The Cave of Death is not much of a cave, so to speak, but it is a really fascinating hole in the ground nonetheless. Extending only about 10 feet into the hillside, it ends at a crack too small to continue. That is, if it were reasonable to continue for other reasons.
Located on the flank of the Poas Volcano in Costa Rica, the Cave of Death just happens to be near some very nice hot springs which have been developed into Recreo Verde. This fine place was our base camp, actually a fabulous cabin, for our work in this area.
And as for the cave, it is a bit of a tourist attraction, and probably one of the few commercial caves where one does not in fact go in the cave. Why? Good question and glad you asked. The reason for the name is fairly simple, as the cave itself is a huge emitter of nearly pure carbon dioxide. This, as one might suspect, is what could mildly be called, "bad air" and it is quite dangerous and often fatal to animals that enter the cave.
But, since carbon dioxide is heavier than air, the "bad air" is mostly along the floor, and in fact pools up at the entrance with the spillover rolling out of the cave and along the ground. How do we know this? Another good question! Guy van Rentergem invented a clever little smoker device out of an e-cigarette machine, which could be placed in specific spots to see exactly where the gases were going. As well, we used a carbon dioxide meter to determine where the gas was and in what concentrations.
Located on the flank of the Poas Volcano in Costa Rica, the Cave of Death just happens to be near some very nice hot springs which have been developed into Recreo Verde. This fine place was our base camp, actually a fabulous cabin, for our work in this area.
And as for the cave, it is a bit of a tourist attraction, and probably one of the few commercial caves where one does not in fact go in the cave. Why? Good question and glad you asked. The reason for the name is fairly simple, as the cave itself is a huge emitter of nearly pure carbon dioxide. This, as one might suspect, is what could mildly be called, "bad air" and it is quite dangerous and often fatal to animals that enter the cave.
But, since carbon dioxide is heavier than air, the "bad air" is mostly along the floor, and in fact pools up at the entrance with the spillover rolling out of the cave and along the ground. How do we know this? Another good question! Guy van Rentergem invented a clever little smoker device out of an e-cigarette machine, which could be placed in specific spots to see exactly where the gases were going. As well, we used a carbon dioxide meter to determine where the gas was and in what concentrations.
Guy and his smoker tracking the flow of carbon dioxide out of The Cave of Death, Costa Rica
Note that the signs in the photo helpfully say "toxic gas", "entry prohibited" and "don't throw trash". The last one is kinda funny, compared to the others, until you realize that any trash thrown in the cave is rather hard to retrieve since you can't just go in there and pull it out.
And just to be thorough, we tracked the gas with smoke all the way out of the protective barrier at the cave's entrance where it eventually drifts off in the breeze, while staying right along the ground.
And just to be thorough, we tracked the gas with smoke all the way out of the protective barrier at the cave's entrance where it eventually drifts off in the breeze, while staying right along the ground.
Smoke-tracking the carbon dioxide coming out of the Cave of Death
And while Don McFarlane was taking a number of scientific measurements and recording data and just being an all around science guy...
Don McFarlane measuring gas concentrations at the Cave of Death
It still baffles me as to exactly what he was doing here...
Some stop and smell the roses, but Don McFarlane...
Anyway, one of the more notable features of the cave is the pool of carbon dioxide on the floor, which is remarkably stable, and nearly 100% CO2. It is just deep enough that any small animals that go in there, end up in that oxygen-free zone and quickly pass out and die. The Recreo Verde folks told us that the most common animals that die in the cave are rats, snakes and small birds. And, just looking in we could see at least one fairly recent fatality (sorry, I can't get a species from this photo).
A dead bird on the floor of Cave of Death, Costa Rica
The smoke was really useful at showing the gas movement out of the cave, but what would it do when placed under the level of the carbon dioxide pool? Man, you have all the great questions today! Turns out that the gas has a very slow-moving eddy effect going on, and after a minute or two of watching the smoke it looked like a galaxy was forming.
Smoke shows the airflow pattern in the carbon dioxide pool in the Cave of Death
And just for an added attraction here at Tropicalbats.com, a video about the cave from none other than Guy van Rentergem!
So that is the Cave of Death, a carbon dioxide-emitting hole that has a penchant for killing small animals. And now I know you have one more question: Did any of us actually go in there? I end with this photo...
What sign?
***Huge thanks to Recreo Verde for allowing us to study their most interesting little cave. Awesome place to stay on all accounts and really enjoyed it there.
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