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Interference from ash
Large quantities of electrically-charged ash can be generated in an eruption column. This charged ash can cause interference to radio waves and render radio and telephone systems inoperative. However, there are examples of radio and telephone communications continuing to function around an erupting volcano and in areas receiving ash falls.
Overloading of systems
During most natural disasters telephone and radio communications are susceptible to overloading by public and emergency services use. Response organizations report frequent overloading of their telephone lines even in cases where the general system remains operative.
Damage caused by ash
Most modern telephone exchanges require air-cooling systems to keep electronic switching gear below critical temperatures. Exchanges with external air-cooling systems are thus vulnerable to over-heating if these units fail or are switched off (due to ash falls), even if the exchange itself is sealed. Some exchanges are sealed to keep out corrosive geothermal gases such as H2S. However, any ash entering telephone exchanges can cause abrasion, corrosion, or conductivity damage to electrical and mechanical systems.
Effects of ash fall on communication systems during recent explosive eruptions in the world.
Volcano; eruption year Overloaded telephone systems Interference in communications Damage to communications Inoperative communications Mount Spurr; 1953 yes Mount St. Helens; 1980 yes Ruapehu; 1995 yes Katmai; 1912 yes Surtsey; 1963 yes Mount Pinatubo; 1991 yes Pacya; 1995 yes
Keeping ash out
The most serious problems to communications systems result from the conductive and abrasive properties of ash. Measures that can help prevent ash falls impacting greatly on communications systems include:
- Teflon insulators should be replaced with ceramic insulators to prevent dust shorting out the communication system.
- Plastic switches and push-buttons also need to be replaced as these abrade quickly.
- Seal up repeater stations and other installations; shut air intakes; internal air circulation and leakage should be sufficient for cooling.
- Install covers; plastic tarp will do in an emergency.
The following recommendations on the removal of ash from communication systems have been based on the experienced gained from the 1980 eruption Mount St. Helens, Washington:
- Blow out or vacuum out radio equipment and brush off.
- Seal equipment that is not already watertight and keep moisture out of equipment.
- Magnetic particles that stick to relay cores should be blown off.
- Clean equipment daily and the increase use of filter paper.
- Clean out microwave dishes, feed horns, and wave guides.
Dillman, D.A., Schwalbe, M.L., and Short, J.F., 1982, Communication behavior and social impacts following the May 18, 1980, eruption of Mount St. Helens, in Keller, S.A.C. (ed.), Mount St Helens: One year later: Eastern Washington University Press, p. 173-179.
Erskine, W.F., 1962, Katmai: a true narrative: Abelard-Schuman, London, 223 p.
Gilbert, J.S., and Lane, S.J., 1994, Electricity phenomena in volcanic plumes, in, Casadevall, T.J., ed., Volcanic ash and aviation safety: proceedings of the first international symposium on volcanic ash and aviation safety: U.S. Geological Survey Bulletin 2047, p. 31-38.
Gilbert, J.S., Lane, S.J., Sparks, R.S.J., and Koyaguchi, T., 1991, Charge measurements of particles fallout from a volcanic plume: Nature, v. 349, p. 598-600.
Labadie, J.R., 1983, Teal Granite: Mitigation of volcanic dust effects: IRT Corporation, (final report prepared for U.S. Air Force Office of Scientific Research and the Defence Advanced Research Projects Agency), 29 p.
Rodolfo, K.S., 1995, Pinatubo and the Politics of Lahars: University of Philippines Press, 341 p.
Wilcox, R.E., 1959. Some effects of recent volcanic ash
with special reference to Alaska: United States Geological
Survey Bulletin 1028-N, p. 409-476.