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The Texas Creek rock avalanche is a prehistoric deposit in the Fraser River Canyon, 17 km south of Lillooet, southwestern British Columbia, Canada. Original mapping suggested that the debris consisted of two landslides: a 45 Mm3 event deposited after the Mazama tephra but before about 2 ka ago, and a 7.2 Mm3 event about 1.1 ka ago. The proposed timing of the younger landslide was correlated with a decline in the First Nations population and was proposed as an agent of cultural collapse driven by its impact on salmon returns vital to the population's sustenance. We provide six surface exposure ages using 10Be from boulder tops, with three samples from each surface that were originally posited to be older and younger debris. The six samples yielded similar ages suggesting the landslide deposit represents a single event with an average age of 2.28 ± 0.19 (2σ external error) ka before 1950 AD. Evidently, the landslide played no role in the cultural collapse. Fraser River Holocene incision rates, estimated pre- and post-landslide are between 13 and 24 mm/yr, consistent with previous estimates for the mid-Fraser River region. Landslide timing is coincident with the explosive eruption of Mount Meager, 120 km to the northwest, and with a possible landslide at Mystery Creek 85 km to the west and 65 km south of Mount Meager. The landslide may have been seismically triggered, but attribution is speculative. [ABSTRACT FROM AUTHOR]

Two catastrophic landslides occurred in quick succession on 13 and 16 May 2019, from the north face of Joffre Peak, Cerise Creek, southern Coast Mountains, British Columbia. With headscarps at 2560 m and 2690 m elevation, both began as rock avalanches, rapidly transforming into debris flows along middle Cerise Creek, and finally into debris floods affecting the fan. Beyond the fan margin, a flood surge on Cayoosh Creek reached bankfull and attenuated rapidly downstream; only fine sediment reached Duffey Lake. The toe of the main debris flow deposit reached 4 km from the headscarp, with a travel angle of 0.28, while the debris flood phase reached the fan margin 5.9 km downstream, with a travel angle of 0.22. Photogrammetry indicates the source volume of each event is 2–3 Mm3, with combined volume of 5 Mm3. Lidar differencing, used to assess deposit volume, yielded a similar total result, although error in the depth estimate introduced large volume error masking the expected increase due to dilation and entrainment. The average velocity of the rock avalanche-debris flow phases, from seismic analysis, was ~ 25–30 m/s, and the velocity of the 16 May debris flood on the upper fan, from super-elevation and boulder sizes, was 5–10 m/s. The volume of debris deposited on the fan was ~ 104 m3, 2 orders of magnitude less than the avalanche/debris flow phases. Progressive glacier retreat and permafrost degradation were likely the conditioning factors; precursor rockfall activity was noted at least ~6 months previous; thus, the mountain was primed to fail. The 13 May landslide was apparently triggered by rapid snowmelt, with debuttressing triggering the 16 May event. [ABSTRACT FROM AUTHOR]

The mating, egg-laying, and larval development of tailed frogs occur in dynamic mountain streams. During the lengthy (up to 5 years) aquatic residency these species are vulnerable to channel disturbances that can be exacerbated by land uses. Researchers have highlighted specific tailed frog habitat associations but never in the context of fluvial system processes. Based on an extensive regional study with a watershed-wide sampling strategy, we demonstrate that the Rocky Mountain tailed frog ( Ascaphus montanus) is limited to contributing basins of roughly 0.3–100 km2 in size, with peak numbers in basins up to 35 km2. We conclude that the primary determinant of tailed frog distribution patterns in a watershed is basin area, a proximate variable for channel process domain and regional stream discharge: tailed frogs are adapted to cascade and step-pool channel morphologies that characterize these small basins, presumably because they afford more bedform stability and pore-space refugia than do smaller, colluvial headwaters, or larger, floodplain-forming plane bed and pool-riffle bedforms of mainstem rivers. Secondarily, climate and physiography interact to influence occurrence and abundance at the watershed level by controlling such variables as runoff, water temperature, and sedimentation regime. This point has important management implications because it forces us to recognize that in complex ecosystems, wildlife habitat associations are contingent on site-specific interactions amongst fluvial system control variables: significance levels of any one variable to tailed frog distribution will not necessarily be consistent among basins. The study clearly shows that case studies can produce conflicting results when they lack a process-based understanding of ecological response. [ABSTRACT FROM AUTHOR]

Mount Meager massif, the northernmost volcano of the Cascade volcanic belt, has been the site of very large (>107 m3) landslides in the Holocene Epoch. We document two complex landslides at Pylon Peak, one of the peaks of the Mount Meager massif, about 7900 14C and 3900 14C years ago (about 8700 and 4400 calendar years ago). Together, the two landslides displaced ~ 6 × 108 m3 of volcanic rock from the south flank of Pylon Peak into nearby Meager Creek valley. Each landslide consisted of at least two phases, an early debris flow resulting from failure of hydrothermally altered pyroclastic rock at mid levels on the mountain and a later rock avalanche from a higher source. Both debris flows likely traveled down Meager Creek, and preliminary evidence from drilling indicates the 4400-year-old event traveled down Lillooet River into areas that are now settled and where population density is increasing rapidly. The mobility of the debris flows was due to the high content of fine, weathered volcanic sediment and the availability of sufficient water. The causes of the landslides are a wet climate and the presence of weak, hydrothermally altered volcanic rock containing abundant phreatic water on glacially oversteepened slopes. The landslides may have been triggered by earthquakes or by upwelling of magma to shallow depths within the volcano. However, they may also have occurred without specific triggers following extended periods of progressive weakening of the volcanic rocks. [ABSTRACT FROM AUTHOR]

Stratigraphy and landforms in the Brohm Creek basin and lowermost Mamquam River valley provide evidence for a readvance of a valley glacier in the southern Coast Mountains of British Columbia during the Younger Dryas interval. At Brohm Creek, till containing wood 10,500 and 10,700 14C yr old (ca 12,500–12,900 cal yr old), overlies an ice-contact terrace that is correlative with similar terraces at the mouth of Mamquam River, 11 km to the south and 900 m lower in elevation. A line linking the two sites has a slope of 5°, which is similar to slopes of termini of present-day valley glaciers in the southern Coast Mountains. We used these observations to reconstruct the Younger Dryas glacier in Squamish valley at the head of Howe Sound. The glacier deflected landslide debris, derived from steep slopes at the head of Cheekye River basin on the west flank of Mt. Garibaldi, southward to an ice-marginal lake at the mouth of Mamquam River. Foreset-bedded sediments in the core of a large fan at the mouth of Cheekye River indicate the glacier terminus had retreated up Squamish valley beyond Cheekye and Mamquam rivers by 10,200 14C yr BP (11,900 cal yr old). Radiocarbon ages on the oldest postglacial sediments in a kettle on the landslide debris show that stagnant ice in the study area had melted before 10,000 14C yr BP (11,500 cal yr BP). The readvance of the Squamish valley glacier during the Younger Dryas Chronozone was probably driven by a regional climate reversal. [Copyright &y& Elsevier]

The article "Observations on the May 2019 Joffre Peak landslides, British Columbia", written by Pierre Friele, Tom H. Millard, Andrew Mitchell, Kate E. Allstadt, Brian Menounos, Marten Geertsema and John J. Clague, was originally published electronically on the publisher's internet portal (currently SpringerLink) on January 2020 without open access. [ABSTRACT FROM AUTHOR]

Cheekye Fan is a large paraglacial debris flow fan in southwest British Columbia. It owes its origin to the collapse of Mount Garibaldi, a volcano that erupted in contact with glacier ice near the end of the Pleistocene Epoch. The fan extended across Howe Sound, isolating a freshwater lake upstream of the fan from a fjord downstream of it. Squamish River built a delta into this lake during the Holocene. We use 28 radiocarbon ages to describe the final infilling of the lake and the subsequent evolution of the Squamish River floodplain over the past 3300 years. These events are recorded in fine-grained lacustrine, wetland, river channel, and overbank sediments exposed in the banks of Squamish River over a distance of more than 10 km upstream of the fan. We link these deposits to construction, persistence, and eventual degradation of the dam formed by Cheekye Fan and a smaller inset fan formed by Cheakamus River, into which Cheekye River flows. The coupled Cheekye Fan - Squamish River floodplain system is similar to other low-gradient valley floors upstream of fans such as at Tulare Lake, California, and Alexandra River in the Canadian Rocky Mountains. Future debris flows and landslides in the headwaters of Cheekye River are likely to continue to affect base level on lower Squamish River. We speculate that future aggradation of Cheekye Fan would cause increased flooding and sediment deposition upstream of this barrier. These landscape linkages should be included in future land-use planning in lower Squamish River valley. [ABSTRACT FROM AUTHOR]

High-resolution topographic modeling has become more accessible due to the development of structure from motion (SfM)-image-matching algorithms in digital photogrammetry. Large archival databases of historical aerial photographs are available in university, public, and government libraries, commonly as paper copies. The photographs can be in poor condition (i.e., deformed by humidity, scratched, or annotated). In addition, the negatives, as well as metadata, may be missing. Processing such photographs using classic stereo-photogrammetry is difficult and, in many instances, impossible. SfM can be applied to these photosets to access the valuable archive of geomorphic changes over the past century. In this paper, we illustrate the utility of the SfM technique using 568 digitized vertical aerial photographs of Mount Meager volcano, located in southwestern British Columbia, Canada. We use the aerial photographs, which span the period from 1947 to 2006, to track glaciers and glacier–landslide interactions on the volcano. Over this period, glaciers have thinned and retreated, interrupted by minor advances in the 1960s and 1970s. Landslides are frequent on the volcano and contribute to debris cover on the glaciers affecting the ablation process. SfM processing of the aerial photographs allowed us to unlock geomorphic information and reconstruct landscape change that would otherwise have been impossible. The results from SfM provide a visually effective way of presenting landscape change to a broad public audience, as a form of virtual geoheritage. The approach can thus be broadly applied in scientific and professional practices for improving land planning and hazard management. [ABSTRACT FROM AUTHOR]

In 2010, the south flank of Mount Meager failed catastrophically, generating the largest (53 ± 3.8 × 106 m3) landslide in Canadian history. We document the slow deformation of the edifice prior to failure using archival historic aerial photographs spanning the period 1948-2006. All photos were processed using Structure from Motion (SfM) photogrammetry. We used the SfM products to produce pre-and post-failure geomorphic maps that document changes in the volcanic edifice and Capricorn Glacier at its base. The photographic dataset shows that the Capricorn Glacier re-advanced from a retracted position in the 1980s then rapidly retreated in the lead-up to the 2010 failure. The dataset also documents 60 years of progressive development of faults, toe bulging, and precursory failures in 1998 and 2009. The 2010 collapse was conditioned by glacial retreat and triggered by hot summer weather that caused ice and snow to melt. Meltwater increased pore water pressures in colluvium and fractured rocks at the base of the slope, causing those materials to mobilize, which in turn triggered several secondary failures structurally controlled by lithology and faults. The landslide retrogressed from the base of the slope to near the peak of Mount Meager involving basement rock and the overlying volcanic sequence. Elsewhere on the flanks of Mount Meager, large fractures have developed in recently deglaciated areas, conditioning these slopes for future collapse. Potential failures in these areas have larger volumes than the 2010 landslide. Anticipated atmospheric warming over the next several decades will cause further loss of snow and glacier ice, likely producing additional slope instability. Satellite- and ground-based monitoring of these slopes can provide advanced warning of future landslides to help reduce risk in populated regions downstream. [ABSTRACT FROM AUTHOR]

Mount Meager is a volcanic complex located in SW British Columbia, Canada. It covers an area of about 225 km² and it supports 32 alpine glaciers (as reported in the GLIMS Glacier Database); it is known for the high landslide frequency and magnitude. In this study we document the present glacier morphology and activity at Mount Meager volcano, as well as landslide events. We digitized over 500 airphotos of the Mount Meager massif consisting of 8 time slices from 1947-2006 using SfM software to provide high-resolution orthophotos (0.42-1.13 m/pixel). The cartographic suitability of these datasets was tested by comparison with a Lidar DTM acquired in 2015-2016. By means of Lidar and orthophotos interpretation we mapped glacier outlines, moraines, landslide deposits, scars, and fractures. Glacier fluctuations were documented and related to geomorphic parameters: glacier length and basin area, headwall height and aspect, elevation of accumulation zone, glacier front position from 1951 to 2016, and relative retreat of front position in 2016. The glaciers at Mount Meager show different parameters and activity, but they are generally retreating. Total cumulated retreat is about 8 km² and retreat is about 20% with respect to the 1951 glacier extension.We recognized mutual conditions posed by present and past glaciations and hydrothermal activity to present-day volcanic massif stability and glacier morphology. We developed a conceptual model to explain the high landslide frequency and the glacial activity at Mount Meager: rocks are fractured and altered by interaction with past ice sheets and today's glaciers are mostly debris-covered and sit in collapse scars from large landslides. Climate-related deglaciation of volcanic mountains not only cause changes in ice cover, but affects regional and local hydrology, slope stability, sediment supply, hydrothermal circulations, leading to short-term and long-term consequences on the overall relief geomorphology. [ABSTRACT FROM AUTHOR]