Modeling based on potential sources can help outline areas of likely impact, with an emphasis on sites with known risk factors. We are able to calculate the volume of the landslide and the volume that entered the fjord. 2018. Having detected the Tyndall Glacier landslide, Stark and Ekstrom located it with a very high resolution satellite image, which Lamont-Doherty have included in their press release : Using a variety of Digital Elevation Modeling (DEM) and imagery sources, the research team was able to estimate the landslide volume, document movement leading up to the event, and map the deposit thickness. On 17 October 2015, a landslide of roughly 60 × 106 m3 occurred at the terminus of Tyndall Glacier in Taan Fiord, southeastern Alaska. In Taan Fiord, currents swept across shallow areas and low hills, sometimes carrying icebergs that left gouges in the soil surface (Figure 3), or were left stranded far above the tide. When they retreat, whether due to changing climate or to regular glacial cycles, they remove that support, allowing slopes to sag and fractures to expand, making them vulnerable to failure. These impacts in Taan Fiord show that development should be sited outside areas of anticipated inundation, and evacuation routes are needed so that anyone within the flood zone can effectively flee. See more pictures of Tyndall Glacier here: Go to Tyndall Glacier. Submarine deposition of a subaerial Landslide in Taan Fiord, Alaska. Der Tsunami hinterließ dicke, charakteristische Ablagerungen, die sich von denen anderer moderner Tsunamis 16 unterschieden, als er mehrere Schwemmfächer entlang des Taan-Fjords überschwemmte und wieder auftauchte (siehe ergänzende Abbildung). 2018, Gullufsen 2018). Part of the debris traversed the width of the fjord and re-emerged onto land, depositing coherent hummocks with preserved source stratigraphy on an alluvial fan and adjacent moraines on the far side of the fjord. A., E. K. Bessette-Kirton, and M. Geertsema. 2017. However, no such preparation was conducted and it’s urgent that we learn from the 2015 event and take steps to assess and mitigate hazards in Icy Bay and elsewhere before another event happens. Signs of active displacement are clearly visible in remote-sensed data extending back to the mid-1990s. 2017). Also see this article in Alaska Park Science. Flow depth here was likely 5 meters based on the height of branches stripped off trees in the background. Even where the wave is not breaking, tsunamis can generate strong currents. The careful documentation of the physical environment of the fjord before and after the landslide, combined with tsunami runup and flow directions, should make this a place where tsunami modelers can test their models to see if they work correctly. Journal of Geophysical Research, Earth Surface DOI: 10.1029/2018JF004608. The slide caused tens of meters of shallowing in some areas, while it eroded sections of the pre-landslide shoreline. Simple scaling of catastrophic landslide dynamics. Russel, I. C. 1893. Giant waves in lituya bay, Alaska. Both of these events thankfully occurred in sparsely populated areas, so few fatalities occurred. In contrast, one small island that used to support supra-tidal vegetation was scoured down such that now it is only a shoal emerging at low tide (location marked on Figure 5). 2006. Researchers employed a variety of instruments to conduct a ground-based tsunami runup survey, including a laser rangefinder, a total station, and two differential Real Time Kinematic (RTK) GPS systems. Areas near stream deltas or other sediment sources might be buried by transported sediment. Courtesy of Ground Truth Trekking 2012. doi:10.7289/V5PN93H7 In the case of Taan Fjord, the result was a massive tsunami," said Dr Dan Shugar, assistant professor of Geoscience at the University of Washington Tacoma and co-author of the report. It triggered a tsunami wave with a runup height exceeding 90 m close to the landslide, ca. We are able to image the landslide and postlandslide deposits, on and beneath the fjord bottom, up to 6 km away from where it entered the water. Sedimentary Geology 364:302-318. In most places, the forest was destroyed by the passing wave. A few sites showed that hills can provide significant protection from the worst tsunami impacts. 2012). Some of the rock slid onto the snout of a tidewater glacier but most slid into the head of Taan Fjord – displacing a massive volume of water. The location shown here is near the mid-length of Taan Fiord, where the survey team set up their primary base camp. Deposits were more typically 12-20 inches (30-50 cm) thick over areas as far as 6 miles (10 km) from the source. The 2015 tsunami was the largest to occur in this narrow window of time, but it likely wasn’t the only tsunami. The October 17th, 2015 Taan Fiord landslide and tsunami generated a runup of 193 m, nearly an order of magnitude greater than most previously surveyed tsunamis. The most dramatic hazard posed to vessels is the breaking tsunami wave in areas where the tsunami height is significant in comparison to the depth of the water. These factors are likely driving an increase in the frequency of large landslides. In Grönland löste ein Erdrutsch an der Westküste im Jahr 2017 eine über 90 Meter hohe Welle aus , die einen Großteil eines nahe gelegenen Fischerdorfes zerstörte und vier Menschen tötete. These long-period tsunamis usually take up to a half-hour to inundate elevations less than twenty meters above the water. 50 m on the opposite shore of the fjord. "Oct. 17, 2015, Taan Fjord, Icy Bay, Alaska. For the readers reference, the force exerted on a object submerged in water moving at 65 mph is the same as the force felt by that object with wind blowing at 2,000 mph. Ultra-rapid landscape response and sediment yield following glacier retreat Icy Bay, southern Alaska. 2018. A systematic analysis of this sort could inform park development planning and public education efforts that could reduce risk. Icy Bay [near Taan Fjord] was full of glaciers as recently as 100 years ago.” A giant boulder moved by the tsunami as it ran down Taan Fjord. Haeussler, P. J., S. P. S. Gulick, N. McCall, M. Walton, R. Reece, C. Larsen, D. H. Shugar, M. Geertsema, J. G. Venditti, and K. Labay. The rapid retreat of the glacier destabilized the steep slopes of the surrounding mountains and a massive landslide occurred on October 17, 2015. Glacial landslides, or glacial detachments, are a phenomenon of a warming planet. 11. Depending on the geometry, size, and speed of this force, the nature of the resulting tsunami wave can vary dramatically. Taan Fjord Landslide and Tsunami. In October 2015, a massive landslide slid into Taan Fjord and created a tsunami in excess of 600 feet. English: Tsunami impacts near the landslide. The resulting tsunami reached elevations as high as 193 m, one of the highest tsunami runups ever documented worldwide. Dufresne, A., M. Geertsema, D. H. Shugar, M. Koppes, B. Higman, P. J. Haeussler, C. Stark et al. Available at: https://www.juneauempire.com/news/scientists-discover-rare-alpine-tsunami-occurred-after-massive-2016-rockfall-near-juneau/ (accessed May 14, 2019) Dufresne, A., M. Geertsema, D. H. Shugar, M. Koppes, B. Higman, P. J.Haeussler, C. Stark, J. G. Venditti, D. Bonno, C. Larsen, S. P. S.Gulick, N. McCall, M. Walton, M. G. Loso, and M. J. Willis. Climate Change. Tyndall Glacier, Taan Fjord Mega-Tsunami. 2018). After crossing the toe of Tyndall Glacier and entering the water, it generated a violent wave that flattened about eight square miles (20 km2) of forest in Wrangell-St. Elias National Park and Preserve and adjacent private lands (Figure 1). No one heard the mountainside fall into the fjord on … Smaller vessels might experience some of the same hazards as can be found in tidal rapids—strong eddy-lines and whirlpools that can capsize and sink boats. Lodge operators and visitors might have been warned of the risk; tsunami modeling likely could have accurately shown the impacts would be potentially severe within the fjord, but would only extend a short way into the main bay. The landslide is enormous – Stark and Ekstrom estimate from the seismic data that it had a mass of about 180 million tonnes, which would give a volume in the order of 72 million cubic metres. Die Folge war ein Tsunami mit knapp 200 Meter Höhe. The resulting landslide generated a megatsunami in Taan Fjord. Photo: Ground Truth Trekking (CC BY-NC 3.0) As Glaciers Melt, Will Deadly Landslides Increase? Those first rocks shoved more rocks, and then more still. They happen quickly and pose a threat to anything and everything in their path. Nonetheless, the hazard from large landslide-generated waves will likely increase in the coming decades. Submarine deposition of a subaerial landslide in Taan Fjord, Alaska. In October 2015, a massive landslide slid into Taan Fjord and created a tsunami in excess of 600 feet. The 2015 Taan Fjord tsunami was generated by a 99 million cubic yards (76 million cubic meters) landslide that occurred following retreat of the Tyndall Glacier. The Taan Fiord tsunami can help us understand subaerial landslide tsunami hazards and prepare for potential impacts. Oktober 2015 landete ein Erdrutsch von rund 180 Millionen Tonnen Gestein auf der Zehe des Tyndall Glacier und im Wasser des Taan Fjords. Inverse and forward modeling can provide the framework of a detailed understanding of the geologic and hazards implications of similar events. At Taan Fjord in 2015, a landslide caused a tsunami that crested at 600 feet. In Alaska stürzten 2015 am Taan Fjord enorme Gesteinsmassen ins Meer. Die daraus resultierende Welle war bis zu 193 Meter hoch 2:55-3:10 New experiments on landslide tsunami on a conical island - Giorgio Bellotti 3:10-3:35 Break 3:35-3:55 The Tsunami Generated by the October 17, 2015 Taan Fjord Landslide - Pat Lynett 3:55-4:20 Model descriptions and results: Globouss and BoussClaw - Finn Lovholt Even below the inundation line on the protected side of this hill, there were more rooted trees and intact soil than in less-protected areas. Other fjords at the head of Icy Bay have steep slopes that haven’t yet been surveyed for potential landslide hazards. Reconstruction of a debris-slide-initiated flood in the southern Kenai Mountains Alaska. Lituya Bay produced at least five giant tsunamis over the course of three centuries (Miller 1960) and Icy Bay could well rack up a similar record. The fjord was exposed by the recent retreat of Tyndall Glacier. Approximately 90% of the landslide entered the fjord, generating a tsunami. A small volume of the total slide mass remains within the source area and is topped by striated blocks (> 10 m across) and standing trees that were transported down the slope in intact positions during the landslide. Flow indicators from satellite imagery suggest that the maximum tsunami runup immediately adjacent to … 2018. Also, while modeled tsunami runup has been widely validated, currents produced by tsunami flows are rarely directly documented, and tsunami models differ substantially in the results they produce (Lynett et al. The friction that held silt to silt and rock to rock began giving way. Furthermore, at higher elevations and in arctic and subarctic climates, permafrost is a significant contributor to the strength of some mountains, and thawing, or even warming of still-frozen permafrost, can greatly weaken those mountains. Taan Fjord is remote, but the Tidal Fjord in tourist-heavy Glacier Bay, Alaska, saw a landslide in June 2016. Colonel Foster, British Columbia, Canada. It wasn’t until the 1960s that four steep-walled fjords began to open at the head of the bay. Fortunately, the debris from that event didn't reach the water, avoiding a tsunami. We are currently working to model the tsunami in more detail, using a numerical model tested against tectonic tsunamis. The Journal of Geology 1: 3. Scientific Reports 8(1): 12993. doi:10.1038/s41598-018-30475-w September 2018, 08:00 57 Postings. A giant boulder moved by the tsunami that ran down Taan Fiord in 2015. The Taan Fiord event would have been a good candidate for active monitoring because precursory motion generated large, easily measured displacements (e.g., visible even in low-resolution Landsat imagery). Fortunately, the debris from that event didn't reach the water, avoiding a tsunami. Photo: Ground Truth Alaska (CC BY-NC 3.0) Responding to this May’s warning, Chugach National Forest officials advised the public to avoid the famously scenic Harriman Fiord, a staple for recreation and tourism activity that provides revenue across south-central Alaska. At the same time, glaciers fill the valley, preventing failure of lower slopes and supporting higher slopes to reduce the chance of slope collapse. It is possible to anticipate areas of potential hazard for vessels using tsunami models. Figure 4 shows the 2012 Hubbard and Lituya landslides (Geertsema 2012). Initial observations of the 11 June 2012 rock/ice avalanche, Lituya mountain, Alaska. Higman, Bretwood, Dan H. Shugar, Colin P. Stark, Göran Ekström, Michele N. Koppes, Patrick Lynett, Anja Dufresne et al. The events at Grewingk Lake, Taan Fiord, and a 2016 landslide tsunami in Cowee Creek near Juneau all occurred in bodies of water that didn’t exist (because their basins were filled with ice) only a few decades before. George, D. L., R. M. Iverson, and C. M. Cannon. Several alluvial fans collapsed into deeper water as the slide moved along their fronts on its way down the fjord. Most of the research on tsunami impacts has focused on longer-period regional tsunamis—especially subduction zone earthquake tsunamis that produce some of the longest period waves. More recently, a 2015 landslide near Alaska’s Taan Glacier produced a 633 feet (193 meter) wave in Taan Fjord that smashed into the opposite wall of the glacial valley. Slope failure at the terminus of Tyndall Glacier on 17 October 2015 sent 180 million tons of rock into Taan Fiord, Alaska. Field work was carried out in the summer of 2016, and by the time this paper was written, almost all of the supraglacial debris was advected into the fjord and half the subaerial hummocks were buried by glacial advance; this rapid change illustrates how highly active sedimentary processes in high-altitude glacial settings can skew any landslide-frequency analyses, and emphasizes the need for timely field investigations of these natural hazards. Tsunami-inducing landslides are rare but have occurred in Alaska and elsewhere. Precursory deformation began decades before failure, and the event left a distinct sedimentary record, showing that geologic evidence can help understand past occurrences of similar events, and might provide forewarning. However, modeling to simulate possible future events will be very sensitive to potential landslide locations, requiring many model runs to capture a range of possible scenarios. These results could then be compared to areas of infrastructure development, popular tourist destinations, and ship course data (e.g., from Automatic Identification System (AIS) ship-tracking systems) to identify areas of particular vulnerability. The larger Lituya landslide (b) came to rest more than 6 miles (10 km) from tidewater in Glacier Bay National Park and Preserve, and thus produced no tsunami. Large landslides are on the increase in southeast Alaska (Coe et al. Visit our keyboard shortcuts docs for details, Next Chapter: Catastrophic Glacier Collapse and Debris Flow at Flat Creek, Previous Chapter: Geohazards in Alaska’s National Parks. Natur Forscher rekonstruieren Mega-Tsunami, der sich 2015 in Alaska ereignete. A century ago, Icy Bay was filled with glaciers (Russel 1893). The wave affected the … A very nice video has been posted on Youtube describing the link between the giant Icy Bay landslide in Alaska in 2015 (this landslide is also variously known as the Taan Fjord landslide and the Tyndall Glacier landslide), which is the largest known recent landslide in North America, and the melting of the adjacent glacier. The wave affected the entire length of the fjord. 2018). One rough result has been published (not related to our study) that jointly models the landslide and tsunami (George et al. Tree trunks that remained standing after the tsunami were scoured by strong sediment-laden currents that sometimes severely abraded the upstream side of trees, leaving them peppered with small rocks (Figure 3). In the last century, 10 of the 14 highest tsunamis in the world were in glaciated mountains and four were in Alaska parks, which include vast tracts of glaciated terrain (Table 1). Adventure kayakers, trophy bear hunters, commercial and sport fishers, and even cruise ships visit Icy Bay (Figure 2). The landslide triggered an enormous local tsunami. Much of the landslide material was deposited on the Tyndall Glacier and into the fjord. Erosion rates during rapid deglaciation in Icy Bay Alaska.
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