By Jenny Neyman
Redoubt Reporter
If the Alaska Volcano Observatory were looking for a theme song, it could turn to The Who and “Won’t Get Fooled Again.”
Current activity at Mount Redoubt volcano is deja vu for Kenai Peninsula residents who lived here during its last period of unrest, in 1989 and 1990.
And while the observatory keeps tabs on the rumbling giant across the inlet, the volcano in turn serves as a measure of how the observatory itself has progressed.
The observatory was formed in 1988, just one year before Mount Redoubt erupted.
“It was really that eruption that sort of showed the state and federal government that that was an important issue,” said Allison Payne, geologist with the observatory.
“It demonstrated how important it is to keep track of those volcanoes. … We can’t predict what the volcano is going to do, but we have a much better grasp of what it might do and a better timetable to work with, and that allows us to be more prepared.”
The observatory has come a long way in the last 20 years, when Redoubt’s eruption came largely as a surprise.
“The onset of the eruption happened quite quickly. We had about 24 hours notice,” Payne said of the 1989 event. “A couple people were looking at seismicity the week before the eruption, and had this premonition that there was going to be an eruption, based on some interesting seismic patterns.”
But the geologists weren’t widely believed until the seismic activity significantly ramped up just prior to the eruption in December 1989. Had the observatory known sooner, it could have sounded the alarm sooner, which would have allowed people to be better prepared for the resulting ash fallout — especially on the Kenai — and possibly could have prevented a KLM jet from flying through the ash plume and nearly crashing.
These days, there isn’t much going on at the volcano that the observatory isn’t aware of.
There’s a Web cam pointed at the summit and geologists monitor real-time seismic data that’s updated every second. They keep a constant watch on satellite data for heat and gas emanations. They do periodic overflights to monitor activity, and take gas measurements to learn about new magma moving in the system. Wind patterns are tracked and particulate matter in the air is monitored. The Web site is continuously updated with new photos and status reports. If unusual activity does occur, the observatory sends out e-mail alerts to anyone who signs up for them, along with its usual communication with government, emergency response, aviation and other agencies.
The observatory will even send out updates via Twitter, a networking service where people send and receive short text messages on cell phones, computers and other devices. That certainly wasn’t around in 1989.
“No, not so much,” Payne said.
So monitoring has changed, but the volcano itself isn’t behaving all that differently this time around. Other than the short notice in 1989, that cycle of activity and the current one share similarities.
Redoubt is displaying two kinds of seismicity, Payne said. Volcanic tremors are small, continuous earthquakes mainly produced from hydrothermal activity, when ground water in the volcano is heated to boiling by magma underneath and moves through the rocks, causing them to break up and jumble round. The other seismicity is more substantial, discreet volcanic events that come in at higher frequencies than the continual tremors.
Both types preceded the eruption in December 1989 and are being measured at Redoubt now, although in 1989 they led to an eruption much more quickly.
“Certainly they were there,” Payne said. “They happened sooner, so right now we’ve had a couple weeks with mostly tremors and just a few events of discrete volcanic events.
“This time we started seeing similar seismicity and we were thinking it could happen rather quickly. This just goes to show nature is very diverse, volcanic systems are really diverse and you never really know what’s going to happen.”
The level of seismic activity at Redoubt over the past month has cycled up and down. During the past two weeks there was a spike in activity Jan. 25, another Jan. 31 and an increase in seismicity over the last several days, Payne said Monday, with the volcano settling down in between.
It’s possible the volcano could quiet back down without an eruption, Payne said, but it’s more likely an event similar to 1989 and 1990 is coming.
“Something comparable to the ’89 eruption, or smaller in scale,” she said. “So that could mean an ash column the same size or smaller — or it could mean more growth of the lava dome, or growth of new lava dome. Or not.
“I think most folks are thinking it’s more probable we’ll have a small eruption. It’s possible nothing will happen, and it’s possible there will be a larger eruption.”
If Redoubt behaves as it did in 1989-90, that means Southcentral Alaska is in for several ash-producing eruptions up to 40,000 feet over a several-month period. Redoubt followed its December 1989 eruption with others in February, April and June.
The 1989-90 eruptions produced several ash plumes up to 40,000 feet, which dusted Kenai with 5 millimeters of ash overall, Payne said. The prevalent wind pattern this time of year blows east, northeast — toward the peninsula. If and when there is an ash-producing event, the peninsula will probably be in the crosshairs.
Eruptions can be from deep within the volcano out through the cone itself, and others are produced by volcanic domes growing and then collapsing, spitting up ash, gas and rock.
The iconic photo from Redoubt’s April 1990 eruption, with a red-tinged mushroom cloud rising into the sky, was caused by a collapse of a lava dome, Payne said, which is why the cloud rose off-center from the volcano, instead of directly from the cone.
Payne recommends continued preparedness, because it may be summer before Redoubt goes dormant again.
“It certainly could. The last one was several months,” she said.
No comments:
Post a Comment