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.

It's Water-Wise Wednesdays with Frannie the Fish! {Christmas Trees Everywhere}

Christmas is past and it’s time to start thinking about putting away the decorations. There are boxes and bags for all of Frannie’s ornaments and strings of lights, but what about the Christmas tree?

Don’t worry Frannie! Real Christmas Trees are biodegradable, which means they can be re-purposed into other natural products very easily.  Christmas trees can add a lot to our environment in ways you might not expect. Check out these unique ways you can re-purpose your Christmas tree!

1) Mulch. Ok, this is an easy one. Many communities and businesses may have a drop off site where you can take your Christmas tree or some kind of tree pick-up service.  Mulching your garden with your old tree will help you save water and money in the summer months ahead.  If your city or county Parks departments have a drop off site for trees, then they might be using the mulch as a natural, renewable trail-lining material that works well for the environment and hikers.

2) Bird Feeders. String up popcorn and fresh orange slices and prop up your old Christmas tree outside. Winter is an especially hard time for birds to find food, so take this opportunity to turn your backyard into a bird sanctuary.

3) Fish Feeders and Refuge. Does a local lake have a drop off site for old Christmas trees? You might not realize it, but they could be throwing your old tree into the lake.  The densely needled branches provide shelter, a safe feeding area, and even food for the fish.

4) Soil Erosion Barriers. The heavy logs are a natural and renewable material that make an excellent foundation for deteriorating lake and river shores.

5) Zoo Animal Enrichment. Re-gift your Christmas tree to your local zoo! Zookeepers are always looking for new ways to make the animal enclosures more interesting for their occupants. The animals can climb, hide in, feed from, or destroy the trees, providing them with physical and mental exercise.

To learn more about how Christmas trees are reused or recycled in your community, reach out to your local zoo, parks department, or arboretum. Share what you find with us on our Facebook, Twitter, or Instagram pages!

Happy Holidays!

It’s Water-Wise Wednesdays with Frannie the Fish! {Awesome Aquifer Kit: Sinkholes}

This week in Frannie’s exploration of the Awesome Aquifer Kit is about sinkholes and how they are formed.

A sinkhole is a hole in the ground caused by the erosion of the soil or bedrock underneath.  They occur when acidic water seeps down and percolates through soluble, or easily dissolved, layers of soil like sandstone, chalk, or limestone.  Over hundreds or thousands of years, more of the rock dissolves while loose soil and sand shifts down to fill the cracks.  For a long time, the land is able to hold its own weight and even the weight of buildings constructed on top of it.  However, as even more of the rock dissolves and becomes empty space, the land becomes too heavy and will collapse suddenly.

For this activity, you will need a pitcher of warm water, sand,
a piece of paper, a cup with a small-medium size hole,
a coffee filter, scissors, and sugar or powdered creamer.

To observe this in our aquifer kits, we’ll start by collecting our materials: a cup, sand, sugar, a paper tube, a pair of scissors, and a coffee filter or sponge.

Frannie starts by cutting a small hole, the same width as the tube, in the bottom of the cup and placing the coffee filter on top of it, keeping it in place with just a little bit of sand.

Next, she puts her tube over the coffee filter and fills the tube a part of the way with sugar.  The sugar represents the soluble rock that will dissolve when the ground gets wet.  While the tube is still in the cup, she pours in the sand so that it comes to about the same height as the sugar.  The sand represents the rest of the ground and will hold the soluble layer in place.

Slowly remove the tube without disturbing the sand or sugar too much and then pour more sand on top, just enough so that none of the sugar is showing.  Carefully pick up the cup and place the bottom into the water and in just a few moments, the water will infiltrate the sand and sugar, dissolving the sugar and creating our sinkhole.

Check out this cool graphic to see what's happening inside the cup!

Graphic by PBS

It's Water-Wise Wednesdays with Frannie the Fish! [Awesome Aquifer Kit: Erosion and Weathering}

This week in Frannie’s exploration of the Awesome Aquifer Kit is all about the concept of erosion and weathering.

Photo credit: howtosmile.org

Weathering is the slow destruction or wearing away of soil or rock which is followed by the process of erosion, where the broken particles are then carried away.  This is a very important concept for groundwater and it can happen in two ways: mechanical weathering or chemical weathering.

Mechanical weathering is when rock or soil is physically broken down by constant exposure to flowing or moving water.

Imagine a river that’s moving quickly, picking up sand from the beaches and carrying it downstream.  That’s an example of the beach being mechanically broken by the stream, which carries the sand downstream and makes those beaches smaller.  The same thing can happen underground where, as water slowly flows and picks up particles of soil or rock, the land might get worn down and even sink slightly. 

 

Photo credit: USGS

If the sinking of the land occurs over a long period of time, we call that subsidence.

Chemical weathering is when the rock or soil mixes with the water and dissolves to become a new substance.

This usually happens when polluted rain seeps down into a carbonate type of bed rock.  The acidic water comes into contact with the basic soil and changes the chemistry of the rock so that it breaks down and forms new particles that move with the water flow.

Photo credit: ABC News

It is this kind of weathering and erosion that is usually the cause of sinkholes, a type of sudden natural disaster that results with a large hole in the ground.  Frannie will show us more about sinkholes next week.