February 3, 2009

• Volcanopalooza

  Last night, I read the following update at the AVO website and decided to save it and post today.  The interesting part is in bold at the end.

  2009-02-02 17:17:58
  Restlessness at Redoubt Volcano continues. Seismic activity remains elevated and is well above background levels.

  The volcano has not erupted.

  A vapor plume is intermittently visible in the AVO web camera. It appears to rise no higher than the volcano’s summit.

  A news story this evening incorrectly reported that Anchorage could receive several inches of volcanic ash should the volcano erupt. This should have been reported as several millimeters (or about 1/10 of an inch).

  I’m not sure I believe that.  I don’t doubt that somebody at AVO had been misquoted by the media.  What I doubt is that anyone has a really accurate and informed idea how much ash might fall from any eruption.  It’s guesswork, and I’m guessing that estimates are minimized to prevent panic.

  Many Anchorage residents, like the one here in 1992, have had to sweep or shovel ash from their roofs, and I remember seeing video of residents of the Kenai Peninsula digging out from 16-18 inches of ash from Augustine three decades ago.  Not until the ash clouds were in the air did anyone have an accurate idea where they were going to fall or how much ash they would dump. 

  Ashfall is more that just a mess.  In terms of the work to remove it, it is a lot like heavy snow that never melts.  However, we don’t need to wear particle masks while shoveling snow.  Those sharp abrasive particles damage breathing passages and clog lungs.

  Internal combustion engines stall when their air filters become clogged, and if they don’t have efficient air filters, the ash damages valves and cylinders.

  Jet engines are not immune from ash clouds, either.  Nineteen years ago, a jetliner almost crashed near here.

  As the crew of KLM Flight 867 struggled to restart the plane’s engines, “smoke” and a strong odor of sulfur filled the cockpit and cabin. For five long minutes the powerless 747 jetliner, bound for Anchorage, Alaska, with 231 terrified passengers aboard, fell in silence toward the rugged, snow-covered Talkeetna Mountains (7,000 to 11,000 feet high). All four engines had flamed out when the aircraft inadvertently entered a cloud of ash blown from erupting Redoubt Volcano, 150 miles away. The volcano had begun erupting 10 hours earlier on that morning of December 15, 1989. Only after the crippled jet had dropped from an altitude of 27,900 feet to 13,300 feet (a fall of more than 2 miles) was the crew able to restart all engines and land the plane safely at Anchorage. The plane required $80 million in repairs, including the replacement of all four damaged engines.

  (from USGS Fact Sheet 030-97)

  Ash is the reason AVO pays attention to volcanoes and we pay attention to AVO.  Ash clouds are hard to distinguish from ordinary clouds, both visually and on radar.  Seismic monitors have been placed on the slopes of all the more active cones in our portion of the Pacific Ring of Fire, and one or more webcams watch many of them.

  With my respiratory condition, I stay alert to what the volcanoes are doing.  When I get the word from AVO about an eruption, with data on the height of the ash cloud, I can use the Puff Volcanic Ash Tracking Model to see if it is blowing my way and how much time I have to prepare before it gets here.  My particle mask is in the same place by my bed as my nebulizer and other “sickroom” equipment.

  The map below compares ashfall areas from some historic twentieth century eruptions of Alaska volcanoes.  The map, the  photo below it of a man standing in an ash drift on Kodiak Island, both captions, and the diagram comparing “cubic miles of magma,”  are from USGS Fact Sheet 075-98.

  
  The ash fall from the cataclysmic 1912 eruption of Novarupta (large gray shaded area) dwarfs that produced by recent eruptions of Augustine (blue area), Redoubt (orange area), and Spurr (yellow area) Volcanoes. Old-timers in Alaska can recall dozens of eruptions from these and other Alaskan volcanoes. Within 500 miles of Anchorage, several volcanoes (brown triangles) have exploded in Novarupta-scale eruptions in the past 4,000 years. Beyond the areas shown here, ash fall from these recent eruptions of Augustine, Redoubt, and Spurr Volcanoes was negligible, but ultrafine dust and sulfurous aerosols were held aloft and transported farther by high-altitude winds. Even though relatively small, the volcanic ash clouds from these eruptions still resulted in airport closures and damage to many jet aircraft. Because of the size and frequency of eruptions and prevailing winds, Alaskan volcanoes present a greater threat to aviation on the west coast of the United States than do the volcanoes of the Cascade Range in the Pacific Northwest.

  On the afternoon of June 6, 1912, an ominous cloud rose into the sky above Mount Katmai on the Alaska Peninsula. The cloud quickly reached an altitude of 20 miles, and within 4 hours, ash from a huge volcanic eruption began to fall on the village of Kodiak, 100 miles to the southeast. By the end of the eruption on June 9th, the ash cloud, now thousands of miles across, shrouded southern Alaska and western Canada, and sulfurous ash was falling on Vancouver, British Columbia, and Seattle, Washington. The next day the cloud passed over Virginia, and by June 17th it reached Algeria in Africa.

  During the 3 days of the eruption, darkness and suffocating conditions caused by falling ash and sulfur dioxide gas immobilized the population of Kodiak. Sore eyes and respiratory distress were rampant, and water became undrinkable. Radio communications were totally disrupted, and with visibility near zero, ships couldn’t dock. Roofs in Kodiak collapsed under the weight of more than a foot of ash, buildings were wrecked by ash avalanches that rushed down from nearby hillslopes, and other structures burned after being struck by lightning from the ash cloud.

  

  The United States Geological Survey’s official position is that, “Such massive eruptions will occur again in southern Alaska.”  Nobody knows when , and they’re only guessing about how big the next one might be.
  

  • 3:52 pm
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