Catastrophic Landscape Modification from Massive Landslide Tsunamis: An Example from Taan Fiord, Alaska

The October 17^th 2015 Taan landslide and tsunami generated a high runup of 192 m, nearly an order of magnitude greater than most previously surveyed tsunamis. Extensive modifications observed and documented on several low gradient fan deltas within the fiord make Taan Fiord an excellent laboratory for characterizing geomorphic signatures of a high runup tsunami event. Although interest in this topic is high, most prior post-tsunami surveys are from earthquake-generated tsunamis with relatively low runup, thus the geomorphic signatures of high runup tsunamis or their potential for preservation are uncharacterized. Additionally, clear modifications described during post-tsunami surveys are typically ephemeral and unlikely to be preserved. Geomorphic changes to Taan’s fan deltas included complete vegetation loss over more than 0.6 km² of fan surfaces, formation of steep fan front scarps up to 7 m high, extensive local alterations of fan topography, and formation of new tsunami retreat channels. Two relatively stable fan deltas in Taan Fiord were heavily vegetated prior to the Taan event and may preserve features of tsunami modification for decades to centuries. If this is the case, fan deltas may be a previously unrecognized location for preservation of tsunami signatures on the decadal scale. As such, fans in poorly monitored regions, such as Greenland, could hold evidence of previously unidentified recent high runup events.

Name thesis:degree_name

Master of Science (MS)

Discipline thesis:degree_discipline

Geological Sciences

Year dc:date.available

2017

Author dc:creator

• Bloom, Colin

Contributors dc:contributor

• Breanyn MacInnes
• Lisa Ely
• Bretwood Higman

• Tsunami
• Landslide
• Icy Bay
• Taan Fiord
• Geology
• Geomorphology

Language dc:language

English

Repository record dc:identifier

https://digitalcommons.cwu.edu/etd/636

OAI identifier oai:identifier

oai:digitalcommons.cwu.edu:etd-1644