how plates move

Question 1

solid convection

Answer 1

known because s-waves don’t travel through liquids
asthenosphere seismic waves slow down = evd of 1% liquid allowing movement of lithosphere plate
radio active decay and reduced pressure in core heats mantle
warm mantle = rock less dense
madam rises

Question 2

ridge push

Answer 2

constructive plate margins
magma squeezes through and fractures crust
rock is pushed aside
older, colder and more dense plate is subjected (oceanic)

Question 3

slab pull

Answer 3

plate subduction aided by gravity
slow rate of movement at subduction zone
main plate driving force but where ineffective ridge push is important