Public service announcement from the City of Valdez
An ice-dammed lake above the Valdez Glacier is undergoing an outburst event, which started on Friday. Water levels in Valdez Creek and Valdez Lake will be seeing a considerable rise.
This is a biannual event, which usually happens in mid June and then again in the fall. Water builds up in the lake above the glacier until the pressure raises the ice, and the water flows down the mountain.
The dammed lake
The image above shows the lake caught behind the ice dam. The ice wall in the picture is approximately 200 feet high.
First image credit: City of Valdez; Second image credit: National Weather Service
A large glacial dam gave way in Southeast Alaska this summer. Known by its Icelandic term: jökulhlaup, the power of this sudden release of pent up water can be incredibly destructive.
The terminus of Lituya Glacier; Photo credit: NPS/J. Capra
Desolation Lake, which sits above the Lituya Glacier in Desolation Valley, collects meltwater from both the Desolation and Fairweather Glaciers. That meltwater is normally blocked by the Lituya Glacier, forming the roughly four square mile lake.
The water level suddenly dropped 200 feet.
A commercial fisherman, Jim Moore, along with his two grandsons, tried to enter Lituya Bay to fish for Chinooks in August. They should have been riding the tide into the bay, but the unusually muddy water was moving outward, and it was filled with trees and other debris. The bay was also filled with small icebergs. Moore managed to bring some of the ancient ice onboard for his coolers, then left the bay, instead of fighting the dangerous current.
Lituya Glacier terminus and delta; Satellite image credit: USGS
It is one of the largest jökulhlaups known to have occurred in Alaska. The water found a path under the Lituya Glacier, causing a rush that would have rivaled the hourly discharge of the Amazon River. It would have lasted for several days.*
Lituya Bay has a history. In 1958, an earthquake triggered a landslide that started one of the largest known tsunamis at over 1700 feet.
