Mt Rainier - Balance of Risks

Mt Rainier and Puget Sound Vessel Traffic, Seattle, Washington (on Photoshelter)

Low probability - high impact events present difficulties in weighing the balance of risks in such events. There may be an intellectual understanding that the risk exists and what its consequences are. However, how that intellectual understanding is translated into that marriage of sense and intellect that informs the weighing of risks, is problematic when the high impact event happens so rarely in our experience. Experience, after all, guides our reactions and decision-making in the face of risk. We experience intellectually and emotionally, and this informs future choices. We are guided by instinctual underpinnings that alert us to danger.

When we weigh the balance of risks we look at how to mitigate the low probability - high impact event. This includes identifying the risks and probabilities, assessing how to prevent them if possible and how to mitigate the impacts should they occur. What is the cost of dealing with the risk versus the impacts of ignoring them as if they could never occur in our lifetimes, putting our heads in the sand and tempting to fate?

Studies that the United States Geological Survey (USGS) have done regarding the various risks associated with Mt Rainier are an example of risk assessment. These studies outline probabilities of various classes or sizes of volcanic events occurring.

In recent blog articles, Mt St Helens 31st Anniversary of May 18, 1980 Eruption and

Mt St Helens and other Cascade Volcanoes I discussed the impact of the Mt St Helens 1980 volcanic eruption and potential volcanic hazards in the Cascade volcanoes.

Risks of volcanic hazards have been closely studied on Mt Rainier and are discussed in the USGS report on “Volcano Hazards From Mount Rainier, Washington”, 1995. Mt Rainier’s proximity to major population centers, and it’s size, with a summit at 14,410 feet, mean that Mt Rainier presents an important risk, both in the scale of a potential geological event and potential population impact. Mt Rainier is 54 miles southeast of Seattle and 37 miles east of Tacoma..

The USGS examines each of the volcanic risks in detail. It discusses risks from tephra (volcanic gas/rock ejecta), ballistic projectiles, pyroclastic flow and surges, lava flows, volcanic gasses, debris avalanches and lahars, lateral blasts and glacial outburst floods. All of these are impressive risks. My previous post on Mt St Helens and other Cascade Volcanoes points to excellent USGS material on these topics.

What impressed me most about the Vocanco Hazards From Mount Rainier, Washington (USGS) was the information regarding hazards from debris avalanches, debris flows and lahars. The report states:

“Circumstances conducive to future debris avalanches and debris flows—substantial volumes
of hydrothermally altered rock, substantial topographic relief, great volumes of ice, and the
potential for renewed volcanism—are all present at Mount Rainier. Thus, debris flows are a greater threat to communities down valley from Mount Rainier than any other volcanic phenomenon.” “Volcano Hazards From Mount Rainier, Washington”, (USGS)

Debris avalanches, flows and lahars can arise from weakened mountain rock that has been hydrothermally altered by the action of acidic volcanic gases below the surface to a clay substance that undermines the structure of the mountain, leaving it susceptible to failure. The USGS report, explains this as: “Like a house infested with termites, the affected part of the volcano eventually becomes so weak that it collapses under its own weight, and generates a debris avalanche”

These type of debris flows, containing high quantities of water and hydrothermally altered material are called “cohesive” debris flows.

What I found particularly interesting was that debris avalanches and flows can occur without the type of warning that is typically available when a mountain begins eruptive activity. This may happen if the debris avalanche is due to causes not related to magma movement within the mountain. Weakening in the mountain structure due to underlying hydrothermally altered rock, or, a steepening in mountain slope walls with attendant loss of stability due to glacial erosion (USGS report) can increase the risk of debris avalanche. The historical retreat of glaciers has let mountain sides steepen as the glacier retreats.

The Osceola Mudflow, 5600 years ago, was a cohesive debris flow and the largest debris flow in the last 10,000 years. The flow reached Commencement Bay. The National Lahar, about 1200 years ago flowed all the way to Puget Sound, inundating the Nisqually River.




Nisqually Tideflats and Boardwalk, Nisqually Wildlife Refuge, Olympia, Washington (on Flickr)

The USGS has grouped debris flows into categories according to severity. Class M, the greatest, applies to the Osceola mudflow. This category occurs too infrequently to allow the USGS to assess an annual probability. The USGS Map Insert Low Probability High Consequence Events shows the extent that would be covered by a class M event.

The USGS Map Volcano Hazards From Mount Rainier similarly displays flows expected from Class I, II and III events. An example of a Class I event is the Electron Mudflow which reached the Puget Sound lowlands. According to the USGS, Category I occurs on average 500 to 1,000 years (over a 5,600 year period) with an annual probability of .1 to .2 percent. Class II occurs on average 100 to 500 years tending towards the lower end of the range with an annual probability of 1 percent. The USGS puts this more in the realm of a engineering categorization of a “100 year flood” in it’s paper. Class III debris flows are more common.




Kautz Creek, Mt Ranier National Park, Washington, March 2008 (on Photoshelter)

The Kautz Creek Debris Flow of October 2-3, 1947 was an intermediate size debris flow of class II. It was the largest debris flow since the park was established. It is thought to have been triggered by heavy rains that triggered an outburst flood from Kautz Glacier. The photo shows Kautz Creek in snow, with the water coloring reflecting the iron deposits and geothermal activity of Mt Rainier.

Tahoma Creek on a Foggy Morning, Mt Rainier National Park, Washington, June 2011 (on Photoshelterl)

Debris flows occur along Tahoma Creek. These debris flows may impact a bridge near the park entry, thus requiring dredging and other maintenance.

Mt Rainier has displayed some powerful rock and snow avalanche activity in recent days. An article and photographs in the Seattle Times portray this powerful activity.

Mt Rainier “speaks to us”. We cannot simply consider our environment an inanimate actor upon which we act; indeed our environment may present us with challenges that tax our abilities just at the moment when we are most complacent.

I can recall being on the Emmons Glacier with a group when it was 90 degrees in Seattle; suddenly boulders were rolling down the moraine and we soon (carefully) crab-like scurried down the moraine. A wonder that a glacier would want to melt in the heat, but apparently it does just that.

Debris flows often have their origin in heavy rains and hot temperatures.

So the challenge is to internalize the risks in a fashion that doesn’t over exaggerate the low probability high impact event, yet at the same time seeks to mitigate the associated risks with all risk classes. This involves enjoying Mt Rainier in its many splendors while at the same time understanding its risks, even those that may at time seem remote.

Mt St Helens and other Cascade Volcanoes

Mt St Helens Crater shrouded by clouds, May 16, 2011 (Image on Photoshelter)

In a recent blog article on Mt St Helen’s 31st anniversary, I discussed a visit to the Mt St Helens National Volcanic Monument and displayed some images of earlier 2006 volcanic steam activity.

Today, in 2011, Mt St Helens today is relatively peaceful. The U.S.G.S. Cascade Volcano Observatory has assigned it a “normal” rating (since July 2008) reflecting its relative quiet. The explosive eruption (and buildup) of May 18, 1980 is far behind us, and the volcano has left some distance between the eruptions of 2004-8 and today. The image shows clouds dancing across the crater, not steam of volcanic origin.

Indications are that Mt St Helens will continue its eruptive activity and is likely to erupt again in this century. (Mt St Helens - A 30 Year Legacy of Volcansim - EOS-AGU). This is based on its age and past history.

In my last article, “Calculating Odds and Probabilities” I discussed the assessment of various odds and probabilities ranging from coin tosses to weather forecasting. It is clear that some predictions are relatively straightforward and others are incredibly complex.

The events, risks and probabilities associated with volcanic hazards present a great challenge because of the wide ranging risks, the variability of impacts and the low probabilities of occurrence associated with very high impact events.

Mt St Helens showed us in 1980 that a low probability, high impact event can happen in our lifetime and region (Washington State). While Mt St Helens is the most active of Cascade Volcanoes, the other Cascade Volcanoes are also of interest.


The USGS provides an interactive map of the Cascade Volcanoes from Washington to Northern California. The summary provides a broad overview picturing the scope of Cascade Volcanoes throughout the region. The map/page provides links to each of the Cascade Volcano “Visit a Volcano Site” providing a photo and information for each volcano.

The difficulty in assessing the risk associated with an event, whether it is meteorological or seismic, is in assessing the probability that it will occur, the severity of the event should it occur, and the impact on the population.

The USGS has done a great deal of work in identifying hazards for the Cascade volcanoes. The Mount St Helens eruption, and other volcanic eruptions have allowed geologists to gain a great deal of information regarding volcanic hazards, and develop advanced monitoring technologies to allow them to better manage volcanic risk.

A USGS Fact Sheet (What are Volcano Hazards?) describes Volcano hazards, both in text and with a graphic that displays the hazards on a simplified Cascade volcano.

The hazards shown in the Fact Sheet include hazards that we saw with the 1980 Mt St Helens eruption. The pyroclastic flow that blasted down numerous trees, scorched others and killed people. The towering ash cloud that rained ash fall on Eastern Washington and continued around the world. The debris flows that sculptured the landscape in destructive lahars , racing down the Toutle River, washing out bridges and silting up the Columbia River.

Entrance to Ape Cave, Mt St Helens National Volcanic Monument (Image on Flickr)

In addition, we see the impact of much earlier lava flows in Mt St Helen’s Ape Cave Lava Tube. Ape Cave contains the continental United States’ longest continuous lava tube, occurring around 2,000 years ago in the Cave Basalt.

Cascade volcanoes have an extensive volcanic history, as displayed in a display of their eruptive history over the past 4,000 years which is available as a pdf or poster to order from USGS.

We can look at the chart of volcanic history and wonder given the frequency and time since last eruption, whether a particular mountain is “due” for an eruption. We do know that future eruptions may occur, we simply may not know when. Once volcanic activity has started, geologists are better able to monitor and respond to the ongoing situation.

It is a matter of living with uncertainty and managing risks.

The USGS has comprehensive risk assessments for each Cascade Volcano. More information can be obtained through the USGS’s Cascade Volcano Observatory Website.

Calculating Odds and Probabilities

1986 Liberty Half Dollar Tossed on Grass (Heads) (Image on Photoshelter)


A team will have an opportunity to call “heads or tails” for a coin toss at the beginning of a football game. If the call is successful, heads in the case of the coin pictured above, the team will have the opportunity to chose to take the ball (go on offense) or defend a particular goal. The choices are non-trivial as a team’s defense may be superior to their offense, or the wind may determine the choice of the goal defended. These choices represent the team’s expectations of their success, given their strengths, weaknesses and prevailing conditions.

The coin toss, for a fair coin, will give a probability (p) of .5, or 50% that the call (either heads or tails) will be successful. Coins flipped successively will tend, over a period of time to “revert to the mean”, or tend towards their expected value of 50% heads and 50% tails. The odds ratio for the coin toss is 1:1. Odds ratio is calcuated as the ratio of the probability of the event happening (p) to the probability that it won’t happen (1-p). Thus, out of 2 possible outcomes (heads or tails), one outcome (out of 2) is successful, one outcome (out of 2) is unsuccessful, for a ratio of 1:1.

While the coin toss is random, there is a balance of risks involved in the result. For example, a team with a superior offense can choose to go on offense, sputter on three downs, punt, and turn the ball over to the other team in good field position, despite their expectation of offensive success.


Two Sixes Dice Toss (infrared digital effect) (image on Photoshelter)

People use probabilities and odd ratios in their daily lives, consciously and unconsciously computing expectations and making decisions based on those expectations.

Some may choose to gamble on the roll of the dice. In this case, the probability of rolling two sixes is (1/36) while the odds are 1 to 35 (1 good outcome, 35 losing outcomes). When gambling in an establishment, the house will include a margin in for themselves, to cover expenses and profit. Given fair dice, the underlying odds (and the probabilities) will tend towards their mathematical expected value (1 to 35 and 1/36), thus giving over time a margin to the house.

Mathematical models can calculate the odds that there will be a city rivalry World Series this year, the odds of a particular candidate winning the 2012 election, and many other events.

Of particular interest are the mathematical models that deal with environmental issues, such as weather and climate change, given the emergence of extreme weather events.

Albert Einstein was quoted as saying “I, at any rate, am convinced that He does not throw dice.” (paraphrased as “God does not play dice with the universe”). However Stephen Hawking is quoted as saying “So Einstein was wrong when he said, "God does not play dice." Consideration of black holes suggests, not only that God does play dice, but that he sometimes confuses us by throwing them where they can't be seen”.

The National Oceanographic and Atmospheric Administration (NOAA) has sophisticated climatological models which forecast the weather, and they are continually improving these models in order to provide the maximum amount of warning possible to the populace. Through their efforts, NOAA is seeking to minimize the amount of risk, and maximize the information provided, seeking the “load the dice” in the publics favor.

We rely on weather forecasts in our daily plans. Should we call off the company picnic with a 70% chance of thunderstorms? How about that outdoor wedding? Do you pack the rain slicker or umbrella or leave it behind? Governments and businesses rely on weather forecasts for their daily operations and long term plans. Seasonal hurricane forecasts are looked at with interest by many sectors in planning ahead into the coming hurricane season.

Two United States Coast Guard Cutters monitoring the Westport, Washington Bar entrance (image on Photoshelter)

Nowhere is the issue of balance of risks and weather forecasting more apparent than in the maritime arena. When is the storm predicted to arrive? Is there a confidence interval around that arrival time, as well as its expected intensity? Sailors will balance the risk of venturing out and making headway to their destination versus the risk that the weather will take an unexpected turn for the worse, making for difficult, or hazardous headway, or worse.

The United States Coast Guard (USCG) is a branch of the U.S. Armed forces and is charged with maritime safety, security and stewardship. In this image, the two Coast Guard Cutters are monitoring the closed Westport Bar / navigational entrance from the Pacific Ocean to Westport, Washington. The USCG monitors ongoing conditions and weather forecasts to decide whether or not to close the bar, thus managing safety for mariners. The United States Coast Guard, in its decision-making, relies on the concept of balance of risk, as it makes decisions that affect the public. The public, in turn, makes decisions using balance of risk as it relies on NOAA guidance, the actions of the Coast Guard, and other factors.

It is human nature to calculate probabilities, calculate odds, consciously or unconsciously assess balance of risks. We do so continuously in our daily lives and rely on others to help us do so. We need to expand that awareness to include the risks we face due to environmental changes, consider the balance of risks inherent in the evolving situation, and find a way to meet the considerable challenges head on.

Mt St Helens 31st Anniversary of May 18, 1980 Eruption

Aerial View of Steam Eruption, Mt St Helens, May 20, 2006, taken from Johnston Ridge Observatory, Mt St Helens National Volcanic Monument, Washington (image on Photoshelter)

Thirty-one years ago, at 8:32 am on May 18, 1980, Mt St Helens erupted, in a cataclysmic eruption, that would change the face of the environment and sow the seeds of future renewal. Nature has its way of promoting renewal, through cycles of creation and destruction, and nowhere is this more evident than at Mt St Helens, where the volcano and environs continue to emerge in their new environment shaped by the vehicles of geological change.

Mt. St Helens National Monument can be reach from I-5 southbound at Toledo, SR 505, or from I-5 northbound at Castle Rock, SR 504 (Spirit Lake Highway). I took the latter route, visiting Washington State’s Silver Lake Visitor Center, 5 miles east along SR 504, and took in their presentation on the Mt St Helens Eruption “Cycle of Chaos and Creation”.

I entered Mt St Helens National Volcanic Monument, stopping at Hoffstadter Bluffs Visitor Center, enjoying a view of Mt St Helens in the distance and an excellent Elk Burger in their dining area before heading up to Johnston Ridge Observatory. As you drive towards Johnston Ridge Observatory, there are opportunities to pull over and enjoy differing views of the mountain as you get closer, including at the Elk Rock and Loowit Viewpoints.

The sense of closeness to the volcano becomes more than distance as you become more and more aware of the impact of the blast area on the landscape. Even as it is being transformed, being renewed, you are aware that there are thirty-one years of renewal, and that contrasts with the age of the landscape you left behind.





Mt St Helens Steam Eruption, May 20, 2006, viewed from Hummocks Trail showing renewal of vegetation, Mt St Helens National Volcanic Monument (image on Photoshelter)

The road heads downward before the last ascent to the Johnston Ridge Observatory. The Hummocks Trail provides an opportunity to hike amongst the hummocks, created by the Mt St Helens debris avalanche. The debris avalanche created by the eruption of Mt St Helens offered geologists an opportunity to learn about and identify such formations elsewhere.

From the Hummocks Trail, the road then climbs upwards towards Johnston Ridge Observatory at 4,255 feet. As you hike up an incline from the parking lot towards the Visitor Center, you are greeted with a marvelous view of Mt St Helens, looking right down into the throat of the volcano. It is up close and personal, looming as a reminder of the blast impact, as the crater opens up its giant maw to the visitor, you are struck by the awesome power that so forcefully reconstructed the landscape in the wake of its eruption.

As the clouds dance across the crater and the lava dome inside it, you are reminded that Mt St Helens, the youngest of Cascade volcanoes, has not been quiet since it’s May 18, 1980 eruption. Eruptive activity continued into 1986 and then resumed during 2004-2006, including dome building activity.

A visit to the Visitor Center gives the opportunity to explore exhibits, view a movie, “Message from the Mountain”, and attend ranger-guided talks. In one talk, the ranger used still photographs to illustrate various stages of Mt St Helens’s activity leading up to and including the eruption events. We saw Mt St Helens’s pre-eruptive recreational splendor as a near-perfect volcanic cone and glimpses of pre-eruptive awakenings.

As explained by the ranger, volcanic activity beneath the surface of the volcano eroded and weakened the rock structure on the side of the mountain, turning it to clay. This weakened area provided an opportunistic path for the upwelling magma to take, versus the hardened rock plug at the top of the volcano. The side of the mountain bulged with pressure and structural weakening. The landslide and accompanying 5.1 earthquake triggered the event that would unleash the power and fury of Mt St Helens, with resultant lateral blast, pyroclastic flows, lahars (mud flows) and an ejection of ash that would circle the globe.

It is sobering to realize that volcanism can eat away at a mountain’s rock structure from within, weakening it and exposing the mountain to risk of collapse. It is yet another example of a “tipping point” where a marginal change can have a result out of proportion to its own magnitude.

Geologists and volcanologists study volcanoes and other geological system and we are all continually learning from their experience. Johnston Ridge Observatory was named in memory of geologist David Johnston, volcanologist, who witnessed the May 18, 1980 eruption from what is now Johnston Ridge, and radioed in the message “Vancouver, Vancouver, this is it” before perishing in the blast.

The Mt St Helens 1980 eruption has resulted in a continued expansion in knowledge and monitoring tools for understanding the behavior of volcanoes.

In one study, the impacts of volcanic hydrothermal systems on Cascade volcanoes is being studied by the United States Geological Survey.

A wide range of information about Cascade Volcanoes can be found on the Cascade Volcano Observatory (CVO) site.