Earth’s Structure

1. Earth’sStructure Part II Continental Drift

2. Continental Drift • Leonardo da Vinci and Sir Francis Bacon wondered about the possibility of the American and African continents having broken apart, based on their shapes. Early Observations Leonardo Sir Francis Bacon Edward Suess an Austrian in 1885 proposed a super continent by studying fossils, rocks, and mountains and suggested it be called Gondwanaland. Alfred Wegener, a German meteorologist, is credited with the hypothesis of continental drift as demonstrated in a 1912 scientific presentation. A book was published in 1915. Edward Suess Alfred Wegener The real Bacon

3. Continental Drift Early Observations • Wegener proposed that all landmasses were originally united into a supercontinent he named “Pangaea” from Greek meaning “all land”. • Shorelines of continents fit together. • Mountain ranges and glacial deposits match up when continents are united into a single landmass • He presented a series of maps showing the breakup of Pangaea. • He amassed a tremendous amount of geologic, paleontologic, and climatologic evidence

4. Continental Drift Evidence The four main lines of evidence supporting the idea that continents had drifted. • Geographic fit of continents • Fossils • Mountain Ranges • Glaciation

5. Continental Drift Evidence Geographic Fit • Continents seem to fit together like pieces of a puzzle

6. Pangea 220 million years ago Pangaea is one land mass surronded by the Panthalassa ocean. Geographic Fit Panthalassa 200 million years ago The growth of the Tethys Sea begins to split Pangaea in Gondwanaland and Laurasia. Laurasia Tethys Sea India Gondwanaland 135 million years ago The South Atlantic Ocean begins opening up splitting Gondwanaland into Africa and South America. India drifts lazily towards Asia. Africa India North Atlantic Europe South America South Atlantic Asia 40million years ago Australia and Antarctica drift apart. Laurasia breaks apart into North America and Europe as the North Atlantic Ocean opens up. North America Australia Antartica

7. Continental Drift Evidence Fossils • Similar distribution of fossils such as the Mesosaurus

8. Continental Drift Evidence Fossils Fossils remains of Cynognathus, a Triassic land reptile approximately 3 m long, have been found in Argentina and southern Africa. Fossils of the fern Glossopteris are found in all of the southern continents adding proof that these were all joined in the past as these seeds are to large to be transported far by the wind. Remains of the freshwater reptile Mesosaurus have been found in both Brazil and Africa Evidence of the Triassic land reptile Lystrosaurus have been found in Africa, Antarctica and India.

9. Continental Drift Evidence Mountains • Mountain ranges match across oceans

10. Continental Drift Evidence Geological Formations of the same period match up across thousands of miles of ocean.

11. Continental Drift Evidence Glaciation • Glacial ages and climate evidence

12. Continental Drift Evidence Glaciation Large ice masses carve grooves in the rocks over which flow. Such masses tend to flow outward (generally downhill) from a central locality.

13. Continental Drift Evidence Jigsaw-puzzle fit of continents Glacial evidence Matching fossils across oceans Matching mountain ranges and rock formations

14. Continental Drift Perceived Problem with Continental Drift • Alfred Wegener presented all his research to other professionals in 1915. • Most geologists of the day (and the day after) did not accept the idea of moving continents. • There was no suitable mechanism to explain how continents could move over Earth’s surface. • Interest in continental drift only revived when • new evidence from studies of Earth’s magnetic field and oceanographic research showed that the ocean basins were geologically young features.