Rationale

Nearly three fourths of the world’s earthquakes and four fifths of historically active volcanoes are found near Subduction zones. This boundary between converging Tectonic plates is characterized by one plate sliding under another or “subducting”. As the plate penetrates into the mantle it heats. At a depth of around 100 km it begins to melt. The melted rock is lighter and thus rises buoyantly to form volcanic mountain ranges (continent – to – ocean plate collision) or volcanic Island Arcs (ocean – to – ocean plate collision).

Focus Question

What is a subduction zone?

Objectives

Students will:

1. Map foci of generated data from a slice of Planet X onto a Depth of Foci graph.

2. Draw the subduction zone from this graph.

3. Repeat the above objectives with actual seismic data from a slice of South America.

Materials

1. Copies of Subduction Zone Activity.

2. Telephone books.

3. Colored markers and paper.

Organization

1. Begin with a brief review of Plate Tectonics and types of plate movement.

2. Demonstrate Telephone Subduction Activity and have students draw a diagram of the “subducting plate”.

3. Introduce Planet X scenario and divide into small groups to complete Subduction Zone Activity.

4. Discuss results and ask students if there are any subduction zones near the U.S. and the implications to residents in these regions. (Pacific N.W. near Cascade Mountains, Aleutian Islands near Alaska.)

This is a link to SUBDUCTION ZONE ACTIVITY.doc

TELEPHONE BOOK SUBDUCTION ZONE DEMONSTRATION.doc

Reference Data

Graph 1 Completed graph of generated data for Planet X showing Wadati-Benioff zone. Dip is as shown on Planet X map.

Graph 2 Completed Graph of actual data showing Wadati-Benioff zone latitude 15 - 25 degrees south and longitude 60 - 90 degrees west. Note that the actual dip is in the opposite direction on a World map.

Core Curriculum Standards Met

Topic 1. Inquiry, Process and Problem Solving.

Topic 8. Composition of the Earth.

Topic 18. Formation of Earth’s features

References

BOLT, Bruce A, Earthquakes, W.H. Freeman and Company, New York, NY, 1999

STRADLER, Arthur N., Plate Tectonics, Geo Books Publishing, Cambridge, MA, 1998

Links to Relevant sites

www.eas.purdue.edu/~braile/educindex/educindex.htm

This site has links to great hands-on activities for earthquake science.

htpp://geology.usgs.gov/pdf/planet.pdf

Download “This Dynamic Planet” (T. Simkins and others.) here or order a copy of the map from US Geological Survey, Box 25286, Denver, CO. 80225. for $7 + $5 shipping.

htpp://pubs.usgs.gov/publications/text/dynamic.html

“This Dynamic Earth, The Story of Plate Tectonics”, is a companion text to the above map.

www.seismo.unr.edu/htdocs/abouteq.html

“About Earthquakes” has links to an excellent collection of lectures.