Introduction: What is the hook, the attention grabber, the interesting beginning?
Do rocks last forever? Structures made out of stone have proven to last a long time relative to a human lifespan, but they do age and erode over time. How do we study this? Do they all erode in a similar way/rate? Use provided images of erosion as visual aids.
Content:
Move to a discussion of what a heritage site is. Introduce students to Mount Rushmore as an American heritage site and discuss how the sculptor, Gutzon Borglum, decided to carve the heads of the four Presidents. Show two pictures of Mount Rushmore: before and after carving. Help the students recognize that the change was brought about through the implementation of a human design. What we have as a result is a monumental sculpture that took a great amount of human and material resources. How do we make sure that we’re taking care of an important heritage site like Mount Rushmore when there are forces like deterioration and destruction at play? To illustrate deterioration, use provided sample photos of deteriorating structures. For destructions, use example of Bamiyan Buddhas that were destroyed by the Taliban in 2002. Begin looking closer at the sculpture by using the provided Measurable 3D PDF of the model, or the 3D viewer on the CyArk website. In both the 3D PDF and online 3D Viewer, the teacher can cut sections through the model to better illustrate the complexity of the mountain’s contours.
Use the PDF entitled “Caring for a Monumental Sculpture” to introduce the students to the specific preservation concerns at Mount Rushmore. Learn about rock blocks and how they can help us determine how the Sculpture could potentially fall/collapse. Brainstorm on what some of the culprits are for erosion and movement. Water and temperature change are two of the most major culprits.
Hands-on activity 1: Learn about the various types of rocks found in Mount Rushmore. Use the provided photos to do a general mapping of the different types of rock veining over the provided blank illustration of Mount Rushmore.
Hands-on activity 2: This activity is to demonstrate the effects of erosion and seeing how different types of one material can erode at different rates. As a demonstration, test the erosion of different types of soap in the classroom by implementing a schedule of repeated washing. Students should collect and organize measurement data collected at the appropriate intervals. Show photographs of cap rocks to exemplify stones of differing composition eroding at different rates.
Hands-on activity 3: This activity is to demonstrate how the freezing/thawing of water absorbed by a material can cause changes in the material itself. To test thawing/melting, conduct an experiment by soaking a sponge in water then freezing it and comparing before/after measurements. Let the sponge thaw and collect measurement data again. In rocks, this freezing/thawing cycle could cause cracking to occur since rocks do not readily expand and contract.
Optional activity: To reinforce the concept from the above activity, students can conduct another experiment using materials like chalk or pumice stone, and soaking them in water (note that with pumice stone, students may need to wait up to a day for the rock to absorb all the water it can hold). Students should collect measurement data at appropriate time intervals (every 15-30 minutes of soaking until rock ceases to increase in weight) and use this data to calculate the change in the volume of the rock.
Summary and Conclusion of Lesson: What helps set a course of action or leaves them thinking?
Summarize the concepts covered through the activities.
Theme Statement: (The "big picture," the final result, the "so what?!")
Do rocks last forever? EVen rocks are not immune to deterioration and damage. External forces can erode rocks. Water might seem like a harmless material (even beneficial, in fact), but it can be a vicious enemy for a sculpture like Mount RUshmore or other structures. We discussed water and temperature as common culprits in erosion, but there are many more.
