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Continental Drift Theory

Deondre Ng - dmartinng Kyle Kua - kylekua Peter Fainsan - zeta99

I. Discovery
 * Alfred Wegener - A German meteorologist
 * Proposed 1912
 * He realized that the plates on each ends of the Atlantic Ocean looks like the fit together (ie. Africa and South America).

II. The Theory

1. His theory was that parts of the crust slowly drifts atop a liquid core. Pangaea, the supercontinent, broke down in time into our continents and islands today. He also said that Pangaea was floating on solid basalt, but later, he was proven wrong about the it.

2. Earth's Plates 2. Fossils
 * 200 Million Years Ago
 * Wegener hypothesized that 200 million years ago, the world was one giant supercontinent thus he called it Pangaea for it meant "all-earth". It later split into Laurasia and Gondwanaland during the Jurrasic Period and it split further more during the Cretaceous Period to continents similar to our present ones.
 * Present
 * Our present world now has 7 continents. Namely Asia, Europe, Africa, North America, South America, Antartica and Australia.
 * Fossils gave a very important role in this theory, see "evidences" below for more details.

III. Evidences 1. Rocks match 2. Match in glacial form 3. Shape of coastlines match 4. Plants and animals match
 * Rocks are the same kind like in America, Africa, India, and Australia.
 * They are also connected properly.
 * Continental ice sheet covered parts of the world 300 years ago.
 * Found in South America, South Africa, India, and Australia
 * Resultant glacial landforms exist in parts of the world.
 * These parts are covered in ice.
 * An example is U-shaped valleys.
 * When connected South America and the west of Africa fit nicely
 * Fossil records match.
 * Late Paleozoic seed ferns found in Gondwanaland.

IV. Controversies/Issues
 * Geologists are having a hard time believing that the earth's crust can simply just separate and move about just like that.
 * The magnetic pattern of underwater volcanoes at the mid-sea crust suggest that if ever the plates do move, it's fast and not in a slow and "takes millions of years" kinda thing that Wegener proposed.
 * Scientists don't believe that there is such a force that can move the continents apart. The mechanism Wegener presented which was about tidal argument and centrifugal force was not strong enough to move the continents.
 * Some scientists thought that the reason why there were similar fossils and resources was because of land bridges and not the Pangaea.

V. Continental Drift vs Plate Tectonic Theory
 * Continental drift theory talks more about that the present-day continents, were once together.
 * The plate tectonic talks more about the plates which the lands are on are the ones having the seismic actions.

VI. Sea Floor Spreading
 * This happens when two plates drift/move apart and forms a gap then magma rises to cover that gap and cools down into new edges of the two plates. The magma continues the moving and it flows out and cools down because of the water. This creates a oceanic ridge and the folded parts of the 2 plates create mountains.
 * As this happens, the ocean floor gets bigger and the plates too. Meanwhile, other plates become smaller and melt back to the Earth which is called subduction.
 * One example of an oceanic ridge is the Mid-Atlantic Oceanic Ridge.

VII. Check-up Quiz 1. What is continental drift theory? 2. Give 3 evidences of the continental drift theory? 3. What is Gondwanaland made up of? (what countries) 4. What is the difference between continental drift theory and plate tectonic theory? 5. Who discovered continental drift theory? 6. When was it discovered? 7. What is sea floor spreading? 8. What is Pangaea? 9. What are the two continents in the Jurrasic period? 10. What is bigger: Pangaea or Gondwanaland?

VIII. Breakthrough

The plate tectonic theory, which is the theory that is mostly accepted, arose from the creation of the continental drift theory. After further studies of the continental drift, they stumbled upon the fact that it's the plates that are moving, and not simply the continents. Sea floor spreading also aided the dawn of the plate tectonic theory.

IX. Sources [] [|www.njc.edu.sg/ip/IS/IS1105_Lesson_2.ppt] [] [|http://www.christiananswers.net/q-aig/aig-c001.htmlhttp://www.scientus.org/Wegener-Continental-Drift.html] http://www.infoplease.com/ipa/A0001765.html http://library.thinkquest.org/17457/platetectonics/4.php http://www.britannica.com/EBchecked/topic/463912/plate-tectonics