Alfred Wegener • Born 1880 • Died 1930 • German meteorological pioneer and polar explorer
Alfred Wegener • He saw that the continents looked like giant puzzle pieces, that seemed to all “fit” together. • He hypothesized that all of the continents were once together in a giant land mass called PANGEA.
Some evidence: • Land Features • Evidence from Fossils. • Climate Change
Land Features • Coal Beds • Mountains
Fossils: • 3 main fossil bands that supported Wegener’s hypothesis. • Glossopteris fern. • Mesosaurus • Lystrosaurus.
Climate Change • Wegener found rocks with glacial scraping in places that are too mild to have glaciers any more.
Why was Wegener initially not supported? • His hypothesis was not complete • It was much later when Harry Hess created his theory of Sea Floor Spreading that Wegener’s theory was accepted in the 1960’s!
“Doesn’t the east coast of South America fit exactly against the west coast of Africa, as if they had once been joined? This is an idea I’ll have to pursue”~ Wegener wrote his future wife in December 1910
Besides Africa and South America seeming to fit together, Wegener noticed that mountain ranges (the Karroo system in South Africa and the Santa Catarina system in Brazil) and coal deposits matched up between the two continents. • “It is just as if we were to refit the torn pieces of a newspaper by matching their edges and then check whether the lines of print ran smoothly across. If they do, there is nothing left but to conclude that the pieces were in fact joined in this way.” - Wegener
Continental Drift • Wegener stated that 300 million years ago all the continents were joined together in a supercontinent he called Pangaea. This began to break apart 200 million years ago and the continents began the move to their current locations. http://eqseis.geosc.psu.edu/~cammon/HTML/Classes/IntroQuakes/Notes/Images_specific/sa_af.gif
Certain fossils appear in continuous bands across continents that are now separated by thousands of miles of ocean. Wegener believed this fact was one of the strongest pieces of evidence for his theory.
Wegener plotted ancient deserts, jungles and ice sheets with Vladimir Koppen on maps based on Wegener’s theory. He found this explained differences in past climates. By Sydney Harris
Wegener’s Problem • Could not explain how the continents moved. • Ideas: centrifugal force caused by rotation of the Earth and tidal forces caused by the pull of the sun and the moon • “It is probable the complete solution of the problem of the forces will be a long time coming. The Newton of drift theory has not yet appeared.” – Wegener 1929 • Believed forces that moved continents caused earthquakes and volcanoes. http://www.uwsp.edu/geo/faculty/ozsvath/images/wegeners_mechanism.htmwww.uwsp,edu/geo
Some of the earliest evidence confirming Wegener's theories of continental drift was revealed when geologists began to explore the ocean floor starting in the 1950s. • Theory of plate tectonics was well accepted by the late 1960s. This theory states that plates, carrying both oceanic and continental crust move. • The force moving the plates has still not been proven, but convection currents are favored, which Wegener thought as a possibility in 1929.
The last photo of Alfred Wegener and Rasmus Villumsen, taken on 1 November 1930 (Wegener's 50th birthday) as they were leaving the "Eismitte" Station (Photograph courtesy of the Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany)
Works Cited Hughes, Patrick. “Alfred Wegener: The Meteorologist Who Started a Revolution.” Pangaea, 1995-2004. “Alfred Wegener” www.ucmp.berkeley.edu/history/wegener.html Untold tragedies of Continental Drift. Mosquito Creek by James Robbins
The Rules of Plate Tectonics 1. Continental crust is less dense, or lighter, than Oceanic crust so it doesn't sink. It is never destroyed and is permanent. 2. Oceanic crust is heavier so it can sink below Continental crust. It is constantly being formed and destroyed at ocean ridges and trenches. 3. Continental crust can carry on beyond the edges of the land and finally end far below the sea. This explains why the edges of all the continents don't have deep trenches right up against their coastlines. 4. Plates can never overlap. This means that they must either collide and both be pushed up to form mountains, or one of the plates must be pushed down into the mantle and be destroyed. 5. There can never be gaps between plates, so if two plates move apart, as in the middle of the Atlantic, new rock will be formed to fill the space. 6. We know the Earth isn't getting bigger or smaller, so the amount of new crust being formed must be the same as the amount being destroyed. 7. Plate movement is very slow. This is partly why Wegener's original ideas were ignored. Nobody could 'see' the continents moving. When the plates make a sudden movement we call it an Earthquake, and it's the only time we are directly aware of the plates moving.