Continental drift

Download Continental drift

Post on 10-Jun-2015

2.360 views

Category:

Education

2 download

Embed Size (px)

DESCRIPTION

project in evolution

TRANSCRIPT

<ul><li> 1. CONTINENTAL DRIFT</li></ul> <p> 2. Movement of the Earths continents relative to each other. 3. Abraham Ortelius(1596) </p> <ul><li>first put forward the hypothesis that continents drift </li></ul> <ul><li>In his work Thesaurus Geographicus suggested that the Americas were torn away from Europe and Africa by earthquakes and floods </li></ul> <p> 4. Alfred Wegener (1596) </p> <ul><li>Continents had once formed a single landmass before breaking apart and drifting to their present locations </li></ul> <ul><li>First use the phrase continental drift </li></ul> <p> 5. 6. Evidence that continents drift </p> <ul><li>Similar plant and animalfossilsare found around different continents shores, suggesting that they were once joined. </li></ul> <p> 7. Examples: </p> <ul><li>Fossils ofMesosaurus , a fresh water reptile rather like a small crocodile, found both in Brazil and South Africa </li></ul> <ul><li>Fossils of the land reptileLystrosaurus from rocks of the same age from South America, Africa and Antartica </li></ul> <p> 8. </p> <ul><li>fossils of theGlossopteris , an ancient fern, are found in South America, Africa, Antarctica, India, and Australia.</li></ul> <ul><li>It was hypothesized that such a distribution could only come about if the continents were all part of the one super-continent. </li></ul> <p> 9. 10. </p> <ul><li>The complementary arrangement of the facing sides of South America and Africa is obvious, but is a temporary coincidence. </li></ul> <p> 11. 12. </p> <ul><li>Wegener noted that therock sequencesin South America, Africa, India, and Australia are very similar. Wegener showed that the same three bottoms layers occurred on each of the continents.</li></ul> <p> 13. </p> <ul><li>The bottom layer, called tillite, was thought to be of glacial origin.</li></ul> <ul><li>The middlelayercomposed of coal beds, shale and sandstone contained Glossopteris fossils, as did the bottom tillite layer.</li></ul> <ul><li>The top most and youngest layer is lava flows. Such a strong similarity in the rock record of these localities, now separated by great geographic distance, lent credence to Wegener's notion of continental drift. </li></ul> <p> 14. </p> <ul><li>The occurrence ofglacial featuresin the geologic record of South America, Africa, India ,and Australia provides further evidence for the notion of continental drift. Glaciers affected all or part of these continents at the same time in Earth history.</li></ul> <p> 15. 16. Rejection of Wegeners theory </p> <ul><li>One problem was that the a plausibledriving force was missing . </li></ul> <ul><li>As late as 1953,Careyintroduced the theory ofplate tectonicsthus the theory of continental drift was rejected by the physicistScheiddiger </li></ul>