It's Water-Wise Wednesdays with Frannie the Fish! {TAPS Manual Part 4: Sinkholes}

Frannie's friends at the Groundwater Foundation recently published the second edition of the Training About Protecting the Source (TAPS) Manual. The manual guides users through hands-on activities that explore potential threats to groundwater and challenges them to think about what can be done to protect this key drinking water source.

This manual can be used inside the classroom and is aligned to the national Next Generation Science Standards, but Frannie loves just learning about groundwater, no matter where she is. For the next few weeks, you can join her as she works through the different activities. 

Frannie will be using the Groundwater Foundation's Awesome Aquifer Kit, but if you don't have one, you can follow along with materials that might be found around your home. This is the second part of Frannie's exploration of the TAPS Manual. You can follow the link to see what she learned about leaky underground storage tanks, improperly abandoned wells and the over-application of fertilizer.

Today's activity is....Sinkholes.

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A sinkhole is a depression that is formed as underlying limestone or a similarly soft rock is dissolved by groundwater. Typically, sinkholes form slowly so that the top layer of land stays intact for a while after the rock below dissolves. Sinkholes vary greatly in area and depth and can be small and shallow or they may be very large. Sinkholes form a direct path to groundwater through which contaminants can easily enter.

For this activity, you will need:

• Awesome Aquifer Kit, OR
• Plastic box
• Gravel
• Sugar cubes (at least 12 cubes)
  
• 16 oz cup of water slightly above room temperature
• Small plastic toy or house (optional)

Activity Steps

1. Read through all the instructions first before you begin to build the model. Make sure you have all the needed materials and supplies.

 

2. Fill the plastic box with gravel until it is about ¼ full.

 

3. Add water so that half of the rocks are covered. (This will represent an aquifer.)

 

4. Place sugar cubes on the gravel, next to one side of the plastic box. The sugar cubes should be at least three cubes across, two cubes wide, and two layers deep. The sugar cubes simulate layers of limestone.

 5. Add more gravel on top to cover the sugar cubes completely. You can either create a hill over the sugar cubes or continue to add gravel so that surface of the model is level.

 

6. If you have a small plastic toy animal or house, place it on top of the gravel directly above the sugar cubes.

  

7. Pour or spray water (preferably warm water) over the buried sugar cubes to simulate rain. Watch and wait.

Frannie noticed that the warm water slowly dissolved the sugar cubes beneath the gravel. The surface of the gravel remained level for a little bit, but eventually it collapsed into the vacuum that was left by the sugar. Like sugar cubes, soluble geologic materials can dissolve over time due to natural causes or human impacts such as over-pumping and over development. Once a sinkhole appears, it can become a direct line for contaminants to enter the water below.