Now most times you go slopping about in a swamp you get some gas bubbles coming up around your feet as the by-products of plant decomposition are released. This is primarily methane and carbon dioxide with some hydrogen sulfide in the mix, created when plants decompose in the mostly oxygen-free zone under the swamp water.
But this swamp was quite different than anything we'd seen. First, it is just a flat spot in the middle of a pasture that looks completely unremarkable other than one small pool of open water barely visible.
We let Carlos go first, and it didn't seem bad at all. He worked his way out into the weeds and didn't seem to be sinking in very far. Oh this wouldn't be bad at all.
We popped the lid off the tube at the top and could actually see the carbon dioxide gas coming out. It's clear gas, but it looks a little bit like heat waves on a very hot day. And it's pretty much pure carbon dioxide gas. But wait...
Previously I noted that swamp gas is methane, carbon dioxide and hydrogen sulfide, and now I am saying that THIS swamp gas is 100% carbon dioxide. Yes, and yes. Because this swamp is located on the flank of the Poas Volcano, in a zone where carbon dioxide is super common in the subsurface, the swamp has become a sort of gas escape spot. From what we could tell, very little gas in this swamp is from plant decomposition, while loads of it is from some effect of the nearby volcano.
Carlos chopped a hole in the grass near the funnel to show the water surface. And it was just bubbling away! This was cool.
We left the swamp and Carlos told us about all the carbon dioxide in the area. It seems that there is so much of it that they drill wells for it and capture it to use in pretty much every can and bottle of beer and soft drink in all of this part of Central America. It's a lot of gas. And on our way out of the area we did get to see one of the wells, which was our last quick stop before heading for dry footwear back at Recreo Verde.