Calthemites: The Urban Stalactites
THIS IS AN EARTHCACHE. As such, there is no container to find, and no log to sign. You will need to visit the location, read the lesson, and complete the tasks in order to log credit for this "find."
On a recent trip to Columbus, GA for an event to celebrate International EarthCaching Weekend, that_earthcache_guy pointed out this feature on a bridge in the park. We all had a lot of fun looking at them and talking about these urban stalactites and I asked him if he was planning to make an EarthCache out of this one, or if he would mind if I did. He told me to go for it!
PLEASE DO NOT TOUCH OR BREAK THE CALTHEMITES SO THEY CAN BE OBSERVED BY FUTURE EARTHCACHE VISITORS.
Tasks
There are four tasks you will need to complete this earthcache. Please send me the answers to the following via the "Send Answers" button before you log your find:
1. In your own words, what are calthemites and how are they formed?
2. Describe the patterns that you see in the calthemites here. What does this tell you about how they were formed? Do you see evidence that they are still growing?
3. What color are the calethemites present on this bridge and do they appear to be leaching additional minerals? If so, which ones?
4. Take a photo of yourself, your group, or your chosen token with the bridge visible behind you. Please post the photo with your log!
Adobe Stock Photo: Close up of soda straw formations in underground cave where ground water leaves small deposits of calcite forming a hollow tube over millions of years.
EarthCache Lesson: Calthemites
You are probably familiar with the term stalactites, which are a type of speleothem. You might even know that stalactites are the icicle shaped calcium deposits that hang down in caves, created by mineral saturated water that drips from the roof of the cave. Stalactites are formed in natural caves, but the same type of calcium deposits can happen on manmade structures as well. Because speleothem literally comes from the Greek words for 'cave' (spēlaion) and 'deposits' (théma), deposits outside of caves cannot be classified as stalactites. These deposits on manmade structures are called calthemites, which comes from both Latin and Greek roots that mean 'lime' (calx) + 'deposits' (thema) + 'rocks or minerals' (ites).
Calthemites are created when lime, concrete, or mortar are used in the construction of a manmade bridge, or other structure. The building materials contain the mineral calcium, which dissolves in water that the structure is exposed to, like rain, mist, and condensation from changing temperatures. as the water carries the calcium to the underside of the bridge and it is exposed to air, the carbon dioxide in the air reacts with the calcium to form calcium carbonate.
Calthemites are typically white in color, as they are composed primarily of calcium carbonate, but they can present as other colors if the water leaches other minerals from the materials in the structure with the concrete. For example, calthemites might be red, orange, or yellow if the structure contains iron, which leaches into the water and oxidizes, creating a rusty color. Calthemites can also be blue or green, if copper pipes are used in the structure and exposed to the calcium-rich water.
Due to the nature of the materials that create them, calthemites have the potential to grow at a rate approximately 200x faster than traditional stalactites. However, the drip rate greatly affects the rate of growth, and even whether growth happens at all. With a drip rate faster than 1 drip per minute, no growth can occur since the chemical processes required do not have time to react. With a drip rate of one drip every eleven minutes, one calthemite was recorded to have grown an astounding 2 mm in length per day! Slow drip rates contribute to calthemites that have thicker diameters than faster dripping counterparts.
Flat Rock Park was constructed in 1907, according to the parks and recreation of Columbus, GA, and they believe this stone archway bridge was probably constructed around that time. No major recorded renovations have been made to this footbridge since that time.
References
Smith, G.K. (2016). "Calcite straw stalactites growing from concrete structures", Cave and Karst Science 43(1), 4–10. http://bcra.org.uk/pub/candks/index.html?j=127
Moore, G. W. (1952). "Speleothems – a new cave term". National Speleological Society News, Vol.10(6), p.2.
Hill, C A and Forti, P, (1997). Cave Minerals of the World, Second Edition. [Huntsville, Alabama: National Speleological Society Inc.] ISBN 1-879961-07-5
White W.B., (1997), "Color of Speleothems", Cave Minerals of the World, (2nd Edition) Hill C. and Forti P. [Huntsville, Alabama: National Speleological Society Inc.] 239–244