Editing Mount Pinatubo

{{Short description|Active stratovolcano in Luzon, Philippines}}
{{Redirect|Pinatubo|the horse|Pinatubo (horse)}}
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{{Use mdy dates|date=November 2024}}
{{Use Philippine English|date=August 2020}}
{{Infobox mountain
| name = Mount Pinatubo
| photo = File:Mt Pinatubo trekking - panoramio (5).jpg
| photo_caption = Mount Pinatubo crater lake in 2012
| map = Philippines
| map_alt = 
| map_caption = Location within the Philippines
| location = [[Luzon]]
| map_relief = 
| label_position = left
| elevation = {{plainlist|
*{{cvt|1486|m|ft}} (current)
*{{cvt|1745|m|ft}} (before 1991 eruption)}}
| prominence_m = 
| prominence_ref = 
| listing = [[List of active volcanoes in the Philippines|Active volcanoes in the Philippines]]
| language = Tagalog
| pronunciation = {{IPAc-en|ˌ|p|iː|n|ə|ˈ|t|uː|b|oʊ}}
| range = [[Zambales Mountains]]
| coordinates = {{coord|15|08|30|N|120|21|00|E|type:mountain_region:PH_scale:100000|format=dms|display=inline,title}}
| topo = 
| coordinates_ref = 
| type = [[Stratovolcano]]<ref name="SI">{{cite web|url=http://volcano.si.edu/volcano.cfm?vn=273083|title=Pinatubo|department=[[Global Volcanism Program]]|publisher=[[Smithsonian Institution]]|access-date=January 23, 2020|archive-date=January 23, 2020|archive-url=https://web.archive.org/web/20200123030236/http://volcano.si.edu/volcano.cfm?vn=273083|url-status=live}}</ref>
| volcanic_arc = [[Luzon Volcanic Arc]]
| age = Between 635,000 ± 80,000<br />and 1.1 ± 0.09 million years<ref>{{cite web|url=http://volcano.phivolcs.dost.gov.ph/update_VMEPD/Volcano/VolcanoList/pinatubo.htm|title=Pinatubo Volcano|publisher=The [[Philippine Institute of Volcanology and Seismology]] (PHIVOLCS)|access-date=August 12, 2008|archive-url=https://web.archive.org/web/20090129222823/http://volcano.phivolcs.dost.gov.ph/update_VMEPD/Volcano/VolcanoList/pinatubo.htm|archive-date=January 29, 2009|url-status=dead}}</ref>
| last_eruption = November 30, 2021<ref>{{cite gvp|title=Pinatubo: Eruptive History|vn=273083|vtab=Eruptions|access-date=August 31, 2021}}</ref>
| first_ascent = 
| easiest_route = 
| map_size = 
| range_coordinates = 
| country = [[Philippines]]
| state = [[Central Luzon]]
| state_type = Region
| region = {{hlist | [[Pampanga]] | [[Tarlac]] | [[Zambales]] }}
| region_type = Provinces
| mapframe = yes
| mapframe-wikidata = yes
}}
{{History of the Philippines}}
'''Mount Pinatubo'''<ref>{{langx|xsb|Bakil nin Pinatobo}}; {{langx|pam|Bunduk/Bulkan ning Pinatubu, Bunduk ning Apu Malyari}}; {{langx|pag|Palandey/Bulkan na Pinatubu}}; {{langx|ilo|Bantay Pinatubo}}; {{langx|tl|Bundok/Bulkang Pinatubo}} {{IPA|tl|pɪ.nɐˈtuː.boʔ|IPA}}</ref> is an active [[stratovolcano]] in the [[Zambales Mountains]] in [[Luzon]] in the [[Philippines]]. Located on the [[tripoint]] of [[Zambales]], [[Tarlac]] and [[Pampanga]] provinces,<ref name="Topo">{{cite web|url=http://www.lib.utexas.edu/maps/ams/philippines/txu-oclc-6539351-nd51-1-450.jpg|title=Tarlac map|publisher=University of Texas in Austin Library|access-date=August 2, 2011|archive-date=July 31, 2019|archive-url=https://web.archive.org/web/20190731132546/https://legacy.lib.utexas.edu/maps/ams/philippines/txu-oclc-6539351-nd51-1-450.jpg|url-status=live}}</ref><ref>[https://books.google.com/books?id=Hv9GAQAAIAAJ "Report of the Philippine Commission to the President, 1901 Vol. III"] {{Webarchive|url=https://web.archive.org/web/20161130023904/https://books.google.com/books?id=Hv9GAQAAIAAJ |date=November 30, 2016 }}, pg. 141. Government Printing Office, Washington, 1901.</ref> most people were unaware of its eruptive history before the pre-eruption volcanic activity in early 1991. Dense [[forest]]s, which supported a population of several thousand indigenous [[Aeta people|Aetas]], heavily [[erosion|eroded]] and obscured Pinatubo.

Pinatubo is known for its [[Volcanic Explosivity Index|VEI]]-6 [[1991 eruption of Mount Pinatubo|eruption on June 15, 1991]], the second-largest terrestrial eruption of the 20th century after the 1912 eruption of [[Novarupta]] in [[Alaska]].<ref name=Pinatubo1991>{{cite web|title=The Cataclysmic 1991 Eruption of Mount Pinatubo, Philippines|url=http://pubs.usgs.gov/fs/1997/fs113-97/|access-date=April 9, 2007|archive-date=August 25, 2013|archive-url=https://web.archive.org/web/20130825233934/http://pubs.usgs.gov/fs/1997/fs113-97/|url-status=live}} {{PD-notice}}</ref> The eruption coincided with [[Typhoon Yunya (1991)|Typhoon Yunya]] making landfall in the Philippines, which brought a dangerous mix of ash and rain to nearby towns and cities. Early predictions led to the evacuation of tens of thousands of people, saving many lives. The eruption severely damaged surrounding areas with [[pyroclastic surge]]s, [[pyroclastic fall]]s, and later, flooding [[lahar]]s caused by rainwater re-mobilizing volcanic deposits. This destruction affected infrastructure and altered river systems for years.<ref name=Pinatubo1991/><ref>{{cite web|author1=Rodolfo|author2=Umbal|author3=Alonso|url=http://pubs.usgs.gov/pinatubo/rodolfo/index.html|title=Two Years of Lahars on the Western Flank of Mount Pinatubo: Initiation, Flow Processes, Deposits, and Attendant Geomorphic and Hydraulic Changes|publisher=USGS Publications|access-date=March 7, 2012|archive-date=March 16, 2012|archive-url=https://web.archive.org/web/20120316034034/http://pubs.usgs.gov/pinatubo/rodolfo/index.html|url-status=live}}</ref> Minor [[lava dome|dome]]-forming eruptions inside the caldera continued from 1992 to 1993.

The 1991 eruption had worldwide effects. It released roughly {{convert|10|e9t|ST|lk=on}} or {{convert|10|km3|cumi|abbr=on}} of magma, bringing large amounts of minerals and toxic metals to the surface. It also released {{convert|20|e6t|e6ST|abbr=off}} of {{chem|S|O|2|link=Sulfur_dioxide}}.  It ejected more [[particulate]] into the [[stratosphere]] than any eruption since [[Krakatoa]] in 1883. In the following months, aerosols formed a global layer of [[sulfuric acid]] haze. Global temperatures dropped by about {{convert|0.5|C-change|F-change|1}} in the years 1991–1993,<ref>{{cite web|url=http://pubs.usgs.gov/pinatubo/self/|title=The Atmospheric Impact of the 1991 Mount Pinatubo Eruption|author1=Stephen Self|author2=Jing-Xia Zhao|author3=Rick E. Holasek|author4=Ronnie C. Torres|author5=Joey McTaggart|name-list-style=amp|year=1999|access-date=July 25, 2014|archive-date=August 2, 2014|archive-url=https://web.archive.org/web/20140802181316/http://pubs.usgs.gov/pinatubo/self/|url-status=live}}</ref> and [[ozone depletion]] temporarily increased significantly.<ref name="Science News">{{cite magazine|url=http://www.thefreelibrary.com/Mt.+Pinatubo's+cloud+shades+global+climate.-a012467057|title=Mt. Pinatubo's cloud shades global climate|magazine=Science News|access-date=March 7, 2010|archive-date=January 7, 2012|archive-url=https://web.archive.org/web/20120107063251/http://www.thefreelibrary.com/Mt.+Pinatubo%27s+cloud+shades+global+climate.-a012467057|url-status=live}}</ref>

==Geography==
[[File:Mount Pinatubo Relief Map, SRTM-1.jpg|left|thumb|Mount Pinatubo relief map]]

The volcano is about {{convert|87|km|mi|sp=us}} northwest of [[Manila]], the capital of the Philippines. Near Mount Pinatubo are former military bases that were maintained by the United States. The [[U.S. Naval Base Subic Bay]] was {{convert|37|km|mi|sp=us}} south of Pinatubo, and the extent of [[Clark Air Base]] was just {{convert|14|km|mi|sp=us}} east of the volcano's summit.<ref name=K-118B>Tactical Pilotage Chart, Sheet K-11B, [[Defense Mapping Agency]], Department of Defense, 1982.</ref> The volcano is near to about 6 million people.<ref>[https://www.census.gov.ph/sites/default/files/attachments/hsd/pressrelease/Population%20and%20Annual%20Growth%20Rates%20for%20The%20Philippines%20and%20Its%20Regions%2C%20Provinces%2C%20and%20Highly%20Urbanized%20Cities%20Based%20on%201990%2C%202000%2C%20and%202010%20Censuses.pdf Philippine Census] {{webarchive|url=https://web.archive.org/web/20130928012059/http://www.census.gov.ph/sites/default/files/attachments/hsd/pressrelease/Population%20and%20Annual%20Growth%20Rates%20for%20The%20Philippines%20and%20Its%20Regions%2C%20Provinces%2C%20and%20Highly%20Urbanized%20Cities%20Based%20on%201990%2C%202000%2C%20and%202010%20Censuses.pdf |date=September 28, 2013 }}</ref>

==History==
Even before the 1991 eruption, Mount Pinatubo had little [[topographic prominence]]: it was {{convert|1745|m|ft|abbr=on}} above sea level, only about {{convert|600|m|ft|abbr=on}} above nearby [[plain]]s, and only about {{convert|200|m|ft|abbr=on}} higher than surrounding peaks, which largely obscured it from view.<ref>[http://library.thinkquest.org/C0112681/Eng/Normal/Volcanoes_World/southeast_asia/philippines/pinatubo.html Pinatubo, Philippines] {{webarchive|url=https://web.archive.org/web/20081204005825/http://library.thinkquest.org/C0112681/Eng/Normal/Volcanoes_World/southeast_asia/philippines/pinatubo.html |date=December 4, 2008 }}</ref> It is part of a chain of [[volcanoes]] which lie along the western side of the island of [[Luzon]] called the [[Zambales Mountains]].<ref>{{Cite web|url=http://www.pinoymountaineer.com/2008/05/central-luzon.html|title=Hiking guide: Central Luzon mountains|date=May 19, 2008|website=Pinoy Mountaineer|access-date=August 21, 2020|archive-date=August 4, 2020|archive-url=https://web.archive.org/web/20200804041713/http://www.pinoymountaineer.com/2008/05/central-luzon.html|url-status=live}}</ref>

Pinatubo belongs to the [[Cabusilan Mountains|Cabusilan sub-range]] of the [[Zambales Mountains]], which consists of [[Mount Cuadrado]], [[Mount Negron]], Mount Mataba and Mount Pinatubo.<ref>U.S. War Department. [https://books.google.com/books?id=Hv9GAQAAIAAJ&pg=141 "Report of the Philippine Commission, 1901 Vol. III"), pg. 141. Government Printing Office, Washington.] {{Webarchive|url=https://web.archive.org/web/20140606151453/http://books.google.com/books?id=Hv9GAQAAIAAJ&pg=141 |date=June 6, 2014 }}</ref> They are [[subduction]] volcanoes, formed by the [[Eurasian plate]] sliding under the [[Philippine Mobile Belt]] along the [[Manila Trench]] to the west. Mount Pinatubo and the other volcanoes on this [[volcanic belt]] arise due to [[magma]]tic occlusion from this [[subduction]] [[plate tectonics|plate]] boundary.<ref>{{cite web|url=http://vulcan.wr.usgs.gov/Volcanoes/Philippines/Pinatubo/description_pinatubo.html|title=Description: Mount Pinatubo, Philippines|date=July 13, 2009|author=Topinka, Lyn|access-date=April 18, 2010|publisher=United States Geological Survey|archive-date=June 3, 2010|archive-url=https://web.archive.org/web/20100603020948/http://vulcan.wr.usgs.gov/Volcanoes/Philippines/Pinatubo/description_pinatubo.html|url-status=live}}</ref>

Pinatubo is flanked on the west by the [[Zambales]] [[Ophiolite]] Complex, which is an easterly-dipping section of [[Eocene]] oceanic crust uplifted during the late [[Oligocene]]. The Tarlac Formation north, east and southeast of Pinatubo consists of marine, nonmarine and volcanoclastic sediments formed in the late [[Miocene]] and [[Pliocene]].<ref name="Newhall"/>

The most recent study of Mount Pinatubo before the activities of 1991 was the overall geological study in 1983 and 1984 made by F. G. Delfin for the [[Philippine National Oil Company]] as part of the surface investigations of the area before exploratory drilling and well testing for [[geothermal energy]] sources in 1988 to 1990. He recognized two life histories of the mountain, which he classified as "ancestral" and "modern" Pinatubo.<ref name="Newhall"/><ref>{{cite web|author1=Delfin, F.G.|author2=Villarosa, H.G.|author3=Layugan, D.B.|url=http://pubs.usgs.gov/pinatubo/delfin/index.html|title=Geothermal Exploration of the pre-1001 Mount Pinatubo Hydrothermal System|publisher=United States Geological Survey Publications|access-date=March 7, 2012|archive-date=March 16, 2012|archive-url=https://web.archive.org/web/20120316033736/http://pubs.usgs.gov/pinatubo/delfin/index.html|url-status=live}}</ref>

===Ancestral Pinatubo===
[[File:Philippine Island - Luzon Island - NARA - 68156975.jpg|thumb|left|Aerial view of Mount Pinatubo before the 1991 eruption, March 1933]]
[[File:Pre-eruption Pinatubo.jpg|thumb|Pinatubo in April 1991, approximately two months before the eruption.<ref>{{Cite web|url=https://pubs.usgs.gov/pinatubo/punong1/|title=Photographic Record, Mount Pinatubo|publisher=United States Geological Survey|access-date=August 21, 2020|archive-date=August 17, 2020|archive-url=https://web.archive.org/web/20200817125702/https://pubs.usgs.gov/pinatubo/punong1/|url-status=live}}</ref><ref>{{Cite web|url=http://pubs.usgs.gov/pinatubo/punong1/fig2a.jpg|title=Photo of Mount Pinatubo|access-date=December 13, 2015|archive-date=March 30, 2017|archive-url=https://web.archive.org/web/20170330173032/https://pubs.usgs.gov/pinatubo/punong1/fig2a.jpg|url-status=live}}</ref>|left]]

Activity of Ancestral Pinatubo seems to have begun about 1.1&nbsp;million years ago and probably ended tens of thousands of years or more before the birth of "modern" Pinatubo. Much of the rugged land around the present volcano consists of remnants of "ancestral" Pinatubo. It was an [[andesite]] and [[dacite]] [[stratovolcano]] whose eruptive activity was much less explosive than modern Pinatubo. Its center was roughly where the current volcano is. The projected height of the mountain is up to {{convert|2300|m|abbr=on}}, or 1.43 miles above [[sea level]] if it were a lone peak, based on a profile fitting to the remaining lower slopes, or lower if it had more than one peak.<ref name="Newhall"/>

The old volcano is exposed in the walls of an old {{convert|3.5|x|4.5|km|abbr=on}} wide [[caldera]], referred to as ''Tayawan Caldera'' by Delfin. Some of the nearby peaks are the remnants of ancestral Pinatubo, left behind when the softer parts of the old mountain slopes were eroded by [[weathering]]. Ancestral Pinatubo is a [[somma volcano]] with modern Pinatubo as the new cone.
Mount Dorst, to the east, is part of the dip slope of the ancestral Pinatubo. Several mountains near modern Pinatubo are old satellite vents of ancestral Pinatubo, forming [[volcanic plug]]s and lava domes. These satellite vents were probably active around the same time as the ancestral volcano and include the domes of Mount Negron, Mount Cuadrado, Mount Mataba and the Bituin and Tapungho plugs.<ref name="Newhall"/>

===Modern Pinatubo===
* c. 79,000 BC:<ref>{{Cite journal|last1=Ku|first1=Yueh-Ping|last2=Chen|first2=Chang-Hwa|last3=Newhall|first3=Christopher G.|last4=Song|first4=Sheng-Rong|last5=Yang|first5=Tsanyao Frank|last6=Iizuka|first6=Yoshiyuki|last7=McGeehin|first7=John|date=February 1, 2008|title=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|url=http://ntur.lib.ntu.edu.tw/bitstream/246246/172549/1/18.pdf|journal=Quaternary International|series=Global Tephra Studies: John Westgate and Andrei Sarna-Wojcicki Commemorative Volume|language=en|volume=178|issue=1|pages=138–145|doi=10.1016/j.quaint.2007.02.025|bibcode=2008QuInt.178..138K |issn=1040-6182}}</ref> After a long period of [[dormant volcano|dormancy]], Modern Pinatubo was born in Ancestral Pinatubo's cataclysmic and most explosive eruptions, estimated to be five times larger than the June 1991 eruption. It deposited all around the volcano up to {{convert|25|km3|cumi|abbr=on}} of [[pyroclastic surge]] material up to {{convert|100|m|sp=us}} thick. The total volume of volcanic material ejected during the eruptions is unknown. The removal of so much material from the underlying [[magma chamber]] resulted in the Tayawan [[caldera]]. The violent eruptive period started by the eruption is referred to by Delfin as the ''Inararo Eruptive Period'', named after a village that was destroyed in the 1991 eruption.<ref name="Newhall"/>

Later eruptions of modern Pinatubo occurred episodically and lasted for periods much shorter than the repose intervals between them. Subsequent eruptions and eruptive period occurred about:
*c. 15,000 BC (Sacobia Eruptive Period)
*c. 7000 BC (Pasbul Eruptive Period). Its eruptions were as energetic, if not as voluminous as the Inararo eruptions. 
*c. 4000–3000 BC (Crow Valley Eruptive Period). This and the Mara-unot period's eruptions were smaller than the Inararo eruptions but about two to three times as big as that of 1991 based on the pyroclastic flow runout distances and depths of valley filling.
*c. 1900–300 BC (Maraunot Eruptive Period)
*c. AD 1500 (Buag Eruptive Period). Its eruptions were roughly the same size as those of 1991.

Each of these eruptions seems to have been very large, ejecting more than {{cvt|10|km3||}} of material and covering large parts of the surrounding areas with pyroclastic flow deposits. Some eruptive periods have lasted decades and perhaps as much as several centuries and might appear to include multiple large explosive eruptions.<ref name="Newhall"/>

The maximum size of eruptions in each eruptive period though has been getting smaller through the more than 35,000-year history of modern Pinatubo, but this might be an artifact of erosion and burial of older deposits. The oldest eruption of modern Pinatubo, Inararo, was also its largest.

The 1991 eruption was among the smallest documented in its geologic record.<ref name="Newhall"/>

The volcano has never grown very large between eruptions, because it produces mostly unwelded, easily erodible deposits and periodically destroys the viscous domes that fill its vents. After the Buag eruption (c. 1500 AD), the volcano lay dormant, its slopes becoming completely covered in dense [[rainforest]] and eroded into gullies and ravines. The c. 500-year repose though between the Buag and present eruptive periods is among the shorter repose periods recognized in its geologic history.<ref name="Newhall">{{cite book|editor-first1=Christopher G.|editor-last1=Newhall|editor-last2=Punongbayan|editor-first2=Raymundo S.|chapter=Eruptive history of Mount Pinatubo|chapter-url=http://pubs.usgs.gov/pinatubo/newhall/index.html|title=FIRE and MUD: Eruptions and Lahars of Mount Pinatubo, Philippines|url=http://vulcan.wr.usgs.gov/Volcanoes/Philippines/Pinatubo/Publications/FireMud/about_the_book.html|publisher=Philippine Institute of Volcanology and Seismology; University of Washington Press|year=1996|isbn=978-0-295-97585-6|access-date=October 5, 2008|archive-date=January 10, 2009|archive-url=https://web.archive.org/web/20090110162823/http://vulcan.wr.usgs.gov/Volcanoes/Philippines/Pinatubo/Publications/FireMud/about_the_book.html|url-status=live}}</ref>

====1991 eruption====
{{Main|1991 eruption of Mount Pinatubo}}
[[File:Pinatubo91eruption plume.jpg|thumb|right|The [[eruption column]] of Mount Pinatubo on June&nbsp;12, 1991, three days before the climactic eruption]]
[[File:Eruption of Mount Pinatubo, June 15, 1991.jpg|thumb|right|View to the west from Clark Air Base of the major eruption of Pinatubo on June 15, 1991. The June 15–16 climatic phase lasted more than fifteen hours, sent tephra about {{Convert|35|km|mi|abbr=on}} into the atmosphere, generated voluminous [[pyroclastic flow]]s, and left a caldera in the former summit region. Later dubbed Black Saturday, the day of darkness stretched for 36 hours.]]
A small blast at 03:41 PST on June 12 marked the beginning of a new, more violent phase of the eruption. A few hours later the same day, massive blasts lasting about half an hour generated big eruption columns, which quickly reached heights of over {{convert|19|km|ft}} and which generated large [[pyroclastic surge]]s extending up to {{convert|4|km|mi|spell=in}} from the summit in some river [[valley]]s. Fourteen hours later, a 15-minute blast hurled volcanic matter to heights of {{convert|24|km|mi|abbr=on}}. Friction in the up-rushing ash column generated abundant [[volcanic lightning]].

In March and April 1991, magma rising toward the surface from more than {{convert|32|km|mi|abbr=on}} beneath Pinatubo triggered small [[volcano tectonic earthquake]]s and caused powerful [[phreatic eruption|steam explosions]] that blasted three [[volcanic crater|craters]] on the north flank of the volcano. Thousands of small earthquakes occurred beneath Pinatubo through April, May and early June and many thousand of tons of noxious [[sulfur dioxide]] gas were also emitted by the volcano.<ref name="Pinatubo1991"/>

From June 7 to 12, the first magma reached the surface of Mount Pinatubo. Because it had lost most of the gas contained in it on the way to the surface, the magma oozed out to form a lava dome but did not cause an explosive eruption. However, on June 12, millions of cubic yards of gas-charged magma reached the surface and exploded in the reawakening volcano's first spectacular eruption.<ref name="Pinatubo1991"/>

When even more highly gas-charged magma reached Pinatubo's surface on June 15, the volcano exploded in a cataclysmic eruption that ejected more than {{Convert|5|km3|mi3|abbr=on}} of material. The [[eruption column|ash cloud]] from this climactic eruption rose {{Convert|35|km|mi|abbr=on}} into the atmosphere. At lower altitudes, the [[volcanic ash]] was blown in all directions by the intense cyclonic winds of a coincidentally occurring typhoon, and winds at higher altitudes blew the ash southwestward. A blanket of ash and larger [[pumice]] [[lapilli]] blanketed the countryside. Fine ash fell as far away as the [[Indian Ocean]] and satellites tracked the ash cloud several times around the globe.<ref name="Pinatubo1991"/>

Huge pyroclastic flows roared down the flanks of Mount Pinatubo, filling once-deep valleys with fresh volcanic deposits as much as {{Convert|200|m|ft|abbr=on}} thick. The eruption removed so much magma and rock from below the volcano that the summit collapsed to form a {{Convert|2.5|km|mi|abbr=on}} wide caldera.<ref name="Pinatubo1991"/>

Following the climactic eruption of June 15, 1991, activity at the volcano continued at a much lower level, with continuous ash eruptions lasting until August 1991 and episodic eruptions continuing for another month.

[[File:Tephra fall from 1991 eruption of Mt Pinatubo.gif|thumb|550px|center|The location of Mount Pinatubo and the regional ash fallout from the 1991 eruption]]

====Later eruptions====
[[File:Mount Pinatubo 20081229 01.jpg|thumb|[[Lake Pinatubo]], the crater lake resulting from the 1991 eruption, pictured here in 2008]]

Activity at the volcano remained low until July 1992 when a new lava dome started growing in the [[caldera]]. Volcanologists suspected that further violent eruptions could be possible, and some areas were evacuated. However, the eruption was only minor. The last eruption of Mount Pinatubo took place in 1993.<ref name="SI"/>

====Lake Pinatubo====
{{Main|Lake Pinatubo}}
[[File:Mount Pinatubo 6.jpg|thumb|An aerial view of Mt. Pinatubo and [[Lake Pinatubo]] in 2006]]
The 1991 caldera afterwards filled with water from annual monsoon rains and a [[Volcanic crater lake|crater lake]], [[Lake Pinatubo]], was formed. In 1992, a growing lava dome formed an island, which was eventually submerged by the lake. Initially, the lake was hot and highly [[acid]]ic, with a minimum [[pH]] of 2 and a temperature of about {{convert|40|C|F}}. Subsequent rainfall cooled and diluted the lake, lowering the temperature to {{convert|26|C|F}} and raising the pH to 5.5 by 2003.

The lake deepened by about {{convert|1|m|ft|sp=us}} per month on average, eventually submerging the lava dome, until September 2001, when fears that the walls of the crater might be unstable prompted the Philippine government to order a controlled draining of the lake. An estimated 9,000&nbsp;people were once again evacuated from surrounding areas in case a large [[flood]] was accidentally triggered. Workers cut a {{convert|5|m|sp=us|adj=on}} notch in the crater rim and drained about a quarter of the lake's volume.<ref>{{cite news|date=September 7, 2001|url=http://news.bbc.co.uk/2/hi/asia-pacific/1530182.stm|title=Filipinos return as volcano lake drains|publisher=BBC News|access-date=May 25, 2010|archive-date=April 21, 2021|archive-url=https://web.archive.org/web/20210421010958/http://news.bbc.co.uk/2/hi/asia-pacific/1530182.stm|url-status=live}}</ref>

===Recent activity===
[[File:The Mount Pinatubo today! Drone footage.webm|thumb|The Mount Pinatubo (Drone footage)]]

On July 10, 2002, the west wall of the crater collapsed, slowly releasing approximately {{convert|160|e6m3|e9cuft|sp=us|}} of water and sediment into the Maraunot River in [[Botolan, Zambales]].<ref>{{Cite web|url=http://glassiris.info/Timeline.php?srch=collapses|title=Timelines Page @ glassiris.info|website=glassiris.info|access-date=August 21, 2020|archive-date=December 18, 2014|archive-url=https://web.archive.org/web/20141218190006/http://glassiris.info/Timeline.php?srch=collapses|url-status=live}}</ref>

On July 26, 2011, a 5.9 magnitude earthquake struck close to Pinatubo; however, no major damages or casualties were reported.<ref>Gonzaga, Robert and Orejas, Tonette (July 26, 2011). [http://newsinfo.inquirer.net/30559/5-9-magnitude-quake-jolts-households-in-luzon-metro-areas "5.9-magnitude quake jolts households in Luzon, Metro areas"] {{Webarchive|url=https://web.archive.org/web/20110813194932/http://newsinfo.inquirer.net/30559/5-9-magnitude-quake-jolts-households-in-luzon-metro-areas |date=August 13, 2011 }}. Inquirer News.</ref>

On March 4, 2021, the PHIVOLCS raised alert level 1 over Mount Pinatubo after reporting an increase on its seismic activity. 1,722 volcanic earthquakes were also recorded within the vicinity of the volcano since January 2021.<ref>{{Cite web|url=https://www.gmanetwork.com/news/scitech/science/778262/alert-level-1-raised-in-mt-pinatubo/story/|title=Alert Level 1 raised in Mt. Pinatubo —PHIVOLCS|website=GMA News Online|date=March 4, 2021|access-date=March 4, 2021|archive-date=March 4, 2021|archive-url=https://web.archive.org/web/20210304050835/https://www.gmanetwork.com/news/scitech/science/778262/alert-level-1-raised-in-mt-pinatubo/story/|url-status=live}}</ref>

On August 11, 2021, PHIVOLCS downgraded Mt. Pinatubo's Alert Level 1 to Level 0, due to "continued decrease in earthquake activity and a return to baseline seismic parameters".

PHIVOLCS said it noted a "significant decrease" in volcanic earthquakes, with a total of 104 quakes or an average 2–3 events per day recorded from July 1 – August 1, 2021.<ref>{{Cite web|last=Ramos|first=Christia Marie|date=August 12, 2021|title=Phivolcs lifts Mt. Pinatubo alert level|url=https://newsinfo.inquirer.net/1472571/phivolcs-lifts-alert-level-off-mt-pinatubo|access-date=August 15, 2021|website=INQUIRER.net|language=en|archive-date=August 15, 2021|archive-url=https://web.archive.org/web/20210815115034/https://newsinfo.inquirer.net/1472571/phivolcs-lifts-alert-level-off-mt-pinatubo|url-status=live}}</ref>

On November 30, 2021, PHIVOLCS reported a weak explosion occurred on Mt. Pinatubo between 12:09&nbsp;p.m. and 12:13&nbsp;p.m., which produced a plume.<ref>{{Cite news|date=November 30, 2021|title='Weak explosion' recorded on Mt. Pinatubo but no magma activity – Phivolcs|url=https://news.abs-cbn.com/news/11/30/21/weak-explosion-recorded-on-mt-pinatubo|access-date=November 30, 2021|work=ABS-CBN News|language=en|archive-date=November 30, 2021|archive-url=https://web.archive.org/web/20211130115457/https://news.abs-cbn.com/news/11/30/21/weak-explosion-recorded-on-mt-pinatubo|url-status=live}}</ref> The agency later confirmed it was a phreatic explosion produced by [[hydrothermal]] fluids near the surface, rather than a magmatic eruption.<ref>{{Cite news|date=November 30, 2021|title=PHIVOLCS confirms Mount Pinatubo phreatic eruption|url=https://www.gmanetwork.com/news/scitech/science/812825/phivolcs-confirms-mount-pinatubo-phreatic-eruption/story/|access-date=November 30, 2021|work=GMA News|language=en|archive-date=November 30, 2021|archive-url=https://web.archive.org/web/20211130121903/https://www.gmanetwork.com/news/scitech/science/812825/phivolcs-confirms-mount-pinatubo-phreatic-eruption/story/|url-status=live}}</ref>

==Cultural history==
The word ''pinatubo'' could mean "fertile place where one can make crops grow", or could mean "made to grow", in [[Sambal language|Sambal]] and [[Tagalog language|Tagalog]], which may suggest a knowledge of its previous eruption in about 1500&nbsp;AD. There is a local oral tradition suggestive of a folk memory of earlier large eruptions. An ancient legend tells of Bacobaco, a terrible spirit of the sea, who could metamorphose into a huge turtle and throw fire from his mouth. In the legend, when being chased by the spirit hunters, Bacobaco flees to the mountain and digs a great hole in its summit showering the surrounding land with rock, mud, dust and fire for three days; howling so loudly that the earth shakes.<ref>Rodolfo, K.S. & Umbal, J.V. (2008) "A prehistoric lahar-dammed lake and eruption of Mount Pinatubo described in a Philippine aborigine legend", J. Volcanol. Geotherm. Res., '''176''', 432–437</ref>

===History among Aetas===
[[Aeta peoples|Aeta]] elders tell many stories about the history of the mountain, the best known being that it was once a Batung Mabye ([[Kapampangan language]] for "living stone"). It was said to have been planted on a kingdom by a displeased sorcerer but relocated by a hero. The mountain was soon turned into the abode of Apo Namalyari ("The lord of happenings/events"), the pagan deity of the [[Sambal people|Sambal]], Aetas and [[Kapampangan people|Kapampangans]] living on the Zambales range.<ref name="hau.edu.ph">{{cite journal|url=http://www.hau.edu.ph/kapampangan_center/publication/pdf/singsing/rivers.pdf|title=Kampangan Folk : The Power and the Glory|journal=Singsing|volume=3|issue=2|issn=1655-6305|access-date=July 4, 2013|archive-date=November 10, 2013|archive-url=https://web.archive.org/web/20131110133354/http://www.hau.edu.ph/kapampangan_center/publication/pdf/singsing/rivers.pdf|url-status=live}}</ref>

It was said to comprise the whole mountain range until Sinukuan of [[Mount Arayat]] (the god of the Kapampangans) became a strong rival of Namalyari.  Their fight, which took place over the center plains, shattered the mountain into smaller bodies and Mount Arayat lost its center peak. Other versions have it that Pinatubo's peak shattered because of Namalyari's immense fury in an attempt to teach humans the meaning of fear and show how misdeeds will be punished.<ref name="hau.edu.ph"/>

According to the native elders, Apo Namalyari induced the June 1991 eruption because of displeasure toward illegal loggers and [[Philippine National Oil Company]] executives who performed deep exploratory drilling and well testing on the volcano looking for geothermal heat from 1988 to 1990.<ref>{{cite news|url=https://archive.seattletimes.com/archive/19910721/1295627/natives-who-worship-pinatubo-feel-its-wrath|title=Natives Who Worship Pinatubo Feel Its Wrath|last=Loeb|first=Vernon|date=July 21, 1991|work=[[The Seattle Times]]|access-date=November 22, 2008|archive-date=November 18, 2011|archive-url=https://web.archive.org/web/20111118142836/http://community.seattletimes.nwsource.com/archive/?date=19910721&slug=1295627|url-status=live}}</ref> Discouraging results from the wells forced the abandonment of the prospect 13 months before the April 2, 1991, explosions.<ref>Delfin Jr., F.G., Villarosa, H.G.. [http://pubs.usgs.gov/pinatubo/delfin/index.html "Geothermal Exploration of the pre-1991 Mount Pinatubo Hydrothermal System"] {{Webarchive|url=https://web.archive.org/web/20111118142708/http://pubs.usgs.gov/pinatubo/delfin/index.html |date=November 18, 2011 }}. USGS. Retrieved on August 14, 2011.</ref>

==Aetas granted ownership of Pinatubo==
After being driven away by the 1991 eruption of Mount Pinatubo, in May 2009 some 454 Aeta families in Pampanga were given the first clean ancestral land ownership on Mount Pinatubo with the Certificate of Ancestral Domain Title (CADT) by the [[National Commission on Indigenous Peoples]] (NCIP), the government agency that deals with issues concerning indigenous people of the Philippines.  The approved and declared net land area of {{convert|7440.1|ha|acre|abbr=on}} covers the [[barangay]]s of Mawakat and Nabuklod in [[Floridablanca, Pampanga]], plus a portion of [[San Marcelino, Zambales]], and a portion of Barangay Batiawan in [[Subic, Zambales]].<ref>(2009-05-27). [https://www.scribd.com/doc/35827181/Aetas-in-Pampanga-Awarded-Land-Title "Aetas in Pampanga awarded first clean title of ancestral domain"] {{Webarchive|url=https://web.archive.org/web/20160306115943/https://www.scribd.com/doc/35827181/Aetas-in-Pampanga-Awarded-Land-Title |date=March 6, 2016 }}. Scribd. Retrieved on August 14, 2011.</ref>

On January 14, 2010, some 7,000 Aeta families from Zambales were officially granted the Certificate of Ancestral Domain Title (CADT) covering the Zambales side of Pinatubo which includes the summit and Lake Pinatubo, officially becoming their ''lutan tua'' (ancestral land).  The ancestral domain title covers {{convert|15984|ha|acre|abbr=on}} and includes the villages of Burgos, Villar, Moraza and Belbel in Botolan and portions of the towns of [[Cabangan, Zambales|Cabangan]], [[San Felipe, Zambales|San Felipe]] and [[San Marcelino, Zambales|San Marcelino]].<ref>Orejas, Tonette (November 27, 2009). [http://www.piplinks.org/it%E2%80%99s-official%3A-pinatubo-now-owned-aetas "It’s official: Pinatubo is now owned by Aetas"] {{webarchive|url=https://web.archive.org/web/20111118144033/http://www.piplinks.org/it%E2%80%99s-official%3A-pinatubo-now-owned-aetas |date=November 18, 2011 }}. PIPLinks (originally from ''[[Philippine Daily Inquirer]]''). Retrieved on August 14, 2011.</ref><ref name="Preda"/>

Ancestral domain titles are awarded to a certain community or indigenous group who have occupied or possessed the land continuously in accordance with their customs and traditions since time immemorial. They have the legal right to collectively possess and to enjoy the land and its natural resources to the exclusion of others.<ref name="Preda"/> Having the land title will protect them from others – including foreigners – exploiting their land without compensation to and consent from the indigenous tribes. In the past, the Aetas had to contend with mining companies, loggers, and recently, tourist companies who earn from Mount Pinatubo but do not compensate the local tribes.<ref name="Preda">Valdez, Katrina Mennen A. (January 14, 2010). [http://www.preda.org/main/archives/2010/r10011401.html "Aetas to receive title to domain at Mt. Pinatubo"] {{webarchive|url=https://archive.today/20130415191840/http://www.preda.org/main/archives/2010/r10011401.html |date=April 15, 2013 }}. [[Preda Foundation]]. Retrieved on August 14, 2011.</ref>

==In popular culture==
[[File:Hiking To Mount Pinatubo.jpg|thumb|Hiking to Mount Pinatubo's Crater]]
Long before Mount Pinatubo became famous for its cataclysmic eruption, [[President of the Philippines|Philippine president]] [[Ramon Magsaysay]], a native of Zambales, named his [[C-47 Skytrain|C-47]] [[Air transports of heads of state and government#Philippines|presidential plane]] ''Mt. Pinatubo''. The [[1957 Cebu Douglas C-47 crash|plane crashed]] into [[Mount Manunggal]] in [[Cebu province]] in 1957, killing the president and twenty-four others on board.<ref>{{cite news|author=Dominico C. Moneva|title=Speak out: Magsaysay's death|url=http://www.sunstar.com.ph/static/ceb/2006/03/18/oped/dominico.c..moneva..html|work=SunStar Cebu|date=March 18, 2006|access-date=March 21, 2008|archive-url=https://web.archive.org/web/20080517202331/http://www.sunstar.com.ph/static/ceb/2006/03/18/oped/dominico.c..moneva..html|archive-date=May 17, 2008|url-status=dead}}</ref>

The shape of Mount Pinatubo's caldera inspired [[New Clark City Athletics Stadium]] in [[Capas]], [[Tarlac]].<ref>{{cite news|last1=Enriquez|first1=Marge|title=Design duo tapped to build 'city of the future'|url=http://lifestyle.inquirer.net/283590/design-duo-tapped-build-city-future/|access-date=March 9, 2018|newspaper=Philippine Daily Inquirer|date=January 3, 2018|archive-date=December 1, 2020|archive-url=https://web.archive.org/web/20201201183631/https://lifestyle.inquirer.net/283590/design-duo-tapped-build-city-future/|url-status=live}}</ref>

==Hiking activity==
The caldera formed and [[Lake Pinatubo]] has, since June 15, 1991, become a tourist attraction with the preferred route through Barangay Santa Juliana in [[Capas, Tarlac]].<ref>{{cite news|title=Trekking-Mt-Pinatubo|newspaper=Philippine Daily Inquirer|url=http://lifestyle.inquirer.net/2bu/2bu/view/20100529-272636/Trekking-Mt-Pinatubo|access-date=June 13, 2012|date=May 29, 2010|url-status=dead|archive-url=https://web.archive.org/web/20121114015117/http://lifestyle.inquirer.net/2bu/2bu/view/20100529-272636/Trekking-Mt-Pinatubo|archive-date=November 14, 2012}}</ref>

==Biodiversity==

===Mammals===

The '''Long-nosed forest mouse''' ([[Apomys sacobianus]]) is a species of [[rodent]] endemic to Mount Pinatubo, Philippines.<ref name="0006-324X-126-4-395">{{cite journal|last1=Heaney|first1=Lawrence R.|last2=Balete|first2=Danilo S.|last3=Veluz|first3=Maria Josefa|last4=Steppan|first4=Scott J.|last5=Esselstyn|first5=Jacob A.|last6=Pfeiffer|first6=Andrew W.|last7=Rickart|first7=Eric A.|title=Two new species of Philippine forest mice (''Apomys'', Muridae, Rodentia) from Lubang and Luzon Islands, with a redescription of ''Apomys sacobianus'' Johnson, 1962|journal=Proceedings of the Biological Society of Washington|date=January 2014|volume=126|issue=4|pages=395–413|doi=10.2988/0006-324X-126.4.395|s2cid=49347286}}</ref>

The '''Zambales forest mouse''' ([[Apomys zambalensis]]) is a species of [[rodent]] endemic to [[Zambales Mountain Range]], Philippines.<ref name="0006-324X-126-4-395">{{cite journal|last1=Heaney|first1=Lawrence R.|last2=Balete|first2=Danilo S.|last3=Veluz|first3=Maria Josefa|last4=Steppan|first4=Scott J.|last5=Esselstyn|first5=Jacob A.|last6=Pfeiffer|first6=Andrew W.|last7=Rickart|first7=Eric A.|title=Two new species of Philippine forest mice (''Apomys'', Muridae, Rodentia) from Lubang and Luzon Islands, with a redescription of ''Apomys sacobianus'' Johnson, 1962|journal=Proceedings of the Biological Society of Washington|date=January 2014|volume=126|issue=4|pages=395–413|doi=10.2988/0006-324X-126.4.395|s2cid=49347286}}</ref>

==See also==
{{Portal|Volcanoes|Philippines}}
*[[List of volcanoes in the Philippines]]
**[[List of active volcanoes in the Philippines]]
**[[List of potentially active volcanoes in the Philippines]]
**[[List of inactive volcanoes in the Philippines]]
* [[List of volcanic eruptions by death toll]]
* [[Timeline of volcanism on Earth]]
{{Clear}}

==Notes==
{{reflist}}

==References==
{{Refbegin}}
* {{cite journal|vauthors=Chakraborty P, etal|year=2009|title=Volcanic mesocyclones|journal=Nature|volume=458|issue=7237|pages=495–500|url=http://web.mechse.illinois.edu/research/gioia/Art/nature07866.pdf|doi=10.1038/nature07866|bibcode=2009Natur.458..497C|pmid=19325632|s2cid=1129142}}{{dead link|date=December 2017 |bot=InternetArchiveBot |fix-attempted=yes }}
* Decker, R. and Decker, B. (1997) ''Volcanoes'', 3rd edition, WH Freeman, New York.
* {{cite journal|author=McCormick, M. Patrick|year=1995|title=Atmospheric effects of the Mt Pinatubo eruption|journal=[[Nature (journal)|Nature]]|volume=373|issue=6513|pages=399–404|doi=10.1038/373399a0|bibcode=1995Natur.373..399M|s2cid=46437912|display-authors=etal}}
* {{cite book|title=Geological Disasters In The Philippines: The July 1990 Earthquake And The June 1991 Eruption of Mount Pinatubo. Description, effects and lessons learned|last=Rantucci|first=Giovanni|year=1994|publisher=Philippine Institute of Volcanology and Seismology (PHIVOLCS)|isbn=978-0-7881-2075-6|url=https://books.google.com/books?id=qK3uy9oMzccC|access-date=August 15, 2009|archive-date=August 6, 2020|archive-url=https://web.archive.org/web/20200806023840/https://books.google.com/books?id=qK3uy9oMzccC|url-status=live}}
* {{cite book|last=Reilly|first=Benjamin|title=Disaster and human history: case studies in nature, society and catastrophe|url=https://books.google.com/books?id=mI77lmwmVDkC|year=2009|publisher=McFarland|isbn=978-0-7864-3655-2|access-date=September 24, 2016|archive-date=January 3, 2014|archive-url=https://web.archive.org/web/20140103123244/http://books.google.com/books?id=mI77lmwmVDkC|url-status=live}}
* {{Cite book|author1=Self S.|author2=Zhao, Jing-Xia|author3=Holasek, R.E.|author4=Torres, R.C.|author5=King, A.J.|year=1998|quote=The atmospheric impact of the 1991 Mount Pinatubo eruption|title=Fire and Mud, Eruptions and Lahars of Mount Pinatubo, Philippines|editor1=Newhall, C.G.|editor2=Punongbayan, R.S.|publisher=Smithsonian Institution – Global Volcanism Program|place=Washington|page=1126|url=http://pubs.usgs.gov/pinatubo/self/index.html|access-date=April 21, 2010|archive-date=November 17, 2017|archive-url=https://web.archive.org/web/20171117014144/https://pubs.usgs.gov/pinatubo/self/index.html|url-status=live}}
* {{cite journal|doi=10.1093/petroj/40.3.381|title=The 15 June 1991 Eruption of Mount Pinatubo. I. Phase Equilibria and Pre-eruption P-T-fO2-fH2O Conditions of the Dacite Magma|year=1999|last1=Scaillet|first1=B.|last2=Evans|first2=B. W.|journal=Journal of Petrology|volume=40|issue=3|pages=381–411|bibcode=1999JPet...40..381S|doi-access=free}}
* {{cite journal|doi=10.1007/s00445-003-0300-3|title=The crater lake and hydrothermal system of Mount Pinatubo, Philippines: Evolution in the decade after eruption|year=2004|last1=Stimac|first1=James A.|last2=Goff|first2=Fraser|last3=Counce|first3=Dale|last4=Larocque|first4=Adrienne C. L.|last5=Hilton|first5=David R.|last6=Morgenstern|first6=Uwe|journal=Bulletin of Volcanology|volume=66|issue=2|pages=149–167|bibcode=2004BVol...66..149S|s2cid=128408824}}
* {{cite journal|doi=10.1007/s00445-003-0306-x|title=Grain size, areal thickness distribution and controls on sedimentation of the 1991 Mount Pinatubo tephra layer in the South China Sea|year=2004|last1=Wiesner|first1=Martin G.|last2=Wetzel|first2=Andreas|last3=Catane|first3=Sandra G.|last4=Listanco|first4=Eddie L.|last5=Mirabueno|first5=Hannah T.|journal=Bulletin of Volcanology|volume=66|issue=3|pages=226–242|bibcode=2004BVol...66..226W|s2cid=128818475}}
* Dhot, S. Mt Pinatubo Safety.
{{Refend}}

==External links==
{{Commons category}}
{{Spoken Wikipedia|Mount_Pinatubo.ogg|date=January 31, 2006}}
* [http://pubs.usgs.gov/pinatubo/contents.html ''Fire and Mud: Eruptions and Lahars of Mount Pinatubo, Philippines''], [[United States Geological Survey]] site
* [https://web.archive.org/web/20020417121320/http://eos.higp.hawaii.edu/education/slide_set1/ "Weather effects of the 1991 eruption"] EOS Volcanology.
* [http://pubs.usgs.gov/fs/1997/fs113-97/fs113-97.pdf "The Cataclysmic 1991 Eruption of Mount Pinatubo, Philippines"]. United States Geological Survey site
* [https://web.archive.org/web/20080918051137/http://volcano.oregonstate.edu/vwdocs/volc_images/southeast_asia/philippines/pinatubo.html Pinatubo, Philippines (volcanic images)]
* [https://volcano.si.edu/volcano.cfm?vn=273083 Entry for Pinatubo] in the Smithsonian Institution's Global Volcanism Program (GVP)

{{Volcanoes of the Philippines}}
{{Authority control}}

{{DEFAULTSORT:Pinatubo, Mount}}
[[Category:Mount Pinatubo|*]]
[[Category:Active volcanoes of the Philippines]]
[[Category:Calderas of Southeast Asia]]
[[Category:Landforms of Pampanga]]
[[Category:Landforms of Tarlac]]
[[Category:Landforms of Zambales]]
[[Category:Mountains of the Philippines]]
[[Category:Stratovolcanoes of the Philippines]]
[[Category:Subduction volcanoes]]
[[Category:VEI-6 volcanoes]]
[[Category:Volcanic crater lakes]]
[[Category:Volcanoes of Luzon]]
[[Category:Holocene stratovolcanoes]]
[[Category:Pleistocene stratovolcanoes]]
[[Category:Zambales Mountains]]