I ask students to review the different types of weathering we have explored in class: mechanical and chemical weathering. I tell them that today we are investigating something else that affects the earth’s crust.
I dump a pail of earth on a table between me and the class. I pick up a hose that is attached to my classroom sink and put my finger on the switch to a classroom fan. I ask students what they think will happen if I turn either one of these devices on and point it at the dirt. Great gasps usually erupt, and someone invariably tells me the principal will be mad! Students then begin to offer ideas such as the dirt will move away from the water and wind sources, the mound of dirt will change shape, dirt will move in different directions. I ask students if there are any processes in nature that might result in similar problems?
I tell students, that today, we will investigate our school grounds/neighborhood for possible signs of erosion (I have already checked that our school grounds show evidence of erosion or I will pre-plan a walking field trip in the neighborhood to observe erosion in the area).
I send students out into the schoolyard in groups of 4-6. Students look for and find areas that they think have been eroded. I give each group a red flag. If they have questions, they can raise the flag and I can go to the group to help out.
When students find a place that is eroded, they make observations about what they see. If possible, they can make an inference about what process caused the erosion. Students then make a scale drawing of the area. Students use a one inch grid and draw the area with a scale of 1 inch = 1 foot. I don’t give them much instruction in how to draw this beforehand as I like to see if students can puzzle it out themselves. We discuss the process back in class after the activity and I troubleshoot any groups that simply cannot figure it out.
When students have completed their drawings, they return to class to complete their reflections about what they think caused this erosion, and how this could be reversed through rehabilitation. Students will eventually come up with a proposal to reverse the erosion process and prevent it from happening again, but this is just a preliminary look at it. Students will generate “I wonder” questions regarding erosion, how to prevent it, and how to fix it.
Grid drawings and “I wonder” questions will serve as an indicator of understanding of the concepts taught in today’s lesson.