Below are ideas for extending this topic beyond the activity & Exploration you just completed.

• Lesson Assessment and Answer Key
• Video: A 10-minute video from Yosemite National Park shows what happens when rocks break off a steep slope.
• Reading: 2,500 Tons of Rock Fell Off Half Dome
• Activity Extension: Add to your Sugar Shake experiment by mixing in softer and harder “rocks.”
  
• Demonstration: Show that seeds can lift weights.
• Activity: Go for a walk and look for plants that are changing your schoolyard.

In the Sugar Shake experiment, you are modeling a situation where identical rocks are tumbling together. You can see what happens when rocks of different types are bumping into each other by adding croutons (softer, more breakable “rocks”) and/or dried beans (harder, less breakable “rocks” to the container before you shake it.

How does the addition of other "rocks" affect the changes in the sugar cubes? How do the croutons and beans change with your shaking?

Use dried beans to demonstrate the power of seeds. Put beans into a paper or plastic cup until it’s about one quarter full. Add water until all the beans are completely covered. Set another cup on top, and add pennies (or other weights) so the cup presses down on the beans. Make a line with a marker to show the cup’s position.

Wait an hour, then check on your beans. (For the “after” photo, see next slide.)

Dried beans are seeds — you can plant them and grow a bean plant. When you add water to dried dried beans, they start soaking up the water and swelling as they get ready to grow.

This is the first step in root wedging -- getting bigger and pushing against the surrounding rock. The beans in this cup lifted the weight of many pennies when they swelled.

Take your class for a walk in your schoolyard and look for plants that have taken root where they don’t belong. You may find grass growing in cracks in a sidewalk or plants sprouting between stones or bricks in a wall.

The roots of these plants are ever-so-slowly expanding the cracks in which they grow. Just as the plants on the side of a mountain break rocks apart, the plants in your schoolyard are breaking the sidewalk and the stone walls.