Wegener’s Theory of Continental Drift Beth Roland Eighth Grade Science

Background of Wegener A German (1880-1930)who completed A Doctorate degree in Astronomy developed the theory of Continent- al Drift. His theory hypothesized that the continents were slowly drifting around the Earth. As he had no way of explaining how the continents moved, he theory was mostly dismissed.

Pangaea Pangaea Overview Pangaea- “all earth” the supercontinent that existed during the Paleozoic and Mesozoic eras about 250 million years ago, before the continents were separated into their current configuration. Panthalassa- “all sea” global ocean that surrounded the supercontinent Pangaea

180 MYA- Pangaea Splits Based on Wegener’s Reasearch, pangaea split Into 2 sub-continents; Laurasia (northern hemisphere) and Gondwana (southern Hemisphere)

65 MYA- subcontinents continue to subdivide Based on plate tectonic research, the image shows the approximate continent configuration that occurs as dinosaurs were becoming extinct

Sea Floor Spreading Throughout all of the Earth’s oceans we find mid-ocean ridges that cause the sea floor to spread outwards of the underwater mountain chains. As oceanic plates diverge away from each other, they create a separation or gap. This gap is quickly filled by magma rising from the Asthenosphere into the Lithosphere that contains the Earth’s crust.

Magnetic Polarity of Earth One major piece of evidence supporting sea floor spreading (further evidence of Wegener’s hypothesis) is the magnetic “fossilized minerals”; trapped in sections of the sea floor that occur around mid-ocean ridges. The Earth at certain intervals, has changed polarity. The magnetic minerals trapped in these sections are frozen in time and are aligned based on the magnetic polarity of the earth at the time. This record of magnetic reversals is the final proof that sea-floor spreading occurs.

Magnetic Reversals and Sea Floor Spreading