|
BOXBOROUGH, Mass., 31 Oct. 2005. Like many volcanoes in the remote region of Unimak Island, Alaska, the Shishaldin Volcano poses little threat to human life or property. Ash from potential eruptions, however, poses a threat to aircraft. The volcano sits beneath one of the heavily traveled north Pacific air routes.
Encounters with volcanic ash by jet aircraft can cause serious damage, and even engine failure. Because of this, the volcano is among several that authorities monitor round the clock.
In 1999, data collected from a pressure sensor from Setra Systems in Boxborough, Mass., helped seismologists understand an eruption of the volcano. Shishaldin has erupted at least 29 times since 1755, making it one of the most active volcanoes in the Alaska.
Visual observations of the volcano are limited to either from either Cold Bay, 56 miles away, or from pilot reports, so capturing eruptive behavior relies heavily on analyzing telemetered acoustic, seismic, and satellite data.
The Setra model 239 pressure sensor, installed in summer 1997, was the source of much of the acoustic data detailing the eruption. Integrated into a network of sensors deployed between 3 and 12 miles from Shishaldin's primary vent, the Setra 239 detected the infrasonic oscillation of eruptions.
Once the sensor detects infrasonic oscillation, it automatically convert the signal to a voltage, which it transmits by radio back to the Alaska Volcano Observatory.
The Setra 239 has a stainless steel diaphragm and insulted electrode, which forms a variable capacitor. As pressure increases or decreases the capacitance changes. The sensor's electronic circuit detects this change in capacitance and converts it to a linear DC high-level voltage output signal. The 239 not only survived the Shishaldin volcano eruption, but it also continued to work long afterward, company officials say.
Jackie Caplan-Auerbach, a seismologist with the Alaska Volcano Observatory, says the Setra 239 sensor was a great help in her team's ability to monitor the volcano. "By sensing an atmospheric eruption, the 239 told us that a Strombolian eruption was on the way," she says. "We were able to monitor the volcano's transitions from Strombolian (primarily lava) to Subplinian (plumes of ash) then back to Strombolian eruptive phases."
| 
Community 
| View all PennWell sites | View all PennWell events
Add RSS Feed