Yousef+and+Dana-PLate+tectonics

Continental Drift Theory

 * Pangea
 * Coasts of continents fit together i.e South America and African coasts
 * Fossil evidence: Same ancient plants and animals found on seperate continents i.e[[image:pangea.jpg width="217" height="246" align="right"]]
 * 1) Cynognathus: found on South America and Africa
 * 2) Mesosaurus found on South America and Africa
 * 3) Lystrosaurus found in Africa India and Antarctica
 * 4) Glossopteris plants found on **all** continents
 * Rock evidence: Appalacian, British isle, and Scandinavian moutains all line up
 * Climate evidence: Glaciers on parts of South America, Africa, India, and Australia lined up and tropical swamps in the North hemisphere line up in Europe, U.S. and Asia.
 * 13 Tectonic Plates
 * Continental fit
 * Oceanic Ridges-**
 * New evidence 20th century for Continental Drift Theory
 * 1) Boats: Radar System
 * Rift Valley discovered in the length of the mid-Atlantic ridge
 * Tensional forces are at work along the Ridge
 * Magma rises from the rift valley and creates new ocean floor, only 200 million years old
 * Harry Hess: Sea-floor spreading Theory- ocean ridges are located above upwelling proportions of large convection cells in the mantle
 * Sea floor renewed new spreads in old oceanic crust moves to mantle

"The earth generates its own magnetic field which periodically flips polarity over thousands of years. Paleomagnetism, the magnetic field and polarity found in ancient rock strata shows this flip has occurred throughout the history of our planet. Scientists report that such a polarity reversal may happen in the near future as the strength of earth’s magnetic field has been declining. Sometimes the field completely flips. The north and the south poles swap places. Such reversals, recorded in the magnetism of ancient rocks, are unpredictable. They come at irregular intervals averaging about 300,000 years; the last one was 780,000 years ago. Are we overdue for another? No one knows." [|-source one], [|source two], Plate Tectonics packets #1,2,3
 * Paleomagnetism-**
 * Like a bar magnet Earth has magnetic north and south
 * Invisible lines of force pass through Earth extending from one pole to another
 * After a volcanic explosion magma that cools below a "Curie Point"(580 degreesC) the iron in it become magnetized and point toward the existing north pole
 * When scientist look at old lava flows they see thata the alignment varies, this is because of polar wandering and continental drift
 * References**