Volcancito: A 8 by 10 foot boiling mud pot

It is now Day 9 and we have all but completed our mission. We remain inside the caldera we arrived at yesterday with a clear view of three majestic peaks. This morning we revisited Volcan Miravalles in order to sample gases at the Miravalles Geothermal Plant.

In the afternoon we drove out of the vast, windblown savanna of the caldera floor and entered the dry forest on the flanks of active Volcan Rincon de la Vieja. In a national park known as Las Pailas, we hiked past a broad waterfall cascading down the face of a prominent basaltic lava flow. We collected gases from hot springs and an effervescent pond, and observed a boiling mud pot known as the "volcancito."

The dry forest is yet another of Costa Rica's many woodland habitats. Desiccated by high winds that blow relentlessly across the savanna, the dry forest is a unique habitat dominated by a gigantic variety of fig tree. These have enormous trunks that fan out into convoluted root systems that crawl across the ground, enmeshing the forest floor in a matrix of roots and rocks. Vines drape downward and creepers reach upward, seeming at times to grip the forest in a stranglehold. Various shrubs and succulents occur throughout the understory, comprising a habitat known to gardeners as a zeriscape. The forest abounds with wildlife such as turkeys, jays, vultures, iguanas, and snakes. Troupes of monkeys were frolicking in the canopy. Despite reports that these monkeys are known to throw fecal matter at onlookers, they didn't seem bothered by our presence. We were also delighted to finally see the giant blue "morpha" butterfly, a national symbol of Costa Rica.

Today's scientific reports begin with Toby's account of sampling geothermal gases:

The geothermal reservoir at Miravalles is a vast underground area that contains water and dissolved gases at high temperatures (above 200°C) and pressures. Geothermal wells tap the reservoir, which lies at a depth of roughly 1,500 meters, and the hot water is brought to turbines on the surface via large diameter pipes. These pipes have valves that allowed us to collect the gas samples. Because the pressure in the pipes is very high, an ICE employee attached a steam separator to the valve, thereby reducing the outlet pressure to about three bars (the pressure of a bicycle tire). We collected good samples representative of gases dissolved in the geothermal reservoir.

Toby's student, Mindy Zimmer continues:

After we sampled the wells at Miravalles, we headed for the national park at Rincon de la Vieja. Though the hike was easy, we had to be careful once we reached the hot springs. The constant venting of volcanic gases has significantly altered the landscape, so the ground is very unstable. After picking our way through the rocks, we found a good site to sample. The water was very acidic and hot (83°C), demonstrating the constant activity of the volcano.

We mentioned before that the volcanic gases contain sulphuric acid, and my pants are dramatic proof. I sat down near some hot springs yesterday, and less than 24 hours later, holes had appeared in my pants! I think this gives new meaning to the phrase "hot seat."