Monday, October 8, 2012

Cave Unit, and Making Stalactites

One of the whole reasons we planned a trip to New Mexico was so we could visit Carlsbad Caverns, and I knew we'd enjoy it lots more if we had a unit on caves. To make the most of our time, I decided we'd try having school on the road, and I thought it worked quite well. I checked out all our library books before we left, and while they took up all my legroom in the car, it was nice to have them along. We had plenty of time in the car for reading books and discussing things! And I printed out some worksheets and other activities (the children particularly liked this quiz) we could do in the hotel at night, along with our math and other daily work. We spent four days on caves---we could easily have spent more time, but I wanted to have time for a unit on hot air balloons too!
This was our nicest hotel. Two rooms! And several nice spots for doing schoolwork. It felt like a little home.

Of course, having school on the road had its limitations, as everything we did had to be portable! So before we left, we started this experiment with growing our own speleothems. We assumed we would get stalactites and stalagmites, and since this is an experiment that takes some time, we hoped we would find some interesting results when we got home to Utah again!
Procedure for this experiment is here. Basically, it involves making supersaturated solutions of epsom salts/water and baking soda/water, and then soaking a string in the solution and stretching it across two jars. Pretty simple, although Abe put the saucepan on the stove with no water in it, and we didn't realize till we smelled it scorching, and then we put the superheated pan on the counter and it burned the granite (?!) . . . but it was all for the cause of science.

Over a week later, when we got home again, our stalactite was small, but interesting. You could see the rings of minerals it had deposited as it slowly formed! Oddly, we didn't get a stalagmite underneath, but just a sort of hardened pool of solution.

Our favorite result was this (I believe this is the epsom salt solution), which looks like a speleothem called "cave popcorn" or, more accurately, pool spar. It forms underwater in caves. It was very dramatic along the string, and you could also see how enthusiastically it had formed under the water! We thought this was a fun experiment. If we did it again, we'd try to dissolve even MORE baking soda into the other water, and see if we could get a more dramatic stalactite!

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