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74-666: The eruption of Mount Pinatubo in 1991 led to the United States abandoning their base in Subic. The Subic International Raceway was established at the site of the former Naval Air Station Cubi Point 's refuelling area for fighter jets. Former Filipino race car driver Pocholo Ramirez with the help of other figures in Philippine racing including Mandy Eduque, Mike Potenciano, Macky Carapiet, Louis Camus, Freddy Masigan set up Sports Values Incorporated (SVI) so that they could convert

148-420: A dichromate solution, turning the solution from orange to green (Cr (aq)). It can also reduce ferric ions to ferrous. Sulfur dioxide can react with certain 1,3- dienes in a cheletropic reaction to form cyclic sulfones . This reaction is exploited on an industrial scale for the synthesis of sulfolane , which is an important solvent in the petrochemical industry . Sulfur dioxide can bind to metal ions as

222-399: A ligand to form metal sulfur dioxide complexes , typically where the transition metal is in oxidation state 0 or +1. Many different bonding modes (geometries) are recognized, but in most cases, the ligand is monodentate, attached to the metal through sulfur, which can be either planar and pyramidal η . As a η -SO 2 (S-bonded planar) ligand sulfur dioxide functions as a Lewis base using

296-558: A high heat of evaporation , sulfur dioxide is a candidate material for refrigerants. Before the development of chlorofluorocarbons , sulfur dioxide was used as a refrigerant in home refrigerators . Sulfur dioxide content in naturally-released geothermal gasses is measured by the Icelandic Meteorological Office as an indicator of possible volcanic activity. In the United States, the Center for Science in

370-420: 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

444-470: A natural satellite of Jupiter , is 90% sulfur dioxide and trace amounts are thought to also exist in the atmosphere of Jupiter . The James Webb Space Telescope has observed the presence of sulfur dioxide on the exoplanet WASP-39b , where it is formed through photochemistry in the planet's atmosphere. As an ice, it is thought to exist in abundance on the Galilean moons —as subliming ice or frost on

518-681: A negative inotropic effect on cardiac output function, thus effectively lowering blood pressure and myocardial oxygen consumption. The vasodilating and bronchodilating effects of sulfur dioxide are mediated via ATP-dependent calcium channels and L-type ("dihydropyridine") calcium channels. Endogenous sulfur dioxide is also a potent antiinflammatory, antioxidant and cytoprotective agent. It lowers blood pressure and slows hypertensive remodeling of blood vessels, especially thickening of their intima. It also regulates lipid metabolism. Endogenous sulfur dioxide also diminishes myocardial damage, caused by isoproterenol adrenergic hyperstimulation, and strengthens

592-462: A preservative for dried apricots, dried figs, and other dried fruits, owing to its antimicrobial properties and ability to prevent oxidation , and is called E 220 when used in this way in Europe. As a preservative, it maintains the colorful appearance of the fruit and prevents rotting . Historically, molasses was "sulfured" as a preservative and also to lighten its color. Treatment of dried fruit

666-619: A total length of 2.900 km (1.802 mi) with 15 turns. It had long straights that allowed for a long and short circuit setup. The fastest official race lap records at the Subic International Raceway are listed as: Mount Pinatubo Events/Artifacts (north to south) Events/Artifacts Artifacts Mount Pinatubo is an active stratovolcano in the Zambales Mountains in Luzon in

740-460: A tourist attraction with the preferred route through Barangay Santa Juliana in Capas, Tarlac . Sulfur dioxide Selenium dioxide Tellurium dioxide Polonium dioxide Sulfur dioxide ( IUPAC -recommended spelling) or sulphur dioxide (traditional Commonwealth English ) is the chemical compound with the formula S O 2 . It is a colorless gas with a pungent smell that

814-459: 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 fluids near the surface, rather than a magmatic eruption. The word pinatubo could mean "fertile place where one can make crops grow", or could mean "made to grow", in Sambal and Tagalog , which may suggest

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888-423: A winery due to the risk of cork taint , a mixture of SO 2 , water, and citric acid is commonly used to clean and sanitize equipment. Ozone (O 3 ) is now used extensively for sanitizing in wineries due to its efficacy, and because it does not affect the wine or most equipment. Sulfur dioxide is also a good reductant . In the presence of water, sulfur dioxide is able to decolorize substances. Specifically, it

962-484: Is exothermic , and the combustion produces temperatures of 1,000–1,600 °C (1,830–2,910 °F). The significant amount of heat produced is recovered by steam generation that can subsequently be converted to electricity. The combustion of hydrogen sulfide and organosulfur compounds proceeds similarly. For example: The roasting of sulfide ores such as pyrite , sphalerite , and cinnabar (mercury sulfide) also releases SO 2 : A combination of these reactions

1036-399: Is a bent molecule with C 2v symmetry point group . A valence bond theory approach considering just s and p orbitals would describe the bonding in terms of resonance between two resonance structures. The sulfur–oxygen bond has a bond order of 1.5. There is support for this simple approach that does not invoke d orbital participation. In terms of electron-counting formalism,

1110-401: Is a key component of the planet's global atmospheric sulfur cycle and contributes to global warming . It has been implicated as a key agent in the warming of early Mars , with estimates of concentrations in the lower atmosphere as high as 100 ppm, though it only exists in trace amounts. On both Venus and Mars, as on Earth, its primary source is thought to be volcanic. The atmosphere of Io ,

1184-402: Is a useful reducing bleach for papers and delicate materials such as clothes. This bleaching effect normally does not last very long. Oxygen in the atmosphere reoxidizes the reduced dyes, restoring the color. In municipal wastewater treatment, sulfur dioxide is used to treat chlorinated wastewater prior to release. Sulfur dioxide reduces free and combined chlorine to chloride . Sulfur dioxide

1258-410: Is an intermediate in the production of sulfuric acid, being converted to sulfur trioxide , and then to oleum , which is made into sulfuric acid. Sulfur dioxide for this purpose is made when sulfur combines with oxygen. The method of converting sulfur dioxide to sulfuric acid is called the contact process . Several million tons are produced annually for this purpose. Sulfur dioxide is sometimes used as

1332-484: Is fairly soluble in water, and by both IR and Raman spectroscopy; the hypothetical sulfurous acid , H 2 SO 3 , is not present to any extent. However, such solutions do show spectra of the hydrogen sulfite ion, HSO 3 , by reaction with water, and it is in fact the actual reducing agent present: In the beginning of the 20th century sulfur dioxide was used in Buenos Aires as a fumigant to kill rats that carried

1406-431: Is often used as a low-temperature solvent/diluent for superacids like magic acid (FSO 3 H/SbF 5 ), allowing for highly reactive species like tert -butyl cation to be observed spectroscopically at low temperature (though tertiary carbocations do react with SO 2 above about −30 °C, and even less reactive solvents like SO 2 ClF must be used at these higher temperatures). Being easily condensed and possessing

1480-586: Is part of a chain of volcanoes which lie along the western side of the island of Luzon called the Zambales Mountains . Pinatubo belongs to the Cabusilan sub-range of the Zambales Mountains , which consists of Mount Cuadrado , Mount Negron , Mount Mataba and Mount Pinatubo. They are subduction volcanoes, formed by the Eurasian plate sliding under the Philippine Mobile Belt along

1554-748: Is produced biologically as an intermediate in both sulfate-reducing organisms and in sulfur-oxidizing bacteria, as well. The role of sulfur dioxide in mammalian biology is not yet well understood. Sulfur dioxide blocks nerve signals from the pulmonary stretch receptors and abolishes the Hering–Breuer inflation reflex . It is considered that endogenous sulfur dioxide plays a significant physiological role in regulating cardiac and blood vessel function, and aberrant or deficient sulfur dioxide metabolism can contribute to several different cardiovascular diseases, such as arterial hypertension , atherosclerosis , pulmonary arterial hypertension , and stenocardia . It

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1628-433: Is produced by the combustion of elemental sulfur . Some sulfur dioxide is also produced by roasting pyrite and other sulfide ores in air. Sulfur dioxide is the product of the burning of sulfur or of burning materials that contain sulfur: To aid combustion, liquified sulfur (140–150 °C (284–302 °F) is sprayed through an atomizing nozzle to generate fine drops of sulfur with a large surface area. The reaction

1702-516: Is responsible for the largest source of sulfur dioxide, volcanic eruptions. These events can release millions of tons of SO 2 . Sulfur dioxide can also be a byproduct in the manufacture of calcium silicate cement; CaSO 4 is heated with coke and sand in this process: Until the 1970s commercial quantities of sulfuric acid and cement were produced by this process in Whitehaven , England. Upon being mixed with shale or marl , and roasted,

1776-424: Is responsible for the odor of burnt matches. It is released naturally by volcanic activity and is produced as a by-product of copper extraction and the burning of sulfur - bearing fossil fuels. Sulfur dioxide is somewhat toxic to humans, although only when inhaled in relatively large quantities for a period of several minutes or more. It was known to medieval alchemists as "volatile spirit of sulfur". SO 2

1850-602: Is still an important compound in winemaking, and is measured in parts per million ( ppm ) in wine. It is present even in so-called unsulfurated wine at concentrations of up to 10 mg/L. It serves as an antibiotic and antioxidant , protecting wine from spoilage by bacteria and oxidation – a phenomenon that leads to the browning of the wine and a loss of cultivar specific flavors. Its antimicrobial action also helps minimize volatile acidity. Wines containing sulfur dioxide are typically labeled with "containing sulfites ". Sulfur dioxide exists in wine in free and bound forms, and

1924-429: Is the active form, while at higher pH more SO 2 is found in the inactive sulfite and bisulfite forms. The molecular SO 2 is active as an antimicrobial and antioxidant, and this is also the form which may be perceived as a pungent odor at high levels. Wines with total SO 2 concentrations below 10 ppm do not require "contains sulfites" on the label by US and EU laws. The upper limit of total SO 2 allowed in wine in

1998-410: Is used in the production of sulfuric acid. Sulfur dioxide dissolves in water to give " sulfurous acid ", which cannot be isolated and is instead an acidic solution of bisulfite , and possibly sulfite , ions. Sulfur dioxide is one of the few common acidic yet reducing gases. It turns moist litmus pink (being acidic), then white (due to its bleaching effect). It may be identified by bubbling it through

2072-614: The Manila Trench to the west. Mount Pinatubo and the other volcanoes on this volcanic belt arise due to magmatic occlusion from this subduction plate boundary. Pinatubo is flanked on the west by the Zambales Ophiolite Complex, which is an easterly-dipping section of Eocene oceanic crust uplifted during the late Oligocene . The Tarlac Formation north, east and southeast of Pinatubo consists of marine, nonmarine and volcanoclastic sediments formed in

2146-495: The Philippines . Located on the tripoint of Zambales , Tarlac and Pampanga provinces, most people were unaware of its eruptive history before the pre-eruption volcanic activity in early 1991. Dense forests , which supported a population of several thousand indigenous Aetas , heavily eroded and obscured Pinatubo. Pinatubo is known for its VEI -6 eruption on June 15, 1991 , the second-largest terrestrial eruption of

2220-663: The Yersinia pestis bacterium, which causes bubonic plague. The application was successful, and the application of this method was extended to other areas in South America. In Buenos Aires, where these apparatuses were known as Sulfurozador , but later also in Rio de Janeiro, New Orleans and San Francisco, the sulfur dioxide treatment machines were brought into the streets to enable extensive disinfection campaigns, with effective results. Sulfur dioxide or its conjugate base bisulfite

2294-420: The caldera . Volcanologists suspected that further violent eruptions could be possible, and some areas were evacuated. However, the eruption was only minor. The last eruption of Mount Pinatubo took place in 1993. The 1991 caldera afterwards filled with water from annual monsoon rains and a crater lake , Lake Pinatubo , was formed. In 1992, a growing lava dome formed an island, which was eventually submerged by

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2368-617: The proliferation rate of endothelial smooth muscle cells in blood vessels, via lowering the MAPK activity and activating adenylyl cyclase and protein kinase A . Smooth muscle cell proliferation is one of important mechanisms of hypertensive remodeling of blood vessels and their stenosis , so it is an important pathogenetic mechanism in arterial hypertension and atherosclerosis. Endogenous sulfur dioxide in low concentrations causes endothelium-dependent vasodilation . In higher concentrations it causes endothelium-independent vasodilation and has

2442-723: The 20th century after the 1912 eruption of Novarupta in Alaska . The eruption coincided with Typhoon Yunya making landfall in the Philippines, which brought a dangerous mix of ash and rain to nearby towns and cities. Early predictions led to the evacuation of tens of thousands of people, saving many lives. The eruption severely damaged surrounding areas with pyroclastic surges , pyroclastic falls , and later, flooding lahars caused by rainwater re-mobilizing volcanic deposits. This destruction affected infrastructure and altered river systems for years. Minor dome -forming eruptions inside

2516-847: The Asian Formula 2000 have all raced here, and it also hosted the Asian 1600 Touring Car Invitational Cup, the Philippine Japan Invitational Historic Car Races and the Hong Kong Classic Car Races. The major visitor to the track was the Asian F3 Series . The racing circuit closed in July 2010 with the three-day "The Last Lap" held as the last racing event. At the time of its closure, the Subic International Raceway had

2590-541: The Buag and present eruptive periods is among the shorter repose periods recognized in its geologic history. 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 19 kilometres (62,000 ft) and which generated large pyroclastic surges extending up to four kilometres (2.5 mi) from

2664-640: The Philippines. The approved and declared net land area of 7,440.1 ha (18,385 acres) covers the barangays of Mawakat and Nabuklod in Floridablanca, Pampanga , plus a portion of San Marcelino, Zambales , and a portion of Barangay Batiawan in Subic, Zambales . On January 14, 2010, some 7,000 Aeta families from Zambales were officially granted the Certificate of Ancestral Domain Title (CADT) covering

2738-504: The US is 350 ppm; in the EU it is 160 ppm for red wines and 210 ppm for white and rosé wines. In low concentrations, SO 2 is mostly undetectable in wine, but at free SO 2 concentrations over 50 ppm, SO 2 becomes evident in the smell and taste of wine. SO 2 is also a very important compound in winery sanitation. Wineries and equipment must be kept clean, and because bleach cannot be used in

2812-562: The United States. The U.S. Naval Base Subic Bay was 37 kilometers (23 mi) south of Pinatubo, and the extent of Clark Air Base was just 14 kilometers (8.7 mi) east of the volcano's summit. The volcano is near to about 6 million people. Even before the 1991 eruption, Mount Pinatubo had little topographic prominence : it was 1,745 m (5,725 ft) above sea level, only about 600 m (2,000 ft) above nearby plains , and only about 200 m (660 ft) higher than surrounding peaks, which largely obscured it from view. It

2886-569: The Zambales side of Pinatubo which includes the summit and Lake Pinatubo, officially becoming their lutan tua (ancestral land). The ancestral domain title covers 15,984 ha (39,500 acres) and includes the villages of Burgos, Villar, Moraza and Belbel in Botolan and portions of the towns of Cabangan , San Felipe and San Marcelino . Ancestral domain titles are awarded to a certain community or indigenous group who have occupied or possessed

2960-618: The abode of Apo Namalyari ("The lord of happenings/events"), the pagan deity of the Sambal , Aetas and Kapampangans living on the Zambales range. It was said to comprise the whole mountain range until Sinukuan of Mount Arayat (the god of the Kapampangans) became a strong rival of Namalyari. Their fight, which took place over the center plains, shattered the mountain into smaller bodies and Mount Arayat lost its center peak. Other versions have it that Pinatubo's peak shattered because of Namalyari's immense fury in an attempt to teach humans

3034-510: The action of aqueous base on sulfur dioxide: Sulfur dioxide is a mild but useful reducing agent . It is oxidized by halogens to give the sulfuryl halides, such as sulfuryl chloride : Sulfur dioxide is the oxidising agent in the Claus process , which is conducted on a large scale in oil refineries . Here, sulfur dioxide is reduced by hydrogen sulfide to give elemental sulfur: The sequential oxidation of sulfur dioxide followed by its hydration

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3108-461: The caldera continued from 1992 to 1993. The 1991 eruption had worldwide effects. It released roughly 10  billion tonnes (1.1 × 10 short tons ) or 10 km (2.4 cu mi) of magma, bringing large amounts of minerals and toxic metals to the surface. It also released 20 million tonnes (22 million short tons) of SO 2 . It ejected more particulate into the stratosphere than any eruption since Krakatoa in 1883. In

3182-421: The combinations are referred to as total SO 2 . Binding, for instance to the carbonyl group of acetaldehyde , varies with the wine in question. The free form exists in equilibrium between molecular SO 2 (as a dissolved gas) and bisulfite ion, which is in turn in equilibrium with sulfite ion. These equilibria depend on the pH of the wine. Lower pH shifts the equilibrium towards molecular (gaseous) SO 2 , which

3256-671: The crater collapsed, slowly releasing approximately 160 million cubic meters (5.7 × 10 ^  cu ft) of water and sediment 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

3330-561: The existing paved roads and taxiways into a racing circuit. The Subic International Raceway was opened in 1994 with SVI initially only able to secure a three-month lease for the racing circuit's site. The lease was extended multiple times during the racing circuit's 17-year operation. It gained approval from the Fédération Internationale de Motocyclisme (FIM) in 1997 and secured a grade four Fédération Internationale de l'Automobile (FIA) license in 1998 which certified

3404-400: The following months, aerosols formed a global layer of sulfuric acid haze. Global temperatures dropped by about 0.5 °C (0.9 °F) in the years 1991–1993, and ozone depletion temporarily increased significantly. The volcano is about 87 kilometers (54 mi) northwest of Manila , the capital of the Philippines. Near Mount Pinatubo are former military bases that were maintained by

3478-420: The lake. Initially, the lake was hot and highly acidic , with a minimum pH of 2 and a temperature of about 40 °C (104 °F). Subsequent rainfall cooled and diluted the lake, lowering the temperature to 26 °C (79 °F) and raising the pH to 5.5 by 2003. The lake deepened by about 1 meter (3.3 ft) per month on average, eventually submerging the lava dome, until September 2001, when fears that

3552-587: 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. Having the land title will protect them from others – including foreigners – exploiting their land without compensation to and consent from the indigenous tribes. In the past, the Aetas had to contend with mining companies, loggers, and recently, tourist companies who earn from Mount Pinatubo but do not compensate

3626-486: The late Miocene and Pliocene . The most recent study of Mount Pinatubo before the activities of 1991 was the overall geological study in 1983 and 1984 made by F. G. Delfin for the Philippine National Oil Company as part of the surface investigations of the area before exploratory drilling and well testing for geothermal energy sources in 1988 to 1990. He recognized two life histories of

3700-567: The local tribes. Long before Mount Pinatubo became famous for its cataclysmic eruption, Philippine president Ramon Magsaysay , a native of Zambales, named his C-47 presidential plane Mt. Pinatubo . The plane crashed into Mount Manunggal in Cebu province in 1957, killing the president and twenty-four others on board. The shape of Mount Pinatubo's caldera inspired New Clark City Athletics Stadium in Capas , Tarlac . The caldera formed and Lake Pinatubo has, since June 15, 1991, become

3774-420: The lone pair on S. SO 2 functions as a Lewis acids in its η -SO 2 (S-bonded pyramidal) bonding mode with metals and in its 1:1 adducts with Lewis bases such as dimethylacetamide and trimethyl amine . When bonding to Lewis bases the acid parameters of SO 2 are E A = 0.51 and E A = 1.56. The overarching, dominant use of sulfur dioxide is in the production of sulfuric acid . Sulfur dioxide

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3848-467: 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 Philippine National Oil Company 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

3922-423: The mountain, which he classified as "ancestral" and "modern" Pinatubo. 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 and dacite stratovolcano whose eruptive activity

3996-421: The myocardial antioxidant defense reserve. Sulfur dioxide is a versatile inert solvent widely used for dissolving highly oxidizing salts. It is also used occasionally as a source of the sulfonyl group in organic synthesis . Treatment of aryl diazonium salts with sulfur dioxide and cuprous chloride yields the corresponding aryl sulfonyl chloride, for example: As a result of its very low Lewis basicity , it

4070-479: The nearby peaks are the remnants of ancestral Pinatubo, left behind when the softer parts of the old mountain slopes were eroded by weathering . Ancestral Pinatubo is a somma volcano with modern Pinatubo as the new cone. Mount Dorst, to the east, is part of the dip slope of the ancestral Pinatubo. Several mountains near modern Pinatubo are old satellite vents of ancestral Pinatubo, forming volcanic plugs and lava domes. These satellite vents were probably active around

4144-525: The north flank of the volcano. Thousands of small earthquakes occurred beneath Pinatubo through April, May and early June and many thousand of tons of noxious sulfur dioxide gas were also emitted by the volcano. 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

4218-661: The prospect 13 months before the April 2, 1991, explosions. After being driven away by the 1991 eruption of Mount Pinatubo, in May 2009 some 454 Aeta families in Pampanga were given the first clean ancestral land ownership on Mount Pinatubo with the Certificate of Ancestral Domain Title (CADT) by the National Commission on Indigenous Peoples (NCIP), the government agency that deals with issues concerning indigenous people of

4292-626: The racing circuit's suitability for international automotive and motorcycle races including the Asian Touring Car Series and Formula 3 races. The racing circuit was also open to amateur racers. Subic Bay has hosted South East Asia's Premier motorcycle, touring car and formula car events. The Marlboro Asia Pacific Road Racing Championship, Asian Festival of Speed (AFOS) featuring the Southeast Asian Touring Car Zone Challenge (SEATCZC) and

4366-537: The same time as the ancestral volcano and include the domes of Mount Negron, Mount Cuadrado, Mount Mataba and the Bituin and Tapungho plugs. 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: Each of these eruptions seems to have been very large, ejecting more than 10 km (2.4 cu mi) of material and covering large parts of

4440-510: The sulfate liberated sulfur dioxide gas, used in sulfuric acid production, the reaction also produced calcium silicate, a precursor in cement production. On a laboratory scale, the action of hot concentrated sulfuric acid on copper turnings produces sulfur dioxide. Tin also reacts with concentrated sulfuric acid but it produces tin(II) sulfate which can later be pyrolyzed at 360 °C into tin dioxide and dry sulfur dioxide. The reverse reaction occurs upon acidification: Sulfites results by

4514-471: The sulfur atom has an oxidation state of +4 and a formal charge of +1. Sulfur dioxide is found on Earth and exists in very small concentrations in the atmosphere at about 15 ppb . On other planets, sulfur dioxide can be found in various concentrations, the most significant being the atmosphere of Venus , where it is the third-most abundant atmospheric gas at 150 ppm. There, it reacts with water to form clouds of Sulfurous acid (SO2 + H2O ⇌ HSO−3+ H+), and

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4588-449: The summit in some river valleys . Fourteen hours later, a 15-minute blast hurled volcanic matter to heights of 24 km (15 mi). Friction in the up-rushing ash column generated abundant volcanic lightning . In March and April 1991, magma rising toward the surface from more than 32 km (20 mi) beneath Pinatubo triggered small volcano tectonic earthquakes and caused powerful steam explosions that blasted three craters on

4662-412: 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 5 km (1.2 cu mi) of material. The ash cloud from this climactic eruption rose 35 km (22 mi) into the atmosphere. At lower altitudes, the volcanic ash

4736-471: 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,

4810-405: The surrounding land with rock, mud, dust and fire for three days; howling so loudly that the earth shakes. Aeta elders tell many stories about the history of the mountain, the best known being that it was once a Batung Mabye ( Kapampangan language for "living stone"). It was said to have been planted on a kingdom by a displeased sorcerer but relocated by a hero. The mountain was soon turned into

4884-565: The trailing hemisphere of Io , and in the crust and mantle of Europa , Ganymede , and Callisto , possibly also in liquid form and readily reacting with water. Sulfur dioxide is primarily produced for sulfuric acid manufacture (see contact process , but other processes predated that at least since 16th century ). In the United States in 1979, 23.6 million metric tons (26 million U.S. short tons) of sulfur dioxide were used in this way, compared with 150,000 metric tons (165,347 U.S. short tons) used for other purposes. Most sulfur dioxide

4958-444: 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

5032-402: The volcano that the summit collapsed to form a 2.5 km (1.6 mi) 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. Activity at the volcano remained low until July 1992 when a new lava dome started growing in

5106-399: 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 was accidentally triggered. Workers cut a 5-meter (16 ft) notch in the crater rim and drained about a quarter of the lake's volume. On July 10, 2002, the west wall of

5180-486: 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 and eroded into gullies and ravines. The c. 500-year repose though between

5254-626: Was blown in all directions by the intense cyclonic winds of a coincidentally occurring typhoon, and winds at higher altitudes blew the ash southwestward. A blanket of ash and larger pumice lapilli blanketed the countryside. Fine ash fell as far away as the Indian Ocean and satellites tracked the ash cloud several times around the globe. Huge pyroclastic flows roared down the flanks of Mount Pinatubo, filling once-deep valleys with fresh volcanic deposits as much as 200 m (660 ft) thick. The eruption removed so much magma and rock from below

5328-512: 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 2,300 m (7,500 ft), or 1.43 miles above sea level if it were a lone peak, based on a profile fitting to the remaining lower slopes, or lower if it had more than one peak. The old volcano is exposed in the walls of an old 3.5 km × 4.5 km (2.2 mi × 2.8 mi) wide caldera , referred to as Tayawan Caldera by Delfin. Some of

5402-572: Was shown that in children with pulmonary arterial hypertension due to congenital heart diseases the level of homocysteine is higher and the level of endogenous sulfur dioxide is lower than in normal control children. Moreover, these biochemical parameters strongly correlated to the severity of pulmonary arterial hypertension. Authors considered homocysteine to be one of useful biochemical markers of disease severity and sulfur dioxide metabolism to be one of potential therapeutic targets in those patients. Endogenous sulfur dioxide also has been shown to lower

5476-467: Was usually done outdoors, by igniting sublimed sulfur and burning in an enclosed space with the fruits. Fruits may be sulfured by dipping them into an either sodium bisulfite , sodium sulfite or sodium metabisulfite . Sulfur dioxide was first used in winemaking by the Romans, when they discovered that burning sulfur candles inside empty wine vessels keeps them fresh and free from vinegar smell. It

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