plate tectonics

Question 1

slab pull

Answer 1

destructive plate margins
denser crust is forced under continental crust
= sinking of edge of plate pulls rest of plate towards the plate boundary

Question 2

convection currents

Answer 2

mantle very hot so lower parts of asthenosphere heat up and rise
as get closer to crust them slow down as cooler and sink
circular movements drag on plates causing them to move

Question 3

gravitational sliding/ridge push

Answer 3

crust moves away from mid-atlantic ridge and cools, becomes denser
denser rock moves downslope

Question 4

sea-floor spreading

Answer 4

constructive plate boundaries
magma rises to fill gap and cools to form new crust
overtime this new crust is dragged apart and more new crust forms
= sea floor gets wider
(evidence from paleomagnetism)