Alert Level 2 remained in effect until the volcano started manifesting a resurgence of activity in July 1992. The highest level is alert level 5, which incidates that a hazardous eruption is in progress. Surprisingly, 8 percent of the respondents (all from Pampanga) reported that they received an evacuation order either from municipal or barangay officials or through the media. The only recommendation for evacuation in 1992 was for the danger zone within <10 km of the summit. To return to the text, close the figure's window or bring the text window to the front. Magmatic, tectonic or hydrothermal disturbance; no eruption imminent. How many times in the last 2,000 years has Mt. Alert Level 4 will be used only for impending hazardous explosive eruptions or for ongoing eruptive activity that involves only small explosions or lava dome extrusions. 1500 earthquakes are measured a day under the volcano, and a (probably phreataic) ash eruption sends a plume to 8 km altitude, suggesting magma is very close to the surface now. 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. The traditional DCC channel would certainly minimize the warning source's need to deal with the media and make it easier to pinpoint responsibility for erroneous reporting. ... raised the alert level on Mt. An evacuation area 20 kilometers (12.4 miles) away from the volcano was established and 25,000 people were evacuated. Hundreds of Aetas with their belongings and work animals lined the roads, waiting for trucks to bring them down to evacuation centers. Communities in which LAKAS, an organization of the indigenous Aetas, was active showed the most exemplary operation of the system:transmission was total and response was consistently appropriate. Initially, volcanologists considered employing an alert level terminology used at other Philippine volcanoes but opted to design a new one for Pinatubo (table 1). How to incorporate these without making the scheme of alert levels inflexible and too specific remains to be studied. Probable intrusion of magma at depth, which may or may not lead to magmatic eruption. Eruption columns reached 40 kilometers in altitude and emplaced a giant umbrella cloud in the middle to lower stratosphere that injected about 17 megatons of SO2, slightly more than twice the largest yielded by the 1982 eruption of El Chichon, Mexico. Either the information drive launched by PHIVOLCS and other disaster response organizations before the eruption did not reach these respondents or the information campaign failed to drive home to them the magnitude of the threat and the urgency as well as the possibility of avoiding the volcano's fury. Rather, it was meant to define a window in which an eruption was possible and to indicate disappearing margins of safety. United Nations Disaster Relief Organization (UNDRO), 1986, Social and sociological aspects, in Disaster prevention and mitigation, v. 12: New York, United Nations. Slight increase in SO2 gas output above the background level. 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. Later, PHIVOLCS' main office might release information to the media to clarify and explain the volcano's condition. Pinatubo's escalation of volcanic activity took months in between alert levels. 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. Empeno, Henry, 1991, Mt Pinatubo already spewing lava, (say) Aetas: The Manila Times, April 23, 1991. 2-95C (Tarlac); and Report No. Intense unrest, continuing seismic swarms, including harmonic tremor and/or “low frequency earthquakes” which are usually felt, profuse steaming along existing and perhaps new vents and fissures. However, there are perennial hazards (sudden explosions, rockfalls and landslides) within the four (4) kilometer-radius Permanent Danger Zone (PDZ) that may occur suddenly and without warning. 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. Mount Pinatubo was an example of Plinian eruption On September 4, the alert level was lowered to 3, and the danger zone was shrunk back to a 10-km radius. Frequent strong ash explosions. But these people changed their minds when they could not read sign boards on the buses that indicated which should be boarded by Villar residents, by Moraza residents, and so on. Alert Level 5 will be used only for large explosive eruptions in progress. Two percent of the respondents evacuated their entire households and another 3 percent evacuated selectively (table 9). Occurrence of low-frequency earthquakes, volcanic tremor, rumbling sounds. A photograph of the eruption of Mt. Danger Zone may be extended up to nine (9) kilometers or more from the active crater. Evacuation orders were issued by concerned Disaster Coordinating Councils or local government officials soon after danger zones were declared on April 7, June 7, and June 14-15, 1991. 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. 62,000 people have … 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). In order to protect against “lull before the storm” phenomena, alert levels will be maintained for the following periods AFTER activity decreases to the next lower level: From level 5 to level 4:            Wait 12 hours after level 5 activity stops, From level 4 to level 3 to 2:    Wait 2 weeks after activity drops below level 4, From level 3 to level 2:            Wait 2 weeks after activity drops below level 3. The Aviation Colour Code is changed to yellow. All (except one old man who chose to die rather than leave his home) prepared and evacuated promptly. The warning communication system was improved in 1992 by the distribution of two-way radios to barangay leaders. ... Pampanga was among the worst hit by the 1991 eruption of Mount Pinatubo and by the ash that the eruption left behind. Life-threatening major eruption producing volcanic hazards that endanger communities. The 1991 survey was by stratified random sampling of respondents who had lived in the danger zones or zones recommended for evacuation. Slight increase in seismicity. Much of the rugged land around the present volcano consists of remnants of "ancestral" Pinatubo. The failure, in 1991, of 18 percent of those who were forewarned to take any defensive action and the delayed or selective evacuation of 34 percent of those who received evacuation orders indicate some failure to stimulate protective action. The United Nations Disaster Relief Office (UNDRO, 1986, 1987) advised, among other things, that warnings should be consistent in content and as specific as practicable in their information concerning the magnitude of the event, the place at which it is expected, and the time when it will occur. Low level seismicity, fumarolic, other activity. 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. 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). 2 Sulfur Dioxide is a major gas component of magma. By June 14, 99 percent of the respondents knew of impending danger, from continued warnings and, especially, from observing the preparoxysmal eruptions (Wolfe and Hoblitt, this volume). If trend is one of increasing unrest, eruption is possible within weeks. GeoNet yesterday raised the volcano alert to level … Velarde, Cherry, and Bartolome, Noel, 1991, Pinatubo erupts: Malaya [Manila], June 10, 1991. 4 levels. Many of them did not believe that the eruption would be strong enough to affect their places. Increasing rates of ground deformation and swelling of the edifice. Activity More Intense Eruption Probable3. 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. 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). 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. Low level seismic, fumarolic, other unrest. Elevated levels of any of the following: volcanic earthquake, steam/gas emission, ground deformation and hot spring temperature. Extension of Danger zone to 8 km or more in the sector where the crater rim is low will be recommended. "While Volcano Alert Level 2 is mostly associated with environmental hazards, eruptions can still occur with little or … 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. Mount Pinatubo, volcano, western Luzon, Philippines, that erupted in 1991 (for the first time in 600 years) and caused widespread devastation.Mount Pinatubo is located about 55 miles (90 km) northwest of Manila and rose to a height of about 4,800 feet (1,460 m) prior to its eruption. In both surveys, sampling size was determined by using a normal variable (z) value of 1.96 (see appendix 1 for the formula and computation). By June 9, Mayor Richard Gordon of Olongapo City was reported to have dispatched trucks to "clear" barangays within the 20-km danger zone where "there were still some Negritoes who chose to stay where they were, because of their livestock and other properties" (Villanueva and Dizon, 1991). At the five most active volcanoes being monitored by PHIVOLCS--Mayon, Bulusan, Taal, Hibok-Hibok, and Canlaon--eruption warnings are usually passed through the appropriate DCC. Cortes, Joseph, 1991, A roof or a wall they carried along, to remind them of home: The Manila Times, June 9, 1991. Elevated levels of any of the following parameters: volcanic earthquake, temperature, acidity and volcanic gas concentrations of monitored springs and fumaroles, steam and ash explosions from the summit crater or new vents, inflation or swelling of the edifice. The alert levels were based on instrumentally derived data and daily visual observations. 15.13 N, 120.35 E. summit elevation 1486 m. stratovolcano. That phrase was variously interpreted to mean "eruption will occur 2 weeks [or 24 h] hence" or that "an eruption would occur within 2 weeks [or 24 h]." Incandescent lava dome, lava fountain, lava flow in the summit area. 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). However, there are hazards. The council even provided vehicles to bring the evacuees to the evacuation centers. In all 60,000 people had left the area within 30 km of the volcano before 15th June. Respondents from the villages Sapangbato and Margot of Angeles City reported that sometime before July 14, 1992, a popular radio announcer, citing PHIVOLCS as his source, broadcast that Mount Pinatubo would erupt within 72 h. It is interesting to note that the PHIVOLCS alert levels do not include one that indicates that the volcano may erupt within 72 h. The signal with the closest time reference is Alert Level 4, which means that eruption is possible within 24 h. But Alert Level 4 was not used in 1992, as the Alert Level jumped from 3 to 5. Low to moderate level of seismic, other unrest with positive evidence for involvement of magma. Hydrothermal, magmatic, or tectonic disturbances. The Mt Pinatubo eruption of 1991 was the second largest eruption of the 20th century. This is how the country's chief seismologist described the rapid escalation of volcanic activity that prompted the Philippine Institute of Volcanology and Seismology to raise Alert Level 4 over Taal Volcano, warning of a possible hazardous eruption. After boarding at random and being twice informed that they were in the wrong bus, they were so embarrassed that they decided to return to the mountain and seek refuge in the so-called caves, saying that Apo Namalyari would protect them. Phivolcs lowered the volcano's alert level to 3 on Sunday morning, January 26. Among those who took other defensive action (table 9), some overreacted by suspending their normal activities, such as going to school or going to work, for 1 to several days. Computation of sampling size, household survey, 1991­92. Map of the Mount Pinatubo area showing recommended evacuation zones ("danger zones") of various radii, and barangays cited in the text. Quiet. Ten years ago today (June 15, 2001), Mount Pinatubo in the Philippines erupted with a tremendous force, ejecting vast amounts of ash and gas high into the atmosphere; so high that the volcano’s plume penetrated into the stratosphere. Eruption Now Likely Possibly WIthin 2 Weeks4. Revised alert levels for Mount Pinatubo (revised December 1992). Eight respondents from the <10-km danger zone who should have evacuated immediately merely took other precautionary actions like preparing for evacuation, seeking additional information, or watching out for further developments. However, because no evacuation was required, the improvement in the percentage of appropriate response may be more apparent than real. In the <10- and 10- to 20-km danger zones, it is possible that the transmission network did not reach the most remote areas or the communities that were on the move. 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. Alert Level. Normally, the source of eruption warning should be the entity tasked to study and monitor active 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. 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. 2-99C (Zambales), Population by City, Municipality and Barangay: NSO, Manila. 3. 13th May 1991 – Alert Level 2. A level 5 alert evacuation of the 2040 km zone on 14th June. Households that evacuated selectively either (1) sent their women, children, sick and elderly to safety while the able-bodied adult males stayed behind or (2) evacuated all together but then allowed some member(s) of the household to return home (usually during daytime). Mount Pinatubo second volcano-tectonic earthquake on August 11, 2020. 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. But it would also limit the area that could be reached, given a short lead time for warning dissemination. Additional danger areas may be declared as eruption progresses. In practice, the latter distinction was largely lost.] Criteria. Communities in this zone are easily accessible but too numerous to reach in such a short time. St. Helens? 7 - Seismographs at Mount Pinatubo Monitoring Observatory site at Clark Air Base, Philippines. Two other informants said half of the residents of sitio Lomboy were very reluctant to evacuate. The alert level-danger zone association, though not intentionally established, lingered, so that when Alert Levels 4 and 5 were released in 1992, an understandable reaction was to react as in 1991 and evacuate the 10- to -20-km danger zone. Magma is close to the crater. The first formal evacuation was ordered on April 7 in the 10 km zone. About 8 percent of the respondents received an evacuation order (table 5), some from their local officials, others through radio. The 1991 alerts were indeed specific--in terms of expected magnitude, areas likely to be affected, and time of occurrence--but they were specific to the 1991 eruptive activities. Sustained increase, or sudden drop, of SO. Five-level alert scheme for Mount Pinatubo, May 13, 1991. Very faint glow of the crater may occur but no conclusive evidence of magma ascent. At Alert Level 3, an eruption was unlikely within less than 24 h, but at Alert Level 4 all reassurances of safety was gone--an eruption could occur at anytime (C.G. 25 Pinatubo volcano. Danger zones may be expanded to fourteen (14) kilometers as eruption progresses. Mt Pinatubo Volcano | John Seach. Details of the monitoring activities and chronology of preeruption events are given by Sabit and others (this volume) and Wolfe and Hoblitt (this volume); details of preeruption warnings are given by Punongbayan and others (this volume). 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. [Number of respondents was 234], Table 8. Contact: Chris Newhall The 1991 eruption of Pinatubo produced about 5 cubic kilometers of dacitic magma and may be the second largest volcanic eruption of the century. Preliminary hazard zonation maps were disseminated by PHIVOLCS on and after May 23, 1991. Magma is near or at the surface, and activity could lead to hazardous eruption in weeks. But when Mount Pinatubo started showing signs of restiveness in April 1991, PHIVOLCS had no monitoring at the volcano and, hence, no warning system for the area. When one of these volcanoes manifests abnormal behavior, PHIVOLCS interprets its changing behavior and decides whether or not to send warnings and, if so, when. In 1992, the receipt of a false evacuation order by 8 percent of the respondents is a clear case of discrepancy between the warning message released by the source and the message transmitted to the concerned inhabitants. We intended that Civil Defense could design and key their mitigation actions to these alert levels. Life-threatening eruption producing volcanic hazards that endanger communities. On 26 February, 36 separate lava eruptions lasting up to 19 minutes occurred. But today, more than 3,000 tourists a month climb the volcano. Intense unrest. 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. Response to preeruption warning and false evacuation order. On the western side, most of the former residents of the sample barangays in this zone were living (officially) in the relocation sites, but many were also spending days, weeks, or even months on their preeruption land planting and gathering food, whenever they felt it safe enough to do so. De Villa, Arturo, 1991, Aetas may go hungry: Daily Globe [Manila], June 10, 1991. The final test of a warning system's effectiveness is the receipt of and appropriate response to the warning by the target recipients. Pinatubo began feeling earthquakes and after several explosions a Level 5 alert was issued indicating an eruption was in progress. Mount Pinatubo, Philippines, 1991. In 1992, renewed seismicity prompted PHIVOLCS to raise the Alert Level to 3 on July 9 and then to 5 on July 14, when viscous lava reached the surface and began to form a dome. Pinatubo has been selected as one of 38 emotion-packed pictures of all time by an American online publication. Alcayde, Jerry, 1991, 1876 families move out of volcano area: The Philippine Star, April 22, 1991. The eruption plume of Mount Pinatubo's various gasses and ash reached high into the atmosphere within two hours of the eruption, attaining an altitude of 34 km (21 miles) high and over 400 km (250 miles) wide. Recommendations to avoid the 10-km … Bulging of the edifice and fissuring may accompany seismicity. Table 6. Danger zones that were delineated by PHIVOLCS served as basis for the DCC's issuance of evacuation orders. The lowest is alert level 0 when a volcano is quiet. According to one informant (a Protestant pastor), a group of Aetas was about to evacuate (on the 15th of June) along with the others who were fetched by chartered buses. Mt. Table 4. 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). Quiescence; no magmatic eruption is foreseen. Evacuation orders were transmitted soon after the danger zones were declared by PHIVOLCS, on April 7, June 7, and June 14-15. 10 times the size of it. It was maintained even when Alert Level 3 was raised on June 5. Magmatic, tectonic or hydrothermal disturbance; no eruption imminent. FIRE and MUD: Eruptions and Lahars of Mount Pinatubo, Philippines, edited by Christopher G. Newhall and Raymundo S. Punongbayan, 1996 The errant evacuation order was traced to two sources: (1) some local government officials, who interpreted the Alert Level 5 released by the Philippine Institute of Volcanology and Seismology on July 14, 1992, to mean an eruption similar to that of June 12, 1991, and, hence, evacuation of the 20-kilometer-radius danger zone and (2) a popular radio announcer who broadcast that an eruption was imminent within 72 hours. Low to moderate level of seismicity, persistence of local but unfelt earthquakes. The broadcast of a warning that an eruption was imminent within 72 h, falsely attributed to PHIVOLCS, triggered discussions on the wisdom of the modified warning transmission procedure adopted at Pinatubo. The alert level was further lowered to 2 on December 4. Relatively high and increasing unrest, including numerous b-type earthquakes, accelerating ground deformation, increased vigor of fumaroles, gas emission. Criteria. This means a MAJOR volcanic eruption is imminent. In 1991, Alert Level 4 was associated with a 20-km danger zone, and Alert Level 5 was associated with both a 20-km and a 40-km danger zone. Magmatic, tectonic or hydrothermal disturbance; no eruption imminent. Delays in transmission were reported in all the danger zones. Revised alert levels for Mount Pinatubo (revised December 1992). Interpretation. Further increase in SO2 flux. 1 Lahars may be generated by intense rainfall over the volcano area and may affect riverside communities far down the PDZ. Vigorous steaming / sustained crater glow. Alert Level 5 will be used … The Philippine Institute of Volcanology and Seismology last night raised Taal Volcano’s alert level to Alert Level 4, warning of a possible hazardous eruption. It is precisely on account of its success that the Pinatubo warning system makes an interesting object of review. 6-km radius Danger Zone may be extended to 7 km in the sector where the crater rim is low. The Philippine Institute of Volcanology and Seismology is maintaining Alert Level 3 at Pinatubo, warning that an explosive eruption is possible. Background, quiet: No eruption in foreseeable future: 1. Unrest probably of magmatic origin; could eventually lead to eruption. Start studying Mt. 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 10-km danger zone, in effect since September 1991, was maintained throughout the 1992 unrest. Respondents were asked if they received any eruption warning and (or) evacuation order, and, if so, when. When Alert Level 4 was declared on June 7, the danger zone's radius was increased to 20 km. In practice, the latter distinction was largely lost.] Other areas within five (5) kilometer. Entry into the PDZ must be prohibited. Moderate unrest. The danger zone was shrunk back to a 20-km radius on June 18, though Alert Level 5 remained. 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