Hands-on Activity Sinkhole Emergency!

Learning Objectives

After this activity, students should be able to:

• Explain how internal erosion can lead to sinkholes.
• Considering specific constraints (material types, material amounts, time), create a design that prevents further internal erosion under a sinkhole.
• Apply steps of the engineering design process.

Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

NGSS: Next Generation Science Standards - Science

State Standards

Materials List

Each group needs:

• large clear funnel (~12 cm opening)
• 3 small/medium plastic containers (example: https://www.amazon.com/dp/B087B46CK8/?coliid=IR99RLS8NI4OF&colid=1M7NTFTYAWDGA&psc=1&ref_=lv_ov_lig_dp_it)
• 250 mL beaker
• Sinkhole Emergency Workbook, one per student

For the entire class to share:

• digital kitchen scale
• tap water
• markers/crayons/colored pencils
• 2 large plastic containers for each material provided
• design materials of choice:
• air-dry clay
• kinetic sand
• soil
• pebbles
• dead leaves (gather from outside)
• computers/devices
• printer paper
• books/articles/media on sinkholes (see Multimedia Support or Technology Integration section below)

Worksheets and Attachments

Pre-Req Knowledge

Students should be familiar with weathering and erosion concepts.

Introduction/Motivation

Sinkholes are a common geographical feature, particularly in Florida. What experiences with sinkholes do you have? (Let students share their experiences). For example, there is a sinkhole called Devil’s Millhopper in, Florida watch: “Museums in the Parks: Devil’s Millhopper Geological State Park” (4:23) by Florida Museum on YouTube. Is this sinkhole dangerous? This sinkhole has created a beautiful ecosystem and a great place for archaeologists to find artifacts that help them to further understand the people that lived there long ago. This one isn’t dangerous, but do you think all sinkholes are harmless? How could a sinkhole be dangerous? This news clip of sinkholes in Central Florida is from 2018 "Sinkholes Appearing in Florida After Heavy Rain" (1:51) by NBC News on YouTube. How does the impact of these sinkholes differ from the impact of Devil’s Millhopper? (Possible answers: Expect students to mention how Devil’s Millhopper provides a home for lots of plants and animals, an archaeologically significant site, and beauty for human pleasure. In contrast, they may discuss the loss of property like homes and businesses, destroyed roadways, costs of repair, and possible injuries or fatalities.)

As we saw from the news clip, sinkholes form when water causes internal erosion. Internal erosion is caused by water seeping under the top layers of the earth and dissolving the bedrock. In Florida, our bedrock is mostly limestone. Based on the news story, it seems like sinkholes happen quite often. Why do we not see very large sinkholes all over the place in Florida? (Have students discuss and lead the class to conclude that experts make sure it doesn’t continue to get worse).

When a sinkhole forms, civil engineers, often with the help of geologists, will determine the risk of the sinkhole spreading. If they think it won’t spread, they typically leave it alone. If the sinkhole is at risk for dangerous spreading, a process called “stabilization” happens. The experts will explore the sinkhole to determine the severity and cause, decide on the best method of repair, and test out their work with water.

Today, you are going to work as civil engineers to stabilize a sinkhole that has opened in a field near the school. Everyone is safe, but it was determined that it needs to be repaired as soon as possible to prevent the hole from spreading and becoming dangerous and destructive. You, as civil engineers, will follow the engineering design process to develop an effective solution for stabilization of the sinkhole. Let’s get to work saving our school and community!

Procedure

Background

 A sinkhole is a natural depression or hole in the ground. In the United States, they are most common in the Southeast because of the karst terrain. Karst terrain is made up of soluble bedrock, most often limestone. When water seeps through the soil, the limestone dissolves and forms cavities. This internal erosion is caused by water that is most likely acidic from its contact with decaying plants and animals and absorption of carbon dioxide from the soil. This is considered erosion, and not weathering, because the sediment is being dissolved or moved. Weathering refers to the breaking down of a source, such as rock, mineral, or soil into sediment, while erosion removes sediment from the source.

There are three types of natural sinkhole formations: dissolution, cover-subsidence, and cover-collapse. Dissolution sinkholes are slowly formed when water seeps through cracks in the bedrock, dissolving it. Cover-subsidence sinkholes are small and gradually forming. They are caused by water dissolving a void in the limestone bedrock and the sediment above sinking with it. Cover-collapse sinkholes occur suddenly when the layers are internally eroded to a point of thinness that cannot hold any longer. Artificial sinkholes are caused by human activities such as drilling, mining, building, over-pumping groundwater, and changing surface water flow.

There are many methods for stabilizing a sinkhole before major damage occurs. These include filling, underpinning, compaction grouting, and geopolymer injection. In the case of a cover-collapse sinkhole, however, it is often too late to use stabilization methods. Repairing a deep sinkhole is done by a filling process that starts with civil engineers and/or geologists inspecting the size and cause of the sinkhole before excavating loose sediment. The goal of sinkhole repair is to prevent the spread and make the land usable again by preventing water from seeping into the bedrock while still being absorbent. Most often, the sinkhole is filled with a concrete base, a middle layer of clay sand, and a top layer of soil. Landscaping can also help to maintain stabilization.

Before the Activity

• Make copies of the Sinkhole Emergency Workbook and the Sinkhole Emergency Post-Assessment, one for each student.
• Prepare research materials and devices. You may want to provide students with a digital menu for accessing specific material choices on devices. Hardcopy research materials should be in a central location.
• Set up each group’s station with a beaker and funnel.
• Put each of the choice materials (Kinetic sand, air-dry clay, soil, pebbles, etc.) into a large plastic container and place in a central location. (Note: This is the class stock of materials.)
• Set out the small-medium containers near the stock containers. Groups will choose which container size they use for each of their materials.
• Place the scale with the other shared materials for convenient weighing.
• Fill a large container with water. A pitcher or watering may also be used.
• Decide on the most effective method to group your students.

With the Students

Day 1

1. Pass out the Sinkhole Emergency Workbook for each student to record their notes, data, and answers throughout the activity.
2. Review the basic steps of the engineering design process, listing them on the board as they are discussed. (Ask, Research, Brainstorm, Plan, Design, Build, Test, Improve.) Record the question with the “Ask” step: What is the best way to repair a sinkhole?
3. Explain to students that they will be using provided materials to fill a funnel to test their design. Ensure students understand their constraints:
• The materials provided are air-dry clay, kinetic sand, pebbles, soil, and dead leaves.
• They may only use three materials from the selection provided.
• The repair should prevent water from leaking through the bottom of the funnel while not causing puddling at the top.
• The design must weigh 200 g (excluding the mass of funnel and beaker).
4. Divide the class into groups of three or four students each.
5. Provide the groups with access to the research materials. (Consider using a menu of resources to ensure quick and easy access to the resources.) As groups research, they should take note of information that could help them solve the problem.
6. Have groups gather back together and share out any information they learned.
7. Have students spend time brainstorming independently before having a group brainstorming discussion.
8. Have groups reorganize and brainstorm as a group. Each group should narrow down their ideas and plan their first design. Make sure the groups decide on the materials they want to use, how much of each material they will use, and how each material will be arranged in the sinkhole. In their notes, each student should justify their design for their group.
9. One student from each group should weigh and record the mass of their funnel and beaker in grams. (This will be used to subtract from the final mass.)
10. The members of each group can take turns weighing out the materials in their containers. Make sure they zero out/tare the scale with the empty container before filling.

    

11. Give students 5-10 minutes to build their repair inside of their funnel. Once finished, they should weigh their funnel and repair and then subtract the mass of their empty funnel and beaker to make sure the final mass of the materials is 200 g.

    

12. To test their repair, one team member slowly pours 50 mL of water into their design. The most successful design will keep all or most of the water from seeping through the bottom, while not having a puddle form on the surface of the repair, after 2 minutes.

Day 2

1. Prepare the same as Day 1.
2. Lead a discussion of the successes and failures from Day 1’s tests.
3. Have students individually brainstorm how their group could improve their design.
4. Have groups discuss and plan an improved design to address any problems they may have had on Day 1.
5. Have groups build their redesign and test it the same way as on Day 1.
6. Have groups work together to analyze their data and make any conclusions about the success of their designs.
7. Have each student design a small poster or slide to display each design’s justification, results, and conclusions.
8. Have students split into new groups that consist of at least one student from each of the engineering groups. They should each share both of their designs’ justifications, results, and conclusions.    
9. Have each student fill out the Sinkhole Emergency Post-Assessment.

Vocabulary/Definitions

bedrock: The solid rock that exists at some depth below the ground surface. Bedrock is rock "in place", as opposed to material that has been transported from another location by weathering and erosion.

dissolve: To chemically disintegrate, destroy, make disappear mineral or rock.

erosion: The action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited.

internal erosion: The formation of voids within a soil caused by the removal of material by seepage.

karst: A type of land formation, usually with many caves formed through the dissolving of limestone by underground drainage.

limestone: A common type of carbonate sedimentary rock that is partially soluble, especially in acid, and therefore forms many erosional landforms.

sediment: A naturally occurring material that is broken down by processes of weathering and erosion.

sinkhole: A depression or hole in the ground caused by some form of collapse of the surface layer.

stabilization: The process of fixing a sinkhole to prevent its spread.

weathering: The deterioration of rocks, soils, and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms.

Assessment

Pre-Activity Assessment

Brainstorm: After playing the news clip, have students discuss possible answers to the questions below in pairs or small groups. Remind students that they are not expected to be right, just participate in thinking and discussing. (If needed, remind the class of the expectations for kind and productive conversations with classmates.)

• How can the impact of sinkholes be harmful or negative?
• Do we see sinkholes everywhere? Why or why not?
• What should we do when a sinkhole happens?

Activity Embedded (Formative) Assessment

Record Keeping: Each student will be responsible for keeping records of ideas, notes, diagrams, plans, data, observations, and reflections on the Sinkhole Emergency Workbook.  

Discussion: As students work through the activity, check in with groups and the class as a whole to promote discussion based around the engineering design process and the Sinkhole Emergency Workbook.

Post-Activity (Summative) Assessment 

Jigsaw Presentation: Have students split into new groups that consist of at least one student from each of the engineering groups. They should each share both of their designs’ justifications, results, and conclusions.      

Post-Assessment: On the Sinkhole Emergency Post-Assessment, students will write a paragraph explaining the importance of stabilizing a sinkhole as soon as possible.

Making Sense Assessment: Have students reflect on the science concepts they explored and/or the science and engineering skills they used by completing the Making Sense Assessment.

Investigating Questions

• How do sinkholes form? (Answer: Sinkholes form when water seeps through the topsoil and the bedrock (limestone) dissolves, forming cavities.)
• What are some possible effects of sinkholes? (Answer: Sinkholes can cause the collapse of ground structures and damage infrastructure, leading to costly repairs. Sinkholes can also cause changes in the ecosystem.)
• How can we repair a sinkhole with local resources? (Answer: We can repair a sinkhole using local resources such as clay and gravel to plug a sinkhole.)
• What does the data show us about our design(s)? (Possible answer: Our data shows that we have found an effective method of sinkhole repair, but it does not properly absorb the surface water. We will need to revise our design to fix this issue.)
• Why is it important to stabilize a sinkhole as soon as possible? (Answer: A sinkhole should be stabilized as soon as possible so it does not spread or collapse. Because of internal erosion occurring under the surface, you cannot be sure how quickly or much a sinkhole has spread. The longer we wait to repair it, the more severe and labor some the repair will need to be. Quick action can help prevent possible damage to homes, businesses, roadways, and lives caused by a sinkhole.)

Safety Issues

• Students should wash their hands in between handling materials to avoid contamination.
• Dispose of materials appropriately, making sure nothing but water goes down the drain.

Troubleshooting Tips

• You may need to adjust the target mass of the design, depending on your supplies.

Activity Extensions

• To test the sustainability of their repair, have students repeat the water test with the design over the course of several days. After a set number of days (3-5), measure the final volume of water in the beaker and examine any damage or changes to the appearance of their design.
• Try the activity again with materials the students find outside at school (i.e., leaves, grass, soil, sand, rocks, etc.). They should still be required to stay within a maximum mass, but they do not need to weigh out the individual materials. They also can use an unlimited number of different materials.
• Have students write a letter to a fellow civil engineer explaining how they repaired the sinkhole. They should include the amount of each material as percentages, which they will convert from fractions.

Activity Scaling

• For younger students, decide on the three best materials to use as a class. With everyone using the same materials, the students can focus their design on the placement of materials.
• For older students, increase the access to materials. Have groups choose any three orderable materials they want to use within a budget. They will complete a cost-benefit analysis to justify the purchases.

Additional Multimedia Support

• Recommended books/articles/media on sinkholes for student research:
• Sinkholes (Devastating Disasters) by Nadia Higgins (available free online through Epic! and for hardcopy purchase here)
• Sinkholes (Disaster Zone) by Vanessa Black (available free online through Epic! and for hardcopy purchase here)
• The Science of a Sinkhole by Robin Koontz (available free online through Epic!)
• Sinkholes (A True Book: Extreme Earth) by Ann O. Squire (available for purchase here)
• “How Do Sinkholes Form?” by Practical Engineering on YouTube 
• “How Do MASSIVE Sinkholes Form?” by Life Noggin on YouTube

References

Copyright

Contributors

Supporting Program

Acknowledgements

This curriculum was based upon work supported by the National Science Foundation under RET grant no. EEC 1711543— Engineering for Biology: Multidisciplinary Research Experiences for Teachers in Elementary Grades (MRET) through the College of Engineering at the University of Florida. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.