Label the Earth
What are the broken sections of the Earth’s crsut and upper mantle that move called?
What type of currents allow these sections of crust and upper mantle to move?
How are the currents that move the plates made?
Radioactive processes in the core
At what speed do the plates move?
Few centimetres a year
Where do earthquakes and volcanoes occur?
At the edges of the plates or plate boundaries
Why do earthquakes occur?
Movement of plates causes stresses and strain to build up between the plates, then they suddenly move.
Why can scientists not accurately predict earthquakes or volcanoes?
Can’t see under the crust
Describe the early ideas about how the mountains were formed.
Earth cooled and contracted, shrinking and causing wrinkling on the surface
Give 3 pieces of evidence that Wegener had observed that supported his ideas of continental drift.
On opposite sides of the Atlantic:
Similar ancient rocks
Very similar fossils
Shapes fitted on the coastline
What is continental drift?
All the continents were once a supercontinent and it broke up and the continents had slowly moved apart
Give 3 reasons why did the other scientists not accept his ideas at the time?
No evidence of how the continents moved
Other explanations eg land bridge
He was not a geologist
Why do scientists now accept his ideas?
New evidence on the ocean floor explained how the crust can move – plate tectonics