While we wait to see if Mt. Spurr will erupt as it continues to experience frequent deep earthquakes, former Cook Inlet Aquaculture Association Executive Director Gary Fandrei shares a surprising story about salmon habitat work at the time of the previous eruption.
Hey, look back!
In August 1992 I was just finishing my second year working for the Cook Inlet Aquaculture Association. I had come up to Alaska two years earlier and was still excited with the many new adventures I was experiencing as a field biologist. On the morning of August 18, 1992, I was looking forward to another day in the field.
On this day we had plans to survey three small remote streams for beaver dams obstructing salmon as they migrated to their natal spawning grounds. All three streams, located across Cook Inlet, were not accessible by road. The prior day I had made arrangements with a local helicopter service to fly us to the streams and survey each site by air to visually look for schools of salmon staged behind any beaver dams. Our plan was to fly from Kenai, Alaska along the Tordrillo Mountains surveying each stream as we flew north. We would return along the same route.
Each stream was surveyed as planned. While we saw many schools of migrating salmon and beaver dams, none of the dams were blocking the migration. As we returned to Kenai we flew low under the clouds, which were starting to break up. On our right we could see about half way up to the peaks of the Tordrillo Mountains and Mt. Spurr.
On our left the broad Susitna Valley was visible. As we returned the pilot radioed the helicopter base to let them know we were about to cross Cook Inlet and we will be returning to base in about thirty minutes.
It was a pleasant flight. We landed at the helicopter base without incident and remained in the helicopter during the two-minute shutdown procedure. As the pilot turned the engine off I noticed staff from the helicopter office come out to greet us as we exited the helicopter. They normally didn’t assist us out of the helicopter when we returned and I wondered what was going on. As we were standing on the tarmac the office staff told us to turn around and look at Mt. Spurr. The volcano had explosively erupted just as we had passed by the mountain on our return flight and was spewing an ash cloud over eleven-kilometers high.
Another new adventure as a field biologist working in Alaska.
Mt. Spurr Eruption Timeline
August 18, 1992
- 15:48 – Pilot report of dark cloud over Mt. Spurr.
- 16:41 – Recorded increase in seismic activity.
- 16:45 – Radar detected an ash plume almost 11-km high.
- 18:41 to 19:41 – Over 170 ash cloud lightning strikes recorded.
- 20:00 to 23:00 – 0.15 to 0.3 cm ash fell on Anchorage.
- 20:20 – Seismic data suggest the main phase of the eruption was over. Anchorage International Airport closed and remained closed through much of the next day.
August 19, 1992
- 02:51 – Data from the Nimbus-7 satellite's Total Ozone Mapping Spectrometer showed an ash cloud about 2,000 km long, covering an area of 370,000 km2 and containing about 240 kilotons of sulfur dioxide.
How volcanic ash may impact salmon and salmon habitat
We appreciate Gary retelling this story. It must have been quite a shock to look back and realize how close they were flying to the eruption!
Speaking of Mt. Spurr, it is a stratovolcano, which is a classic looking volcano—think middle school science fair. When stratovolcanoes erupt, it’s typically a violent, explosive event that sends ash into the atmosphere. The spread and extent of which depends on the winds at the time. No matter which way the wind blows the ash is likely to fall into salmon streams because they are abundant within the Cook Inlet watershed.
Ash can have devastating effects on salmon and their habitat. Ash fall can increase sedimentation in rivers and lakes, which can smother salmon eggs. Key insects that juvenile salmon rely on as a food source can also be negatively impacted, which could ultimately reduce salmon survival.
The ash may also increase the turbidity and change the pH of the water, which may affect salmon physiology, making it harder for their bodies to function properly. In systems close to Mt. Spurr volcanic mudflows can completely and quickly eliminate a salmon stream by trapping or suffocating fish as they migrate or prepare to spawn.
The negative effects of an imminent Mt. Spurr eruption on salmon systems will depend on the severity of the eruption and the amount of ash that is released into the atmosphere. But an eruption is not all bad, volcanic activity can eventually lead to the creation of new and potentially high-quality salmon habitat as landscapes recover and streams reestablish over time—time being the key factor. The North Fork of the Toutle River after the Mount St. Helens eruption is a great example of the benefits of volcanic eruptions on salmon populations.
We’ll just have to wait and see what happens! In the meantime, we are making sure our field crews are prepared for an eruption.
