PLATE TECTONICSBy: Betsy Butcher

4th Bell

Section 1: History of Plate Tectonics

The first idea of Pangaea was thought up by Alfred Wegner (1880-1930). He was not only a geologist but also, an astronomer. While he was a respectable scientist in his day, his theory was not generally accepted by his fellows in his field.

Alfred Wegner Pangaea

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Alfred Wegner had his P.H.D. in astronomy, which gave him a lot of insight into how planets work and what would be likely based on other planets.

While his ideas were just being released, scientists were debating the ‘Contraction Theory’, saying that the Earth was once a great ball of molten hot magma.

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Wegner’s theory was that there was once a super continent that had moved apart over time. The name Pangaea, meaning “all lands”, seemed rather fitting. However, according to Wegner, it had not been intact sine the Carboniferous period, 300 million years ago.

It was not until years later that fellow scientist Arthur Holms rejuvenated his theory by bringing up thermal convection inside the Earth. This helped explained how the continents could be forced to move.

Section 2:Convergent Boundaries

Convergent Boundaries: When one plate is being forced under another. The crust is then melted into magma in the mantle. These are usually formed in the shape of a trench or an island arc system.

Example: The San Andres Fault, where the North American Plate meets the Pacific Plate.

Oceanic Trench

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Convergent boundaries can be the location of severe earthquakes and volcanoes.

They also can be the cause of the formation of mountains. This occurs when two continental plates meet and crinkle. (Such as when the Indo-Australian Plate and the Eurasian Plates met to form the Himalayan Mountains.)

Himalayan Mountains

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San Diego Earthquake :

Mt. Vesuvius Volcano

Section 3:Divergent Boundaries

Divergent Boundaries: When two plates move away from one another. These movements create mid-ocean ridges and sea floor spreading when magma from the mantle seeps through these vents and cool.

Example: The Mid-Atlantic Ridge where the North and South American Plates are being separates from the African and Eurasian Plates.

Section 4:Transform Boundaries

Transform Boundaries: When two plates slide right past each other with no crust being created or lost. These can result in earthquakes, landslides, and mudslides.

A Transform Boundary

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Examples: The San Andreas Fault in California where the North American Plate and the Pacific Plates are passing each other. The pressure builds up and releases in natural disasters that are very common in that are.

Mudslide Landslide

Section 5:Recap/ Connections

We personally live on the planet Earth, and more specifically, the North American Plate. We are bordered by the Pacific Plate, the Atlantic Plate, and the South American Plate.

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As you can see, we have many boundaries in the United States. Our greatest danger here in Ohio would be earthquakes. From 1983-1985 there were 13 small earthquakes felt in the Buckeye State. Earthquakes also occur often along the San Andreas Fault in California, as do landslides and mudslides. Other common disasters caused by plate tectonics in the U.S. include

Citations: www.ucmp.berkeley.edu/geology/techist.

html http://scign.jpl.nasa.gov/learn/plate2.html http://vulcan.wr.usgs.gov/Glossary/PlateT

ectonics/description_plate_tectonics.html http://geology.com/plate-tectonics.shtml http://www.dnr.state.oh.us/geosurve/html

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