Life-threatening eruption producing volcanic hazards that endanger communities. Punongbayan, R.S., Newhall, C.G., Bautista, M.L.P., Garcia, D., Harlow, D.H., Hoblitt, R.P., Sabit, J.P., and Solidum, R.U., this volume, Eruption hazard assessments and warnings. Describe the 4 alert levels for volcanic eruptions:1. 3rd August 1990 In 1992, PHIVOLCS advised the inhabitants of the 10- to 20-km danger zone to avoid the 10-km danger zone (where some residents would otherwise hunt or gather food or tend farm plots), be alert to possible deterioration in the volcano's condition, and prepare for this possibility. Table 8 lists some of the reasons given by those who dallied or evacuated selectively. Sustained increase, or sudden drop, of SO. On June 15th 1991, the second largest volcanic eruption of the twentieth century took place when Mt Pinatubo erupted at 1:42 pm local time. The warning message consisted of hazard zonation maps, alert levels, and "danger zones," which were zones of recommended evacuation, simplified from the hazard maps. One Municipal Disaster Coordinating Council (MDCC) official admitted that the council decided to order evacuation of barangays beyond the 10-km but within the 20-km radius (including one community that was already living in a relocation center) on the night of July 15. Velarde, Cherry, and Bartolome, Noel, 1991, Pinatubo erupts: Malaya [Manila], June 10, 1991. In April, Aeta tribesmen who refused to move out reportedly said "they were afraid to leave their 'precious belongings&'" (Alcayde, 1991) or reasoned that they could not leave because their camote crops were due for harvesting. National Statistics Office, 1990, 1990 census of population and housing, Report No. United Nations Disaster Relief Organization (UNDRO), 1986, Social and sociological aspects, in Disaster prevention and mitigation, v. 12: New York, United Nations. Sporadic explosions from the summit crater or new vents. Response to preeruption warning in each of the danger zones. The survey covered only the survivors and is biased in favor of those who took precautions. 13th May 1991 – Alert Level 2. These communities were reached by an information drive that featured the Maurice Krafft videotape on volcanic hazards, which he made for the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI). Start studying Mt. Table 1. 62,000 people have … Alert levels were designed to describe various levels of eruptive activity and danger. On June 15th 1991, the second largest volcanic eruption of the twentieth century took place when Mt Pinatubo erupted at 1:42 pm local time. Hazardous eruption is possible within days. The warning communication system was improved in 1992 by the distribution of two-way radios to barangay leaders. Activity Detected Eruption Not Imminent 2. Response to preeruption warning and false evacuation order. Hazardous eruption is possible within days. The following day (June 10), Clark Air Base, a U.S. military installation near the volcano, was evacuated. The Mount Pinatubo 1991 eruption provides an excellent example of how accurate forecasting and timely warning saved lives from the destructive agents unleashed by a violent eruption. The denser oceanic philippine plate subducted under the less dense continental Eurasian plate. Danger to aircraft, by way of ash cloud encounter, depending on height of eruption column and/or wind drift. Levels 3 and 4 of the Pinatubo scheme anticipated forecast time windows (2 weeks and 24 h) within which an eruption might occur, and each level had an interpretation of activity. 1 Lahars may be generated by intense rainfall over the volcano area and may affect riverside communities far down the PDZ.. 2 Sulfur Dioxide is a major gas component of magma.. STAND-DOWN PROCEDURES. how many alert levels are there? About 81 percent of those who received forewarning took appropriate action, by evacuating immediately (the response that was called for in the case of those living within the 10-km radius as early as April and those living within the 10- to 20-km radius starting June 7) or by taking some other defensive action (such as preparing for evacuation, convening a meeting, disseminating the warning, seeking further information or confirmation, or observing for further signs, responses that were appropriate at radii of 10 to 20 km from April to June 7 and at radii of 20 to 40 km until June 15). FIRE and MUD: Eruptions and Lahars of Mount Pinatubo, Philippines, edited by Christopher G. Newhall and Raymundo S. Punongbayan, 1996 The source of activity is shallow, near crater or in the vicinity of Irosin Caldera. In contrast, 13 percent of those who were forewarned either waited for the eruption or ignored the warning; and 5 percent ran without definite destination, prayed, or cried without taking any defensive action (table 6). The organization ensured that everyone received the warning and evacuation order. Figure 1. Eighty-six percent of the respondents received an evacuation order, but 30 percent of these people received it 2 or more days after it was issued. Mount Pinatubo, Philippines, 1991. The highest alert level 4 is issued, meaning that a significant eruption might happen any time now. 2. Most of them did not want to leave their belongings, crops, and livestock and believed that Apo Namalyari would not let them come to harm. An evacuation area 20 kilometers (12.4 miles) away from the volcano was established and 25,000 people were evacuated. Level 5, the highest, is reserved for an eruption in progress. Other areas within five (5) kilometer. In 1992, 94 percent of the respondents learned of the impending eruption on or before July 14, the day PHIVOLCS issued Alert Level 5 (table 5). These maps illustrated the probable extent of the most probable hazards and served as guides for evacuation of endangered communities. On the eastern side of the volcano, most barangays within the 10- to 20-km danger zone that were sampled in 1992 had only about half of their original pre-1991 eruption populations. The formation of Mount Pinatubo begins with the formation of the chain of volcanoes, the Luzon Volcanic arc. Unrest probably of magmatic origin; could eventually lead to eruption. In the case of Mt. Subtracting the 9 percent (roughly) who knew only through their own observation, it appears that about one-fourth of the respondents were not reached by warnings before explosive eruptions began. Entry within PDZ must be prohibited. Early, perceptible signs from the volcano and prompt warning and mobilization of disaster-response officials minimized the human losses. A chain of volcanoes most likely means that a destructive plate boundary must have occurred there, which in fact is what actually happened. Swelling of edifice may be detected. Increased water and/or ground probe hole temperatures, increased bubbling at Crater Lake. He added that the men may have wanted to stay to harvest their palay and camote crops so they could repay their loans to the Land Bank of the Philippines (anonymous, 1991a). Shortly after the explosion, a new lava dome is observed 1 km NW of the main crater: new lava is now at the surface, but the viscous lava effectively blocks the gas-rich magma beneath it. Low level seismicity, fumarolic, other activity. Last updated 06.11.99. The effectiveness of the modified transmission procedure adopted at Pinatubo was assessed by use of two indicators: (1) consistency between the warning message released by the source (PHIVOLCS) and the message received by the recipients and (2) the time gap between issuance from the source and receipt by the target public. Further increase in SO2 flux. In another barangay, Belbel, the barangay captain reported that some 252 tribesmen also refused to leave their homes (Anonymous, 1991b). Intermittent steam/ash explosion and above baseline Sulfur Dioxide2(SO2) emission rates. Eruption Possible Within 24 Hours 9. Criteria. [Note that the criteria for each alert level are qualitative, not quantitative, and that the "meaning" is not strictly a forecast, but rather, a statement of what might occur. Volcanic quakes and tremor may become more frequent. In order to minimize unnecessary changes in declaration of Alert Levels, the following periods shall be observed: From Level 5 to Level 4: Wait at least 24 hours after hazardous activity stops 1990 census figures indicate that the barangays within the 10-km and 10- to 20-km danger zones had 7,653 households, or 41,100 residents; the 20- to 40-km danger zone, which included 106 barangays in 17 towns, had 58,696 households and more than 331,000 inhabitants (National Statistics Office, 1990). Household respondents were randomly selected from lists of household heads provided by barangay leaders, with substitutions when the original respondents were either unavailable or unwilling. 2-74C (Pampanga); Report No. The following day (June 10), Clark Air Base, a U.S. military installation near the volcano, was evacuated. The 1991 survey was by stratified random sampling of respondents who had lived in the danger zones or zones recommended for evacuation. Two other informants said half of the residents of sitio Lomboy were very reluctant to evacuate. The original alert levels focused mainly on the imminence or occurrence of a large explosive eruption. Earthquakes and steam explosions announced the reawakening of Mount Pinatubo in 1991, surprising many geologists because Pinatubo was not even listed in catalogs of world volcanoes. The increased alert level and heightened activity at Mt Ruapehu’s Crater Lake isn’t an indication that an eruption will happen – but it is possible. The source of activity may be shallow, near the summit crater or in the vicinity of the edifice. A Pilipino version of the alert level scheme could be pilot tested the next time one of our volcanoes becomes restive. The extrusion of a lava dome on June 7 led to the issuance of a Level 5 alert on June 9, indicating an eruption in progress. Of those forewarned, 82 percent took protective action, including 46 percent who evacuated. Frequent strong ash explosions. Ashfall will occur from secondary explosions for several years after the 1991 Plinian (calderagenic) eruption, whenever rainfall and lahars come in contact with still hot-hot 1991 pyroclastic flow deposits. Later, PHIVOLCS' main office might release information to the media to clarify and explain the volcano's condition. Mt Ruapehu is being closely monitored for signs of activity after the active volcano's crater lake (Te Wai ā-moe) heated to 43C, prompting an escalation in alert levels. The extrusion of a lava dome on June 7 led to the issuance of a Level 5 alert on June 9, indicating an eruption in progress. The first quake was followed by a M3.2 in the same area, approximately 12 km northeast of Olongapo city at a depth of 6 km. Pinatubo began feeling earthquakes and after several explosions a Level 5 alert was issued indicating an eruption was in progress. Two posteruption surveys, one in 1991 and another in 1992, assessed whether eruption warnings were received, understood, and used by citizens to take protective action. The Philippine Institute of Volcanology and Seismology is maintaining Alert Level 3 at Pinatubo, warning that an explosive eruption is possible. Since the major eruption of June 15, 1991, the lahar hazard part of these maps has been updated several times. Fig. These were characterized by quiet effusion of lava and dome building punctuated by minor explosions and hence were not as explosive and hazardous as the 1991 events. Another 13 respondents (from the 20- to 40-km danger zone) overreacted by evacuating before they were ordered to do so. ... told CNN that the alert level … Quiescence; nno magmatic eruption is foreseen. An Aeta in Moraza who defied the evacuation order and stayed on to keep an eye on his home, farm, and carabao (water buffalo) was quoted to have said "We fear the volcano, but if we left our carabaos, we'll die" (Morella, 1991). This prompted the Philippine Institute for Volcanology and Seismology (Phivolcs) to raise the alert level to 4 (out of 5) to signify an imminent hazardous eruption. The highest level is alert level 5, which incidates that a hazardous eruption is in progress. [Household survey, 1991; number of respondents was 69]. A photograph of the eruption of Mt. These maps delineated the areas likely to be affected by the destructive agents, namely, pyroclastic flows, ash fall, and lahars. Magma is near or at the surface, and activity could lead to hazardous eruption in weeks. Eruption Now Likely Possibly WIthin 2 Weeks4. FIRE and MUD: Eruptions and Lahars of Mount Pinatubo, Philippines, edited by Christopher G. Newhall and Raymundo S. Punongbayan, 1996 The lowest is alert level 0 when a volcano is quiet. These problems indicate a need for hazard-awareness promotion that is more intensive and broader in outreach than was possible during the 2-month period from the time the volcano started showing signs of restiveness up to the time of the major explosions. No alert . Low level seismic, fumarolic, other unrest. The first three alert levels were retained with only a slight revision of Alert Level 3 interpretation, but Alert Levels 4 and 5 were substantially modified (table 3). No alert . The warning, no matter how timely, accurate, and precise, will not be of any value unless the recipient of the warning takes appropriate defensive action. 4 levels. Some looked on the relocation site as a kind of "bakasyunan" or vacation home. Sabit, J.P., Pigtain, R.C., and de la Cruz, E.G., this volume, The west-side story: Observations of the 1991 Mount Pinatubo eruptions from the west. Low level seismic, fumarolic, other unrest. Low-level magmatic eruption underway, which can progress to highly hazardous major eruption within hours or days. A) If trend is one of increasing unrest, hazardous eruption is possible within days to weeks. Some who did not evacuate as advised thought the eruption would not be strong enough to affect their places; others were reluctant to leave behind their houses and household effects, livestock, and crops, especially at harvest time; still others had no ready means of transport and could not walk long distances, or they believed that their God, Apo Namalyari, would not let them come to harm. All monitored parameters within background levels. Most received their evacuation orders on the day or 1 day after the danger zone was declared by PHIVOLCS; others received the evacuation order 2 or more days later, reflecting some delay in the transmission. 7 - Seismographs at Mount Pinatubo Monitoring Observatory site at Clark Air Base, Philippines. 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