Ch. 17 Sec. 1 Drifting Continents

Early Observers Mapmakers were the first people to consider the idea of moving landmasses in late 1500’s Abraham Ortelius noticed a fit of continents Believed that continents were separated by earthquakes and floods

Continental Drift Theory Proposed by Alfred Wegener Theory proposes that all the continents were once joined together as a single landmass Pangaea, Greek word meaning “all Earth” Broke apart about 200 million years ago Continents look like puzzle pieces

Theory Evidence Rock Formations At separation, large land masses would have broken apart Mountain ranges Noticed that Appalachian Mts. & rocks in Greenland were similar

Theory Evidence Fossils Similar fossils from plants and animals found on different continents 1) Land dwelling animals could not have swam a great distance Kannemeyrid and Labyrinthodont 2) Mesosaurus, which is a fresh water reptile, could not have survived the salt water swim 3) Glossopteris, a fern in tropical weather, is found on lower continents proving that they were once closer together

Fossils

Theory Evidence Climatic Evidence Coal deposits found on Antarctica Coal form from dead swap plants from wet and spongy areas Glacial deposits in Africa, India, and Australia

Rejected Hypothesis Two Flaws First Second Scientists did not believe that there couldn’t be enough force to move a continent Second Continents could not push through the ocean floor Crustal rock way to brittle