Moving mountains: Landslides and Volcanoes in a Warming Cryosphere
Mount Joffre landslide. May 2019. Photo by Wilfried Braun.
At 7:40 am on May 13th, 2019, 2.3 million cubic metres of rock hurtled downslope from Mount Joffre in southwest British Columbia. Moving at up to fifty metres-per-second, it traveled four kilometres down Cerise Creek, obliterating backcountry ski trails and climbing routes and destroying swaths of forest. Three days later, a similar volume of material collapsed in a second slope failure on the mountain. These massive events created considerable concern in the surrounding communities, and they were not the first large landslides to cause extensive destruction in the region.
The Mount Joffre landslide is just one recent, and fortunately non-fatal, example of alpine hazards that surround us. Living and playing in the mountains always has a certain risk. Landslides, snow avalanches, and volcanoes are just some of the hazards in mountainous areas. However, many of these hazards are increasing in both frequency and severity as the climate warms and alpine permafrost melts. In this article, we highlight the emerging hazards of landslides and volcanic activity that are associated with a warming cryosphere in British Columbia. There are many similarities between these examples and the hazards that exist in other mountainous areas around the world.
Throughout history, hazards in mountainous areas have posed a significant risk to people and property. These risks are increasing due to an apparent increase in frequency of events, caused in part by climate change and by increasing population density and infrastructure in the mountains. Simply put, the more people and infrastructure (buildings, roads, power lines, pipelines, telecommunication cables) in warming mountains means an increased likelihood of being affected by these hazards.
Loss of the Cryosphere Causes Mountain Slopes to Fail
The cryosphere is a zone of the Earth where cold temperatures and frozen surfaces prevail, including glaciers, snow, and permafrost (frozen ground). Both permafrost thaw and glacial thinning are thought to play a major role in mountain landslides, and both of these factors are considered preconditioning triggers for sudden slope failures. Permafrost is ground that is at or below zero degrees Celsius for more than two consecutive years, and its degradation can exacerbate hazards. British Columbia has patchy permafrost at low elevations in the north, but also at high elevations throughout the province.[i] Degradation, triggered by warmer winters and summers, causes both small and larger scale hazards. Thawing permafrost reduces rock strength, and it allows meltwater to penetrate into bedrock fractures, which increases pore pressures, further weakening the rock.
More than two-thirds of the large rockslides in northern B.C. have been found to originate from steep cirque faces, where permafrost was likely present.[ii] Recent studies have attributed a significant increase in rock avalanches in southeastern Alaska to permafrost degradation in high mountain peaks.[iii] Not only were high-elevation rockslides increasing, but peak years correlated with the warmest years on record. Heat advection by the movement of meltwater in bedrock cracks can also lead to increased degradation rates of mountain permafrost, further destabilizing slopes.[iv]
When glaciers erode mountain valleys, they impart stresses and fractures into the valley walls, but at the same time provide support for these slopes. So, when glaciers thin, melt, and retreat, these slopes become unsupported (or “debuttressed”), and the fractures widen, sometimes to the point of slope failure.[v] A 2004 study found that landslides were more common in recently deglaciated areas in southern B.C. than elsewhere.[vi]
Landslides
“Landslide” is a generic term to describe the downward movement of soil, rock, or other earth material under the influence of gravity.[vii] One of the simplest ways to describe a landslide is to name its material and its movement style, such as rock fall, debris flow, or earth slide. Smaller landslides are commonly described in this simple way, but larger ones are usually more complicated. For example, a rock mass can slide down a bedrock slope onto a mountain soil can trigger a debris avalanche. This is referred to as complex landslide, or more specifically in this case a “rock slide - debris avalanche.” An extreme example of a rock slide - debris avalanche is the 2010 Mount Meager landslide, which traveled twelve kilometres.[viii]
Landslides can also extend their devastation by transforming into other hazards, by creating what’s called “process chains.” For example, on the Alaskan coast, glacial debuttressing in fjords has resulted in some very large landslide-generated tsunamis: a 2015 landslide producing a 193-metre high wave in Taan Fiord,[ix] and the 1958 Lituya Bay earthquake produced a mega-tsunami that downed timber up to an elevation of 520 metres at the entrance of Gilbert Inlet.[x] Researchers recently identified an unstable mountain slope above the toe of a rapidly receding glacier near Prince William Sound that has the potential to fail and generate a mega-tsunami of similar size.
Volcanoes
Volcanoes can come in many shapes, sizes, and compositions, but are broadly considered as sites through which magma (molten rock and gases) can reach the Earth’s surface.[xi] It may be news to many Canadians that the country’s west coast, which, as part of the infamous Pacific Ring of Fire, is home to a wide range of dormant and active volcanoes. These include low-viscosity systems that produce lavas similar to those seen in Hawaii (such as at Tseax volcano in the Interior Ranges of northwestern BC), as well as more explosive volcanoes with high-viscosity magmas similar to Mount St. Helens, including Mount Garibaldi, Mount Cayley, and Mount Meager volcanoes in the province’s southwest.
Figure 1. Summit crater of Tseax Volcano in northwestern B.C. Photo: Glyn Williams-Jones, 2019
Figure 1b. The Tseax Volcano’s thirty-two-kilometre-long lava flow field in the Nass Valley. Photo: Glyn Williams-Jones, 2019
Unlike the distinctive volcanoes of Oregon and Washington states, the high rates of tectonic uplift in conjunction with glacier interactions have shaped the volcanoes of the Garibaldi Volcanic Belt into broad and highly-eroded massifs that are difficult to distinguish from the surrounding mountains. By and large, the Canadian volcanoes are relatively “quiet,” and remote, with the last eruption in 1800 at Lava Fork volcano in northwestern B.C. This is not to imply that these volcanoes are not dangerous. In fact, a seventeenth-century eruption of Tseax volcano (Figure 1) destroyed a number of villages of the Nisga’a Nation and may have caused as many as two thousand deaths.[xii]
Infrastructure and People at Risk
Landslides have a significant effect on communities, disrupting infrastructure by severing lifelines, cutting off contact, delaying the transportation of goods and services, and in some cases, killing and injuring people. With more and more people moving to and throughout the mountains, the risk is increasing. Towns like Canmore in Alberta and Hope and Pemberton in B.C. are seeing increased population growth as people move out of larger urban centres for quality of life, retirement, and job opportunities. Canmore, located just outside Banff National Park’s eastern boundary, is a case in point. With restrictions on development in the neighbouring park, Canmore has seen rapid growth, with part of the town built on the alluvial fan of Cougar Creek. The town and associated infrastructure was severely impacted by debris floods in June, 2013: houses and yards were swept away, roads (including the Trans-Canada highway) were cut, and many people were evacuated (Figure 2). In response, Canmore has recently received approval to build a large protection structure at a cost of about fifty-million dollars. Construction will start this summer and temporary retention nets are in place until the more permanent solution is completed (Figure 3).
Figure 2. Cougar Creek during just after the 2013 floods. The trans-Canada highway was blocked. Photo: Town of Canmore.
Figure 3 Temporary retention net installed on Cougar Creek upstream of Canmore. It is designed to slow and capture debris flows before they affect downstream infrastructure. A larger permanent structure is presently being build. Photo: Brent Ward, 2018.
The 2013 damage in Canmore was triggered by intense rainfall that exacerbated spring snowmelt. This was a regional event with a large area adversely affected with numerous landslides and flooding, causing extensive damage, notably serious flooding in Calgary, High River, and many other communities. Obviously, this received extensive national media coverage.
Figure 4. One of several debris flows that affected the Trans-Canada Highway and the CPR Railway, November 2019. This debris flow blocked both lanes of the highway and the railway line, engulfing a semi-trailer truck. Photos: Matthias Jackob
But it is not just large events that affect mountain communities. Many smaller events have significant impacts. Areas around Hope, B.C., are affected every ten years or so by individual debris flows with periods of regionally extensive clusters occurring in 1951, 1983/1984, 2007, and 2018. These affect buildings, railways, and the highway, as happened again in November in 2019 (Figure 4). Indeed, January 2020 was the wettest on record since the 1930s, and, at the end of the month, a large “Pineapple Express” hit southwest B.C. These warm moist air masses drop extreme amounts of rain, which can also melt existing snow, liberating even more water. This particular event caused extensive regional disruption: flooding occurred in many areas, debris flows blocked roads, culverts became plugged, and roads washed out, in one case trapping skiers at Hemlock Valley. In the same event, a relatively small debris flow in the Fraser Canyon cut a fiber-optical cable, disrupting phone and internet service in the lower mainland. Pipelines are infrastructure that are also at risk. Large rock-debris avalanches have ruptured a gas pipeline in northwestern B.C. at least four times over the last forty years (Figure 5).[xiii]
Figure 5. A 2002 rock slide – debris flow ruptured a natural gas pipeline and resource road adjacent to Zymoetz River. Note the debris fan in the river. Photo: Marten Geertsema
Two Mountains to Watch Closely
Mount Joffre
The recent Mount Joffre landslide is a good example of a landslide pre-conditioned by climate warming, and how citizen science and social media assisted with the research.[xiv] Permafrost was likely present in the initiation zone of the landslide. However, warming over the last few decades may have thawed the permafrost enough to weaken the rock mass. In fact, spring 2019 was one of the warmest in over thirty years and caused rapid melting of the snow pack. This rapid melting caused instabilities that were evident to observant locals, who posted pictures on social media (Figure 6). Not quite reaching the Duffey Lake Road (Highway 99), the landslide was first reported by a helicopter pilot. Once reported, landslide researchers traveled to the site, where they documented the failure and noted other areas in the head scarp that could fail. Determining the timing of the landslide was accomplished by examining sequential satellite imagery. However, the more accurate dating of the landslide was made by examining seismic records. Large landslides create “earthquakes” that have a much different seismic signature than that of earthquakes.[xv] This landslide was large enough that it appeared on seismographs hundreds of kilometres away, and thus could be dated to the minute. The second landslide, which occurred three days later, serves as a cautionary tale for all landslide investigators and curious observers; there could have easily been some first responders at the landslide when this failure occurred.[xvi]
Figure 6. Mount Joffre showing the headscarp after the May 13 and May 16th, failures, giving an idea of the volume of each failure. Photos: Tom Millard
Mount Meager
The Mount Meager Volcanic Complex is of particular interest as it is an active volcano 160 kilometres northwest of Vancouver, B.C. Formed over the last two million years, Mount Meager is also the site of Canada’s most recent large explosive eruption about 2,400 years ago. The widespread hydrothermal activity (that is, the flow of hot and acidic fluids through the volcano), which is the source of many of the area’s hot springs, has also resulted in pervasive geochemical alteration and weakening of the rock. This weak rock has resulted in so many landslides, some fatal, that Mount Meager has been called Canada’s “most dangerous mountain.” Most of the recorded landslides occurred during heat waves, being triggered by the melting of snow and ice, which saturate and further weaken the rock. Mount Meager is also the site of Canada’s largest recorded landslide: a rock slide - debris avalanche, carrying approximately fifty-three million cubic metres of debris, occurred in August 2010 during another heat wave.[xvii] This failure was so large that it generated an earthquake equivalent to M 2.6, and was recorded in US neighbouring states of Washington and Alaska[xviii]; it also briefly damned the Upper Lillooet River Valley and forced the temporary evacuation of nearly 1,500 people from Pemberton meadows due to the threat of flooding.
This unstable volcanic mountain will certainly continue to generate landslides. Ongoing satellite radar monitoring has detected over twenty-seven active slopes with volumes exceeding half-a-million cubic metres of active material. In fact, one of these slopes contains 300-500 million cubic metres of material – for scale, that’s ninety-thousand Goodyear blimps – and is moving downslope at three-and-a-half centimetres per month in the late summer. When this slope fails, a nearby hydro-electric facility will be directly impacted, and there is a significant likelihood that, as in 2010, secondary flooding will affect the village of Pemberton sixty kilometres downstream.
Figure 7. Keyhole falls and slot canyon incised through the welded volcaniclastic deposits in the Upper Lillooet River Valley. Photo: Steve Quane
Mount Meager is also still very much an active volcano. Its geologically recent explosive eruption only 2,400 years ago was approximately the same size as the 1980 eruption of Mount St. Helens in Washington State, sending an eruption column of fifteen-to-seventeen kilometres into the air. Ash was deposited as far east as Calgary, Alberta.[xix] During this eruption, clouds of superheated volcanic gas and debris (a block and ash flow) flowed down the mountain’s eastern flank into the Upper Lillooet Valley creating an impermeable welded deposit and a 100-metre high dam, which blocked the Lillooet River and created a temporary lake. The dam subsequently failed, and the resulting outburst flood carved a slot canyon into the dam, now known as Keyhole Falls (Figure 7).[xx] While Mount Meager is currently quiet, it is nevertheless still active. Hot volcanic gases, with toxic levels of hydrogen sulphide and carbon dioxide, have melted their way through the Job Glacier on the mountain’s northwest flank (Figure 8).
Conclusion
Both landslides and volcanoes pose hazards to the public and infrastructure in British Columbia. Volcanoes can trigger rock slides and mobile lahars that may impound rivers. Some volcanoes may even erupt. Mountain landslides are increasingly sensitive to climate change, with both permafrost degradation and glacier retreat likely contributing to the increase in the number of large rockslides province-wide. These landslides can harm people and infrastructure, but they can also transform into debris flows or even cause a local tsunami.
Figure 8. Glaciovolcanic cave on Mount Meager’s Job Glacier created actively degassing volcanic fumaroles. Photo: Rachel Warwick
Fortunately, there is increasing interest in monitoring these potential hazards. For example, the Centre for Natural Hazard Research (CNHR: http://www.sfu.ca/cnhr/), formed in 2005 and hosted at Simon Fraser University, is conducting innovative research on geophysical processes that are a threat to the population and economic infrastructure of Canada. While CNHR has a western Canada focus, the research and tools developed are applicable to the whole of Canada and the world. By integrating physical science with social policy research, CNHR aims to lead the way in making Canada more resilient to natural disasters.
Authors Bios
Brent Ward is a Professor and Chair of the Department of Earth Sciences at Simon Fraser University, and Co-Director Centre for Natural Hazards Research; Glyn Williams-Jones is a Professor (and incoming Chair) in the Department of Earth Sciences at Simon Fraser University, where he leads the Physical Volcanology Group and is Co-Director Centre of Natural Hazards Research; Marten Geertsema is a Research Geomorphologist in the Department of Forests, Lands, and Natural Resources, Government of British Columbia.
[i]Hasler A., M. Geertsema. Provisional permafrost map of British Columbia. http://www.env.gov.bc.ca/esd/distdata/ecosystems/Permafrost/PermaFrostModel/ (2013).
[ii]Geertsema, M., J.J. Clague, J.W. Schwab & S.G. Evans. An overview of recent large catastrophic landslides in northern British Columbia, Canada. Engineering Geology 83, 120-143 (2006).
[iii]Coe, J., E.K. Bessette-Kirton & M. Geertsema. Increasing rock-avalanche size and mobility in Glacier Bay National Park and Preserve, Alaska detected from 1984 to 2016 Landsat imagery. Landslides 15, 393-407 (2018).
[iv]Gruber, S., and Haeberli, W. Permafrost in steep bedrock slopes and its temperature-related destabilization following climate change. Journal of Geophysical Research 112 (2007); Noetzli, J., and Gruber, S. Transient thermal effects in Alpine permafrost. The Cryosphere 3, 85-99 (2009).
[v]McColl, S.T. Paraglacial rock slope stability. Geomorphology, 153, 1-16 (2012); Geertsema, M. & M. Chiarle. Mass movement: Effects of glacial thinning. In John F. Shroder (ed.) Treatise on Geomorphology, Vol. 7, Academic Press, San Diego, 217-222 (2013); McColl, S.T. & T.R. Davies. Large ice‐contact slope movements: glacial buttressing, deformation and erosion. Earth Surface Processes and Landforms, 38, 1102-1115 (2013); Deline, P., et al. Ice Loss and Slope Stability in High Mountain Regions. In J.F. Shroder, W. Haeberli, C. Whiteman (eds) Snow and Ice-Related Hazards, Risks and Disasters, Elsevier Book Series, Amsterdam, 521-561 (2015); Kos, A., F. Amann, T. Strozzi, R. Delaloye, J. von Ruette & S. Springman. Contemporary glacier retreat triggers a rapid landslide response, Great Aletsch Glacier, Switzerland. Geophysical Research Letters, 43, 12-466 (2016); Cloutier C., J. Locat, M. Geertsema, M. Jakob & M. Schnorbus. Potential Impacts of climate change on landslides occurrence in Canada. In Ho, K., S. Lacasse, L. Picarelli (eds), Slope Safety Preparedness for Impact of Climate Change CRC, Boca Raton, 71-104 (2106).
[vi]Holm, K., M. Bovis & M. Jakob. The Landslide Response of Alpine Basins to Post-Little Ice Age Glacial Thinning and Retreat in Southwestern British Columbia. Geomorphology 57, 3-4, 201-216 (2004).
[vii]Cruden D.M, D.J. Varnes. Landslide types and processes. In: A.K. Turner and R.L. Schuster (eds) Landslides investigation and mitigation. Transportation research board, US National Research Council. Special Report 247, Washington, DC, Chapter 3, 36–75, (1996).
[viii]Roberti, G., P. Friele, B. van Wyk de Vries, B. Ward, J.J. Clague, L. Perotti, and M. Giardino. Rheological evolution of the Mount Meager 2010 debris avalanche, southwestern British Columbia. Geosphere 13, 2, 369–390 (2017).
[ix]Higman, B., D.H. Shugar, C.P. Stark, G. Ekstrom, M.N. Koppes, P. Lynett, A. Dufresne, P.J. Haeussler, M. Geertsema, S. Gulick, A. Mattox, J.G. Venditti, M. Walton, N. McCall, E. McKittrick, B. MacInnnes, E.L. Bilderback, H. Tang, M.J. Willis, B. Richmond, R.S. Reece, C. Larsen, B. Olson, J. Capra, A. Ayca, C. Bloom, H. Williams, D. Bonno, R. Weiss, A. Keen, V. Skanavis & M. Loso. The 2015 landslide and tsunami in Taan Fiord, Alaska. Scientific Reports 8, 1-12 (2018).
[x]Dai, C., B. Higman, P.J. Lynett, M. Jacquemart, I. Howat, A.K. Liljedahl, A. Dufresne, J.T. Freymueller, M. Geertsema, M. Ward Jones & P.J. Haeussle. (In review). Large slow moving landslide and potential tsunami following rapid glacier retreat, Barry Arm Fjord, Alaska. Journal of Geophysical Research; Miller, D.J. The Alaska earthquake of July 10, 1958: Giant Wave in Lituya Bay. Bulletin of the Seismological Society of America 50, 253-266 (1960); Ward, S.N., S. Day. The 1958 Lituya Bay landslide and tsunami – A tsunami ball approach. Journal of Earthquake and Tsunami 4, 285–319 (2010); DeMarban, A. Barry Arm Landslide Working Group Letter, Anchorage Daily News, https://www.documentcloud.org/documents/6890609-5-14-20-Barry-Arm-Landslide-Working-Group-Letter.html (2020).
[xi]Francis, P. Volcanoes: A Planetary Perspective, Oxford University Press, Oxford, 443 (1993); Geertsema, M., A. Bevington. A cautionary note for rock avalanche field investigation – recent sequential and overlapping landslides in British Columbia. Canadian Geotechnical Journal, doi 10.1139/cgj-2019-0751 (2020).
[xii]Le Moigne, Y., G. Williams-Jones, J.K. Russell & S. Quane. Physical volcanology of Tseax volcano, British Columbia, Canada. Journal of Maps 16, 363-375 (2020); Williams-Jones, G., R.W. Barendregt, J.K. Russell, Y. Le Moigne, R.J. Enkin & R. Gallo. The age of the Tseax volcanic eruption, British Columbia, Canada. Canadian Journal of Earth Sciences, doi: 10.1139/cjes-2019-0240 (2020).
[xiii]Schwab, J.W., M. Geertsema & A. Blais-Stevens. The Khyex River landslide of November 28, 2003, Prince Rupert British Columbia Canada. Landslides 1, 243-246 (2004); Boultbee, N., D. Stead, J. Schwab & M. Geertsema. The Zymoetz River rock avalanche, June 2002, British Columbia, Canada. Engineering Geology 83, 76-93 (2006); Geertsema, M., J.W. Schwab, A. Blais-Stevens & M.E. Sakals. Landslides impacting linear infrastructure in west central British Columbia. Natural Hazards 48, 59-72 (2009).
[xiv]P. Friele, T.H. Millard, A. Mitchell, K.E. Allstadt, B. Menounos, M. Geertsema & J.J. Clague. Observations on the May 2019 Joffre Peak landslides, British Columbia. Landslides 17, 913-30 (2020).
[xv]Hibert, C., D. Michea, F. Provost, J.P. Malet & M. Geertsema. Exploration of continuous seismic recordings with a machine learning approach to document 20 yr of landslide activity in Alaska. Geophysical Journal International 219, 2, 1138-47 (2019).
[xvi]Geertsema M., A. Bevington. A cautionary note for rock avalanche field investigation - recent sequential and overlapping landslides in British Columbia. Canadian Geotechnical Journal. doi:10.1139/cgj-2019-0751 (2020).
[xvii]Roberti, G., et al. Landslides and glacier retreat at Mt. Meager volcano: Hazard and risk challenges. Proceedings of the 7th Canadian Geohazards Conference: Engineering Resiliency in a Changing Climate (2018).
[xviii]Guthrie, R.H., et al. The 6 August 2010 Mount Meager rock slide-debris flow, Coast Mountains, British Columbia: characteristics, dynamics, and implications for hazard and risk assessment. Natural Hazards & Earth System Sciences 12, 1277-1294 (2012).
[xix]Hickson, C.J., J.K. Russell, M.V. Stasiuk. Volcanology of the 2350 B.P. eruption of Mount Meager Volcanic Complex, British Columbia, Canada: implications for hazards from eruptions in topographically complex terrain. Bulletin of Volcanology, 60, 489–507 (1999); Jensen, B.J., A.B. Beaudoin, M.A. Clynne, J. Harvey & J.W. Vallance. A re-examination of the three most prominent Holocene tephra deposits in western Canada: Bridge River, Mount St. Helens Yn and Mazama. Quaternary International 500, 83-95 (2019).
[xx]Andrews, G.D., J.K. Russell & M.L. Stewart. The history and dynamics of a welded pyroclastic dam and its failure. Bulletin of Volcanology 76, 811 (2014).