According to a news article, on 22 January tourists noticed that the usually blue-to-green water in Pinatubo's crater lake was very dark brown. Scientists from the Pinatubo Volcano Observatory excluded renewed volcanism as the source of the discoloration due to the lack of increased seismicity, and an absence of new emissions in the crater or any increase in the water's temperature. They believed the change in water color was due to near-surface processes, such as biogenic activity or a steady supply of nutrient rich soil from landslides that have entered the crater since its formation after the June 1991 eruption. Visitors were warned against swimming in or consuming the water in the lake.

4 February 2004            Back to Top

According to a news article, on 22 January tourists noticed that the usually blue-to-green water in Pinatubo's crater lake was very dark brown. Scientists from the Pinatubo Volcano Observatory excluded renewed volcanism as the source of the discoloration due to the lack of increased seismicity, and an absence of new emissions in the crater or any increase in the water's temperature. They believed the change in water color was due to near-surface processes, such as biogenic activity or a steady supply of nutrient rich soil from landslides that have entered the crater since its formation after the June 1991 eruption. Visitors were warned against swimming in or consuming the water in the lake.

Sources: ABS-CBN News

7 August 2002            Back to Top

On 10 July the western wall of Pinatubo's crater collapsed, gradually releasing about 160 million m3 of water and sediments. The collapse occurred at the crater wall's lowest point leading to the Maraunot River in Botolan, Zambales. About a year earlier workers had removed a section of the crater wall in an effort to gradually release the rapidly rising water in the crater and prevent a larger crater-wall collapse. PHIVOLCS reported to Philstar news that if the notch had not been created at least 320 million m3 of water and sediment could have been released into inhabited areas.

Sources: Philstar News

5 September 2001            Back to Top

On 6 September workers began to partially drain Pinatubo's rapidly rising crater lake following the evacuation of ~40,000 NW-flank residents the previous day. Initially water flowed slowly at ~50 m3 per hour through the newly completed ~100-m-long spillway, but after workers increased the gradient at the canal's exit the flow rate increased to ~1,800 m3 per hour. According to news reports, over several days the draining aimed to release ~25% of the water in the crater towards the NW down the Bucao River to the South China Sea. Most residents were permitted to return to their homes on 7 September. According to reports on 10 September, the level of the crater lake continued to rise following the draining. Therefore, further preventative measures may be implemented.

Sources: Associated Press , CNN , Reuters

29 August 2001            Back to Top

Due to the threat of Pinatubo's crater lake overflowing during draining procedures, Philippine officials plan to evacuate ~40,000 residents of the town of Botolan 40 km NW of Pinatubo's crater to higher ground on 5 September. The crater lake is ~2.5 km wide, and contains ~210 million cubic meters of water. According to a Guardian news article, water in the crater rose to ~80 cm below the lowest point of the crater rim on 3 September. In comparison, water was 1.5 m below the rim on 31 August, and 4.5 m below it 5 weeks earlier. On 6 September workers plan to remove a 5-m-large portion of the crater's wall that will cause the water to be released towards the N.

Sources: Agence France-Presse (AFP) , ABC News - Australian Broadcasting Corporation , The Guardian News

8 August 2001            Back to Top

Several news reports stated that rising water in Pinatubo's crater is now approaching dangerous levels. If the water exceeds the crater lip, it could cause the crater to partially collapse and water could inundate the town of Botolan. The town is 40 km NW of the volcano and has 46,000 residents. In recent weeks the water surface has risen from ~6.4 to 5 m below the crater lip. Scientists are worried that the intense rain during the current rainy season will cause the water level to continue to rise. In the next few weeks, with oversight by Philippine officials and geologists, local residents will dig a 5-m notch in the side of the crater that will drain the water away from inhabited areas.

Sources: Associated Press , Philippine Institute of Volcanology and Seismology (PHIVOLCS) , Reuters , Disaster Relief.org

Below is a summary of eruption dates and Volcanic Explosivity Indices (VEI).

The following references are the sources used for data regarding this volcano. References are linked directly to our volcano data file. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title. Additional discussion of data sources can be found under Volcano Data Criteria.

Catane S G, Taniguchi H, Goto A, Givero A P, Mandanas A A, 2005. Explosive volcanism in the Philippines. {CNEAS Monograph Ser, Tohoku Univ}, 18: 1-146

Delfin F G Jr, Villarosa H G, Layugan D B, Clemente V C, Candelaria M R, Ruaya J R, 1996. Geothermal exploration of the pre-1991 Mount Pinatubo hydrothermal system. {In}: Newhall C G, Punongbayan R S (eds) {Fire and Mud: Eruptions and Lahars of Mount Pinatubo, Philippines}. Quezon City, Philippines: Philippine Inst Volc Seism, and Seattle: Univ Wash Press, p 197-212

Hoblitt R P, Wolfe E W, Scott W E, Couchman M R, Pallister J S, Javier D, 1996. The preclimactic eruptions of Mount Pinatubo, June 1991. {In}: Newhall C G, Punongbayan R S (eds) {Fire and Mud: Eruptions and Lahars of Mount Pinatubo, Philippines}. Quezon City, Philippines: Philippine Inst Volc Seism, and Seattle: Univ Wash Press, p 457-511

Ku Y-P, Chen C-H, Newhall C G, Song S-R, Yang T F, Iizuka Y, McGeehin J, 2008. Determining an age for the Inararo Tuff eruption of Mt. Pinatubo, based on correlation with a distal ash layer in core MD97-2142, South China Sea. {Quat Internatl}, 178: 138-145

Lagmay A M F, Rodolfo K S, Siringan F P, Uy H, Remotigue C, Zamora P, Lapus M, Rodolfo R, Ong J, 2007. Geology and hazard implications of the Maraunot notch in the Pinatubo caldera, Philippines. {Bull Volc}, 69: 797-809

Newhall C G, Daag A S, Delfin F G Jr, Hoblitt R P, McGeehin J, Pallister J S, Regalado T M, Rubin M, Tubianosa B S, Tamayo R A Jr, Umbal J V, 1996. Eruptive history of Mount Pinatubo. {In}: Newhall C G, Punongbayan R S (eds) {Fire and Mud: Eruptions and Lahars of Mount Pinatubo, Philippines}. Quezon City, Philippines: Philippine Inst Volc Seism, and Seattle: Univ Wash Press, p 165-195

Newhall C G, Punongbayan R S (eds), 1996. {Eruptive history of Mount Pinatubo}. Quezon City, Philippines: Philippine Inst Volc Seism, and Seattle: Univ Wash Press, 1126 p

Pallister J S, Hoblitt R P, Meeker G P, Knight R J, Siems D F, 1996. Magma mixing at Mount Pinatubo: petrographic and chemical evidence from the 1991 deposits. {In}: Newhall C G, Punongbayan R S (eds) {Fire and Mud: Eruptions and Lahars of Mount Pinatubo, Philippines}. Quezon City, Philippines: Philippine Inst Volc Seism, and Seattle: Univ Wash Press, p 687-731

PHIVOLCS, 2004-. Volcanoes. {http://www.phivolcs.dost.gov.ph/Volcanolist/}

Pierson T C, Janda R J, Umbal J V, Daag A S, 1992. Immediate and long-term hazards from lahars and excess sedimentation in rivers draining Mt. Pinatubo, Philippines. {U S Geol Surv, Water Resour Invest Rpt}, 92-4039: 1-35

Pinatubo Volcano Observatory Team, 1991. Lessons from a major eruption: Mt. Pinatubo, Philippines. {Eos, Trans Amer Geophys Union}, 72: 545, 552-553, 555

Rodolfo K S, Umbal J V, 2008. A prehistoric lahar-dammed lake and eruption of Mount Pinatubo described in a Philippine aborigine legend. {J Volc Geotherm Res}, 176: 432-437

Scott W E, Hoblitt R P, Torres R C, Self S, Martinez M L, Nillos T Jr, 1996. Pyroclastic flows of the June 15, 1991, climactic eruption of Mount Pinatubo. {In}: Newhall C G, Punongbayan R S (eds) {Fire and Mud: Eruptions and Lahars of Mount Pinatubo, Philippines}. Quezon City, Philippines: Philippine Inst Volc Seism, and Seattle: Univ Wash Press, p 545-570

Smithsonian Institution-GVN, 1990-. [Monthly event reports]. {Bull Global Volc Network}, v 15-33

Stimac J A, Goff F, Counce D, Larocque A C L, Hilton D R, Morgenstern U, 2004. The crater lake and hydrothermal system of Mount Pinatubo, Philippines: evolution in the decade after eruption. {Bull Volc}, 66: 149-167

Torres R, Mouginis-Mark P, Self S, Garbeil H, Kallianpur K, Quiambao R, 2004. Monitoring the evolution of the Pasig-Potrero alluvial fan, Pinatubo volcano, using a decade of remote sensing data. {J Volc Geotherm Res}, 138: 371-392

Wiesner M G, Wetzel A, Catane S G, Listanco E L, Mirabueno H T, 2004. Grain size, areal thickness distribution and controls on sedimentation of the 1991 Mount Pinatubo tephra layer in the South China Sea. {Bull Volc}, 66: 226-242

Wolfe E W, Hoblitt R P, 1996. Overview of the eruption. {In}: Newhall C G, Punongbayan R S (eds) {Fire and Mud: Eruptions and Lahars of Mount Pinatubo, Philippines}. Quezon City, Philippines: Philippine Inst Volc Seism, and Seattle: Univ Wash Press, p 3-20

Wolfe J A, Self S, 1983. Structural lineaments and Neogene volcanism in southwestern Luzon. {In}: Hayes D E (ed) {The Tectonic and Geological Evolution of Southeast Asian Seas and Islands: Part 2}, Amer Geophys Union Monograph 27

Prior to 1991 Pinatubo volcano was a relatively unknown, heavily forested lava dome complex located 100 km NW of Manila with no records of historical eruptions. The 1991 eruption, one of the world's largest of the 20th century, ejected massive amounts of tephra and produced voluminous pyroclastic flows, forming a small, 2.5-km-wide summit caldera whose floor is now covered by a lake. Caldera formation lowered the height of the summit from 1745 to 1486 m. Although the eruption caused hundreds of fatalities and major damage with severe social and economic impact, successful monitoring efforts greatly reduced the number of fatalities. Widespread lahars that redistributed products of the 1991 eruption have continued to cause severe disruption. At least six major eruptive periods, interrupted by lengthy quiescent periods, have occurred from modern Pinatubo volcano during the past 35,000 years. Most of these have produced major pyroclastic flows and lahars that were even more extensive than in 1991.