Earth Science Essentials North Farmington High School Plate Tectonics Earth Science Essentials North Farmington High School

What is Plate Tectonics Crust of the Earth FLOATS on top of the mantle. Crust is broken into slabs (plates) that MOVE, slide, collide, and spread apart. Cause of earthquakes, mountains, and volcanoes. Click HERE to see crust of the Earth FLOATING on the mantle.

Continental Drift In 1912, Alfred Wegener first proposed that the continents are moving. He claimed the “continents are drifting like rafts in the water.” He called it Continental Drift. Initially all the continents were connected in 1 super continent call Pangaea

Evidence for plate movement Wegener collected 6 major pieces of evidence that the plates were moving. He failed to convince the geological society at the time because he could not explain WHY the plates were moving. Plate tectonics was not fully accepted until the 1970s. SAD

1. Shorelines Shorelines fit like pieces of a puzzle Click HERE to watch an animation of the breakup of Pangaea PANGAEA

2. Fossils of extinct species Fossils of now extinct animals and plants were found on BOTH sides of the Atlantic.

Petoskey Stone (fossil) was a tropical coral! 3. Tropical Fossils Fossils of tropical plants found in extremely cold climates or vice-versa. Michigan itself has tropical fossils! During Pangaea we were MUCH closer to the equator! MICHIGAN Petoskey Stone (fossil) was a tropical coral!

4. Fossils and evolution Fossils of species on one side of the Atlantic found on the other side. Today the species appear much different from each other due to evolution BUT they have a common ancestor

5. Mountains line up Mountain ranges from opposing sides of the Atlantic match in age and rock type. Ex: The N. American Appalachian Mountains line up with the Atlas mountains of Africa!!! Both ranges are roughly 200 million years old. The same time Pangaea split apart. Appalachian Mtns Atlas Mtns

6. Glacier Scratches There have been MANY ice ages. One occurred during Pangaea. The weight of the ice SCRATCHES the bedrock below leaving scars called striations. Scratches found on many continents don’t line up or make sense UNTIL you put the continents together as Pangaea. Glacier scratches do NOT make sense. Seem haphazard or random. As Pangaea, the glacier scratches line up and make sense.

How did Plate Tectonics become a theory? Earth is a giant magnet. Magnetic north, currently near the North Pole, REVERSES and is found near the South pole. This occurs about once every million years.

Paleomagnetism The history of Earth’s magnetic field is recorded in the crust of the oceans. Ocean crust contains lots of iron (mafic) that gets magnetized AND points to magnetic NORTH. Watch the paleomagnetism animation, click HERE