Movements of Earth's Plates

Name: _________________________________       Date: _____________

The huge tectonic plates that make up Earth's surface fit together like a giant jigsaw puzzle. The plates sit on top of a layer of molten rock that is in constant motion. Although you can't feel it, Earth's plates slowly but constantly move a measurable distance each year as well. Over millions of years, the plates and the continents they carry can move great distances.

Is this activity, you'll find out how far the plates have migrated in the past. You'll then take a look at where two of them might be millions of years from now.

1. First, you'll see 250 million years of Earth's history compressed into less than ten seconds. View this USGS Pangaea animation showing continental movement since the time of the supercontinent called Pangaea. Sketch how Pangaea looked 250 million years ago.
   
   
   
   
   
   
   
   
2. Now you'll calculate how far the continents moved over that time. Assume the continents moved at an average rate of 5 centimeters/year. How many kilometers would they move in one year at that rate? (100 centimeters = 1 meter and 1,000 meters = 1 kilometer.)
   
   
   
   
3. Multiply your answer to question 2 (in km) by 250,000,000 to find out how many kilometers the plates moved over that span of years.
   
   
   
   
4. To see where the plates are now, view this USGS plate animation. Use colored pencils to sketch Earth's plates and the continents they carry.
   
   
   
   
   
   
   
   
   
   
5. In which directions are the plates moving? To find out, view the USGS plate movement animation. On your sketch for question 4, add arrows to show which way the plates are headed.
   
   
6. In California, the San Andreas Fault runs through much of the state. The Pacific plate is on the west side of the fault and the North American plate is on its east side. View this NASA/JPL flyover movie of the fault.
   
   
   
   
7. Along the San Andreas Fault, the Pacific plate slowly grinds to the north. Los Angeles lies on the Pacific plate side of the fault, while San Francisco is on the North American side. Millions of years from now (theoretically, at least) the two cities (or their current locations) will be neighbors! Your job is to figure out how long this might take. Assume the Los Angeles to San Francisco distance is about 600 kilometers and the rate of plate movement along the San Andreas Fault is 3.5 centimeters/year. (Hint: First calculate how far the plates move apart in one year.)