Last fall's massive Icy Bay landslide launched a megatsunami

Alaska Dispatch News ^ | 4/9/2016 | Chris Larsen

[JimSEA]

A landslide last fall caused a giant wave not seen in Alaska since a storied 1958 event in Lituya Bay.

After a period of heavy rains, a mountainside near Tyndall Glacier collapsed into a fiord of Icy Bay on Oct. 17, 2015. The displaced water generated a wave that sheared alders more than 500 feet up on a hillside across from the slide at the Southeast Alaska location.

To put that in perspective, the 2011 tsunami in Japan reached about 130 feet above sea level. The Icy Bay wave may be the largest since a magnitude-8 earthquake shook much of a mountain into Lituya Bay on a July day in 1958. The wave that followed ripped spruce from 1,700 feet up a mountain slope and left trim-lines in the bay that are visible today.

Last October, seismologists at Columbia University in New York detected the Icy Bay landslide on their instruments. Göran Ekström and Colin Stark specialize in picking up landslide signals. They figured the slide spilled 200 million tons of rock in 60 seconds.

Winter snows hid the extent of the wave generated from the rock avalanche. Upon hearing a report from a pilot colleague the landslide area of Icy Bay was free of snow, glaciologist Chris Larsen flew there in his Cessna 180 from his home in Fairbanks. The Geophysical Institute professor used a camera system mounted in his plane to make a high-resolution map of the landslide and the path of the megatsunami.

[JimSEA]

There’s quite a bit of difference between a landslide caused tsunami and a plate subduction tsunami. The first is material pushing the water out from a shoreline. The second involves the movement of the edge of two plates moving up or down from the bottom of a trench. A lot more energy is generated in the massive movement of the second.

[Vinnie]

Cumbre Vieja, Canary Islands
Glad I moved from Miami. :)