Types of Plate Boundaries

Question 1

What are the diff. types of plate boundaries?

Answer 1

• destructive (convergent): towards each other
• collision (convergent): towards each other
• constructive/divergent: away from each other
• conservative/transform: parallel to each other

Question 2

What happens at a divergent (constructive) plate boundary?

Answer 2

[O-O]:
- magma rises from gap left by 2 plates separating, forming new land (sea floor spreading)
- less explosive underwater volcanoes (ocean ridges) formed

[C-C]:
- any land in middle of separation is forced apart, causing a rift valley
- volcanoes form where magma rises
- eventually gap fills w water + separates from main island
- magnetic stripes record polarity at time of creation

Question 3

What happens at a conservative (transform) boundary?

Answer 3

Between any crust:
- parallel plates move in diff. directions/at diff. speeds
- no landforms created as no plates destroyed
- when plates move lots of pressure builds up
- on C crust, fault lines may occur where ground is cracked by movement

Question 4

What happens at a convergent (destructive) plate boundary?

Answer 4

[C-O]:
- denser O plate melts as subducts under C leaving a deep ocean trench
- fold Mts. occur when sediment is pushed up during subduction
- xtra magma created, causes pressure to build up: forces magma through faults in C plate forming composite volcanoes

[O-O]:
- heavier plate subducts leaving an ocean trench. fold Mts. occur
- built up pressure causes volcanoes underwater to burst through O plate
- lava cools + creates island arcs

Question 5

What happens at a convergent (collision) boundary?

Answer 5

[C-C]
- both plates less dense than O so lots of pressure builds
- causes C crust to pile up to form fold Mts. on top of lithosphere

• e.g. Himalayas formed by collision of Eurasian + Indian plates