Stalactite growth

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Notoriousliz7
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Joined: Sun May 22, 2022 5:02 pm
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Stalactite growth

Post by Notoriousliz7 »

We are researching stalactites and visited a cave where the tour guide wanted to prove creationism by showing how quickly stalactites form dripping from cement.. tens of years instead of thousands. We’re trying to find a scientific explanation as to why “urban stalactites” grow faster, but all our searches just lead us to religious websites.
drstein2022
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Joined: Tue Aug 16, 2022 9:46 am
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Re: Stalactite growth

Post by drstein2022 »

Hello!

Great question. a) One of the main things controlling the rate of growth for any speleothem (stalactite, stalagmite) is drip rate. Urban stalactites (i.e., "calthemites") have much faster drip rates than any cave stalactites. There are a few reasons for this: 1) typically, above caves, you have a significant amount of vegetation growing (which uses the water above) so not all of the water being deposited at the surface reaches the cave). 2) Speleothems in caves are often deeper than calthemites, which means more surface to go through than say, a tunnel in a subway. 3) Porosity of the material above urban and non-urban speleothems are often different, so water flow-through rates are different.

b) pH of solution also plays a role in rate of growth for speleothems. Often, urban stalactites (calthemites) grow in hyperalkaline solutions because of all of the human chemicals we dump into our urban "ecosystems." Cave speleothems tend to form in near neutral (7ish) pH. In hyperalkaline solutions, calcite and other minerals precipitate out faster!

Hopefully these two points help.
-Rebekah
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