Continental Drift

• In 1912, Alfred Wegener suggested all of the continents were once joined together in one supercontinent, called Pangaea, and over millions of years they drifted apart.
• Wegener’s evidence:

  • Coastlines of the different continents appeared to match and could fit together like jigsaw pieces - E.G. west coast of Africa and the east coast of South America.
• Wegener’s evidence:

  • Rocks that were the same age and made of the same minerals were found in different continents.
• Wegener’s evidence:

  • Fossils of various plants and animal species were found on different continent (opposite sides of huge oceans).
• Theory of the continental drift

  
• Wegener couldn’t prove his theory as he wasn’t able to explain how and why the continents had moved over such large distances.
• After 1950s, more evidence supported his idea:

  • Rock found in ocean floor was no older than 175 million years old, whereas rock found on land could be several billion years old.
• More evidence supporting:

  • Rock on the floor of the Atlantic ocean was found to be older as its signage from the centre of the ocean increased.
• More evidence supporting:

  • Analysis of the magnetism of rock on the ocean floor showed alternating patterns of magnetic direction.
• • Convection currents in the mantle were proposed by some scientists as an explanation for the plate movement.
• • The hot magma near the core rises while the cooler magma near the crust falls, creating a convection current that moves the tectonic plates.
• Convection currents in the mantle