We still see continued deformation and movement in the Barry Arm landslide as reported on September 16. Scientists at the U.S. Geological Survey, the Alaska Division of Geological & Geophysical Surveys, and the National Tsunami Warning Center have suspended non-essential boat-based operations and will continue to monitor the landslide movement and provide further details on Friday, September 30, unless significant changes warrant earlier updates.
(Last updated September 16, 2022)
A ground-based synthetic aperture radar instrument installed on the east side of Barry Arm revealed the movement of a portion of the Barry Arm landslide beginning early in the morning on August 23, 2022. More recent data identified additional areas that are also moving. Satellite data and imagery from nearby cameras confirmed that a larger portion of the Barry Arm landslide is now moving at rates between 40 and 70 millimeters per day (1.6 to 2.7 inches per day). We are currently unable to estimate potential slide volumes as the depth of the current motion is unknown.
Based on analysis of historical topographic and satellite data for the Barry Arm landslide, movement at this part of the landslide is common. Previous studies at Barry Arm have identified ground movement at similar or much greater rates since 2008. However, the recent ground movement identified in multiple data sources is notable in that (a) it includes a much larger area than previous data, (b) the movement is at rates at least 2x greater than the last period of similar patterns of motion in 2020, and (c) it is in a location that is perched directly above the water.
Localized ground movement is not necessarily a precursor to partial or complete failure of the Barry Arm landslide. Continued movement at this rate, or increases in the rate of motion, would further increase the potential for failure of this portion of the landslide. If the area failed rapidly, it would generate a life-threatening tsunami in nearby waterbodies, such as Harriman Fiord, Barry Arm, College Fiord, Port Wells, Cochrane Bay, Blackstone Bay, and Passage Canal. Tsunami inundation and dangerous waves and currents would also be expected in Whittier, Alaska.
(Last updated September 16, 2022)
U.S. Geological Survey scientists will continue to track the landslide for signs that hazard may be increasing, such as an acceleration in the rate of movement. Systematic monitoring of optical imagery and remote sensing data is conducted throughout the year. Ground-based radar observations are made multiple times per day during avalanche-free conditions (May through October). New satellite observations are available bi-monthly with favorable atmospheric conditions.
There is a local monitoring network in Barry Arm that includes two seismometers, an infrasound array, a ground-based radar, several weather stations, and four cameras. In addition, there is an infrasound array located in the town of Whittier, Alaska, approximately 50 km (31 miles) from the Barry Arm landslide. The National Tsunami Warning Center (NTWC) also operates three water level sensors in Barry Arm.
The National Tsunami Warning Center in Palmer, Alaska, is testing a developmental real-time warning system in place for the Barry Arm landslide and potential tsunami. Updates on the status of the landslide as determined by current monitoring capabilities will be provided through the Alaska Division of Geological & Geophysical Surveys Barry Arm landslide webpage and email list (linked below).
The Barry Arm landslide is a large (~500 M m3 or 650 M yd3) landslide located in the northwestern corner of Prince William Sound, Alaska. Rapid, catastrophic failure of the landslide could generate a tsunami that would be life-threatening for anyone in Barry Arm, Harriman Fiord, and parts of Port Wells. A significant risk might also exist in other, more distal locations of western Prince William Sound, including the town of Whittier, Alaska.
The existence of the landslide is evident in imagery dating back to the 1920s. Slow ground motion has been documented going back several decades. Increased movement was documented during the rapid recession of the Barry Glacier from 2010 - 2016, with observed rates up to 26 ± 3 m/yr observed from May 2010 to September 2013. Deformation rates returned to a background level of approximately 1.3 ± 0.7 m/yr in March of 2017 as the retreat of the Barry Glacier ceased.
Alaskans should be aware of the ongoing risk and follow the advice of local emergency managers and harbormasters and have a plan in place if a tsunami occurs. Although there are several instruments operating near the Barry Arm landslide, a real-time landslide and subsequent tsunami warning system is not yet operational. From the National Tsunami Hazard Mitigation Program and the California Office of Emergency Services:
For a large, local-source tsunami that may arrive in 10-20 minutes:
The City of Whittier recently performed maintenance on and tested their existing tsunami siren and is investigating adding a second alert siren.
The Alaska Department of Homeland Security & Emergency Management (DHS&EM) provided the City of Whittier with new tsunami evacuation signage.
Coastal communities, mariners, and all visitors in Prince William Sound should remain informed, heed U.S. Coast Guard (USCG) and U.S. Forest Service (USFS) warnings to avoid the immediate area, and review emergency response and evacuation plans in the event of a tsunami. For more information, please contact your local emergency management authority and see these web resources:
If you have questions or more information about the Barry Arm landslide, we encourage you to reach out to DGGS via Facebook or Twitter, or by emailing email@example.com.
This message will be updated on September 30, 2022, or earlier if the threat level changes. For more information, please see our Barry Arm Summary Information & FAQ page.