Development and persistence of hazardous atmospheres in a glaciovolcanic cave system—Mount Rainier, Washington, USA

Christian Stenner, Andreas Pflitsch, Lee J. Florea, Kathleen Graham, and Eduardo Cartaya


Glaciovolcanic cave systems, including fumarolic ice caves, can present variable atmospheric hazards. The twin summit craters of Mount Rainier, Washington, USA, host the largest fumarolic ice cave system in the world. The proximity of fumarole emissions in these caves to thousands of mountaineers each year can be hazardous. Herein we present the first assessment and mapping of the atmospheric hazards in the Mount Rainier caves along with a discussion on the microclimates involved in hazard formation and persistence. Our results are compared to applicable life-safety standards for gas exposure in ambient air. We also describe unique usage of Self-Contained Breathing Apparatus (SCBA) at high altitude. In both craters, subglacial CO2 traps persist in multiple locations due to fumarole output, limited ventilation, and cave morphology. CO2 concentrations, calculated from O2 depletion, reached maximum values of 10.3 % and 24.8 % in the East and West Crater Caves, respectively. The subglacial CO2 lake in West Crater Cave was persistent, with atmospheric pressure as the main factor influencing CO2 concentrations. O2 displacement exacerbated by low O2 partial pressure at the high summit altitude revealed additional cave passages that can be of immediate danger to life and health (IDLH), with O2 partial pressures as low as 68.3 mmHg. Planning for volcanic research or rescue in or around similar cave systems can be assisted by considering the implications of atmospheric hazards. These findings highlight the formation mechanisms of hazardous atmospheres, exploration challenges, the need for mountaineering and public awareness, and the broader implications to volcanic hazard assessment and research in these environments


Cave systems created by glaciers and volcanoes, including ones with steam vents (fumaroles) inside ice caves, can sometimes have dangerous atmospheric conditions. Mount Rainier in Washington, USA, has the world's biggest system of these ice caves. Because of the close proximity of the gas emissions from these caves to many mountain climbers each year, they can be dangerous. In this study, the researchers provide the first assessment and map of the potential dangers in the Mount Rainier caves. They also discuss the local climates inside the caves that contribute to creating and maintaining these hazards. The results are then compared to safety standards for exposure to gases in the air. The researchers also discuss the use of Self-Contained Breathing Apparatus (SCBA), which are systems that allow you to breathe in environments where the air might be unsafe, at high altitudes. They found that in both craters of Mount Rainier, pockets of the gas CO2 (carbon dioxide) form in several places because of the steam vents, lack of air circulation, and the shape of the caves. The highest levels of CO2 they found were 10.3% and 24.8% in the East and West Crater Caves, respectively. The West Crater Cave also has a persistent "lake" of CO2 gas, with the concentration of the gas mostly influenced by atmospheric pressure. Additionally, lower levels of O2 (oxygen) due to being at high altitudes can make certain parts of the cave immediately dangerous to life and health (IDLH), with oxygen levels dropping as low as 68.3 mmHg. These findings are important for planning any volcanic research or rescue operations around similar cave systems. It's crucial to consider the potential dangers of the cave atmosphere. These findings emphasize how these dangerous atmospheres are formed, the challenges of exploring these caves, the need to make climbers and the public aware of the risks, and the broader implications for assessing and researching dangers in these environments.