Friday, August 04, 2006
In last January's volcano eruption, Augustine followed predictions
“Is Augustine following the script?” asked Tom Murray, chief scientist in charge of the Alaska Volcano Observatory at a talk Tuesday at the Alaska Islands and Ocean Visitor Center.
“The script” was Murray’s term for the predicted behavior of Cook Inlet’s most-active volcano. With four eruptions since 1970 before Augustine blew this year, scientists have developed a scenario of how Augustine should have acted. The usual behavior is a period of restlessness characterized by increasing local earthquakes and ground movement or swelling.
Then, the volcano blows off steam and gases, followed by a full throat-clearing blast. After weeks of big eruptions, dome building continues, with rock falls and pyroclastic, or hot ash and gas flows. Eventually, the volcano calms down. If Augustine deviated from the script, such as it did in 1883 when a flank collapse caused a tsunami in English Bay, it would be a bad actor, Murray said.
“In this eruption in 2006, it followed the script very well,” Murray said. “Augustine was well behaved in 2006 — at least so far,” he added.
Augustine still remains at code yellow in the Alaska Volcano Observatory’s four-color level of concern code. Green is the lowest level of activity, with normal seismicity, and orange and red are the highest levels of concern. AVO put Augustine at code orange in mid-January and at code red right before the first large steam and gas eruption on Jan. 11.
According to last week’s update, seismicity has declined to nearly pre-eruption levels, with small rock falls occurring infrequently. Lava flows at the dome have ended.
“It’s pretty much stopped, which is why we think the eruption is over,” Murray said of the dome building activity on Augustine.
Visitors seeing Augustine on a clear day might have noticed a long, thin plume extending from the summit. Looking west from the viewpoint at Baycrest Hill, Augustine is the cone-shaped peak on its own island. Mount Iliamna is the four-peaked volcano north of Augustine, with Mount Redoubt north of Iliamna.
The Alaska Volcano Observatory is a consortium of scientists from the U.S. Geological Survey, The University of Alaska Fairbanks Geophysical Institute and the Alaska Division of Geological and Geophysical Surveys. Its 25 full-time employees monitor activity on 40 historically active volcanoes — 80 percent of America’s active volcanoes and 8 percent of the world’s. When the frequency of small earthquakes increased in early December 2005, AVO ramped up its monitoring. When it began to steam, it sent up flights to monitor gases. When it blew, AVO put its staff on 24-hour coverage.
“I don’t remember hardly anything that happened in January,” Murray said. “It became a blur, a crisis situation, like being on a fire line.”
In late January, seismographs on Augustine recorded a steady series of intense earthquakes — “drumbeat earthquakes,” Murray called them.
“This is really staying on script,” he said of the quakes.
Murray said the biggest hazard from Alaska volcanoes is airborne ash on airplanes. He mentioned an incident from the 1989 eruption of Mount Redoubt when a Boeing 747 jet flew into an ash cloud, shutting down the jet’s engines for four minutes. Located in Kamishak Bay 75 miles southwest of Homer, a sudden collapse of the volcano’s flank could cause a tsunami, as happened in 1883. In the past 2,200 years, Augustine has had 13 debris avalanches. Murray said a line of steam fumaroles across Augustine’s dome had scientists worried a crack might have been developing. That never happened.
To better track tsunamis, the Alaska Tsunami Warning Center is putting up experimental wave detectors along the Augustine Island’s shore this summer. Other scientists are on the island this month repairing monitoring stations, such as geographical positioning satellite receivers or seismographs. Since the previous eruption in 1986, scientists have had Augustine heavily monitored.
“This ongoing work between eruptions is preparing for the next eruption,” Murray said.
Web cameras on Augustine gave the world a near real time view of its progress. AVO also had a Web camera and a low-light camera on the Homer bluff. Because Augustine blew at the darkest time of the year, the low-light camera gave scientists a great view of flowing lava and hot gases when Augustine erupted at night.
After Murray’s talk, people from the standing-room crowd of about 60 asked questions. Did Augustine contribute to global warming — or lessen it? Jennifer Adleman, another AVO geologist at the presentation, said Augustine didn’t produce enough ash like Novarupta, the Katmai National Park volcano that blew in 1912, and lowered Northern Hemisphere temperatures by 1 degree Fahrenheit.
Adleman also showed off rock and ash samples collected from Augustine. Her prize was a melon-sized gray rock streaked with darker gray — the newest rock created by the earth. Adleman also had samples of ash collected. She said Augustine didn’t produce much more than a dusting of ash in Homer. Ash also fell on Seldovia, Nanwalek, Port Graham and Iliamna across Cook Inlet, places where citizen volunteers reported and collected ash for AVO.
Murray said reports from local residents provided some of the best information about Augustine’s early activity. For example, scientists began to suspect something was up when people in Nanwalek reported a sour-egg smell. Fishermen near Augustine also reported such smells.
“We can’t do it without citizens helping us,” Murray said.
When will Augustine next erupt? one visitor asked. Murray said scientists weren’t ready to predict that, although he noted the pattern of Augustine erupting in years ending in six — 1976, 1986 and now 2006. Whatever happens, AVO will be monitoring it, he said.
“We’re really preparing for the next eruption,” Murray said. “Because it will erupt again.”