The 2015 landslide and tsunami in Taan Fiord, Alaska

Abstract

Glacial retreat in recent decades has exposed unstable slopes and allowed deep water to extend beneath some of those slopes. Slope failure at the terminus of Tyndall Glacier on 17 October 2015 sent 180 million tons of rock into Taan Fiord, Alaska. The resulting tsunami reached elevations as high as 193 m, one of the highest tsunami runups ever documented worldwide. 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. The event was detected within hours through automated seismological techniques, which also estimated the mass and direction of the slide - all of which were later confirmed by remote sensing. Our field observations provide a benchmark for modeling landslide and tsunami hazards. Inverse and forward modeling can provide the framework of a detailed understanding of the geologic and hazards implications of similar events. Our results call attention to an indirect effect of climate change that is increasing the frequency and magnitude of natural hazards near glaciated mountains.

Submarine Deposition of a Subaerial Landslide in Taan Fiord, Alaska

“…The 2015 landslide and tsunami provided a unique opportunity to document and study the effect of an STS landslide. A large group of researchers coalesced with the goal to document the event and collect ephemeral and time-sensitive observations (e.g., Dufresne et al, 2017;Higman et al, 2018). This paper focuses on the submarine observations of bathymetry, high-resolution submarine seismic profiling, and surface change.…”

“…We had the rare opportunity to document the mass transfer of a large subaerial-to-submarine landslide, which occurred in Taan Fiord, Alaska, on 17 October 2015. This remarkable landslide produced the fourthhighest tsunami runup ever recorded (Higman et al, 2018). We are unaware of any previous studies that geophysically image a large subaerial-to-submarine landslide deposit.…”

“…Satellite images soon after the event also identified the slide, direction of travel, deposition in the fjord, and significant tsunami runup in Taan Fiord. An overview of the Taan Fiord landslide and tsunami is given by Higman et al (2018) and documents tsunami runup to 193 m. Dufresne et al (2017) described the subaerial landslide deposits. A model of the subaerial-induced tsunami generation was given by George et al (2017) with no input from ground-based observations.…”

“…Recent retreat of the Tyndall Glacier combined with relatively weak sedimentary rock outcrops, high relief, and rapid tectonic deformation all contributed to preconditioning the slope to failure in Taan Fiord (Higman et al, 2018). Taan Fiord is an arm of Icy Bay, which deglaciated sincẽ 1900 CE (Barclay et al, 2006;Porter, 1989).…”

“…The landslide deposit lies above and below sea level (Dufresne et al, 2017;Higman et al, 2018). The subaerial part of the deposit includes the volume within the landslide scar, discussed above, as well as material on the toe of the Tyndall Glacier and the hummocks on the east side of the fjord and on the Hoof Hill fan (Table 1; Figure 7).…”