types of plate boundaries

Question 1

what is a destructive (converging) plate boundary?

Answer 1

when two plates move towards each other due to convection currents

Question 2

what happens when an oceanic plate and continental plate converge?

Answer 2

1. the denser oceanic plate subducts underneath the continental plate
2. at the Benioff/subduction zone the oceanic crust melts into magma

Question 3

what is formed when an oceanic and continental plate converge?

Answer 3

• deep ocean trench
• volcano
• earthquake
• fold mountains

Question 4

why do fold mountains continue to grow?

Answer 4

plates are constantly moving

Question 5

what happens when two oceanic plates converge?

Answer 5

1. the denser oceanic plate subducts underneath the less dense oceanic plate
2. at the Benioff zone, the denser oceanic crust melts to magma

Question 6

what forms when two oceanic plates meet?

Answer 6

• underwater volcano
• island arcs
• deep ocean trench

Question 7

what happens when two continental plates converge?

Answer 7

1. neither of them subducts as they’re always of the same density
2. a collision margin occurs
3. there will be some subduction if there are faults in the crust

Question 8

what is formed when two continental plates converge?

Answer 8

1. High-fold mountains, e.g. the Himalayas
2. earthquakes

Question 9

what is a constructive (diverging) plate boundary?

Answer 9

when two plates are moving apart due to convection currents

Question 10

what occurs at a constructive plate boundary?

Answer 10

1. magma will rise in the gap between the plates
2. this may cool to form a new crust or erupt as a volcano
3. seafloor spreading may occur

Question 11

what is formed at a constructive plate boundary?

Answer 11

• mid-ocean ridge, e.g. mid-Atlantic ridge
• when the ridge rises to sea level, new islands are made
• regular breaks (transform faults) that cause minor earthquakes
• regular volcanic eruptions (submarine volcanos)
• rift valleys (steep-sided valleys where crust is stretched and pulled apart)

Question 12

what is a transform (conservative) plate boundary?

Answer 12

where two plates are moving alongside each other due to convection currents

Question 13

what happens at a transform plate boundary?

Answer 13

1. two plates move past each other causing a build-up of stress and friction

Question 14

what occurs/forms at a transform plate boundary?

Answer 14

• shallow focus powerful earthquakes due to the release of pressure
• transform faults also cause earthquakes

Question 15

what are convection currents?

Answer 15

occurring in the mantle in circular motions, heating as they rise to the crust due to heat from the core and cooling as they fall, causing plates to move.