Mount Pinatubo is an

active Active may refer to: Music * ''Active'' (album), a 1992 album by Casiopea * Active Records, a record label Ships * ''Active'' (ship), several commercial ships by that name * HMS ''Active'', the name of various ships of the British Royal ...

stratovolcano A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and per ...

in the

Zambales Mountains The Zambales Mountains is a mountain range on western Luzon island in the Philippines. The mountains separate Luzon's central plain from the South China Sea. Its most prominent section is known as the Cabusilan Mountain Range composed of Mount ...

, located on the

tripoint A tripoint, trijunction, triple point, or tri-border area is a geographical point at which the boundaries of three countries or subnational entities meet. There are 175 international tripoints as of 2020. Nearly half are situated in rivers, l ...

boundary of the

Philippine province In the Philippines, provinces ( fil, lalawigan) are one of its primary political and administrative divisions. There are 82 provinces at present, which are further subdivided into component cities and municipalities. The local government unit ...

s of

Zambales Zambales, officially the Province of Zambales ( fil, Lalawigan ng Zambales; ilo, Probinsia ti Zambales; Pangasinan: ''Luyag/Probinsia na Zambales''; xsb, Probinsya nin Zambales), is a province in the Philippines located in the Central Luzon re ...

Tarlac Tarlac, officially the Province of Tarlac ( pam, Lalawigan ning Tarlac; pag, Luyag/Probinsia na Tarlac; ilo, Probinsia ti Tarlac; tgl, Lalawigan ng Tarlac; ), is a landlocked province in the Philippines located in the Central Luzon region. It ...

and

Pampanga Pampanga, officially the Province of Pampanga ( pam, Lalawigan ning Pampanga; tl, Lalawigan ng Pampanga ), is a province in the Central Luzon region of the Philippines. Lying on the northern shore of Manila Bay, Pampanga is bordered by Tarlac ...

, all in

Central Luzon Central Luzon ( pam, (Reyun ning) Kalibudtarang Luzon, pag, (Rehiyon na) Pegley na Luzon, tgl, (Rehiyon ng) Gitnang Luzon, ilo, (Rehion/Deppaar ti) Tengnga ti Luzon), designated as Region III, is an administrative region in the Philippines, ...

on the northern island of

Luzon Luzon (; ) is the largest and most populous island in the Philippines. Located in the northern portion of the Philippines archipelago, it is the economic and political center of the nation, being home to the country's capital city, Manila, as ...

. Its eruptive history was unknown to most before the pre-eruption volcanic activity of early 1991. Pinatubo was heavily

eroded Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust, and then sediment transport, tra ...

and obscured from view by dense

forest A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' ...

s which supported a population of several thousand indigenous Aetas. Pinatubo is most notorious for its VEI-6

eruption Several types of volcanic eruptions—during which lava, tephra (ash, lapilli, volcanic bombs and volcanic blocks), and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are often ...

on June 15, 1991, the second-largest terrestrial eruption of the 20th century after the 1912 eruption of

Novarupta Novarupta (meaning "newly erupted" in Latin) is a volcano that was formed in 1912, located on the Alaska Peninsula on a slope of Trident Volcano in Katmai National Park and Preserve, about southwest of Anchorage. Formed during the largest volca ...

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...

. Complicating the eruption was the arrival of Typhoon Yunya, bringing a lethal mix of ash and rain to towns and cities surrounding the volcano. Predictions at the onset of the climactic eruption led to the evacuation of tens of thousands of people from the surrounding areas, saving many lives. Surrounding areas were severely damaged by

pyroclastic surge A pyroclastic surge is a fluidised mass of turbulent gas and rock fragments that is ejected during some volcanic eruptions. It is similar to a pyroclastic flow but it has a lower density or contains a much higher ratio of gas to rock, which makes i ...

pyroclastic fall A pyroclastic fall is a uniform deposit of material which has been ejected from a volcanic eruption or plume such as an ash fall or tuff. Pyroclastic air fall deposits are a result of: # Ballistic transport of ejecta such as volcanic blocks, volca ...

s, and subsequently, by the flooding

lahar A lahar (, from jv, ꦮ꧀ꦭꦲꦂ) is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a river valley. Lahars are extreme ...

s caused by rainwater re-mobilizing earlier volcanic deposits. This caused extensive destruction to infrastructure and changed river systems for years after the eruption. Minor

dome A dome () is an architectural element similar to the hollow upper half of a sphere. There is significant overlap with the term cupola, which may also refer to a dome or a structure on top of a dome. The precise definition of a dome has been a m ...

-forming eruptions inside the caldera continued from 1992 to 1993. The effects of the 1991 eruption were felt worldwide. It erupted roughly or of magma, and of , bringing vast quantities of minerals and toxic metals to the surface environment. It ejected more

particulate Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) – are microscopic particles of solid or liquid matter suspended in the air. The ter ...

into the

stratosphere The stratosphere () is the second layer of the atmosphere of the Earth, located above the troposphere and below the mesosphere. The stratosphere is an atmospheric layer composed of stratified temperature layers, with the warm layers of air ...

than any eruption since

Krakatoa Krakatoa (), also transcribed (), is a caldera in the Sunda Strait between the islands of Java and Sumatra in the Indonesian province of Lampung. The caldera is part of a volcanic island group (Krakatoa archipelago) comprising four islands. Tw ...

in 1883. Over the following months, the aerosols formed a global layer of

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...

haze. Global temperatures dropped by about in the years 1991–1993, and

ozone depletion Ozone depletion consists of two related events observed since the late 1970s: a steady lowering of about four percent in the total amount of ozone in Earth's atmosphere, and a much larger springtime decrease in stratospheric ozone (the ozone l ...

temporarily saw a substantial increase.

Geography

The volcano is about northwest of

Manila Manila ( , ; fil, Maynila, ), officially the City of Manila ( fil, Lungsod ng Maynila, ), is the capital of the Philippines, and its second-most populous city. It is highly urbanized and, as of 2019, was the world's most densely populate ...

, 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 Naval Base Subic Bay was a major ship-repair, supply, and rest and recreation facility of the Spanish Navy and subsequently the United States Navy located in Zambales, Philippines. The base was 262 square miles, about the size of Singapore. Th ...

was south of Pinatubo, and the extent of

Clark Air Base Clark Air Base is a Philippine Air Force base on Luzon Island in the Philippines, located west of Angeles City, about northwest of Metro Manila. Clark Air Base was previously a United States military facility, operated by the U.S. Air Forc ...

was just east of the volcano's summit.Tactical Pilotage Chart, Sheet K-11B,

Defense Mapping Agency The National Geospatial-Intelligence Agency (NGA) is a combat support agency within the United States Department of Defense whose primary mission is collecting, analyzing, and distributing geospatial intelligence (GEOINT) in support of national ...

, Department of Defense, 1982. The volcano is near to about 6 million people.

History

Mount Pinatubo's summit before the 1991 eruption was above sea level, only about above nearby

plain In geography, a plain is a flat expanse of land that generally does not change much in elevation, and is primarily treeless. Plains occur as lowlands along valleys or at the base of mountains, as coastal plains, and as plateaus or uplands ...

s, and only about higher than surrounding peaks, which largely obscured it from view. It is part of a chain of

volcanoes A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates are ...

which lie along the western side of the island of

called the

. Pinatubo belongs to the Cabusilan sub-range of the

, which consists of Mount Cuadrado,

Mount Negron ''Mount Negron'', also known as ''Negron Volcano'', is a mountain located on the border of Porac, Pampanga and San Marcelino, Zambales, Philippines at the Zambales Mountains in the region of Central Luzon. It has a height of 1,583 m (5,194& ...

, Mount Mataba and Mount Pinatubo. They are

subduction Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...

volcanoes, formed by the

Eurasian Plate The Eurasian Plate is a tectonic plate that includes most of the continent of Eurasia (a landmass consisting of the traditional continents of Europe and Asia), with the notable exceptions of the Indian subcontinent, the Arabian subcontinent and ...

sliding under the

Philippine Mobile Belt In the geology of the Philippines, the Philippine Mobile Belt is a complex portion of the tectonic boundary between the Eurasian Plate and the Philippine Sea Plate, comprising most of the country of the Philippines. It includes two subduction z ...

along the Manila Trench to the west. Mount Pinatubo and the other volcanoes on this

volcanic belt A volcanic belt is a large volcanically active region. Other terms are used for smaller areas of activity, such as volcanic fields. Volcanic belts are found above zones of unusually high temperature () where magma is created by partial melting ...

arise due to

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...

tic occlusion from this

plate Plate may refer to: Cooking * Plate (dishware), a broad, mainly flat vessel commonly used to serve food * Plates, tableware, dishes or dishware used for setting a table, serving food and dining * Plate, the content of such a plate (for example: ...

boundary. Pinatubo is flanked on the west by the Zambales

Ophiolite An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed above sea level and often emplaced onto continental crustal rocks. The Greek word ὄφις, ''ophis'' (''snake'') is found i ...

Complex, which is an easterly-dipping section of

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

oceanic crust uplifted during the late

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

. The Tarlac Formation north, east and southeast of Pinatubo consists of marine, nonmarine and volcanoclastic sediments formed in the late

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

and

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58 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 The Philippine National Oil Company (PNOC) is an energy company created on November 9, 1973, as a government-owned and controlled corporation founded during President Ferdinand Marcos' era to supply oil to the Philippines. Since then, its char ...

as part of the surface investigations of the area before exploratory drilling and well testing for

geothermal energy Geothermal energy is the thermal energy in the Earth's crust which originates from the formation of the planet and from radioactive decay of materials in currently uncertain but possibly roughly equal proportions. The high temperature and pres ...

sources in 1988 to 1990. He recognized two life histories of the mountain, which he classified as "ancestral" and "modern" Pinatubo.

Ancestral Pinatubo

Philippine Island - Luzon Island - NARA - 68156975

Activity of Ancestral Pinatubo seems to have begun about 1.1 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 Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomi ...

and

dacite Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. ...

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 , or 1.43 miles above

sea level Mean sea level (MSL, often shortened to sea level) is an average surface level of one or more among Earth's coastal bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datuma standardised g ...

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. The old volcano is exposed in the walls of an old wide

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...

, 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 Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement), ...

. Ancestral Pinatubo is a

somma volcano A somma volcano (also known as a sommian) is a volcano, volcanic caldera that has been partially filled by a new central volcanic cone, cone. The name comes from Mount Somma, a stratovolcano in southern Italy with a summit caldera in which the ...

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 A volcanic plug, also called a volcanic neck or lava neck, is a volcanic object created when magma hardens within a vent on an active volcano. When present, a plug can cause an extreme build-up of high gas pressure if rising volatile-charged mag ...

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.

Modern Pinatubo

* c. 33,000 BC: After a long period of

dormancy Dormancy is a period in an organism's life cycle when growth, development, and (in animals) physical activity are temporarily stopped. This minimizes metabolic activity and therefore helps an organism to conserve energy. Dormancy tends to be clo ...

, 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 of

material up to thick. The total volume of volcanic material ejected during the eruptions is unknown. The removal of so much material from the underlying

magma chamber A magma chamber is a large pool of liquid rock beneath the surface of the Earth. The molten rock, or magma, in such a chamber is less dense than the surrounding country rock, which produces buoyant forces on the magma that tend to drive it upw ...

resulted in the Tayawan

. 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. 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 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. 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. 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 Rainforests are characterized by a closed and continuous tree canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforest can be classified as tropical rainforest or temperate rainfores ...

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.

1991 eruption

Eruption of Mount Pinatubo, June 15, 1991

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 and which generated large

s extending up to from the summit in some river

valley A valley is an elongated low area often running between Hill, hills or Mountain, mountains, which will typically contain a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers ...

s. Fourteen hours later, a 15-minute blast hurled volcanic matter to heights of . Friction in the up-rushing ash column generated abundant

volcanic lightning Volcanic lightning is an electrical discharge caused by a volcanic eruption rather than from an ordinary thunderstorm. Volcanic lightning arises from colliding, fragmenting particles of volcanic ash (and sometimes ice), which generate static e ...

. In March and April 1991, magma rising toward the surface from more than beneath Pinatubo triggered small

volcano tectonic earthquake A volcano tectonic earthquake is caused by the movement of magma beneath the surface of the Earth. The movement results in pressure changes where the rock around the magma has experienced stress. At some point, this stress can cause the rock to bre ...

s and caused powerful steam explosions that blasted three 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 Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...

gas were also emitted by the volcano. 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. 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 of material. The

ash cloud Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, created during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to refer t ...

from this climactic eruption rose into the atmosphere. At lower altitudes, the

volcanic ash Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, created during volcano, volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used t ...

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 Pumice (), called pumicite in its powdered or dust form, is a volcanic rock that consists of highly vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicular vol ...

lapilli Lapilli is a size classification of tephra, which is material that falls out of the air during a volcanic eruption or during some meteorite impacts. ''Lapilli'' (singular: ''lapillus'') is Latin for "little stones". By definition lapilli range f ...

blanketed the countryside. Fine ash fell as far away as the

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by th ...

and satellites tracked the ash cloud several times around the globe. Huge pyroclastic flows roared down the flanks of Mount Pinatubo, filling once-deep valleys with fresh volcanic deposits as much as thick. The eruption removed so much magma and rock from below the volcano that the summit collapsed to form a wide caldera. 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. Tephra fall from 1991 eruption of Mt Pinatubo

Tephra fall from 1991 eruption of Mt Pinatubo

Later eruptions

Activity at the volcano remained low until July 1992 when a new lava dome started growing in the

. 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.

Lake Pinatubo

The 1991 caldera afterwards filled with water from annual monsoon rains and a

crater lake Crater Lake (Klamath language, Klamath: ''Giiwas'') is a volcanic crater lake in south-central Oregon in the western United States. It is the main feature of Crater Lake National Park and is famous for its deep blue color and water clarity. The ...

Lake Pinatubo Lake Pinatubo ( fil, Lawa ng Pinatubo) is the summit crater lake of Mount Pinatubo formed after its climactic eruption on June 15, 1991. The lake is located in Botolan, Zambales, near the boundaries of Pampanga and Tarlac provinces in the Philip ...

, 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 In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...

ic, with a minimum pH of 2 and a temperature of about . Subsequent rainfall cooled and diluted the lake, lowering the temperature to and raising the pH to 5.5 by 2003. The lake deepened by about 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 people were once again evacuated from surrounding areas in case a large

flood A flood is an overflow of water ( or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study of the discipline hydrol ...

was accidentally triggered. Workers cut a notch in the crater rim and drained about a quarter of the lake's volume. Mt Pinatubo trekking - panoramio (5)

Recent activity

On July 10, 2002, the west wall of the crater collapsed, slowly releasing approximately of water and sediments into the Maraunot River in Botolan, Zambales. On July 26, 2011, a 5.9 magnitude earthquake struck close to Pinatubo; however, no major damages or casualties were reported. 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. 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. On November 30, 2021, PHIVOLCS reported a weak explosion occurred on Mt. Pinatubo between 12:09 p.m. and 12:13 p.m., which produced a plume. The agency later confirmed it was a phreatic explosion produced by

hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...

fluids near the surface, rather than a magmatic eruption.

Cultural history

The word ''pinatubo'' could mean "fertile place where one can make crops grow", or could mean "made to grow", in

Sambal Sambal is an Indonesian chilli sauce or paste, typically made from a mixture of a variety of chilli peppers with secondary ingredients, such as shrimp paste, garlic, ginger, shallot, scallion, palm sugar, and lime juice. ''Sambal'' is an Indo ...

and Tagalog, which may suggest a knowledge of its previous eruption in about 1500 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.

History among Aetas

Aeta The Aeta (Ayta ), Agta, or Dumagat, are collective terms for several Filipino indigenous peoples who live in various parts of the island of Luzon in the Philippines. They are considered to be part of the Negrito ethnic groups and share common ...

elders tell many stories about the history of the mountain, the best known being that it was once a Batung Mabye (

Kapampangan language Kapampangan or Pampangan is an Austronesian language, and one of the eight major languages of the Philippines. It is the primary and predominant language of the entire province of Pampanga and southern Tarlac, on the southern part of Luzon's c ...

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

, Aetas and

Kapampangans The Kapampangan people ( pam, Taung Kapampangan), Pampangueños or Pampangos, are the sixth largest ethnolinguistic group in the Philippines, numbering about 2,784,526 in 2010. They live mainly in the provinces of Pampanga, Bataan and Tarlac, as ...

living on the Zambales range. It was said to comprise the whole mountain range until Sinukuan of

Mount Arayat Mount Arayat is a potentially active stratovolcano located in the province of Pampanga on the island of Luzon, Philippines, rising to a height of . The volcano has a breached crater on its northwest side with a smaller andesitic dome in the ...

(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. According to the native elders, Apo Namalyari induced the June 1991 eruption because of displeasure toward illegal loggers and

executives who performed deep exploratory drilling and well testing on the volcano looking for geothermal heat from 1988 to 1990. Discouraging results from the wells forced the abandonment of the prospect 13 months before the April 2, 1991 explosions.

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 The National Commission on Indigenous Peoples (NCIP) is the agency of the national government of the Philippines that is responsible for protecting the rights of the indigenous peoples of the Philippines. The commission is composed of seven comm ...

(NCIP), the government agency that deals with issues concerning indigenous people of the Philippines. The approved and declared net land area of covers the

barangay A barangay (; abbreviated as Brgy. or Bgy.), historically referred to as barrio (abbreviated as Bo.), is the smallest administrative division in the Philippines and is the native Filipino term for a village, district, or ward. In metropolitan ...

s of Mawakat and Nabuklod in

Floridablanca, Pampanga Floridablanca, officially the Municipality of Floridablanca ( pam, Balen ning Floridablanca; fil, Bayan ng Floridablanca) is a 1st class municipality in the province of Pampanga, Philippines. According to the 2020 census, it has a population of ...

, plus a portion of

San Marcelino, Zambales San Marcelino, officially the Municipality of San Marcelino ( ilo, Ili ti San Marcelino; tgl, Bayan ng San Marcelino), is a 1st class municipality of the Philippines, municipality in the Philippine Province, province of Zambales, Philippines. A ...

, and a portion of Barangay Batiawan in

Subic, Zambales Subic, officially the Municipality of Subic ( ilo, Ili ti Subic; tl, Bayan ng Subic), is a 1st class municipality in the province of Zambales, Philippines. According to the 2020 census, it has a population of 111,912 people. It is located alon ...

. 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 and includes the villages of Burgos, Villar, Moraza and Belbel in Botolan and portions of the towns of

Cabangan Cabangan, officially the Municipality of Cabangan, is a 4th class municipality of the Philippines, municipality in the Philippine Province, province of Zambales, Philippines. According to the 2020 census, it has a population of 28,118 people. C ...

, San Felipe and

San Marcelino San Marcelino, officially the Municipality of San Marcelino ( ilo, Ili ti San Marcelino; tgl, Bayan ng San Marcelino), is a 1st class municipality in the province of Zambales, Philippines. According to the 2020 census, it has a population of 37 ...

. Having the land title will protect them from others – including foreigners – exploiting their land without compensation and consent to 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.Valdez, Katrina Mennen A. (January 14, 2010)
"Aetas to receive title to domain at Mt. Pinatubo"
.

Preda Foundation The People's Recovery Empowerment Development Assistance Foundation, commonly referred to as the PREDA Foundation or PREDA, is a charitable organization that was founded in Olongapo City, Philippines in 1974. Its purposes include the promotion and ...

. Retrieved on 2011-08-14. 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.

In popular culture

Long before Mount Pinatubo became famous for its cataclysmic eruption,

Philippine President The president of the Philippines ( fil, Pangulo ng Pilipinas, sometimes referred to as ''Presidente ng Pilipinas'') is the head of state, head of government and chief executive of the Philippines. The president leads the executive branch of t ...

Ramon Magsaysay Ramon del Fierro Magsaysay Sr. (August 31, 1907 – March 17, 1957) was a Filipino statesman who served as the seventh president of the Philippines, from December 30, 1953, until his death in an aircraft disaster on March 17, 1957. An automo ...

, a native of Zambales, named his

C-47 The Douglas C-47 Skytrain or Dakota (Royal Air Force, RAF, Royal Australian Air Force, RAAF, Royal Canadian Air Force, RCAF, Royal New Zealand Air Force, RNZAF, and South African Air Force, SAAF designation) is a airlift, military transport ai ...

presidential plane ''Mt. Pinatubo''. The plane crashed into

Mount Manunggal Mount Manunggal is the third-highest peak in the island of Cebu after Osmena Peak and Lugsangan Peak. It is located in Barangay Magsaysay in Balamban, Cebu province, rising above sea level. It is the site of the crash of the presidential plane ...

Cebu province Cebu (; ceb, Sugbo), officially the Province of Cebu ( ceb, Lalawigan sa Sugbo; tl, Lalawigan ng Cebu; hil, Kapuroan sang Sugbo), is a province of the Philippines located in the Central Visayas region, and consists of a main island and 167 ...

in 1957, killing the President and twenty-four others on board. The shape of Mount Pinatubo's caldera inspired

New Clark City Athletics Stadium The New Clark City Athletics Stadium is a multi-purpose stadium located at the New Clark City in Capas, Tarlac, Philippines. It is the primary venue of the New Clark City Sports Hub, which is part of the National Government Administrative Center. ...

Capas Capas, officially the Municipality of Capas ( pam, Balen ning Capas; tgl, Bayan ng Capas), is a 1st class municipality in the province of Tarlac, Philippines, and one of the richest towns in the province. The town also consists of numerous su ...

Hiking activity

The caldera formed and

has, since June 15, 1991, become a tourist attraction with the preferred route through Barangay Santa Juliana in

Capas, Tarlac Capas, officially the Municipality of Capas ( pam, Balen ning Capas; tgl, Bayan ng Capas), is a 1st class municipality in the province of Tarlac, Philippines, and one of the richest towns in the province. The town also consists of numerous su ...

Notes

References

* * Decker, R. and Decker, B. (1997) ''Volcanoes'', 3rd edition, WH Freeman, New York. * * * * * * * * Dhot, S. Mt Pinatubo Safety.

External links

Mount Pinatubo page

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

site
"Weather effects of the 1991 eruption"
EOS Volcanology.
"The Cataclysmic 1991 Eruption of Mount Pinatubo, Philippines"
United States Geological Survey site

Entry for Pinatubo
in the Smithsonian Institution's Global Volcanism Program (GVP) {{DEFAULTSORT:Pinatubo, Mount Active volcanoes of the Philippines Calderas of Southeast Asia Landforms of Pampanga Landforms of Tarlac Landforms of Zambales Mountains of the Philippines Stratovolcanoes of the Philippines Subduction volcanoes VEI-6 volcanoes Volcanic crater lakes Volcanoes of Luzon Holocene stratovolcanoes Pleistocene stratovolcanoes