Management of Volcanic Gas Risks Using Specific Route and Terrain Choices on Mount Hood
During Specific Atmospheric Conditions [revised 2023]
Author note: I want to get this article right; but with Grace’s stage 3 Liver Fibrosis and narrowed IVC and hepatic veins along with Vivienne recovering from a tonsillectomy still. I haven’t been able to read up enough on an interesting portion related to CO2. Newer research notes that at greater than 30% CO2 produces an odor that is not an olfactory hallucination. An older source notes that CO2 produces olfactory hallucinations. If CO2 produces olfactory hallucinations at lower percentages; could that be an olfactory warning?
2010, the last official day of Winter we stood on the summit of Mount Hood during a rare calm afternoon. We had just climbed Cooper Spur after bailing from a different route. The calm weather was a unique experience, there was barely a breeze to move a nose hair. We had to descend the standard southside routes to return to our car at Timberline. The Old Chute was our route down, I had already finished my water; descending the Old Chute is steep but the Hogsback and easier walking was not far away. We approached the Old Chute, I was low on energy and decided to sit just below the rim and took note of the classic volcano smell, but the longer I sat the harder it became to regain motivation. A significant amount of time passed before I started to move. My partner already on the Hogsback, stood for awhile to see when I'd start moving again. Once I did he continued further down, we eventually returned to the car and our respective homes.
That evening, I had a significant respiratory crisis when I began to rehydrate; after a half glass of water I noticed my airway get sore and restrict. My ability to speak and breathe was decreased, I'm not sure why, but in that moment I considered a hot steam shower. Deep inhales of steam gradually relaxed the irritation.
Over the years, I've returned to this experience to understand it. A couple years ago I found an article that explains the hazards related to Sulfur Dioxide (SO2). Which, I assumed was the cause of my respiratory crisis. The article Hazards of Volcanic Gases explains that “approximately 90% of inhaled SO2 is absorbed in the upper respiratory tract, where it forms sulfurous acid which then oxidizes to form sulfuric acid.” This is what I thought coated my parched airway in 2010 during that windless descent. When I sat at an inversion layer ceiling preventing the gases from escaping the crater rim and there was no wind to mix the local atmosphere.
I recently was able to connect with Peter Kelly of the USGS Cascade Volcano Observatory; for significant clarity.
At Mt. Hood the primary gas hazard is from hydrogen sulfide (H2S), which can accumulate in toxic levels in some of the caverns (> 100 ppm). CO2 is another potential bad actor that can also accumulate in depressions. Since the gases from Mt. Hood are sourced from relatively low-temperature hydrothermal fluids, SO2 (a magmatic gas) is not emitted. There are certainly reasons to respect the gases at Mt. Hood: in 1934 a UW student named Victor van Norman was overcome by the gases (or lack of O2, or both) and fell and died after entering the cavern on the NE side of Crater Rock. This sad episode is recounted in Chapter 22 of McNeil’s Mount Hood (1990). Likely in response to Mr. van Norman’s death, the USGS made the first-ever gas measurements at Mt. Hood the next summer, in 1935. The gas measurement techniques they used were somewhat crude by today’s standards, but the reported gas compositions and temperatures of the vents measured in 1935 are roughly similar to what we find now. Results from USGS gas sampling at Mt. Hood and other Cascade volcanoes are summarized online (link).
-Peter Kelly
USGS Cascades Volcano Observatory (CVO)
Reading the Volcanic Hazards article indicates a need to understand weather conditions, while climbing volcanoes, that increase risks related to the mountain's terrain and its emitted gas composition. It is not just falling into a fumarole that is dangerous. If volcanic activity is elevated and there’s little to no wind, the toxic gases will not be mixed well with oxygen near the fumaroles. Those that fall from the Pearly Gates or Old Chute can end up in the associated basins below these two routes—Hot Rocks or Devils Kitchen. This is where, in specific conditions, H2S and/or CO2 can collect in and near the fumaroles. Each volcano has it’s own gas compositions which makes events at one volcano to be pure speculation when applied to a potential occurrence at a different volcano. At a different location than Hood “in 1971 on the flanks of Kusatsu-Shirana volcano, Honshu, when six downhill skiers died almost instantly after passing through a depression filled with H2S.” H2S has the classic rotten egg smell. On more than one occasion I've been hit with a small dose while riding Timberline Ski Area lifts.
The incidents of sensing H2S at Timberline or Meadows brings me to another point described in the article, a gravity current. A unique example at another volcano—different gas composition with different risks—on February 20, 1979 in the Dieng Volcanic Complex a number of villagers were killed by a gravity current of gases after a second eruption from vents south and west of the main craters.
The gas releases at Dieng are very different than what we have on Hood. The Dieng gas expulsions are periodic and the compositions are quite different than on Hood. It’s true both are derived from hydrothermal fluids and contain H2O-CO2-H2S, but at Hood, the most abundant gas is water (H2O ~96-97%) with subordinate amounts of CO2 (~3%) and H2S (~0.3%). In Dieng, the dense gases are >30% CO2 and can have over 1000 ppm H2S. The mechanism of release is different, and the gas hazards are much greater in Dieng.
-Peter Kelly; CVO
The closest comparison to a Hood situation would be the incident at Mammoth Mountain in 2006 when a number of ski patrollers working near the fumarole fell in when snow collapsed. Peter Kelly notes, “Mammoth gases are around 30% CO2 (much greater than Hood) and are more dangerous. The article says the gases are ~99% CO2, which is the anhydrous composition.” Anhydrous is the composition of a gas free from water.
…the snow around the covered vent collapsed. Two members (victims 1 and 2) slid into the 21-feet–deep hole and rapidly lost consciousness. An emergency distress call was placed and additional ski patrollers arrived with rescue equipment soon after. While others attempted to dig a rescue hole through a lower section of the vent to reach the victims, one ski patrol member (victim 3) descended into the hole with a nonrebreathable oxygen mask in hand, but lost consciousness within 30 seconds before he could affix the mask. An additional patroller (victim 4) descended partway down the hole, quickly recognized the dangers of the overwhelming fumes, called out for rescue, and affixed his oxygen mask just prior to losing consciousness.
…
Many of the ski patrol members involved in the rescue experienced transient nausea, vomiting, and dizziness. Victim 4 was alert and oriented soon after extraction. All symptomatic patients were admitted to a local hospital for overnight observation, but none required significant medical intervention. Pulse oximetry and carboxyhemoglobin levels were normal for all patients tested. Victims 1, 2, and 3 were all in cardiopulmonary arrest upon extraction and could not be resuscitated. Autopsies on the 3 deceased patrollers revealed pulmonary edema, enlargement of all 4 cardiac chambers, and subperiosteal hemorrhages in the areas of the petrous pyramids. These findings, combined with the history of exposure, were deemed consistent with asphyxiation deaths. Postmortem carboxyhemoglobin concentrations were not measured.
…
…it is plausible that the amount of CO2 trapped in the fumarole at the time of the incident caused the rapid loss of consciousness in the victims inside the vent as well as the symptoms experienced by rescuers in and around the vent. Additionally, because the MMF sits at an altitude of 2743 m above sea level, any relative hypoxemia experienced by those exposed could have potentially made them more susceptible to the effects of an asphyxiant exposure.
-Wilderness and Environmental Medicine, 20, 77 79 (2009)
The air I was breathing in 2010 at the top of the Old Chute, though it had some plausible amount of H2S; I have no way to know how much, it was enough to cause discomfort to my upper airway once I attempted hydration.
On Mount Hood, the terrain of the standard southside is prime to create any number of incidents that mimic altitude sickness from exposure to volcanic gases. The impact of H2S is nearly the same as Acute Mountain Sickness or worse: headache, fatigue, dizziness and staggered gait; but can develop into bronchitis and bronchopneumonia or at highest concentrations death.
With CO2 “symptoms appear only when such high concentrations are reached that there is insufficient oxygen to support life. Inhalation may cause rapid breathing and increase heart rate (at >7.5%), headache, sweating, dizziness, shortness of breath, muscular weakness, mental depression, drowsiness, and ringing in the ears. Concentrations at >11% result in unconsciousness in 1 minute or less. Convulsions may occur at concentrations of >25%. Rapid recovery occurs on removal from exposure.” The challenge is, we have no live feed of volcanic gas activity. I also just learned that CO2 can induce olfactory hallucinations known as Phantosmia. A study on Parosmia as of 2022 noted:
There is currently little understanding of its pathophysiology, and the prevailing hypothesis for the underlying mechanism is aberrant growth of regenerating olfactory sensory neurons after damage.
-Jane Parker et al.
Another website notes definitions:
Hyposmia is a partial loss of smell, whereas anosmia is the total inability to perceive the odorants. Parosmia is a distorted smell perception in the presence of an odorant stimulus. Phantosmia is an olfactory hallucination perceived when no odorants are present.
-link
Peter Kelly of the CVO noted in a conversation that there is the possibility of installing a live feed monitor for volcanic gas emissions on Hood somewhere in the Crater. But, the challenge is finding a suitable spot away from public hands that may damage the device. Only time will tell if we get a live feed of Hood’s gas activity.
Management
There is a need to assess climate conditions while undertaking activities on volcanoes similar to management of avalanche terrain. Where are the vents? Where are the basins that gases can collect? Is there an inversion? Is there wind to create a slightly more healthy mix of oxygen? Is today a more active day for the volcano? Is our planned route crossing or above any depressions? Think avalanche terrain traps and consider volcanic gas traps
A simple framework to remember what to ask:
Atmosphere
Is there wind mixing the gases with fresh oxygen?
Terrain
Can this terrain trap gases if there is no wind?
AT, consider when Alpine Touring on volcanoes an assessment of Atmosphere and Terrain is required.
Management of these risks will initially occur in the planning: weather forecast: calm or no wind is a potential risk; terrain choices based on weather forecast and fumarole locations. If there's a forecast of no wind, consider the Wy'east or Leuthold routes on Hood to eliminate the risk of a fall into a fumarole . An interesting aspect of gas emissions on a volcano Peter described, known as scrubbing where gases that are water soluble like sulfuric gases and H2S being discussed here. When there’s a significant melt cycle or rain event the gas that emits from the vents will be scrubbed while still in the fumarole. The water from melting snow or rain will alter the H2S to a liquid acid and will travel with gravity. Decreasing the amount that escapes into the atmosphere. An inverse note of that is when there’s a good plume of gas; CVO occasional gets measurements from helicopter.
If you want to further decrease volcanic gas exposure consider Mount Adams, if you can’t climb Adams maybe you’re not ready for Hood. Just because Timberline Lodge is right there doesn’t mean it’s a simple task to summit Hood.
During my conversation with Peter at the CVO he directed me to a paper on the Acute Exposure Guideline Levels or AEGL for H2S which dives deep into the impacts of H2S. A significant note is the level of odor awareness (LOA). LOA is like a warning system where the “threshold ranges between 0.008 and 0.13 ppm and olfactory fatigue may occur at 100 ppm. Paralysis of the olfactory nerve has been reported at 150 ppm.” Therefore, not smelling rotten eggs on a volcano that is known to emit H2S could mean two things—the vent is inactive or enough H2S has accumulated to be hazardous. Another key to assess H2S—short of spending $300+ on a gas monitor—is how eye irritation begins between 6 and 20 ppm where 50 to 100 ppm results is acute conjunctivitis also known as gas eye. Based on the table for AEGLs in a mountaineering environment if your eyes are irritated you may have started your clock of one to four hours and you will experience disabling effects. The big ones from an ability to climb perspective would be loss of equilibrium and loss of consciousness; these are noted as “nonlethal H2S effects” but on the Old Chute or Pearly Gates these would produce undesirable results.
There is a section on PBPK Modeling that is a separate approach in the AEGL document, which is summarized here:
The difference between a PBPK-based and a traditional dose-response assessment is that the PBPK method relies on an internal measure of exposure rather than an external one. An internal measure of exposure can be thought of as the exposure of the target tissue to the chemical, or “dose.” If the dose of chemical that reaches a target tissue can be determined with reasonable accuracy, then the pharmacokinetic issues described above can be dealt with by using known biology rather than UFs and empirical techniques. PBPK approaches are further empowered through the use of different methods for integrating the measure of dose.
-page 383 AEGL Document
If you don’t carry an H2S monitor and until a live feed monitor is installed on Hood; understanding how your physiology responds to H2S while being aware of CO2 combined with understanding the influence of terrain and weather is valuable to longevity in climbing on Cascade Volcanoes and others around the world.
Most of us understand the busy days on Hood better now. But, here I’ll show three images.
I meant four images along with one speculative question; As noted above, Hood emits ~3% CO2, in the Literature Review of Volcanic Gases they note that 10% CO2 produces unconsciousness in about 10 minutes. If there’s no wind and the Crater Rock Fumarole is venting how long could it take for enough CO2 to settle in the Hot Rocks basin to be a problem for rescuers and a patient that fall into the basin?
You can snoblade Adams!! Which place looks more pleasant when considering H2S?
AEGL screenshots from the document:
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1 Williams-Jones, Glyn & Rymer, Hazel. (2015). Hazards of Volcanic Gases.
https://www.researchgate.net/publication/302989533_Hazards_of_Volcanic_Gases
https://www.oregonlive.com/pacific-northwest-news/2015/04/fumaroles_mount_hood_rescuers.html
McNeil, F. H. (1990). McNeil’s Mount Hood (Revised Ed). Zig Zag, Oregon: The Zig Zag Papers
Wilderness and Environmental Medicine, 20, 77 79 (2009) Case Report: Fatal Fall into a Volcanic Fumarole
Anna Hansell & Clive Oppenheimer (2004) Health Hazards from Volcanic Gases: A Systematic Literature Review, Archives of Environmental Health: An International Journal, 59:12, 628-639
Jane K. Parker, Christine E. Kelly & Simon B. Gane 3; Insights into the molecular triggers of parosmia based on gas chromatography olfactometry
Olfactory Hallucinations without Clinical Motor Activity: A Comparison of Unirhinal with Birhinal Phantosmia
Out of Thin Air: Sensory Detection of Oxygen and Carbon Dioxide
P.S. support Greg Coulter if you’re needing ski stuff worked on:
This next clip is for Asit; because Pooh said, “I always get to where I’m going by walking away from where I’ve been.”
Volcanic Podcasts for those interested.