Lesson 5-Plate movement and plate boundaries

Question 1

Mechanisms for plate movement: Convection currents

Answer 1

• Therman convection currents generated in asthenosphere cause magma to rise towards the crust and then spread before cooling and sinking
  -this is the vehicle on which plates move

Question 2

Mechanisms for plate movement: Sea floor spreading

Answer 2

• Movement of two oceanic plates away from each other, results in formation of new oceanic crust above the Mid Ocean Ridge

Question 3

Mechanisms for plate movement: Ridge push and Slab pull

Answer 3

• Ridge push- newly formed rock ages and cools it becomes more dense, gravity causes this cooler, denser lithosphere to slide away from the ridge
• Slab pull- losses of heat from the lithosphere over time after it has formed casuses it to become cold and heavy so it sinks into asthenosphere and drags the rest of the plate with it

Question 4

Mechanisms of plate movement-Gravitational sliding

Answer 4

• Tectonic plates are raised up as they are hotter at constructive plate boundaries, it gradually cools with age and distance from the ridge
• Cool oceanic lithosphere is denser than the hot mantle material from which it comes from

Question 5

Oceanic-Continental collision

Answer 5

Oceanic crust is denser so it subducts into the asthenosphere, earthquake occurs at the Benioff zone.
-Viscous lava, Co2 is emitted
-Pacific ring of fire

Question 6

Oceanic-Oceanic collision

Answer 6

Older plate subducts, oceanic lithosphere partially melts forming andesitic magma
-rises through crust and creates volcanoes
-chain, island arc
-Mariana trench l

Question 7

Continental-Continental

Answer 7

Have the same density so neither subducts
-plates forced upwards, creating huge mountains: Himalayas
-some is forced down into mantle, forms mountain roots

Question 8

Oceanic-Oceanic (divergent)

Answer 8

Plates pull apart and leave space for rising magma that forms new ocean floor
-Islands with shield volcano activity

Question 9

Transform/Conservative

Answer 9

Made up of brittle rock that’s jagged so is difficult to slide
-gets stuck and pressure builds up and jerks forward
-San Andreas Fault on West Coast of North America
-potentially forms small mountains

Question 10

Transform faults

Answer 10

Constructive
-as the plates don’t pull apart evenly everywhere
-Mid Atlantic ridge
-forms rift valleys