Touring the Is Zuddas Caves
May. 29th, 2025 01:16 amItaly Travelog #19
Santadi, Sardinia - Wednesday, 28 May 2025, 1pm
Our organized activity at Club today was a cave tour at the Is Zuddas Grotto in Sardinia. We could have opted for ruins and wine touring, mountain biking, or horseback riding instead but chose this because it was the most up our alley. As a serendipity we learned a lot about Sardinian history from our tour guide on the van ride over here, even though at the cave she handed us over to a cave specialist.

As we started into the cave I wondered if I'd chosen the wrong activity. I mean, limestone caves are basically all the same. And we've seen a lot of them. Maybe we should have done the ruins and wine tasting tour instead... though Hawk doesn't/can't drink, so that's why.

One interesting formation we saw is "Medusa". ...Okay, maybe that's more interesting linguistically than geologically because "medusa" is the name in Romance languages for jellyfish. It's like only we stupid anglophones have a different name for jellyfish that doesn't evoke the Greek myth of Medusa. And this formation does look more like a jellyfish than a demonic woman with snakes on her head.

Anyone who's visited a bunch of limestone caverns probably looks at the photo above and puzzles for a moment, "Wait, what's going on here?" That's because stalactites and stalagmites are virtually always oriented vertically, their shapes driven by gravity. Well, what happened here is that a block of stalactites fell from the ceiling. They're at an angle because that's how the block landed when it fell to the floor of the cave. And note it fell, like, millions of years ago, because of the size of stalagmites growing atop it.

Above I noted that stalactites and stalagmites virtually always form vertically. There's a category of stalactites that don't. They're called helictites, and they can grow in crazy shapes, thin tendrils extending sideways, curving around, forming curls and "S" bends, and even forking.
"What does Science know about why helictites form in such eccentric shapes?" I politely asked the guide, who'd been getting a bit frustrated about the parallel lesson in limestone formations I'd been whispering to a colleague who'd never been in a cave before.
Strangely I'd never though to ask this before. I mean, other cave guides have pointed out helictites, so I've known what they are, by definition, but not the science behind them. To his great credit, this guide had an education answer.
First, there are multiple theories, the guide explained. That's classic science right there. Science includes uncertainty, and true scientists acknowledge when/where it exists— an unfortunate fact that is frequently exploited by demagogues nowadays to dismiss science as wild theories that are merely personal opinion, all equally valid.
The leading theory, which our guide holds, is that helictites develop in eccentric formations because their rate of water flow is so slow that water evaporates quickly. Remember, all these cave formations are driven by the action of water responding to gravity. Rain water seeping through small cracks in the rocks above dissolves limestone. It flows downward along existing formations and forms droplets at the bottom. Rock re-crystalizes from these droplets. But with helictites it's thought that the water flow is so minimal that the water doesn't even form a droplet; it evaporates before it gets to that stage. Thus limestone deposits may form on the side of an existing limestone structure, or— via capillary action— at its upper tip.
Santadi, Sardinia - Wednesday, 28 May 2025, 1pm
Our organized activity at Club today was a cave tour at the Is Zuddas Grotto in Sardinia. We could have opted for ruins and wine touring, mountain biking, or horseback riding instead but chose this because it was the most up our alley. As a serendipity we learned a lot about Sardinian history from our tour guide on the van ride over here, even though at the cave she handed us over to a cave specialist.

As we started into the cave I wondered if I'd chosen the wrong activity. I mean, limestone caves are basically all the same. And we've seen a lot of them. Maybe we should have done the ruins and wine tasting tour instead... though Hawk doesn't/can't drink, so that's why.

One interesting formation we saw is "Medusa". ...Okay, maybe that's more interesting linguistically than geologically because "medusa" is the name in Romance languages for jellyfish. It's like only we stupid anglophones have a different name for jellyfish that doesn't evoke the Greek myth of Medusa. And this formation does look more like a jellyfish than a demonic woman with snakes on her head.

Anyone who's visited a bunch of limestone caverns probably looks at the photo above and puzzles for a moment, "Wait, what's going on here?" That's because stalactites and stalagmites are virtually always oriented vertically, their shapes driven by gravity. Well, what happened here is that a block of stalactites fell from the ceiling. They're at an angle because that's how the block landed when it fell to the floor of the cave. And note it fell, like, millions of years ago, because of the size of stalagmites growing atop it.

Above I noted that stalactites and stalagmites virtually always form vertically. There's a category of stalactites that don't. They're called helictites, and they can grow in crazy shapes, thin tendrils extending sideways, curving around, forming curls and "S" bends, and even forking.
"What does Science know about why helictites form in such eccentric shapes?" I politely asked the guide, who'd been getting a bit frustrated about the parallel lesson in limestone formations I'd been whispering to a colleague who'd never been in a cave before.
Strangely I'd never though to ask this before. I mean, other cave guides have pointed out helictites, so I've known what they are, by definition, but not the science behind them. To his great credit, this guide had an education answer.
First, there are multiple theories, the guide explained. That's classic science right there. Science includes uncertainty, and true scientists acknowledge when/where it exists— an unfortunate fact that is frequently exploited by demagogues nowadays to dismiss science as wild theories that are merely personal opinion, all equally valid.
The leading theory, which our guide holds, is that helictites develop in eccentric formations because their rate of water flow is so slow that water evaporates quickly. Remember, all these cave formations are driven by the action of water responding to gravity. Rain water seeping through small cracks in the rocks above dissolves limestone. It flows downward along existing formations and forms droplets at the bottom. Rock re-crystalizes from these droplets. But with helictites it's thought that the water flow is so minimal that the water doesn't even form a droplet; it evaporates before it gets to that stage. Thus limestone deposits may form on the side of an existing limestone structure, or— via capillary action— at its upper tip.