How do minerals form in caves?
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From the brains behind Brains On, this is the Moment of Um. Moment of Um comes to you from APM Studios. I'm Batty Crocker, the bat. That's right, Batty Crocker, not Betty Crocker. I'm a little brown bat who just happens to have a very similar name to a famous baking brand mascot.

Do we both enjoy making soft, fluffy cakes with pillowy clouds of sweet frosting? Yes. Do we both have warm, welcoming personalities? Yes, obviously. And do we both enjoy soaring through the night air, eating delicious insects? Yes. But that's where the similarities end between Betty Crocker, the baking mascot, and me, Batty Crocker, the bat.

Although, I guess I do own that gingham apron. But that's besides the point. The point is, as a bat, I get to do tons of things that Betty Crocker doesn't get to do. Like living in this awesome cave surrounded by rock formations. See these icicle-looking things? They're huge rocks called stalactites that hang from the ceiling.

And those over there, jutting up from the ground, those are stalagmites. And here's a little batty secret for you. I always remember which is which because stalagmites has a G in it, just like the word ground. Stalagmites, ground. Stalagmites come out of the ground. Anyway, all these rock formations are made out of minerals, just like the rocks above ground.

But how are they made? Amber had a question about this too. There's lots of different kinds of minerals that form in caves. My name is Hazel Barton. I'm a professor of geology and I study caves. So one of the ones that people are most familiar with would be stalagmites and stalactites.

And those form when that water that picks up CO2 from the surface that's dissolving the rock to come into the cave, when that water comes in, it just drops as a drip. And instead of giving its carbon dioxide to the water to make the acid to make the cave, it gives its carbon dioxide to the atmosphere. And when it does that, it's no longer acid.

And because it's no longer acid, it can't dissolve the rock anymore. And what happens is the opposite of when it became acid. So you get something called precipitation, which is where a little bit of limestone rock is formed. So this is exactly the same process that forms the cave, but it's happening in a dry cave. So it just drops this little bit of rock behind. And then the next drop comes through and it drops this little bit of rock behind. And then over time, they build up and build up and build up.

First thing you get is something called a soda straw, where you get this tiny rind of crystals around the drop of water. And that builds up over and over time, and it looks just like a drinking straw. Then you get a little bit of dirt come through that clogs the straw. And just like a drinking straw, if it gets a clog in it, you can't suck your drink through it. You also can't drop your drop through it. So the water has to go outside the drinking straw. And then you get a salactite.

and then its little drip will hit the ground and you get a little bit of rock there. And that's called a stalagmite. And those build up from the floor because it might reach the ceiling. Sometimes they meet in the middle and that's where we call it a column. Sometimes they drift along walls and you get things that we call curtains because it looks like a curtain of rock. And there's a lot of other minerals that form. There's one cave that's got over 300 types of mineral in it.

And those minerals tell us about how the cave formed. You can actually use stalagmites and stalactites to understand the history of the weather where the cave is. Um, uh,

So these rock structures form in caves when water seeps underground. It soaks into the ground and dissolves the rock. Eventually, those water drips sneak down through the ceiling of a cave. And because it dissolved that rock on the way, the water has bits of minerals in it. So as it enters the cave, the minerals turn back into rock.

Over long, long periods of time, the dripping water creates rock structures. Some can be long and pointy, like icicles. Others are round, like cakes. Oh, speaking of which, my Funfetti cupcakes are done. Eat your heart out, Betty Crocker. Batty Crocker is here to stay.

If you like this episode, take a second to subscribe to Moment of Um, wherever you listen to podcasts. And if you want to hear about another incredible rock, check out the Brains On podcast, where we have a whole episode all about whether it would be possible to build a house on the moon. So cool. Want to see our shows come to life? Head over to YouTube, where we've got other shows.

See you next time and the next day and every weekday. Until then, um...

Hey, who moved my gingham apron and mixing bowls? I'm not joking!