Transcript Plate Tectonics - Noadswood Science

Plate Tectonics
L.O: To understand how tectonic
plates move and the theory of
continental drift.
http://www.bbc.co.uk/news/world-asia-pacific12709598
Boxing Day Tsunami – 2004. Can you
explain what caused it?
http://news.bbc.co.uk/1/hi/world/4136289.stm
http://www.youtube.com/watch?v=T1cES1Ekto
An old theory about the continents
and surface of the earth
• Mountains, continents and volcanoes were formed as
a result of the shrinking of the crust as the earth
cooled. A bit like cooling custard
• Earthquakes were an action of
God.
Wegener’s hypothesis on continental drift
The coastlines of South America and
Africa look like they used to fit
together, over time all of the
continents have moved apart
Alfred
Wegener
Try to make the jigsaw by joining the
continents together. What other evidence is
there that the continents used to be joined
up?
Tectonic theory
People once thought that the oceans and the continents were formed by
shrinkage from when the Earth cooled down after being formed.
Alfred Wegener proposed something different. People didn’t believe him
because he couldn’t prove it, so he had to find some evidence:
These continents look
like they “fit” together.
They also have similar
rock patterns and fossil
records. These are the
two pieces of evidence
that led me to believe
that there was once a
single land mass. This is
my TECTONIC THEORY.
Wegener had trouble convincing people
his theory.
The continents fit together and have similar
fossils; they must have once been joined.
Perhaps they moved apart because of tidal
forces and the earths rotation.
Impossible! continents can’t move the force
needed would be so big it would stop the
earth rotating. They have the same fossils
because there must have once been land
bridges that joined them. The land bridges
must have been flooded over time.
Sort out the other scientists opinions into for
and against Wegener’s theory
The Evidence:
Tectonic theory
1) Some continents look like they used to
“fit” together
2) Similar rock patterns and fossil records
The Problems:
Wegener couldn't explain how continental drift
happened so nobody believed him
The Answer:
1) Scientists discovered 50 years later that the Earth generates massive
amounts of heat through radioactive decay in the core. This heat
generated convection currents in the mantle causing the crust to move
2) We also now know that the sea floor is spreading outwards from plate
boundaries
Conclusion – scientists now believe Wegener’s Tectonic Theory
Continental Drift
Crossword