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Encyclopedia > Mount Pinatubo
Mount Pinatubo

Ash plume of Pinatubo during 1991 eruption
Elevation 1,486 meters (4,875 ft) 1745 meters before 1991 eruption
Location Zambales, Luzon, Philippines
Tarlac, Luzon, Philippines
Pampanga, Luzon, Philippines
Range Zambales Mountains
Coordinates 15°7.8′N 120°21.0′E / 15.13, 120.35Coordinates: 15°7.8′N 120°21.0′E / 15.13, 120.35
Type Stratovolcano
Age of rock 1.1 million years[citation needed]
Last eruption 1991[1]

Mount Pinatubo is an active stratovolcano located on the island of Luzon in the Philippines, at the intersection of the borders of the provinces of Zambales, Tarlac, and Pampanga. Ancestral Pinatubo was a stratovolcano made of andesite and dacite. Before 1991, the mountain was inconspicuous and heavily eroded. It was covered in dense forest which supported a population of several thousand indigenous people, the Aeta, who had fled to the mountains from the lowlands when the Spanish conquered the Philippines in 1565. USGS.gov picture of Mt Pinatubo eruption File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... A topographical summit is a point on a surface which is higher in elevation than all points immediately adjacent to it. ... REPUBLIC OF THE PHILIPPINES Province of Zambales Region: Central Luzon (Region III) Capital: Iba Founded: 1578 Population: 2000 census—627,802 (39th largest) Density—169 per km² (49th highest) Area: 3,714. ... Map of the Philippines showing the island groups of Luzon, Visayas, and Mindanao. ... Tarlac is a landlocked province of the Philippines located in the Central Luzon region. ... Map of the Philippines showing the island groups of Luzon, Visayas, and Mindanao. ... REPUBLIC OF THE PHILIPPINES Province of Pampanga Region: Central Luzon (Region III) Capital: City of San Fernando Founded: December 11, 1571 Population: 2000 census—1,882,730 (10th largest) Density—863 per km² (4th highest) Area: 2,180. ... Map of the Philippines showing the island groups of Luzon, Visayas, and Mindanao. ... For exotic financial options, see Mountain range (options). ... The Zambales Mountains are on the western side of Luzon, in the Philippines. ... Map of Earth showing lines of latitude (horizontally) and longitude (vertically), Eckert VI projection; large version (pdf, 1. ... Map of Earth showing lines of latitude (horizontally) and longitude (vertically), Eckert VI projection; large version (pdf, 1. ... Mountains can be characterized in several ways. ... A cutaway diagram of a stratovolcano Mount St. ... // For other uses, see time scale. ... Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station For other uses, see Volcano (disambiguation). ... A cutaway diagram of a stratovolcano Mount St. ... Map of the Philippines showing the island groups of Luzon, Visayas, and Mindanao. ... REPUBLIC OF THE PHILIPPINES Province of Zambales Region: Central Luzon (Region III) Capital: Iba Founded: 1578 Population: 2000 census—627,802 (39th largest) Density—169 per km² (49th highest) Area: 3,714. ... REPUBLIC OF THE PHILIPPINES Province of Tarlac Region: Central Luzon (Region III) Capital: Tarlac City Founded: 1872 Population: 2000 census—1,068,783 (23rd largest) Density—350 per km² (14th highest) Area: 3,053. ... REPUBLIC OF THE PHILIPPINES Province of Pampanga Region: Central Luzon (Region III) Capital: City of San Fernando Founded: December 11, 1571 Population: 2000 census—1,882,730 (10th largest) Density—863 per km² (4th highest) Area: 2,180. ... A sample of andesite (dark groundmass) with amygdaloidal vesicules filled with zeolite. ... Grey, red, black, altered white/tan, flow-banded pumice dacite Dacite (IPA: ) is an igneous, volcanic rock with a high iron content. ... For morphological image processing operations, see Erosion (morphology). ... This article is about a community of trees. ... The Aeta are an indigenous people who live in scattered, isolated mountainous parts of the Philippines. ...


The volcano's eruption in June 1991 produced the second largest terrestrial eruption of the 20th century.[2] The 1991 eruption had a Volcanic Explosivity Index (VEI) of 6, and came some 450-500 years after the volcano's last known eruptive activity (estimated as VEI 5, the level of the 1980 eruption of Mount St. Helens), and some 500-1000 years after previous VEI 6 eruptive activity.[3] Successful predictions of the onset of the climactic eruption led to the evacuation of tens of thousands of people from the surrounding areas, saving many lives, but as the surrounding areas were severely damaged by pyroclastic flows, ash deposits, and later, lahars caused by rainwater remobilizing earlier volcanic deposits, thousands of houses and other buildings were destroyed.[2] VEI and ejecta volume correlation The Volcanic Explosivity Index (VEI) was devised by Chris Newhall of the U.S. Geological Survey and Steve Self at the University of Hawaii in 1982 to provide a relative measure of the explosiveness of volcanic eruptions. ... The 1980 eruption of Mount St. ... Pyroclastic flows sweep down the flanks of Mayon Volcano, Philippines, in 1984 A pyroclastic flow (also known as a pyroclastic density current) is a common and devastating result of some volcanic eruptions. ... Lahar from a March 1982 eruption of Mount St. ...


The effects of the eruption were felt worldwide. It ejected roughly 10 billion metric tons of magma, and 20 million tons of SO2, bringing vast quantities of minerals and metals to the surface environment. It injected large amounts of aerosols into the stratosphere—more than any eruption since that of Krakatoa in 1883. Over the following months, the aerosols formed a global layer of sulfuric acid haze. Global temperatures dropped by about 0.5 °C (0.9 °F), and ozone depletion increased substantially, but has since recovered. Sulfur dioxide (or sulphur dioxide) has the chemical formula SO2. ... Particulates, alternatively referred to as particulate matter (PM), aerosols or fine particles, are tiny particles of solid or liquid suspended in a gas. ... Atmosphere diagram showing stratosphere. ... For the 1969 film about the Krakatoa eruption, see Krakatoa, East of Java. ... R-phrases S-phrases , , , Flash point Non-flammable Related Compounds Related strong acids Selenic acid Hydrochloric acid Nitric acid Related compounds Hydrogen sulfide Sulfurous acid Peroxymonosulfuric acid Sulfur trioxide Oleum Supplementary data page Structure and properties n, εr, etc. ... For other uses, see Celsius (disambiguation). ... For other uses, see Fahrenheit (disambiguation). ... For other uses, see Ozone (disambiguation). ...

Contents

Overview of the Mount Pinatubo area

Location of Mt. Pinatubo, showing area over which ash from the 1991 eruption fell

Pinatubo is part of a chain of volcanoes which lie along the western edge of the island of Luzon. They are subduction volcanoes, formed by the Philippine Plate sliding under the Eurasian Plate along the Manila Trench to the west. Mount Pinatubo lies on a destructive plate boundary.The word 'pinatubo' means 'to have made grow' in Tagalog and Sambal {²}, which may suggest a knowledge of its previous eruption in about AD 1500, although there is no oral tradition among local people of earlier large eruptions. Pinatubo might instead mean a fertile place where crops can be made to grow. Area over which tephra from 1991 eruption of Mt Pinatubo fell. ... Area over which tephra from 1991 eruption of Mt Pinatubo fell. ... Map of the Philippines showing the island groups of Luzon, Visayas, and Mindanao. ... Geometry of a subduction zone - insets to show accretionary prism and partial melting of hydrated asthenosphere. ... Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station For other uses, see Volcano (disambiguation). ...  The Philippine plate, shown in dull red The Philippine Plate is an oceanic tectonic plate beneath the Pacific Ocean to the east of the Philippines. ...  The Eurasian plate, shown in green The Eurasian Plate is a tectonic plate covering Eurasia (a landmass consisting of the traditional continents of Europe and Asia) except that it does not cover the Indian subcontinent, the Arabian subcontinent, and the area east of the Verkhoyansk Range in East Siberia. ... The Manila Trench is an ocean trench in the South China Sea, west of the Philippines. ... Tagalog (pronunciation: ) is one of the major languages of the Republic of the Philippines. ... Sambal (Spanish: zambal) is a Sambalic language spoken primarily in the province of Zambales in the Philippines. ... This article does not cite any references or sources. ...


Before the catastrophic eruption of 1991, Pinatubo was an inconspicuous volcano, unknown to most people in the surrounding areas. Its summit was 1,745 m (5,725 ft) above sea level, but only about 600 m above nearby plains, and about 200 m higher than surrounding peaks, which largely obscured it from view. An indigenous people, the Aeta (also spelt Ayta), had lived on the slopes of the volcano and in surrounding areas for several centuries, having fled the lowlands to escape persecution by the Spanish. They were a hunter-gatherer people who were extremely successful in surviving in the dense jungles of the area. These people also grew some staple crops such as wheat, barley and rice. In geography, a plain is a large area of land with relatively low relief. ... The Aeta are an indigenous people who live in scattered, isolated mountainous parts of the Philippines. ... In anthropology, the hunter-gatherer way of life is that led by certain societies of the Neolithic Era based on the exploitation of wild plants and animals. ...


In total, about 30,000 people lived on the flanks of the volcano in barangays (villages) and other small settlements. The dense jungle covering most of the mountain and surrounding peaks supported the hunter-gathering Aeta, while on the surrounding flatter areas, the abundant rainfall (almost 4 m annually) provided by the monsoon climate and the fertile volcanic soils provided excellent conditions for agriculture, and many people grew rice and other staple foods. About 500,000 people continue to live within 40 km of the mountain, with population centres including the 150,000 in Angeles City, and 20,000 at Clark Air Base. A barangay (Tagalog: baranggay , pronounced as ba-rang-gai, gai as in guy), also known by its former name, the barrio, is the smallest local government unit in the Philippines and is the native Filipino term for a village, district or ward. ... For other uses, see Monsoon (disambiguation). ... For other uses, see Rice (disambiguation). ... Nickname: Motto: Sulong Angeles. ... Clark Air Base, 1975. ...


Several important river systems have their sources on Pinatubo, with the major rivers being the Bucao, Santo Tomas, Maloma, Tanguay and Kileng rivers. Before the eruption, these river systems were important ecosystems, but the eruption filled many valleys with deep pyroclastic deposits. Since 1991, the rivers have been clogged with sediment, and the valleys have seen frequent lahars. Studies show that the river systems will take many years yet to recover from the 1991 eruption. A coral reef near the Hawaiian islands is an example of a complex marine ecosystem. ... This article or section cites very few or no references or sources. ... Lahar from a March 1982 eruption of Mount St. ...


Geological history

Although there seems to be no local knowledge of the previous large eruptions in the Pinatubo area, several Aeta residents reported in 1991 that their elders recalled small explosions in the past. Pinatubo was a known geothermal area before the 1991 eruption, and small steam explosions are quite common in such areas. It was only after volcanic activity began in 1991 that geologists studied the eruptive history of the region in any detail. Eruptions at the site can be divided into two major eras. Earth cutaway from core to exosphere. ...


Ancestral Pinatubo

Pinatubo before the major eruption of 1991
Pinatubo before the major eruption of 1991

Much of the rugged land surrounding the present volcano consists of remnants of 'ancestral' Pinatubo. This volcano was located roughly in the same place as the present mountain, and activity seems to have begun about 1.1 million years ago. Ancestral Pinatubo may have reached a height of up to 2,300 m (7,550 ft) above sea level, based on profile fitting to the remaining lower slopes. Mount Pinatubo in April 1991, before the onset of magmatic eruptions. ... Mount Pinatubo in April 1991, before the onset of magmatic eruptions. ... For other uses, see M (disambiguation). ... A foot (plural: feet or foot;[1] symbol or abbreviation: ft or, sometimes, ′ – a prime) is a unit of length, in a number of different systems, including English units, Imperial units, and United States customary units. ... For considerations of sea level change, in particular rise associated with possible global warming, see sea level rise. ...


Several mountains near modern Pinatubo are old satellite vents of ancestral Pinatubo, formed from volcanic plugs and lava domes. Some nearby peaks are also remnants of ancestral Pinatubo, formed from erosion-resistant parts of the old mountain slopes left behind when the less resistant parts were eroded away by weathering. Volcanic plug near Rhumsiki, Far North Province, Cameroon A volcanic plug, also called a volcanic neck or lava neck, is a volcanic landform created when lava hardens within a vent on an active volcano. ... One of the Mono Craters, an example of a rhyolite dome. ... For morphological image processing operations, see Erosion (morphology). ... Weathering is the decomposition of rocks, soils and their minerals through direct contact with the Earths atmosphere. ...


The eruptive activity of ancestral Pinatubo was much less explosive than modern Pinatubo, and probably ended about 45,000 years ago. After a long period of dormancy, modern Pinatubo was born in eruptions beginning about 35,000 years ago.


Modern Pinatubo

The birth of modern Pinatubo occurred in the most explosive eruption in its history, which deposited pyroclastic flow material up to 100 meters thick on all sides of the mountain. The total volume of material erupted may have been up to 25 cubic kilometers (6 mile³), and the removal of this amount of material from the underlying magma chamber led to the formation of a large caldera. Pyroclastic flows sweep down the flanks of Mayon Volcano, Philippines, in 1984 A pyroclastic flow (also known as a pyroclastic density current) is a common and devastating result of some volcanic eruptions. ... A magma chamber is a chamber typically between 1 km and 10 km beneath the surface of the Earth formed as rising magma forms a reservoir if it is unable to rise any further. ... Satellite image of Santorini. ...


Later large eruptions occurred 17,000, 9000, 6000–5000 and 3900–2300 years ago. Each of these eruptions seems to have been very large, ejecting more than 10 km³ of material and covering large parts of the surrounding areas with pyroclastic flow deposits. Scientists estimate that the most recent eruption before 1991 happened about 500 years ago, and after that, the volcano lay dormant. Its slopes became completely covered in dense rainforest, and eroded into gullies and ravines. The Daintree Rainforest in Queensland, Australia. ...


1991 awakening

One of the early explosive eruptions at Pinatubo after the April 1991 onset of ash eruptions
One of the early explosive eruptions at Pinatubo after the April 1991 onset of ash eruptions

On July 16, 1990, an earthquake of magnitude 7.8 (comparable in size to the 1906 San Francisco earthquake and the 2005 Kashmir Earthquake) struck central Luzon. Its epicenter was at Cabanatuan City, about 100 km northeast of Pinatubo, leading some volcanologists to speculate that it might ultimately have triggered the 1991 eruption, although this is impossible to prove conclusively. Two weeks after the earthquake, local residents reported steam coming from the volcano, but scientists visiting the mountain found that small landslides rather than any eruptive activity were responsible. Photo: T. J. Casadevall, U.S. Geological Survey. ... Photo: T. J. Casadevall, U.S. Geological Survey. ... is the 197th day of the year (198th in leap years) in the Gregorian calendar. ... Year 1990 (MCMXC) was a common year starting on Monday (link displays the 1990 Gregorian calendar). ... Map of Nueva Ecija showing the location of Cabanatuan City. ... The Richter magnitude test scale (or more correctly local magnitude ML scale) assigns a single number to quantify the size of an earthquake. ... San Francisco Earthquake redirects here. ... The Kashmir earthquake (also known as the South Asia earthquake or the Great Pakistan earthquake) of 2005 of which the epicenter was the Pakistan-administered Kashmir. ... The City of Cabanatuan is a first class city in the province of Nueva Ecija, Philippines. ... For other uses, see Steam (disambiguation). ... This article is about geological phenomenon. ...


On March 15, 1991, a succession of earthquakes was felt by villagers on the north-western side of the volcano. Further earthquakes of increasing intensity were felt over the next two weeks, and it became clear some kind of volcanic activity was imminent. On April 2, the volcano awoke, with phreatic eruptions occurring near the summit along a 1.5 km long fissure. Over the next few weeks, small eruptions continued, dusting the surrounding areas with ash. Seismographs recorded hundreds of small earthquakes every day. is the 74th day of the year (75th in leap years) in the Gregorian calendar. ... Year 1991 (MCMXCI) was a common year starting on Tuesday (link will display the 1991 Gregorian calendar). ... is the 92nd day of the year (93rd in leap years) in the Gregorian calendar. ... Phreatic eruption at the summit of Mount St. ... Fissure (Latin fissura, Plural fissurae) is a groove, natural division, deep furrow, or cleft found in the brain, spinal cord, and liver; or a tear in the anus. ... Ash plume from Mt Cleveland, a stratovolcano Diamond Head, a well-known backdrop to Waikiki in Hawaii, is an ash cone that solidified into tuff Volcanic ash consists of very fine rock and mineral particles less than 2 mm in diameter that are ejected from a volcanic vent. ... Seismographs (in Greek seismos = earthquake and graphein = write) are used by seismologists to record seismic waves. ...


Scientists immediately installed monitoring equipment and analysed the volcano for clues as to its previous eruptive history. Radiocarbon dating of charcoal found in old volcanic deposits revealed the three major explosive eruptions in recent millennia, about 5500, 3500 and 500 years ago. Geological mapping showed that much of the surrounding plains were formed by lahar deposits from previous eruptions. Radiocarbon dating is a radiometric dating method that uses the naturally occurring isotope carbon-14 (14C) to determine the age of carbonaceous materials up to about 60,000 years. ... Lahar from a March 1982 eruption of Mount St. ...


Volcanic activity increased throughout April and May. Measurements of sulfur dioxide emission showed a rapid increase from 500 tons per day by May 13 to 5,000 tons/day by May 28. This implied that there was a rising column of fresh magma beneath the volcano. After May 28, the amount of SO2 being emitted decreased substantially, raising fears that the degassing of the magma had been blocked somehow, leading to a pressure build-up in the magma chamber and a high likelihood of explosive eruptions. Sulfur dioxide (or Sulphur dioxide) has the chemical formula SO2. ... Look up ton in Wiktionary, the free dictionary. ... is the 133rd day of the year (134th in leap years) in the Gregorian calendar. ... is the 148th day of the year (149th in leap years) in the Gregorian calendar. ... Magma is molten rock located beneath the surface of the Earth (or any other terrestrial planet), and which often collects in a magma chamber. ... is the 148th day of the year (149th in leap years) in the Gregorian calendar. ... This article is about pressure in the physical sciences. ... A magma chamber is a chamber typically between 1 km and 10 km beneath the surface of the Earth formed as rising magma forms a reservoir if it is unable to rise any further. ...


The first magmatic eruptions occurred on June 3, and the first large explosion on June 7 generated an ash column 7 km (4.5 miles) high. The Philippine Institute of Volcanology and Seismology (PHIVOLCS) led by Raymundo Punongbayan issued a warning indicating the possibility of a major eruption within two weeks. Magma is molten rock located beneath the surface of the Earth (or any other terrestrial planet), and which often collects in a magma chamber. ... is the 154th day of the year (155th in leap years) in the Gregorian calendar. ... is the 158th day of the year (159th in leap years) in the Gregorian calendar. ... Volcanology (also spelled vulcanology) is the study of volcanoes, lava, magma, and related geological phenomena. ... Seismology (from the Greek seismos = earthquake and logos = word) is the scientific study of earthquakes and the propagation of elastic waves through the Earth. ... Dr. Raymundo Santiago Punongbayan (1937-2005) was the former director of Philippine Institute of Volcanology and Seismology (PHIVOLCS). ...


Evacuation

Pinatubo evacuation zones

Given all the signs that a very large eruption was imminent, PHIVOLCS worked in cooperation with the US Geological Survey to convince people in the local area of the severity of the threat. A false warning might have led to cynicism about any later warnings but delaying a warning until an eruption began might lead to thousands of deaths, so the volcanologists were under some pressure to deliver a timely and accurate assessment of the volcanic risk. Download high resolution version (1000x719, 95 KB)Volcanic hazard areas surrounding Mount Pinatubo. ... Download high resolution version (1000x719, 95 KB)Volcanic hazard areas surrounding Mount Pinatubo. ... The United States Geological Survey (USGS) is a scientific agency of the United States government. ... Volcanology (also spelled vulcanology) is the study of volcanos, lava, magma and related geological phenomena. ...


Three successive evacuation zones were defined, the innermost containing everything within 10 km of the volcano's summit, the second extending from 10 to 20 km from the summit, and the third extending from 20 to 40 km from the summit (Clark Air Base and Angeles City were in this zone). The 10 km and 10–20 km zones had a total population of about 40,000, while some 331,000 people lived in the 20–40 km zone. Five stages of volcanic alert were defined, from level 1 (low level seismic disturbances) up to level 5 (major eruption in progress). Daily alerts were issued stating the alert level and associated danger area, and the information was announced in major national and local newspapers, radio and television stations, nongovernmental organizations (NGOs), and directly to the endangered inhabitants. Clark Air Base, 1975. ... Nickname: Motto: Sulong Angeles. ... A non-governmental organization (NGO) is an organization which is not a part of a government. ...


Many of the Aeta who lived on the slopes of the volcano left their villages of their own volition when the first explosions began in April, gathering in a village about 12 km from the summit. They moved to increasingly distant villages as the eruptions escalated, with some Aeta moving up to nine times in the two months preceding the cataclysmic eruption.


The first formal evacuations were ordered from the 10 km zone on 7 April. Evacuation of the 10–20 km zone was ordered when a level 4 alert was issued on 7 June. A level 5 alert triggered evacuation of the 20–40 km zone on 14 June, and in all some 60,000 people had left the area within 30 km of the volcano before 15 June. Most people temporarily relocated to Manila and Quezon City, with some 30,000 using the Amoranto Sports Stadium in Quezon City as a refugee camp. April 7 is the 97th day of the year in the Gregorian calendar (98th in leap years). ... is the 158th day of the year (159th in leap years) in the Gregorian calendar. ... is the 165th day of the year (166th in leap years) in the Gregorian calendar. ... is the 166th day of the year (167th in leap years) in the Gregorian calendar. ... For other meanings of the word, see Manila (disambiguation). ... Nickname: Map of Metro Manila showing the location of Quezon City Coordinates: 14°38 N, 121°2 E Country Philippines Region National Capital Region Districts 1st to 4th districts of Quezon City Barangays 142 Incorporated (town) October 12, 1939 (as Balintawak) Incorporated (city) October 12, 1939 Government  - Mayor Feliciano Sonny... bjhgfshudgfgbfsfas Refugee camp for Rwandans located in what is now the eastern Democratic Republic of Congo following the Rwandan Genocide A camp in Guinea for refugees from Sierra Leone. ...


Eruptions build to a climax

Explosive eruption, early June 1991
Explosive eruption, early June 1991

In early June, tiltmeter measurements had shown that the volcano was inflating, evidently due to growing amounts of magma filling the reservoir beneath the summit. At the same time, seismic activity, previously concentrated at a depth of a few kilometers below a point about 5 km northwest of the summit, shifted to shallow depths just below the summit. On June 7, the first magmatic eruptions took place with the formation of a lava dome at the summit of the volcano. The dome grew substantially over the next five days, reaching a maximum diameter of about 200 m and a height of 40 m. Ahy eruption column at Mt. ... Ahy eruption column at Mt. ... A tiltmeter is an instrument designed to measure very small changes from the horizontal level, either on the ground or in structures. ... is the 158th day of the year (159th in leap years) in the Gregorian calendar. ... One of the Mono Craters, an example of a rhyolite dome. ...


A small explosion at 03:41 on June 12 marked the beginning of a new, more violent phase of the eruption. A few hours later, large explosions lasting about half an hour generated an eruption column which quickly reached heights of over 19 km, and which generated pyroclastic flows extending up to 4 km from the summit in some river valleys. Fourteen hours later, a 15 minute eruption hurled ash to heights of 24 km. Friction in the uprushing ash column generated abundant lightning. is the 163rd day of the year (164th in leap years) in the Gregorian calendar. ... Eruption column over Mount Pinatubo in the Philippines An eruption column consists of hot volcanic ash emitted during an explosive volcanic eruption. ... Pyroclastic flows sweep down the flanks of Mayon Volcano, Philippines, in 1984 A pyroclastic flow (also known as a pyroclastic density current) is a common and devastating result of some volcanic eruptions. ... Fljótsdalur in East Iceland, a rather flat valley In geology, a valley (also called a vale or dale) is a depression with predominant extent in one direction. ... Not to be confused with lighting. ...


A third large eruption began at 08:41 on June 13, after an intense swarm of small earthquakes over the previous two hours. It lasted about five minutes, and the eruption column once again reached 24 km. After three hours of quiet, seismic activity began, growing more and more intense over the next 24 hours, until a three-minute eruption generated a 21 km-high eruption column at 13:09 on June 14. is the 164th day of the year (165th in leap years) in the Gregorian calendar. ... is the 165th day of the year (166th in leap years) in the Gregorian calendar. ...


Tephra fall from these four large eruptions was extensive to the southwest of the volcano. Two hours after the last of these four explosions, a series of eruptions began which lasted for the next 24 hours, and which saw the production of much larger pyroclastic flows and surges which travelled several kilometres down river valleys on the flanks of the volcano.


Dacite was the igneous rock making up the tephra in these eruptions and in the following climactic event. The most abundant phenocryst minerals were hornblende and plagioclase, but an unusual phenocryst mineral was also present—the calcium sulfate, anhydrite. The dacite magma was more oxidized than most magmas, and sulfur-rich nature of the eruption probably was causally related to the redox state. Grey, red, black, altered white/tan, flow-banded pumice dacite Dacite (IPA: ) is an igneous, volcanic rock with a high iron content. ... Volcanic rock in North America Plutonic rock in North America Igneous rocks (etymology from Latin ignis, fire) are rocks formed by solidification of cooled magma (molten rock), with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ... Example of phenocrysts in rhomb porphyry from the Oslo rift area in Norway A phenocryst is a relatively large and usually conspicuous crystal formed in the mass of a porphyritic igneous rock. ... Amphibole (Hornblende) Hornblende is a complex inosilicate series of minerals. ... Lunar Ferroan Anorthosite #60025 (Plagioclase Feldspar). ... Anhydrite is a mineral - anhydrous calcium sulfate, CaSO4. ... Magma is molten rock located beneath the surface of the Earth (or any other terrestrial planet), and which often collects in a magma chamber. ... In geology, a mineal redox buffer is a mineral assemblage which constrains a particular range of oxygen fugacity or sulfur fugacity within a naturally occurring rock composition. ...


The climactic eruption

The eruption cloud shortly before the climactic eruption

June 15 saw the onset of the climactic eruption. Large tremors starting at 13:42 saturated all the seismographs at Clark Air Base, and by 14:30 all had been rendered inoperative, mostly by pyroclastic density currents. Intense atmospheric pressure variation was also recorded. Image File history File links VulcanoPinatuboJune1991. ... Image File history File links VulcanoPinatuboJune1991. ... is the 166th day of the year (167th in leap years) in the Gregorian calendar. ... Eruption can refer to: Volcanic eruption The eruption of teeth through the gum Eruption (band) This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Clark Air Base, 1975. ... Air redirects here. ...


On the same day, Typhoon Yunya struck the island, passing about 75 km (50 miles) north of the volcano. The typhoon rains made direct visual observations of the eruption impossible, but measurements showed that ash was ejected to heights of 34 km by the most violent phase of the eruption, which lasted about three hours. Pyroclastic flows poured from the summit, reaching as far as 16 km away from it. Typhoon rains mixed with the ash deposits caused massive lahars. The 1991 Pacific typhoon season has no official bounds; it ran year-round in 1991, but most tropical cyclones tend to form in the northwestern Pacific Ocean between June and December. ... Compass rose with north highlighted and at top Look up North in Wiktionary, the free dictionary. ... Pyroclastic flows sweep down the flanks of Mayon Volcano, Philippines, in 1984 A pyroclastic flow (also known as a pyroclastic density current) is a common and devastating result of some volcanic eruptions. ... Cyclone Catarina, a rare South Atlantic tropical cyclone viewed from the International Space Station on March 26, 2004. ... A lahar is a mixture of rock, mud, and water that flows down from a volcano (or occasionally other mountains), typically along a river valley. ...


The ash cloud from the volcano covered an area of some 125,000 km² (50,000 mi²), bringing total darkness to much of central Luzon. Almost all of the island received some ashfall, which formed a heavy, rain-saturated snow-like blanket. Tephra fell over most of the South China Sea and ashfall was recorded as far away as Vietnam, Cambodia and Malaysia. Tephra refers to air-fall material produced by a volcanic eruption regardless of composition or fragment size. ... Filipino name Tagalog: Luzon Sea Portuguese name Portuguese: Mar da China Meridional Vietnamese name Vietnamese: The South China Sea is a marginal sea south of China. ...


By about 22:30, nine hours after the onset of the climactic phase, atmospheric pressure waves had decreased to the pre-eruption levels. No seismic records were available at this time, but volcanologists believe 22:30 marked the end of the climactic eruption.


Vast quantities of minerals and metals were brought to the surface. Overall, introduced to the surface environment, was an estimated 800,000 tons of zinc, 600,000 tons of copper, 550,000 tons of chromium, 300,000 tons of nickel, 100,000 tons of lead, 10,000 tons of arsenic, 1000 tons of cadmium, & 800 tons of mercury.[4] General Name, symbol, number zinc, Zn, 30 Chemical series transition metals Group, period, block 12, 4, d Appearance bluish pale gray Standard atomic weight 65. ... For other uses, see Copper (disambiguation). ... REDIRECT [[ Insert text]]EWWWWWWWWWWWWW YO General Name, symbol, number chromium, Cr, 24 Chemical series transition metals Group, period, block 6, 4, d Appearance silvery metallic Standard atomic weight 51. ... For other uses, see Nickel (disambiguation). ... General Name, Symbol, Number lead, Pb, 82 Chemical series Post-transition metals or poor metals Group, Period, Block 14, 6, p Appearance bluish gray Standard atomic weight 207. ... General Name, Symbol, Number arsenic, As, 33 Chemical series metalloids Group, Period, Block 15, 4, p Appearance metallic gray Standard atomic weight 74. ... General Name, Symbol, Number cadmium, Cd, 48 Chemical series transition metals Group, Period, Block 12, 5, d Appearance silvery gray metallic Standard atomic weight 112. ... This article is about the element. ...


Aftermath

Snow-like ashfall caused by heavy rain mixing with ash columns
Snow-like ashfall caused by heavy rain mixing with ash columns

In all, the eruption ejected about ten cubic kilometres (2.5 mile³) of material, making it the largest eruption since that of Novarupta in 1912 and some ten times larger than the 1980 eruption of Mount St. Helens. Ejected material such as tephra fallout and pyroclastic flow deposits are much less dense than magma, and the volume of ejected material was equivalent to about four cubic kilometres (1 mile³) of unerupted material. This colossal eruption had a Volcanic Explosivity Index of 6.[5] The former summit of the volcano was replaced by a caldera 2.5 km wide. The highest point on the caldera rim now stood 1,485 m above sea level, some 260 m lower than the pre-eruption summit. Ashfall from Mount Pinatubos 1991 eruption. ... Ashfall from Mount Pinatubos 1991 eruption. ... Novarupta, meaning new eruption, is a volcano located on the Alaska Peninsula in the Katmai area, about 290 miles southwest of Anchorage. ... The 1980 eruption of Mount St. ... Tephra refers to air-fall material produced by a volcanic eruption regardless of composition or fragment size. ... VEI and ejecta volume correlation The Volcanic Explosivity Index (VEI) was devised by Chris Newhall of the U.S. Geological Survey and Steve Self at the University of Hawaii in 1982 to provide a relative measure of the explosiveness of volcanic eruptions. ... Satellite image of Santorini. ...


About 300 people were killed by the eruption, mostly by roofs collapsing under the weight of accumulated wet ash, a hazard that was greatly exacerbated by the simultaneous arrival of Typhoon Yunya. The evacuation in the days preceding the eruption certainly saved tens of thousands of lives, and has been hailed as a great success for volcanology and eruption prediction.

Before and after the eruption: a river valley filled in by pyroclastic flow deposits
Before and after the eruption: a river valley filled in by pyroclastic flow deposits

However, since the eruption, each rainy season has brought further lahars, which have caused the displacement of thousands of people. Hundreds have died from poor sanitation in relocation camps. Agriculture in the region also suffered badly from the effects of the eruption, with hundreds of square kilometres of formerly arable land being rendered infertile, destroying the livelihoods of thousands of farmers. River valley filled in by pyroclastic flows from 1991 eruption of Mt. ... River valley filled in by pyroclastic flows from 1991 eruption of Mt. ... Pyroclastic flows sweep down the flanks of Mayon Volcano, Philippines, in 1984 A pyroclastic flow (also known as a pyroclastic density current) is a common and devastating result of some volcanic eruptions. ... The wet season is a term commonly used when describing the weather in the tropics. ... A lahar is a mixture of rock, mud, and water that flows down from a volcano (or occasionally other mountains), typically along a river valley. ... E. Coli bacteria under magnification Sanitation is the hygienic disposal or recycling of waste, as well as the policy and practice of protecting health through hygienic measures. ... In geography, arable land is a form of agricultural land use, meaning land that can be (and is) used for growing crops. ...


The United States maintained two large military bases in the region; U.S. Naval Base Subic Bay was 75 km (50 mi.) to the southwest, while Clark Air Base was less than 25 km (16 mi.) to the east of the volcano's summit. Both were abandoned after being severely damaged by the eruption. U.S. Naval Base Subic Bay was a major ship-repair, supply, and rest and recreation facility of the United States Navy located in Zambales, Philippines. ... Clark Air Base, 1975. ...


Although the 1991 eruption was one of the largest and most violent of the 20th century, it was weaker than any of the historical eruptions uncovered by geologists. There is some evidence that eruptions at Pinatubo are getting weaker over time, but this is by no means conclusively established.


Local economic and social effects

Aircraft hangars at Clark Air Base destroyed by ashfall
Aircraft hangars at Clark Air Base destroyed by ashfall

The eruption of Pinatubo severely hampered the economic development of the surrounding areas. Extensive damage to buildings and infrastructure cost billions of pesos to repair, and further costs were incurred in constructing dikes and dams to control the post-eruption lahars. Hangars at Clark Air Base destroyed by ashfall from Pinatubo eruption. ... Hangars at Clark Air Base destroyed by ashfall from Pinatubo eruption. ... Clark Air Base, 1975. ... Economic development is the development of economic wealth of countries or regions for the well-being of their inhabitants. ... ISO 4217 Code PHP User(s) Philippines Inflation 2. ... Afsluitdijk, a 32 km dike in the Netherlands. ... This article is about structures for water impoundment. ...


In total, 364 communities and 2.1 million people were affected by the eruption, with livelihoods and houses being damaged or destroyed. More than 8,000 houses were completely destroyed, and a further 73,000 were damaged. In addition to the severe damage sustained by these communities, roads and communications were damaged or destroyed by pyroclastic flows and lahars throughout the areas surrounding the volcanoes. The estimated cost of repairing the damage to infrastructure was 3.8 billion pesos.


Many reforestation projects were destroyed in the eruption, with a total area of 150 square kilometres (37,000 acres) valued at 125 million pesos destroyed. Agriculture was heavily disrupted, with 800 square kilometres (200,000 acres) of rice-growing farmland destroyed, and almost 800,000 head of livestock and poultry killed. The cost to agriculture of eruption effects was estimated to be 1.5 billion pesos. Biodiversity on a 15-year-old reforested plot of land. ... An acre is the name of a unit of area in a number of different systems, including Imperial units and United States customary units. ... For other uses, see Rice (disambiguation). ... Ducks amongst other poultry The Poultry-dealer, after Cesare Vecellio Poultry is the category of domesticated birds kept for meat, eggs, and feathers. ...


Damage to healthcare facilities, and the spread of illnesses in relocation facilities, led to soaring death rates in the months following the eruption. Education for thousands of children was seriously disrupted by the destruction of schools in the eruption. The gross regional domestic product of the Pinatubo area accounted for about 10% of the total Philippine gross domestic product. The GRDP had been growing at 5% annually before the eruption, but fell by more than 3% from 1990 to 1991. Health care or healthcare is one of the worlds largest and fastest growing professions. ... Students in Rome, Italy. ... This article is about GDP in the context of economics. ...


Global environmental effects

Space Shuttle (Mission STS-43) photograph of the Earth over South America taken on August 8, 1991, showing double layer of Pinatubo aerosol cloud (dark streaks) above high cumulonimbus tops
Space Shuttle (Mission STS-43) photograph of the Earth over South America taken on August 8, 1991, showing double layer of Pinatubo aerosol cloud (dark streaks) above high cumulonimbus tops

The powerful eruption of such an enormous volume of lava and ash injected significant quantities of aerosols and dust into the stratosphere. Sulfur dioxide oxidised in the atmosphere to produce a haze of sulfuric acid droplets, which gradually spread throughout the stratosphere over the year following the eruption. The injection of aerosols into the stratosphere is thought to have been the largest since the eruption of Krakatoa in 1883, with a total mass of SO2 of about 17 million tons being injected—the largest volume ever recorded by modern instruments (see chart and figure). Space Shuttle (Mission STS 43) photograph of the Earth over South America taken on August 8, 1991, showing double layer of Pinatubo aerosol cloud (dark streaks) above high cumulonimbus tops. ... Space Shuttle (Mission STS 43) photograph of the Earth over South America taken on August 8, 1991, showing double layer of Pinatubo aerosol cloud (dark streaks) above high cumulonimbus tops. ... STS-43 was a NASA space shuttle mission in 1991. ... South America South America is a continent crossed by the equator, with most of its area in the Southern Hemisphere. ... is the 220th day of the year (221st in leap years) in the Gregorian calendar. ... Year 1991 (MCMXCI) was a common year starting on Tuesday (link will display the 1991 Gregorian calendar). ... Particulates, alternatively referred to as particulate matter (PM), aerosols or fine particles, are tiny particles of solid or liquid suspended in a gas. ... Look up dust in Wiktionary, the free dictionary. ... Atmosphere diagram showing stratosphere. ... Sulfur dioxide (or Sulphur dioxide) has the chemical formula SO2. ... R-phrases S-phrases , , , Flash point Non-flammable Related Compounds Related strong acids Selenic acid Hydrochloric acid Nitric acid Related compounds Hydrogen sulfide Sulfurous acid Peroxymonosulfuric acid Sulfur trioxide Oleum Supplementary data page Structure and properties n, εr, etc. ... For the 1969 film about the Krakatoa eruption, see Krakatoa, East of Java. ... Download high resolution version (839x500, 165 KB)TOMS chart of sulfur dioxide emissions from volcanoes. ... TOMS sulfur dioxide from the June 15, 1991 eruption of Mount Pinatubo, Philippines. ...


This very large stratospheric injection resulted in a reduction in the normal amount of sunlight reaching the earth's surface by roughly 10% (see figure). This led to a decrease in northern hemisphere average temperatures of 0.5–0.6 °C (0.9–1.1 °F), and a global fall of about 0.4 °C (0.7 °F). At the same time, the temperature in the stratosphere rose to several degrees higher than normal, due to absorption of radiation by the aerosols. The stratospheric cloud from the eruption persisted in the atmosphere for three years after the eruption. Prism splitting light High Resolution Solar Spectrum Sunlight in the broad sense is the total spectrum of the electromagnetic radiation given off by the Sun. ... Mauna Loa Observatory atmospheric transmission. ... Northern hemisphere highlighted in yellow. ... For other uses, see Celsius (disambiguation). ...

Satellite measurements of ash and aerosol emissions from Mount Pinatubo.

The eruption had a significant effect on ozone levels in the atmosphere, causing a large increase in the destruction rate of ozone. Ozone levels at mid-latitudes reached their lowest recorded levels, while in the southern hemisphere winter of 1992, the ozone hole over Antarctica reached its largest ever size until then, with the fastest recorded ozone depletion rates. The eruption of Mount Hudson in Chile in August 1991 also contributed to southern hemisphere ozone destruction, with measurements showing a sharp decrease in ozone levels at the tropopause when the aerosol clouds from Pinatubo and Hudson arrived. TOMS ash and aerosol from the June 15, 1991 eruption of Mount Pinatubo, Philippines. ... TOMS ash and aerosol from the June 15, 1991 eruption of Mount Pinatubo, Philippines. ... Particulates, alternatively referred to as particulate matter (PM), aerosols or fine particles, are tiny particles of solid or liquid suspended in a gas. ... For other uses, see Ozone (disambiguation). ... southern hemisphere highlighted in yellow (Antarctica not depicted). ... Image of the largest antarctic ozone hole ever recorded in September 2000. ... Mount Hudson is a stratovolcano in Chile, and the site of one of the largest eruptions in the twentieth century. ... The tropopause is between the troposphere and the stratosphere. ...


Another noticeable effect of the dust in the atmosphere was the appearance of lunar eclipses. Normally even at mid-eclipse, the moon is still visible although much dimmed, but in the year following the Pinatubo eruption, the moon was hardly visible at all during eclipses, due to much greater absorption of sunlight by dust in the atmosphere. Time lapse movie of the 3 March 2007 lunar eclipse A lunar eclipse occurs whenever the Moon passes through some portion of the Earth’s shadow. ...


The area since 1991

Thick ash deposits from Pinatubo are evident in this 1992 photo from the Space Shuttle Atlantis
Thick ash deposits from Pinatubo are evident in this 1992 photo from the Space Shuttle Atlantis

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. Activity then remained low until July 1992, when a new lava dome began to grow in the caldera. Download high resolution version (639x640, 405 KB)Mount Pinatubo as seen from space shuttle Atlantis in 1992. ... Download high resolution version (639x640, 405 KB)Mount Pinatubo as seen from space shuttle Atlantis in 1992. ... Space Shuttle Orbiter Atlantis (NASA Orbiter Vehicle Designation: OV-104) is one of the fleet of space shuttles belonging to the U.S. National Aeronautics and Space Administration (NASA). ... is the 166th day of the year (167th in leap years) in the Gregorian calendar. ... Year 1991 (MCMXCI) was a common year starting on Tuesday (link will display the 1991 Gregorian calendar). ... One of the Mono Craters, an example of a rhyolite dome. ... Satellite image of Santorini. ...


This dome appeared to be composed of fresh lava from the deep magma reservoir beneath the volcano, rather than material 'left over' in a shallow reservoir from the 1991 eruption. Thus, volcanologists suspected that further violent eruptions could be possible, and some areas were once again evacuated. However, the eruption did not become violent, perhaps due to outgassing from the deep reservoir reducing the explosivity of the lava reaching the surface. Since 1992, the volcano has been dormant. Magma is molten rock located beneath the surface of the Earth (or any other terrestrial planet), and which often collects in a magma chamber. ...


The Aeta people were the hardest hit by the eruption. The total destruction of many villages by pyroclasts and lahar deposits meant that many Aeta were unable to return to their former way of life. After the areas surrounding the volcano were declared safe to return to, those whose villages had not been destroyed moved back, but most people moved instead to government-organized resettlement areas. Conditions on these were poor, with each family receiving only small plots of land, which were not ideal for growing crops. Many Aeta found casual labor working for lowland farmers, and overall Aeta society became much more fragmented, and reliant on and integrated with lowland culture. For other uses, see Farmer (disambiguation). ...


After eruptions ended, a crater lake formed in the 1991 caldera, with the 1992 lava dome forming an island. At first, the lake was small, hot and highly acidic, with a minimum pH of 2 and a temperature of about 40 °C. Abundant rainfall cooled and diluted the lake, lowering the temperature to 26 °C and raising the pH to 5.5 by 2003. A crater lake that simply goes by the name Crater Lake, in Oregon, USA Heaven Lake (Chonji / Tianchi), North Korea / China Cuicocha, Ecuador Lake formed after 1991 eruption of Mount Pinatubo, Philippines Mount Katmai, Alaska, USA Mount Wenchi crater lake, Ethiopia Nemrut, Turkey Volcán Irazú, Costa Rica This page... For other uses, see Acid (disambiguation). ... For other uses, see PH (disambiguation). ...


The lake increased in depth by about 1 metre per month on average, 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. 9,000 people were once again evacuated from surrounding areas in case a large flood was accidentally triggered. Workers cut a 5 m notch in the crater rim, and successfully drained about a quarter of the lake's volume. Flooding in Amphoe Sena, Ayutthaya Province, Thailand. ...


Ecotourism

As of 2007, Mt. Pinatubo is a popular tourist destination in Central Luzon. Tour operators offer a whole-day package which includes a 4x4 jeep ride that starts off at Capas, Tarlac, taking tourists across the barren plains. A 2-3 hour trek then commences on a trail that leads to the crater lake. There, facilities include a viewdeck, cottages, and kayaks. Swimming in the lake is allowed although it is restricted to the proximal banks.[6] Capas is a 1st class municipality in the province of Tarlac, Philippines. ...


Related images

Wikimedia Commons has media related to:
Mount Pinatubo

Image File history File links Commons-logo. ...

Notes

  1. ^ Smithsonian Institution Global Volcanism Program: Mount Pinatubo
  2. ^ a b The Cataclysmic 1991 Eruption of Mount Pinatubo, Philippines, <http://pubs.usgs.gov/fs/1997/fs113-97/>. Retrieved on 9 April 2007
  3. ^ Global Vulcanism Program: Pinatubo — Eruptive History, Smithsonian Institution, <http://www.volcano.si.edu/world/volcano.cfm?vnum=0703-083&volpage=erupt>. Retrieved on 22 January 2008
  4. ^ Garret, R.G. (2000) Natural sources of metals in the environment. Human and Ecological Risk Assessment., (6), 945–963.
  5. ^ Mt. Pinatubo, Luzon, Philippines, National Geophysical Data Center (U.S. NOAA), <http://www.ngdc.noaa.gov/seg/hazard/stratoguide/pinfact.html>. Retrieved on 2 December 2007
  6. ^ PinoyMountaineer: Mount Pinatubo, 24 August 2007, <http://www.pinoymountaineer.com/2007/08/mt-pinatubo-960.html>. Retrieved on 26 October 2007

References

  • Decker, R. and Decker, B. (1997) Volcanoes, 3rd edition, WH Freeman, New York.
  • Hiromu Shimizu (2002), Struggling for Existence after the Pinatubo Eruption 1991: Catastrophe, Suffering and Rebirth of Ayta Communities. Paper presented inter-congress of the International Union of Anthropological and Ethnological Sciences, Tokyo, Japan.
  • McCormick, M. Patrick et al. (1995). "Atmospheric effects of the Mt Pinatubo eruption". Nature 373: 399–404. doi:10.1038/373399a0.
  • Newhall, C. and Punongbayan, R., eds. (1997) Fire and Mud: Eruptions and Lahars of Mount Pinatubo, Philippines. ISBN 0-295-97585-7.
  • Scaillet, B. and Evans, B. W. (1999) The 15 June 1991 Eruption of Mount Pinatubo. I. Phase Equilibria and Pre-eruption P–T–fO2–fH2O Conditions of the Dacite Magma. Journal of Petrology, v. 40, 381–411.
  • Stimac J.A., Goff F., Counce D., Larocque A.C.L., Hilton D.R. (2003), The crater lake and hydrothermal system of Mount Pinatubo, Philippines: evolution in the decade after eruption, Bulletin of Volcanology, v. 66, p. 149–167
  • Wiesner, M.G., Wetzel, A. Catane, S.G., Listanco, E.L. and 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. Bulletin of Volcanology, v. 66, 226–242.
  • Dhot, S. Mt Pinatubo Safety.

Nature is a prominent scientific journal, first published on 4 November 1869. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... Dr. Raymundo Santiago Punongbayan (1937-2005) was the former director of Philippine Institute of Volcanology and Seismology (PHIVOLCS). ...

External links

Image File history File links Mount_Pinatubo. ... Image File history File links Sound-icon. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 31st day of the year in the Gregorian calendar. ...


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