The restless earth

• The Theory of Continental Drift proposes that the original land surface of the earth fractured and drifted for over 200 million years across the earth's surface, forming the continents.
• The Theory of Thermal Convection explains the process of Global Crustal Plate Movement.
• Water that is boiled in a saucepan expands and rises.
• As water rises it cools, flows sideways and sinks, repeating the process over again.
• Plates move in exactly the same way as water in a saucepan.
• Hot rock rises from within the earth to the surface.
• The hot rock cools, flows sideways and sinks, dragging the lithosphere with it, this is the Theory of Thermal Convection.
• The Theory of Thermal Convection was put forward by Alfred Wegner, a German meteorologist in 1915.
• Fossils of animals that could not have swam across oceans have been found in different continents, indicating that the continents were once all joined together and that the animals could walk from one continent to another.
• The species dispersed when the continents were connected and later carried to their present positions when the continents drifted.
• A fern, glossopteris, was found on the continents of South America, Africa, India and Australia.
• If the continents are reassembled into Pangaea, the distribution of glossopteris can be accounted for over a much smaller geographic area.
• Wegner argued that the similarities in the shapes of the continents particularly the shapes of the African and South American coastlines were proof of his theory.
• Many mountain ranges on the different continents are of comparable age, similar structure and rock type e.g. the Appalachian mountains of the USA and the Caledonian mountains of Ireland, Britain and Scandinavia (Fold Mountains).
• Using this evidence he argued that the continents as we know them were all joined together forming a super continent, called Pangaea which was surrounded by an ocean, the lapetus Ocean.