By: Ann Wolf

plates Earth’s crust isn’t one piece, it’s broken into pieces called plates The plates constantly move all over the world (continental drift) There are 14 different major plates (we are on the North American Plate) Continents.shtml

Alfred Wegener created the idea of a super continent in Explorers such as Magellan noticed that the continents fit together like puzzle pieces, but Wegener was the first to suggest that the earth’s surface changes over time. He didn’t have any evidence to support his idea, just observations. So many people didn’t believe him. People who supported his idea were called Mobilists, and people who didn’t were called Anti-mobilists

Studies showed that the north pole seemed to wander around in different times. Since the north pole can’t actually move, it proved Wegener’s theory that the continents moved. chist.html

Pangaea was a continent until the Carboniferous period (about 300 million years ago) Pangaea means “all lands” chist.html

Some theories in Wegener’s time about continental placement: – a land bridge connected Brazil and Africa, which is how the same fossils were found in both places – Heating and cooling of the land caused it to expand and contract chist.html

Geophysicist and a meteorologist He published Origin of Continents and Oceans in 1915, which stated his ideas about continental drift He thought the continents plowed through the ocean floor Scientists such as Alexander Du Toit and Emile Argand supported his theory gener.html

Convergent Boundaries- Places where plates crush together and crust is destroyed Plates move slowly, so collisions last hundreds of years Mountains, earthquakes, and volcanoes form from convergent boundaries

The cascade range in north America was formed from a convergent boundary Along the western coast of South America, the Nazca Plate and the South American Plate form a continental-oceanic subduction zone

The mid-Atlantic ridge is one of the best known. The north American plate and the Eurasian plate separate right in the middle of Iceland.

Divergent Boundaries- Places where plates are being pulled apart. The two plates separate and new crust forms. Earthquakes are common and volcanoes form from the magma between the two plates Plate separation is very slow, usually moving about 2cm per year

Transform Boundaries- Plates slide past each other and crust is neither created nor destroyed Cause a lot of earthquakes The San Andreas fault cause a massive earthquake in 1906 that destroyed much of San Francisco and killed over 600 people

Earthquakes, mudslides, volcanoes, landslides, and trenches can be formed. The only danger to us is mudslides or earthquakes, but they are usually only present near fault lines such as in California MudslideLandslide Mountain nding.html

Map of areas that earthquakes occur -occur at all plate boundaries, but mainly transform boundaries nding.html

Venus’ crust has thickened in the past hundred years Mars has a magnetic field and volcanoes caused by plate tectonics (because it has water, in the form of ice) Saturn’s moon, Titian, has satellite pictures that show plate-tectonic activity

Earth’s Continental Plates: omy/planets/earth/Continents.shtml omy/planets/earth/Continents.shtml History of Plate tectonics Plate Tectonics: History Earth Floor: Plate tectonics /plates4.html /plates4.html

Alfred Wegener html html Convergent Boundaries ysflr/plates2.html ysflr/plates2.html Understanding plate motions Plate Tectonics ate_tectonics#Plate_tectonics_on_other_planets