Changing Earth's Surface - Breaking Up is Hard to Do
It's spring. You are going up the canyon with your family as you've done many times before; and all of you know this road. Its twists and turns provide treasured glimpses of the beauty of nature when suddenly - bonk! bumpity-bump! bonk! Your nature trek becomes a dodge-the-pothole challenge. The road has been changed; attacked by weathering and erosion. During the winter, water penetrated the road's surface. It froze and expanded, creating cracks. More water got into the cracks and it froze, making the cracks wider. Melting snow carried particles of road away. What remains is a changed surface, and not for the better. Earth's surface is also constantly changing. Weathering breaks rocks into smaller pieces. Erosion carries the pieces away. Together these forces slowly wear down Earth's surface. The main agent of weathering and erosion is running water.Living Agents of Change
Living things can also weather and erode rock. Plants have roots as you know. The roots can force themselves between rocks. As the plant grows, the roots grow, forcing rocks apart. This is called root pry.
- Take a walk around your neighborhood.
- Look for signs of plant weathering. Describe what you observe.
- If you have a camera. Take pictures of the evidence that plants have caused sidewalks, roads or even playgrounds to weather.
Do it again!
- At home and with parent permission, you will use a frosted pastry such as a Zingers® or Ho Ho’s® for this activity.
- You will also need toothpicks.
- With a friend, begin inserting toothpicks into the pastry, applying a bit of upward pressure.
- What changes in the pastry do you observe, what happens to the frosting?
- How is the pastry like a structure affected by plant weathering?
- How are the toothpicks like plant roots?
Animals can physically break rock down and move particles away. Marmots scratch and move material while digging dens. Ants haul pebbles. We humans skip rocks across the lake.
Remember the cracks made by the roots? When winter comes water will penetrate those cracks just like it did the road surface. The water will freeze, widening the cracks and breaking the rock. Spring's thaw will carry particles away. Gusty winds hit the rock's surface, picking up tiny particles. These particles blow about, not unlike a sandblaster, wearing down even more of the surface.