Tectonic Boundaries

Question 1

Where does oceanic lithosphere get thinner?

Answer 1

crest of oceanic ridge system

Question 2

What is denser? Oceanic lithosphere or continental lithosphere?

Answer 2

oceanic

Question 3

How does the lithosphere respond to forces acting upon it?

Answer 3

bending or breaking

Question 4

Plates definition

Answer 4

broken down fragments of the lithosphere with irregular size and shape that are in constant motion relative to each other

Question 5

Difference btw a plate boundary and edge of a continent

Answer 5

plate can include all or part of a continent and part of an ocean basin

Question 6

Divergent plate boundaries

Answer 6

plates move apart, creating fractures, upwelling of asthenosphere and partial melting of mantle (release of pressure from plates moving apart), magma rises through fractures, solidifies at depth to thicken crust or to create new seafloor

Question 7

What happens to the lithosphere with transform plate boundaries

Answer 7

no production or destruction, just grinding

Question 8

What boundaries do eqs happen? volcanic activity?

Answer 8

all
divergent and convergent

Question 9

What kind of structure does divergent plate boundaries produce?

Answer 9

rift volcanoes

Question 10

What are deep ocean trenches

what are they offshore of

Answer 10

long linear depression offshore of continent or chain of volcanic islands

Question 11

what type of plate boundary produces trenches

Answer 11

2/3 types of convergent boundaries (ones with subduction)

Question 12

Subduction angles and age

Answer 12

old lithosphere is denser and less buoyant so it subducts at vertical angles, young lithosphere is less dense and more buoyant so it subducts at small angles

Question 13

symbol for divergent plate boundary

Answer 13

rectangle with lines sticking out

Question 14

OC Convergence

Answer 14

1. Oceanic crust is more dense (3.0g/cm^3) than cc (2.7 g/cm^3) so it subducts
2. depth of 100km, water crystals in oc triggers partial melting of the asthenosphere
3. the molten material (magma) is less dense bc the water lowered the melting temp and pressure
4. rises through fractures created when oc pushed and cracked cc
5. makes it to surface: continental volcanic arcs
   doesn’t make it to surface: thickens crust

Question 15

Where along boundaries are the trenches located?

Answer 15

oceanic lithosphere descends into mantle along subduction zones

Question 16

OO Convergence

Answer 16

Oceanic crust that’s more dense subducts
2. depth of 100km, water crystals in oc triggers partial melting of the asthenosphere
3. the molten material (magma) is less dense bc the water lowered the melting temp and pressure
4. rises
5. makes it to surface: volcanic island arcs

Question 17

EX of OO Convergence

Answer 17

japan

Question 18

CC Convergence
what causes it?

Answer 18

subduction of seafloor causes two landmasses to move towards each other
1. cc too buoyant to subduct so a collision causes an accumulation of sediments and sedimentary rocks along cont. margins
2. forms mt belts

Question 19

example of CC convergence

Answer 19

himalaya mts indian plate and eurasia

Question 20

Accretionary wedge

Answer 20

build up of sediment scraped off an oceanic plate by the overriding plate during subduction.

Question 21

Symbol for convergent boundary

Answer 21

triangles

Question 22

Where are transform boundaries found? what do they offset? what do they produce

Answer 22

ocean floor (fracture zones) or continental vs continental (san andres fault)
offset segments of the ridge system, step like plate margin

Question 23

Where do active transform faults lie? how are they generally defined

Answer 23

btw 2 offset ridge segments
weak, shallow eq (move in opp. directions)

Question 24

inactive zones

Answer 24

fractures are preserved direction of plate motion at time of formation (move in same direction)

Question 25

symbol for transfrom plate boundary

Answer 25

line

Question 26

Volcanic island arcs develop on what type of crust?

Answer 26

oceanic crust

Question 27

Why are volcanoes largely absent where two continental blocks collide?

Answer 27

Volcanoes are absent because there is no magma being created, this happen with 2/3 convergent boundaries