The main crater, which is 950 feet deep.
The volcano is located within Poás Volcano National Park, so naturally there was a gift shop. It had a wonderful selection of books that were 50% off, and I found one about lichens! This was a pretty big deal to me, since it's difficult enough to find books about lichens in the United States, so I promptly bought it. It's Líquenes de Costa Rica, by Loengrin Umaña and Harrie Sipman, and is published by INBio, the Instituto Nacional de Biodiversidad, a huge Biodiversity institute in Costa Rica. The book has some general information about lichens, and identification information for 55 species of Costa Rican lichens.
It's always nice to find some extra information about lichens since they are generally overlooked. It's amazing to think that a lichen is a symbiosis between a fungus and an algae; it looks radically different from either of those. They're grouped in the Kingdom fungi, and are referred to as lichenized fungi, showing the limits of our taxonomic systems.
Lichens are useful as biomonitoring agents. They're slow-growing and are apt to acquire minerals and things from the air. They hold onto these materials for a long time, and so can be used to monitor air pollution levels in an area. This particular characteristic is something important for at least two studies going on in Marietta, Ohio, measuring manganese levels and air quality. In the above picture, the lichen doesn't look terribly healthy, and this is probably due to the sulfur levels in the area.
Kayford Mountain lichen, notice the discoloration near the top.
Another example of air quality and lichen biomonitoring can be found in the area near Kayford Mountain, West Virginia, where a mountaintop removal mining site's air pollution can be seen in the lichens.
Lichens are pretty useful, and a lot more interesting than they get credit for. Hopefully I'll find some more information about them while I'm down here. I might even learn something I can take back to Ohio and use.