plate tectonic theory

Question 1

continental drift theory date

Answer 1

1912

Question 2

continental drift evidence

Answer 2

jigsaw fit
geology and living species similar on opposite sides of world
climate conditions similar

Question 3

sea floor spreading date

Answer 3

1950s
Harry hess 1962

Question 4

sea floor spreading theory

Answer 4

proposed that new oceanic crust forms as a result of volcanoes at mid-atlantic ridges (seafloor moves apart) and sonar technology supports this as mountain ranges were mapped in oceanic areas

Question 5

palaeomagnetism date

Answer 5

1960s

Question 6

palaeomagnetism theory

Answer 6

every 400,000 years there are reversals in earth’s magnetic field (recorded through iron oxide)
sea floor mirrors each other on either side of divergent plate boundaries (indication crust is created + continents drift)

Question 7

slab pull date

Answer 7

2010s

Question 8

slab pull rules (3)

Answer 8

1 - gravity pulls plate in to mantle
2 - angle of subducting plate directs convection currents downwards
3 - plate breaks off and sinks into mantle creating ‘trench suction’

Question 9

ridge push definition

Answer 9

oceanic litosphere slides down the sides of oceanic ridges due to gravity, contributing to plate movement

Question 10

convection current definition

Answer 10

magma is heated by the outer core, so it rises as the density decreases, magma is very viscous so the litosphere is moved. magma cools and sinks as it becomes dense

Question 11

evidence for plates floating

Answer 11

narzca plate moves 10cm per year
mantle moves 5cm per year

Question 12

ideas today about plate tectonic

Answer 12

the litosphere is cut into continental plates that are able to move
earth’s crust is recycled through tectonic processes
geological events occur at plate boundaries