I call students to the gathering area. We review what we have learned about weathering. Weathering is the break down of natural materials without movement from their place. I tell students that rarely do we see weathering without erosion. When materials break down they like to move by air, water, or gravity. This is the process erosion.
An Alaska Note: We live in Alaska, there are many different forms of erosion, glacial erosion is one that most children know well. Many of our glaciers have receded in recent years, showing the moraine (debris dropped by glaciers receding). Students can easily identify glacial silt by its powder-like consistency. Water is colored by glacial outflow and becomes turquoise in color. In addition, large boulder-strewn fields can be seen when glaciers recede. We discuss how these materials have moved a long way from their original weathering place. In fact, with glaciation, materials can move miles from their original position.
We also talk about other types of erosion. Materials are weathered and eroded as rivers move, over time, canyons are formed, natural materials are also moved by wind and rain as well. As I talk about these examples of erosion, I show students pictures of examples of erosion.
Once I have shown examples of erosion, I introduce students to the community-service project that we will be completing for this unit. We will be working to reverse erosion damage in a small part of our community. We will be planning a series of natural remedies to an erosion area.
You may know of other similar disasters or threats in your own community.
I tell students that now that they know about how weathering occurs and how erosion can change the landscape, they will need to brainstorm what they can do, using natural materials, to restore an erosion problem. I show them a picture of a community erosion example. This example is an area where water has eroded the earth and keeps growing and is now threatening to cause trees to fall as the base for their roots is eroded away. I tell them that this process may occur over time and may not be an instant remedy. Students will write their ideas on an idea tree to present to the class.
Students move to groups to discuss the issue and brainstorm potential ideas for their solution. I give them about 5 minutes to talk about it and then we reconvene in the gathering area to discuss our ideas. Some students offer ideas to build a wooden wall to hold up the area and pack it with soil. Others suggest that we plant other vegetation to hold the soil in place.
After our discussion, I tell students that we will be experimenting with these ideas to see the merits of their ideas. We will do this in a mini-erosion table during our next class.