (what is magnetic striping)

recording evi of polarity at that time

Question 18

1 Divergent Boundary example

Answer 18

North American, Eurasian Plate

Question 19

1 Convergent Boundary Example

Answer 19

Nazca, South American Plate

Question 20

What forms at o-o divergent plate boundaries?

Answer 20

• Mid oceanic ridges
• Volcanoes
• Rift valley
• Earthquake

Question 21

How does Mid-Oceanic Ridge + Oceanic Crust form?/ Desc seafloor spreading

Answer 21

1. Two oceanic plates move apart -> seafloor spreading
2. Decrease in overlying pressure, melt underlying mantle -> magma
3. Magma rises thru weak areas in crust, fills gaps caused by diverging plates
4. Lava cools, solidifies to form basaltic rocks
5. Rocks make up new oceanic crust -> mid oceanic ridge
6. over time, continuous formation, new crust at mid-oceanic ridge push older crust outwards

Mid oceanic ridge forms aft new oceanic crust

1. Heat from Earth’s core -> mantle material to decrease in density
2. Mantle material rises to surface
3. Rising convection currents spreads magma (melts due to increase overlying pressure) beneath plates, dragging them apart.

Question 22

Example of Mid-Oceanic Ridge

Answer 22

Mid-Atlantic Ridge

LINK
Recall the example for o-o divergence

Eurasian and North American Plate diverge

Question 23

What is formed in divergent c-c plate boundaries?

Answer 23

• Rift valley
• Volcanoes
• Earthquakes

Same As O-O diverge except for no mid-oceanic range

Question 24

Example of Rift Valley

Answer 24

East African Rift Valley

Question 25

Example of Oceanic Trench

Answer 25

Mariana Trench

Question 26

What forms at convergent oceanic-oceanic boundaries?

Answer 26

- Oceanic trench - Volcanoes - Earthquakes

Question 27

What forms at c-c convergence

Answer 27

- Fold mountains - Earthquakes

Question 28

Example of a fold mountain

Answer 28

Himalayas

Question 29

What forms at oceanic-continental convergent boundaries?

Answer 29

- Oceanic trench - Volcanoes - Fold mountains - Earthquakes

Question 30

what is a chain of volcanoes called?

Answer 30

island arc

Question 31

What forms at transform plate boundaries

Answer 31

- faults - earthquakes

Question 32

Example of fault

Answer 32

San Andreas Fault, USA ## Footnote North American Plate slide past Pacific Plate

Question 33

rift valley formation

Answer 33

1. 2 continental plates move apart 2. rocks fracture, form parellel faults 3. rock btwn faults collapses, form deep rift valley, steep sides 4. plates move apart, decrease overlying pressure, causing underlying mantle, melt -> magma 5. Magma rise thru weak area -> Earth surface, form volcano

Question 34

describe features of mid-oceanic ridge

Answer 34

- center, ridge, deep rift valley, steep sides - magma rise thru weak areas, crust -> surface, submarine volcanoes - successive eruptions, volcanoes break surface, ocean -> volcanic islands ## Footnote occurence of earthquakes

Question 35

describe o-o convergence (special features)

Answer 35

2. denser oceanic plate subducts under less dense plate 3. forms deep depression, oceanic trench 4. high pressure force out water, O crust, lower melting pt, **overlying** mantle, **overlying** mantle -> magma 5. form chain of volcanoes, volcanic island ## Footnote for subduction, always mention that oceanic trench is formed (deep depression)

Question 36

describe o-c convergence

Answer 36

1. oceanic plate collide w/ continental plate 2. denser oceanic plate subduct under continental plate 3. subducting O plate sink -> mantle, high pressure force water out of O crust, reduce mp of overlying mantle, melt overlying mantle -> magma 4. magma rise -> weak areas, crust, Earths surface 5. form volcanoes on continental plate 6. enormous pressure, plate boundary cause rocks, continental plate uplifted, form fold mountain ## Footnote friction along (subduction zone/diverging plate boundary) causes earthquake, occur

Question 37

describe a fault

Answer 37

1. stress caused by plate movement -> fault 2. one plate suddenly slips, another -> earthquake 3. magma does not rise -> surface, no volcano