Continental drift



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  1. About how many earthquakes occur each day?

Thousands a day with around 50 of them reported by the National Earthquake Information Center (NEIC).

  1. A tectonic plate boundary can be defined as convergent, divergent, or transform. Define convergent boundary and give three examples of mountains around the world formed at convergent boundaries.

A convergent boundary is where two plates are colliding. Mountains formed at convergent boundaries include the Himalayas in northern India, the Andes in South America, and the Alps in Europe. The Appalachians and Rockies in the United States formed at ancient convergent boundaries.

All three types of boundaries are shown in the diagram below.



http://www.livescience.com/37706-what-is-plate-tectonics.html



  1. If two continents collide at a convergent boundary, folded mountains will form. The Appalachian Mountains outside our window formed in this way when continents slammed together as Pangaea was beginning to form between 400 and 300 million years ago. When ocean crust collides with continental crust, however, folded mountains will not form. Explain what happens when ocean crust collides with continental crust and name at least two features that will form as a result.

The ocean crust will subduct beneath the continental crust because the ocean crust made of basalt is denser than the continental crust made of granite.

A trench will form at the subduction zone and volcanoes will form on the continent.





  1. Ocean crust can also collide with other ocean crust. When this occurs one ocean crust will subduct beneath the other ocean crust. A trench will form and a line of volcanic islands will form above the trench. This line of volcanic islands is commonly called a volcanic arc, or volcanic island arc. What volcanic island arc is located off the coast of Alaska and what is the name of the trench next to these volcanic islands?

The Aleutian Islands are the volcanic islands and the trench is called the Aleutian Trench.

http://home.earthlink.net/~dengelhardt/images/zonesmedium.jpeg



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