EGU21-9148, updated on 04 Mar 2021
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

A landslide-generated tsunami and outburst flood at Elliot Creek, coastal British Columbia  

Marten Geertsema1, Brian Menounos2, Dan Shugar3, Tom Millard1, Brent Ward4, Göran Ekstrom5, John Clague4, Patrick Lynett6, Pierre Friele7, Andrew Schaeffer8, Jennifer Jackson9, Bretwood Higman10, Chunli Dai11, Camille Brillon8, Derek Heathfield9, Gemma Bullard12, Ian Giesbrecht9, and Katie Hughes1
Marten Geertsema et al.
  • 1British Columbia Ministry of Forests, Lands, Natural Resource Operations and Rural Development, Canada (
  • 2University of Northern British Columbia, Canada
  • 3University of Calgary, Canada
  • 4Simon Fraser University, Canada
  • 5Lamont-Doherty Earth Observatory, USA
  • 6University of Southern California, USA
  • 7Cordilleran Geoscience, Canada
  • 8Natural Resources Canada, Canada
  • 9Hakai Institute, Canada
  • 10Ground Truth Alaska, USA
  • 11Ohio State University, USA
  • 12BGC Engineering, Canada

On 28 November 2020, about 18 Mm3 of quartz diorite detached from a steep rock face at the head of Elliot Creek in the southern Coast Mountains of British Columbia. The rock mass fragmented as it descended 1000 m and flowed across a debris-covered glacier. The rock avalanche was recorded on local and distant seismometers, with long-period amplitudes equivalent to a M 4.9 earthquake. Local seismic stations detected several earthquakes of magnitude <2.4 over the minutes and hours preceding the slide, though no causative relationship is yet suggested. More than half of the rock debris entered a 0.6 km2 lake, where it generated a huge displacement wave that overtopped the moraine at the far end of the lake. Water that left the lake was channelized along Elliot Creek, deeply scouring the valley fill over a distance of 10 km before depositing debris on a 2 km2 fan in the Southgate River valley. Debris temporarily dammed the river, and turbid water continued down the Southgate River to Bute Inlet, where it produced a 70 km turbidity current and altered turbidity and water chemistry in the inlet for weeks. The landslide followed a century of rapid glacier retreat and thinning that exposed a growing lake basin. The outburst flood extended the damage of the landslide far beyond the limit of the landslide, destroying forest and impacting salmon spawning and rearing habitat. We expect more cascading impacts from landslides in the glacierized mountains of British Columbia as glaciers continue to retreat, exposing water bodies below steep slopes while simultaneously removing buttressing support.

How to cite: Geertsema, M., Menounos, B., Shugar, D., Millard, T., Ward, B., Ekstrom, G., Clague, J., Lynett, P., Friele, P., Schaeffer, A., Jackson, J., Higman, B., Dai, C., Brillon, C., Heathfield, D., Bullard, G., Giesbrecht, I., and Hughes, K.: A landslide-generated tsunami and outburst flood at Elliot Creek, coastal British Columbia  , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9148,, 2021.


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