After the exhausting ascent of Sabancaya, a day of rest was called for, and what better way to spend a day of rest than by carrying on working. Still based in Chivay (and still with our INGV and OVI colleagues) the team decided to head to the nearby Hualca Hualca volcano to investigate some fumeroles on its lower flanks. Since it was our “day off” we took the opportunity to stop at a view point over the Colca Canyon on the way. Admittedly, we throw a lot of superlatives into these blog posts, but the Colca Canyon is truly spectacular. Sheer cliffs plunging over a kilometer down to the Colca river below, impossible agriculture perched on terraces (or “andenes”, possibly from which the Andes take their name) set into the canyon walls and, to top it all, swooping Andean Condors - giant and majestic birds with wingspans of up to 3.2 metres. Admittedly, the condors that we witnessed from the viewpoint were a long way off, and, had we not known better, could easily have been confused with smaller birds that were much closer. Regardless, it was quite a sight, and the fact that we were not gasping for breath at the top of Sabancaya made it seem all that much better.
After the canyon, we drove up a rough dirt track up towards Hualca Hualca until we reached the point where floods had turned the track into a deep gulley. Not even our trusty Land Rover could negotiate this, so we packed our equipment into rucksacks and started hiking. Fortunately, it was not too far and, less than an hour later, we crested the edge of a hill to be met by the deafening roar of a fumerole spouting from the riverbed below us. The noise was incredible, and accompanied by clouds of steam, a mixture of river water and hot water from the hydrothermal system was being fountained high into the air. Our gas monitor showed that the ambient air was good to breathe - no need for gas masks here - so we unpacked our equipment and set to work. Unfortunately, with a slight change of wind, the litres of airborne water stopped falling into the river and started falling on us instead. The few minutes it took to grab our stuff and retreat was enough that we were soaked through, and the rest of the afternoon’s science was conducted in our underpants.
In addition to collecting gas samples, taking temperature measurements and using the multiGas instrument to determine the composition of the gases being emitted, we were also curious to know the flux of gas from the fumerole. Normally, we would do this by measuring the flux of SO2 using UV spectrometers or UV cameras and then combine this measurement with the composition data to get a flux for all gas species. However, this technique requires clear sky behind the plume, and with the Hualca Hualca fumerole being situated at the bottom of a river gulley, this was clearly not going to work. Instead, Fredy, Sandro and Giancarlo performed a transect of the plume using the multiGas connected to a long pipe that was taped to some walking poles (see the video below). The idea behind this slightly bizarre looking exercise is to get a cross-section of gas concentrations across the whole plume. These data can then be combined with the plume velocity (measured from video footage) to obtain a flux.
The science done, we headed back to Chivay for a hearty lunch of delicious Peruvian food before hitting the road back to Arequipa. All in all, a good “day off”. Except that we got fined by the police on the way back to Arequipa for having an insufficient number of license plates on the Land Rover. Apparently you need four, and trying to claim that the “#AboveAndBeyond” printed on the sides of the bodywork was also our registration clearly wasn’t going to work. Given that 80% of the other cars on the road also only had two (not to mention their balding tyres, lack of headlights...etc.), we did feel a little victimized - but what can you do? As the silhouette of the mighty El Misti volcano came into view again behind the skyline of Arequipa, the whole incident was rapidly forgotten and our feelings of indignation turned to trepidation - are we really going to climb that?!