Plate Tectonics

In this exercise you will examine evidence for the changing nature of Earth’s tectonic plates during the past 290 million years.  The exercise is in three parts, and each part has several questions related to images and animations of maps.  Submit your answers as a separate Word document. 

Part 1.  Go to http://www.ngdc.noaa.gov/mgg/image/WorldCrustalAge.gif and view a map showing the age of the oceanic crust.

• Look at the legend. Which color represents the oldest crust? Which color represents the youngest?
• Where is the youngest oceanic crust found?
• Where is the oldest crust found? Is there a plate tectonic explanation for its location there?
• Did the North Atlantic or the South Atlantic start to form first?
• What part of the Atlantic opened last? What is the evidence?

Part 2.  Go to this Paleogeographic animation that shows the paleogeography of the North Atlantic during the last 290 million years.  Review the movie several times, and take notes about the important plate tectonic events.

• What is the best way to describe the motions of the plates involved?  As simple horizontal or vertical movements, or as rotations?
• What type of plate margin was eastern North America during the early stages of this animation?
• In relation to North America, where was Africa 250 million years ago?
• Describe Africa's subsequent movements.
• List the sequence of events that occurred along the eastern margin of North America.

Part 3.  Examine the topographic features of the seafloor around Hawaii that are shown on this web site http://topex.ucsd.edu/marine_topo/gif_topo_track/topo7.gif

• What is the origin of the long topographic swell shown in light blue that surrounds the Hawaiian Island chain?
• Why does the swell end abruptly at the southern end of the island chain?
• Why is there a narrow trough (image) on top of the swell near the island of Hawaii—the southernmost island?
• Why doesn't the Hawaiian Island chain parallel the fracture zones on the floor of the Pacific Ocean?

Visit the US Geological Survey Web site that describes the island of Hawaii at http://hvo.wr.usgs.gov/earthquakes/seismicity/.  Focus specifically on the earthquakes.

• Are earthquakes common on the island of Hawaii?
• How large are they?
• What causes the earthquakes?
• Do you think earthquakes are as common on the other islands in the state of Hawaii? Explain.