Cracked Plates & Tectonics

Activity Source:

In this activity, you’ll  investigate dynamics in Earth’s crust that explain multiple Earth science phenomena. For the full activity, go to http://esriurl.com/ESW2016.

Materials

• A computer/projector with internet connection

Take these “tech tips.”

• Measure: At the top of the map, click the Measure button. Hover and click the Distance button. Click continuously along what you want to measure. Double-click to finish.
• Bookmarks: At the top of the map, click the Bookmarks button. Choose your bookmark; the map will take you there.
• The Map URL is http://esriurl.com/earthgeoinquiry6.

Procedure

1. Engage. Click the map link and project the map onto a screen for the whole class to see. With the Details pane visible, click the button, Show Map Contents. Turn on the layer, Global Quakes Of Large Magnitude 5.8 Or Greater.

• Do you see any pattern to where this larger collection of quakes occurs? A common misconception is that quakes occur just around continents or oceans. Quakes define plates around both sections of continents and oceans together. There are exceptions, of course.
• What is happening to the entire area within any ring of earthquakes? This area moves as one piece, so no collisions are happening inside a single piece of crust called a plate.

2. Explore. Turn on the layer, Relative Motion At Plate Boundaries. (Note that you will not see anything until you perform the next step.) Click each of the bookmarks: South America, California, and Mid Atlantic Ridge.

• How would you describe the different ways these plates could interact? South America would have a direct collision, California would have a side swipe, and Mid Atlantic would be torn apart.

3. Explain. Earthquakes occur where large pieces of Earth’s crust run into, pull away from, or slide against other pieces of independent crust. Turn on the layer, Plate Boundaries. To show the legend, click the layer name, Plate Boundaries. Choose each bookmark in turn (South America, California, and Mid Atlantic Ridge).

• What are plates that collide head-on called? Convergent.
• What are boundaries called where plates are stretched apart? Divergent.
• What are boundaries called where plates hit at other directions, causing a sideswipe collision? Transform.
• Turn off the Global Quakes Of Large Magnitude 5.8 Or Greater layer.