The Theory of Continental Drift (Now Plate Tectonics)
- Was devised by ____________________ in 1912
- The theory states that the earth is made up of about ___ giant rock
plates about ____km’s thick
- These plates ________ on the earth’s semi-molten asthenosphere (the
top layer of the earth’s mantle) and are driven by convection (______)
cycles in the mantle.
- __________ plates move about 10 cm/year
- _________________ plates about 2 cm/year
- It is believed that the plate movements have carried ______________
across the earth.
- It is believed that about 250 million years ago there was one large
continent called _____________.
- Gradually due to tectonic forces, Pangea broke into northern
_____________ and southern _____________________.
- It is believed that as the plates continue to move, in about 50 million
years, ___________ will break apart and some of ________________
will break apart and drift north.
Wegner’s Evidence to Support Continental Drift
1) _____________ - Many continents appear to fit together like a puzzle.
2) _____________ - He found similar fossils on different continents
which are currently far apart. (Africa & S. America)
3) _________________ – rock types and mountain ranges are similar on
different continents which are far apart.
(North America & Europe)
4) __________– Ice covered Africa, India, Australia and S. America
about 250 million years ago. Only possible if they
moved.
Additional Evidence to Support Continental Drift
1) Plate Movements – plate movements along plate boundaries
(Earthquakes, Volcanoes)