Search

Water (H2O) is by far the most abundant volcanic volatile species and plays a predominant role in driving volcanic eruptions. However, numerous difficulties associated with making accurate measurements of water vapor in volcanic plumes have limited their use as a diagnostic tool. Here we present the first detection of water vapor in a volcanic plume using passive visible-light differential optical absorption spectroscopy (DOAS). Ultraviolet and visible-light DOAS measurements were made on 21 May 2016 at Sabancaya Volcano, Peru. We find that Sabancaya's plume contained an exceptionally high relative water vapor abundance 6 months prior to its November 2016 eruption. Our measurements yielded average sulfur dioxide (SO2) emission rates of 800–900 t/d, H2O emission rates of around 250,000 t/d, and an H2O/SO2molecular ratio of 1000 which is about an order of magnitude larger than typically found in high-temperature volcanic gases. We attribute the high water vapor emissions to a boiling-off of Sabancaya's hydrothermal system caused by intrusion of magma to shallow depths. This hypothesis is supported by a significant increase in the thermal output of the volcanic edifice detected in infrared satellite imagery leading up to and after our measurements. Though the measurement conditions encountered at Sabancaya were very favorable for our experiment, we show that visible-light DOAS systems could be used to measure water vapor emissions at numerous other high-elevation volcanoes. Such measurements would provide observatories with additional information particularly useful for forecasting eruptions at volcanoes harboring significant hydrothermal systems. Volcanoes emit large amounts of water vapor, but these emissions are difficult to measure because they are immediately mixed into the atmosphere which also contains significant water vapor. Here we present a new technique for remote detection of volcanic water vapor output. Applying our technique to Sabancaya Volcano, Peru, in May 2017, we found that the volcano was emitting 10 times more water vapor than we expected based on typical gas compositions measured elsewhere. We now know that the volcano would erupt in November 2017, just 6 months after our measurements. We believe that hot magma rising within the volcano led to a boiling of groundwater beneath the surface, which in turn caused the high water vapor emission rates that we measured. We expect that, using our new technique, similar signals might be detected prior to eruptions at other volcanoes around the world, thus helping observatories improve eruption forecasts. Volcanic water vapor emissions were measured with passive differential optical absorption spectroscopy (DOAS) for the first timeExceptionally high water vapor emissions were detected at Sabancaya, most likely due to boiling-off of the hydrothermal systemThe DOAS method could be used to detect similar, preeruptive water vapor plumes at other volcanoes, thus improving eruption forecasts

The freezing point and supercooling process are discussed for their impact on the traditional Andean freeze-dried potatoes called chuño. The freezing point depends on potato species, but typically it is slightly below zero to −3 ​°C; supercooling always occurs before the potatoes freeze, and the lowest supercooling point (LSP) can reach −4.3 ​°C. Recently many of the potato fields near Lake Titicaca are not cold enough to freeze tubers for chuño, and the loss of this food source will be critical in the future.