index

News flash on Mayon volcano's latest activity

Tue, 22 Sep 2009 15:34:18 +0100

The Mayon volcano in Albay spewed ash at around 5:30 a.m. on Tuesday, according to the Philippine Institute of Volcanology and Seismology (Phivolcs).

Resident volcanologist Ed Laguerta said the volcano emitted light brown smoke with very minimal ash content.

He reiterated that the minor ash puff is normal to a volcano under alert level two.

He said the ashes will not affect the residents and farms in the southwest portion of the volcano comprising the towns of Camalig and Guinobatan.

The ash column reached 700 meters high and it drifted towards the southwest portion of the volcano.

Meanwhile, in the latest monitoring of Phivolcs, seven low frequency volcanic quakes were recorded on Monday.

In addition, it recorded a hundred-plus metric tons of sulfur dioxide. This is lower from the normal sulfur dioxide emission of 500 metric tons per day.

The Phivolcs, however, maintained its advice to residents living near the 6-kilometer permanent danger zone and the 7- to 8-km extended danger zones to be extra cautious for a possible eruption.

The Mayon volcano alert level was raised to 2 last July because of the volcano’s abnormal increase in activity.

Volcanic activity

The Phivolcs conducted an aerial survey of the volcano in July 8 which showed a cone-shaped pile of “hot, steaming old rocks, possibly remnants from previous eruptions which could be the source of the glow at the crater.”

A report from the National Disaster Coordinating Council (NDCC) released last July 10 stated that beginning June 2009 there was an increase in the current activity of the Mayon Volcano.

According to the report, the number of recorded low frequency volcanic earthquakes, or earthquakes with not much seismic tremors, rose to a higher level. The report said that this signified possible movement of magma beneath the volcano edifice at a shallow depth.

The cone-shaped pile of materials found at the crater are caused by the low frequency volcanic earthquakes and ground uplift—moving fresh volcanic materials upward.

Aside from recommending residents and tourists to stay away from the danger zones, active river channels and areas perennially identified as lahar-prone should also be avoided, especially during extreme weather conditions such as heavy and prolonged rainfall.

by Jose Carretero, ABS-CBN News Bicol

SOURCE

Spending time with a rumbling GIANT (Mayon Volcano)

Tue, 22 Sep 2009 15:27:14 +0100

Last February 2006, The Philippines had an unfortunate event of having its one of many active volcanoes erupt again and this time it is the majestic Mayon Volcano of Albay in the Bicol region. I was the assigned satellite engineer Broadcast Network to go on location. I, with the rest of the Television News team went to Albay province to provide live up to date broadcasts.

We stayed approximately 11 kilometers away from the volcano, 5 kilometers clear of the 6 kilometers danger zone radius. We situated ourselves on a hilltop called Lignon Hill to have a clear view of the volcano. I then with the help of production assistants to help carry and assemble the fly – away satellite that we brought to the location.

We then aired the news to the Philippines and to the world of the mumbling and lava spewing of the Majestic Mayon Volcano.

At first when we saw a small dot of red/ember color at the tip of the imposing 8,000 feet tall volcano. We thought hey maybe we're not safe here and if there would be a really big eruption that it might reach us. So we were already drawing up evacuation plan for ourselves if ever that happens.

We stayed on the hill for three weeks to cover the eruptions, molten rocks as big as Sports Utility Vehicles rolled down thunderously on the once perfect cone. The flow of lava from the mouth of the Volcano reached almost its base and it presented a beautiful view at night which attracted some of the local, photographers, and tourists as well.

The locales living near the volcanoes described the Volcano as a giant mumbling and thumping the ground as the rocks rolled down. The air near the Volcano smelled of burn’t sulfur, “Asupre” in tagalog. A hole on the side of the volcano became evident as it billowed smoke and a pool of lava and molten rocks.

The last scare that we had for this latest rumble of this regal giant was the small explosion that caused the pyroclastic cloud and dust. It actually brought to mind scenes from the Dante’s Peak movie starring 007 himself, Pierce Brosnan.

All in all, this amazing meeting between me and this Colossal Natural wonder was an unforgettable one that I guess only a few would be able to experience.

*****Recent Bulletins states that the Volcano is now on Alert level 2 which is of moderate unrest... where there is a slight chance of ash explosion and eventual eruption.

Taal Lake

Tue, 22 Sep 2009 15:26:11 +0100

Taal Lake is a freshwater lake in the province of Batangas, on the island of Luzon, Philippines. The lake is situated within a caldera formed by very large eruptions between 500,000 and 100,000 years ago. It is the country's third largest lake (the largest being Laguna de Bay). The active Taal Volcano, which is the one responsible for the lake's sulfuric content, lies on an island in the center of the lake, called Volcano Island. The island is called pulo or islet by the locals. In addition, there is a crater lake on Volcano Island, which is in Lake Taal, which in turn is on Luzon (an island). That crater lake is the world's largest lake on an island in a lake on an island.

Taal Lake
Satellite image showing Taal Lake with Volcano island within it

History

Taal Lake was once just an arm of Balayan Bay. However, after a series of major eruptions in the 16th century, the lake was closed off from the sea by newly-formed land bridges. Taal Lake's sole connection to the sea narrowed down into its sole draining river, the Pansipit River. Several centuries of precipitation have diluted the lake's once-saline waters into pure freshwater.

Succeeding eruptions buried numerous lakeside towns. Presently, only three towns are on the lake's shore. Old lakeside towns with buildings and walls are reported to be seen under the lake's waters.

Ecology

Because the lake was until recently, connected to the sea, it is home to many endemic species that have evolved and adapted to the desalination of the lake's waters.

Its most popular endemic species is the overharvested tawilis, the world's only freshwater sardine.

The lake has a freshwater-adapted population of trevally, Caranx ignobilis. These fish, also found in the Pansipit River, are locally called maliputo.

Taal Lake is also home to one of the world's rarest sea snakes, Hydrophis semperi. This particular species is only one of two "true" sea snake species that are known to live entirely in freshwater.

Bull sharks, Carcharhinus leucas, used to be part of the lake's once-diverse ecosystem. They were exterminated by the locals in the 1930s.

Fishkill

On January 5, 2008, the Bureau of Fisheries and Aquatic Resources (Philippines) (BFAR) announced that a fishkill at Taal Lake (January 2 to 4) caused the 50 metric tons or PhP 3.25-million (US$1=PhP41) loss of cultured tilapia in the villages of Leviste and Balakilong in Laurel and in Barangay Aya and Barangay Quiling in Talisay. 6,000 maliputo fishes (P 230,000) also died at Quiling. Toxic sulfur and high level of hydrogen sulfide in Ambulong while low dissolved oxygen caused the deaths.

Tourism

Batangas and Taal Lake.

Regular tours of the lake are available to tourists. After crossing the lake, visitors travel to the top of Volcano Island on horseback. During their trip up and down the mountain, visitors are treated to a stunning view of the lake and its surroundings.

In mid-2007, controversy ensued when the Korean firm Jung Ang Interventure was given clearance to build a health spa on Volcano Island itself along the lake's edge. Over the course of the next few weeks, several government officials expressed their disapproval of the construction project.

On June 28, the DENR suspended the Korean firm's environmental clearance certificate, rendering them incapable of pursuing further construction on the island until they secure other necessary permits.Because of the unpopular public reaction to the project, the Korean company's permit was permanently revoked by the DENR in early July 2007.

Mount Pinatubo

Tue, 22 Sep 2009 15:21:47 +0100

Mount Pinatubo
Ash plume of Pinatubo during 1991 eruption

Mount Pinatubo is an active stratovolcano located on the island of Luzon, at the intersection of the borders of the Philippine provinces of Zambales, Tarlac, and Pampanga. It is located in the Cabusilan Mountain range separating the west coast of Luzon from the central plains, and is 42 km (26 mi) west of the dormant and more prominent Mount Arayat, occasionally mistaken for Pinatubo. 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 during the protracted Spanish conquest of the Philippines which first commenced in 1565.

The volcano's ultra-Plinian eruption in June 1991 produced the second largest terrestrial eruption of the 20th century (after the 1912 eruption of Novarupta) and the largest eruption in living memory. The colossal 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 1000 years after previous VEI 6 eruptive activity 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 surrounding areas were severely damaged by pyroclastic flows, ash deposits, and later by lahars caused by rainwater remobilizing earlier volcanic deposits: thousands of houses and other buildings were destroyed.

The effects of the eruption were felt worldwide. It ejected roughly 10 billion metric tonnes (10 cubic kilometres) 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 temporarily increased substantially.

Overview of the Mount Pinatubo area

Pinatubo is part of a chain of volcanos which lie along the western edge of the island of Luzon. They are subduction volcanos, formed by the Philippine Mobile Belt sliding over the Eurasian Plate along the Manila Trench to the west. Mount Pinatubo and the other volcanoes of the West Luzon volcanic arc arise due to magma occlusion from this subduction plate boundary.

The volcano is located 87 km (55 miles) northwest of Manila, 14 km (9 miles) west of the former Clark Air Base, and 37 km (23 mi) north of the former U.S. Naval Base Subic Bay ^[6]. Clark Air Base's residential areas and petroleum storage facilities were in much closer proximity to the volcano than the airfield complex and neighboring Angeles City.

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.

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 Freeport Zone.

Cultural history

The word 'pinatubo' means 'to have made grow' in Tagalog and Sambal, 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. An indigenous group of people, the Aetas (also spelled as 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.

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. Philippine President Ramon Magsaysay, a native of Zambales, named his C-47 presidential plane "Mt. Pinatubo". The plane crashed in 1957, killing the President and 24 others onboard.

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.

Aetas living near Pinatubo worship a god named Apo Mallari who lives at the peak. According to them, he caused the 1991 eruption because of displeasure toward illegal loggers and Philippine National Oil Company executives who have drilled for geothermal heat into the mountain. However after the quake they felt as if their god had betrayed them.

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.

Ancestral Pinatubo

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.

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.

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.

Earlier 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 450 years ago, and after that, the volcano lay dormant. Its slopes became completely covered in dense rainforest, and eroded into gullies and ravines.

1991 awakening

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

On July 16, 1990, the major 1990 Luzon earthquake of magnitude 7.7 struck central Luzon.^[10] This was the largest earthquake recorded in 1990,^[10] comparable in size to the 1906 San Francisco earthquake and the 2008 Sichuan earthquake. Its epicenter was in Rizal, Nueva Ecija municipality, ^[11] about 100 km northeast of Pinatubo, and faulted northwest-southeast through three provinces. It also followed the Philippine Fault System west as far as Baguio, which was devastated, and is located about 80 km north-northeast of Pinatubo, leading 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 who visited the mountain in response, only found small landslides rather than any eruptive activity.

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 likely. 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 Volcanic ash. Seismographs recorded hundreds of small earthquakes every day.

Scientists immediately installed monitoring equipment and analyzed the volcano for clues as to its previous eruptive history. Radiocarbon dating of charcoal found in old volcanic deposits revealed 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.

Volcanic activity increased throughout 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.

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) issued a warning indicating the possibility of a major eruption within two weeks.

Evacuation

Given all the signs that a very large eruption was imminent, the Philippines Institute of Volcanology and Seismology (PHIVOLCS) assisted by the US Geological Survey, worked 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.

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.

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 April 7. Evacuation of the 10–20 km zone was ordered when a level 4 alert was issued on June 7. A level 5 alert triggered evacuation of the 20–40 km zone on June 14, and in all some 60,000 people had left the area within 30 km of the volcano before June 15. Most people temporarily relocated to Manila and Quezon City, with some 30,000 using the Amoranto Velodrome in Quezon City as an evacuee camp.

Eruptions build to a climax

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.

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.

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.

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.

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.

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 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.

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.^[12]

Aftermath

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.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.

Over 800 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

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.

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. The United States Air Force initiated a massive airlift effort to evacuate American servicemembers and their families during and immediately following the eruption. Most personnel were initially relocated to Guam, Okinawa, and Hawaii, although some returned to the continental United States. Clark Air Base was ultimately abandoned by the United States military, and Subic Bay reverted to Philippines control the next year following the breakdown of lease negotiations.

Local economic and social effects

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.

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.

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.

Global environmental effects

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).

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.

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.

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.

The Area in 1991

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.

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 not been erupting.

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.

After eruptions ended, a crater lake, Lake Pinatubo, 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.

The lake increased in depth by about 1 meter 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.

Activity since 1991

Since 1991, Pinatubo has remained active, with twenty activity events reported in 1992, three in 1993, four in 1994, two in 1995, and one each in 1996 and 2002.

The strongest eruption in Philippine History of the 20th century.

Taal Volcano

Tue, 22 Sep 2009 15:19:36 +0100

Taal Volcano is a complex volcano on the island of Luzon in the Philippines. It is situated between the towns of Talisay and San Nicolas in Batangas. It consists of an island in Lake Taal, which is situated within a caldera formed by an earlier, very powerful eruption. It is located about 50 km (31 Miles) from the capital, Manila. It is one of the active volcanos in the Philippines, all part of the Pacific ring of fire.

The volcano has erupted violently several times, causing loss of life in the populated areas surrounding the lake, the current death toll standing at around 5,000 - 6,000. Because of its proximity to populated areas and eruptive history, the volcano has been designated a Decade Volcano worthy of close study to prevent future natural disasters. It was thought to be named as "a volcano inside a volcano" because many believed that the lake that circles the volcano was once a crater or mouth of a volcano.

A level 1 Alert is in force for Taal which is giving signs of increased activity in June/July 2009.

Geological history

Taal Volcano is part of a chain of volcanos along the western side of the island of Luzon, which were formed by the subduction of the Eurasian Plate underneath the Philippine Mobile Belt. Taal Lake lies within a 25-30 km caldera formed by four explosive eruptions between 500,000 and 100,000 years ago. Each of these eruptions created extensive ignimbrite deposits, reaching as far away as where Manila stands today.

Since the formation of the caldera, subsequent eruptions have created another volcanic island, within the caldera, known as Volcano Island. This island covers an area of about 23 km², and consists of overlapping cones and craters. 47 different cones and craters have been identified on the island.

Eruption of 1754

The greatest recorded eruption in historical times of Taal Volcano was in 1754. Fr. Buencuchillo who was then stationed in Taal reported:

On May 15, 1754, at about 9 or 10 o'clock in the night, the volcano quite unexpectedly commenced to roar and emit, sky-high, formidable flames intermixed with glowing rocks which, falling back upon the island and rolling down the slopes of the mountain, created the impression of a large river of fire. During the following days there appeared in the lake a large quantity of pumice stone which had been ejected by the volcano. Part of these ejecta had also reached the hamlet of Bayuyungan and completely destroyed it.

The volcano continued thus until June 2, during the night of which the eruption reached such proportions that the falling ejecta made the entire island appear to be on fire, and it was even feared that the catastrophe might involve the shoresof the lake. From the said 2nd of June until September 25, the volcano never ceased to eject fire and mud of such bad character that the best ink does not cause so black a stain.

During the night of September 25, the fire emitted was quite extraordinary and accompanied by terrifying rumbings. The strangest thing was, that within the black column of smoke issuing from the volcano ever since June 2, there frequently formed thunderstorms, and it happened that the huge tempest cloud would scarely ever disappear during two months.

At daybreak of September 26 we found ourselves forced to abandon our dwelling for fear lest the roofs come down upon us under the weight of ashes and stones which had fallen upon them during that hapless night. In fact, some weaker buildings collapsed. The depth of the layer of ashes and stones exceeded two "cuartas" (45 centimeters), and the result was that there was neither tree nor other plant which it did not ruin or crush, giving to the whole region an aspect as if a devastating conflagration had swept over it. After this the volcano calmed down considerably, though not sufficiently to offer any prospect of tranquility.

During the night of November 1, Taal resumed its former fury, ejecting fire, rocks, sand, and mud in greater quantities than ever before. On November 15, it vomited enormous boulders which rolling down the slopes of the island, fell into the lake and caused huge waves [note(added by Saderra Maso): The waves mentioned were most probably due to the earthquake rather than to the falling rocks]. The paroxysms were accompanied by swaying motions of the ground which caused all the houses of the town to totter. We had already abandoned our habitation and were living in a tower which appeared to offer greater security; but on this occasion we resolved that the entire population retire to the Sanctuary of Casaysay, only the "Administrator" and myself to remain on the spot.

At 7 in the evening of November 28 occurred a new paroxism, during which the volcano vomited forth such masses of fire and ejecta that in my opinion, all the material ejected during so many months, if taken together, would not equal the quantity which issued at the time. The columns of fire and smoke ascended higher than ever before, increasing every moment in volume, and setting fire to the whole island, there being not the smallest portion of the latter which was not covered by the smoke and the glowing rocks and ashes. All this was accompanied by terrific lightning and thunder above, and violent shocks of earthquakes underneath. The cloud of ejecta, carried on by the wind, exented itself toward west and south with the result that we saw already some stones fall close to our shore. I, therefore, shouted to all those who were still in the town to take to flight and we all ran off in a hurry; otherwise we would have been engulfed on the spot; as the waves of the angry lake began already to flood the houses nearest to the beach.

We left the town, fleeing this living picture of Sodom, with incessant fear lest the raging waters of the lake overtake us, which were at the moment invading the main part of the town, sweeping away everything they encountered. On the outskirts of the town, I came upon a woman who was so exhausted by her burden of two little children and a bundle of clothing that she could proceed no farther. Moved by pity, I took one of the taddlers from her and carried him, and the little indio who has been wailing while in the arms of his mother, stopped short when I took him into mine and never uttered a sound while I was carrying him a good piece of the way.

Having reached a secure place on elevated ground at a distance of about half a league (2 kilometers) from the town, we halted in a hut to rest a little and take some food. From this spot the volcano could be contemplated with a little more serenity of mind. It still continued in full fury, ejecting immense masses of material. Now I also observed that the earth was in continuous, swaying motion, a fact which I had failed to notice during the excitement and fear of the flight.

Shortly afterwards the volcano suddenly subsided almost suddenly; its top was clear and apparently calm. We, therefore, returned on the following day, the 29th, to the town with the intention of surveying the havoc wrought during the preceeding night.

The 29th had dawned calm, but while we were still trying to persuade ourselves that the tragedy was overand the volcano had exhausted its bowls, at about 8 o'clock, we heard a crash and then I noticed that smoke was rising from the point of the island that looks towards east. The smoke spread very gradually as far as the crater of the volcano, while there were many whiffs issuing from points in the direction of another headland. I realized that the island had opend in these places and fearing that, if a crater should open below the water, an explosion might follow, much more formidable than the preceding ones, I mounted a horse and retired permanently to the Sanctuary of Caysasay.

Between 3 and 4 o'clock in the afternoon of the said 29th, it began to rain mud and ashes at Caysasay [12 miles from the volcano] and this rain lasted three days. The most terrifying circumstance was that the whole sky was shrouded in such darkness that we could not have seen the hand placed before the face, had it not been for the sinister glare of incessant lightnings. Nor could we use artifical light as this was extinguished by the wind and copius ashes which penetrated everywhere. All was horror those three days, which appeared rather like murky nights and we did not occupy ourselves with anything but see to it that the natives swept off the roofs the large quantities of ashes and stones which kept on accumulating upon them and threatened to bring them down upon us, burying us alive beneath their weight. But fearing that even these precautions might prove unavailing, we 3 Europeans - viz. Fr. Prior, the Alcalde, and myself - the only ones who were at the time in the Convento of Caysasay, took refuge on the landing of the stairs; as the safest place, and awaited there whatever God might dispose with regard to us. To all this was added incessant thunder and lightning, and it really looked as if the world was going to pieces and its axis had been displaced.

During the night of the 30th we had not a moment of repose, as every moment we heard the loud crush of houses collapsing under of stones, mud, and ashes piled upon them, and feared that the turn of the convento and the church of Casasay would come in next. Shortly before daybreak of December 1 there was a tremendous crash as if the house were coming down on our heads: the roof of the apsis of the church had caved in! Not long afterward, the roof of their kitchen gave away with a thud. Both were tile roofs.

The first of December broke somewhat clear and our eyes contemplated everywhere ruins and destruction. The layer of ashes and mud was more than 5 spans [1.10 m] thick, and it was almost a miracle that the roof of the church and convento sustained so great a weight. We caused the bulk of the material to be removed, while new continued to fall on that day and the following, on which latter the direction of the wind changed, carrying the ejecta toward Balayan. On the 3rd and 4th we had a formidable typhoon, and thereafter the volcano quieted down.

Soon afterward I resolved to visit my town of Taal; nothing was left of it except the walls of the church and convento. All the rest, the government house, the walks of the rope factory, the warehouse, everything was buried beneath a layer of stones, mud, and ashes more than 10 spans [2.20 m] thick; only here and there could be seen an upright post, the only remnant of a comfortable dwelling. I went down to the river and found it completely filled up, with a boat belonging to the alcalde and many of private persons buried in the mud. After incredible efforts I finally succeeded in unearthing in what had once been the church and sacristy, the chests which contained the sacred vestments and vessels. Nearly all of them were demolished by the rocks and beams which had fallen upon them, and filled with foul-smelling mud that had ruined or disfigured their contents. With the aid of some natives of Bauang I likewise recovered some property from among the ruins of the convento.

Twelve persons are known to have perished - some carried away by the waves of the lake, others crushed beneath their collapsing houses. Thus the beautiful town of Taal remains a deserted wilderness and reduced to the utmost misery, while once it was one of the richest and most flourishing places. In the villages to the west of the lake, which were the greater and better part, all the houses have either collapsed under the load of material which had been piled upon them or have disappeared completely, swept away by the waves which in these places were so violent that they dug three ditches or channels, too wide and deep to be forded, and thus rendered impassable the road which joins the town with Balayan. In other parts of the lake shore have likewise opened manycracks and occurred very extensive slides. The worst of all is, that, the mouth of the river Pansipit having been blocked, the lake is rising and invading the towns of Lipa and Tanauan, both being on the lowest level, and inundating their buildings. All the animals of whatever kind have perished, some by being buried, others by drowning, the rest by starving, as not a green blade remained anywhere.

The same fate as Taal has befallen the towns of Lipa, Tanauan, and so much of Sala as still existed. These towns, together with Taal, lay around the lake, being situated within easy reach of it, and less than one league [4 kilometers] from the volcano. The bulk of the population left this neighbourhood and settled in more distant places. Thus out of 1200 taxpayers whom Taal contained formerly, hardly 150 remain in the poorest and least respectable villages, which suffered little from the rain of ashes.

Crater Lake & Vulcan Point

Volcano Island contains a lake about 2 km across, called Crater Lake. Within Crater Lake is another small volcanic island, called Vulcan Point. Vulcan Point is frequently cited in the Philippines as the world's largest volcanic island within a lake on an island within a lake on an island, namely, Vulcan Point within Crater Lake, on Taal Island within Lake Taal, on the island of Luzon.

Recent activity

There have been 33 recorded eruptions at Taal since 1572. One of the more devastating eruptions occurred in 1911, which claimed more than a thousand lives. The deposits of that eruption consisted of a yellowish, fairly decomposed (non-juvenile) tephra with a high sulfur content.

The most recent period of activity lasted from 1965 to 1977, and was characterized by the interaction of magma with the lake water, which produced violent phreatic explosions. In particular, the 1965 eruption led to the recognition of base surge^[3] as a process in volcanic eruption (due to the fact that one of the American geologists, who visited the volcano shortly after the 1965 eruption, had witnessed an atomic bomb explosion when he was a soldier). The eruption generated base surges and cold pyroclastic flows, which traveled several kilometers across Lake Taal, devastating villages on the lake shore and, killing about a hundred people. The population of the island was evacuated only after the onset of the eruption. Precursory signs were not interpreted correctly until after the eruption. Eruptions in 1968 and 1969 were characterized partly by Strombolian activity and produced a massive lava flow that reached the shore of lake Taal. The 1977 eruption merely produced a small cinder cone within the main crater.

Current activity

Although the volcano has been quiet since 1977, it has shown signs of unrest since 1991, with strong seismic activity and ground fracturing events, as well as the formation of small mud pots and mud geysers on parts of the island.

The Philippine Institute of Volcanology and Seismology (Phivolcs) regularly issues notices and warnings about current activity at Taal, including ongoing seismic unrest.

For instance a notice on 28 August 2008, notified "the public and concerned authorities" that the "Taal seismic network recorded ten (10) volcanic earthquakes from 5:30 A.M. to 3:00 P.M. today. Two (2) of these quakes that occurred at 12:33 and 12:46 P.M. were both felt at intensity II by residents at barangay Pira-piraso. These quakes were accompanied by rumbling sounds. The events were located northeast of the volcano island near Daang Kastila area with depths of approximately 0.6km (12:33 P.M.) and 0.8km (12:46 P.M.)"

On 20 July 2009, National Disaster Coordinating Council (NDCC) NDCC executive officer Glenn Rabonza warned that although there were no volcanic quakes detected at Taal since the detection of nine volcanic quakes from June 13 to July 19, and there had been no steaming activity monitored since the last recorded on June 23, Phivolcs Alert stands at Level 1, warning Taal’s main crater is off-limits to the public because steam explosions may suddenly occur or high concentrations of toxic gases may accumulate.

“The public is reminded that the Taal Volcano Island is a high-risk area and a PDZ, hence habitation is strictly not recommended," he said.

Eruption precursors at Taal

In light of its proximity to populated areas and violent eruptive history, Taal has been designated one of sixteen Decade Volcanoes, making it a focus for research efforts and disaster mitigation plans. While seismic activity is a common precursor to eruptive activity, another useful indicator at Taal is the temperature of Lake Taal. Before the 1965 eruption began, the lake's temperature rose to several degrees above normal. However, the lake's temperature does not always rise before an eruption. Before some eruptions, the dissolution of acidic volcanic gases into the lake has resulted in the death of large numbers of fish.

Earthquake precursors in the Taal region

An interesting observation on Volcano Island was made in 1994. Volcanologists measuring the concentration of radon gas in the soil on the island measured an anomalous increase of the radon concentration by a factor of six in October 1994. This increase was followed 22 days later by a magnitude 7.1 earthquake on November 15, centred about 50 km south of Taal, off the coast of Luzon.

A typhoon had passed through the area a few days before the radon spike was measured, but when Typhoon Angela, one of the most powerful to strike the area in ten years, crossed Luzon on almost the same track a year later, no radon spike was measured. Therefore, typhoons were ruled out as the cause, and there is strong evidence that the radon originated in the stress accumulation preceding the earthquake.

Mayon Volcano

Tue, 22 Sep 2009 15:18:03 +0100

Posted by Jayson Suratos on Friday, September 11, 2009

Mayon Volcano, also known as Mount Mayon, is an active stratovolcano in the province of Albay, in the Bicol Region, on the island of Luzon, in the Philippines.

Renowned as the "Perfect Cone" because of its almost perfectly conical shape, Mayon is situated 15 kilometres northwest of Legazpi City.

A level 2 alert is in force for Mayon because of increased activity in June-July 2009.

On 13 October 2008 it was included in New7Wonders of Nature Top 10 list. However, it didn't made the cut to the Top 25 finalists,giving way to Puerto Princesa Subterranean River, another site in the Philippines.

Geomorphology

Mayon is an active stratovolcano. The current cone was formed through pyroclastic and lava flows from past eruptions. Mayon is the most active of the active volcanos in the Philippines, having erupted over 49 times in the past 400 years.

It is located on the eastern side of Luzon, beside the Philippine Trench which is the convergent boundary where the Philippine Sea Plate is driven under the Philippine Mobile Belt. Where a continental plate or belt of continental fragments meets an oceanic plate, the lighter continental material overrides the oceanic plate, forcing it down into the earth's mantle. Magma, formed where the rock melts, may be forced through weaknesses in the continental crust caused by the collision of the tectonic plates. One such exit point is Mayon.

Like other volcanoes located around the rim of the Pacific Ocean, Mayon is part of the Pacific Ring of Fire.

Location and formation

Mayon Volcano in Albay showing its distance from the Albay Gulf

Mayon Volcano,as seen from Camarines Sur,Albay's neighboring province.

Mayon Volcano is the main landmark of Albay Province, Philippines. It is ten kilometres (6 mi) from the Gulf of Albay,in the municipalities of Legazpi City, Daraga, Camalig, Guinobatan, Ligao City, Tabaco City, Malilipot, and Santo Domingo (clockwise from Legazpi). It rises 2462 m (8,077 ft) above the gulf.

Mayon Volcano is the Philippines' most active volcano and is considered to be the world's most perfectly formed volcano^[1] for its symmetrical cone. It is a basaltic-andesitic volcano. The upper slopes of the volcano are steep averaging 35-40 degrees and are capped by a small summit crater. Its sides are layers of lava and other volcanic material.

Recorded eruptions

Mayon Volcano in the hemp-producing district of Luzon as depicted in history and conquest of the Philippines and our other island possessions; embracing our war with the Filipinos by Alden March, published in 1899. Caption (cropped out) read: "This is said to be the most beautiful volcano in the world. It is 8,223 feet high, its shape is a perfect cone and its crest is always fiery. It has indulged in several destructive eruptions. In 1814 many houses were destroyed and 2500 people were killed and wounded. At its base are famous springs of great medicinal value".

Mayon has had forty-nine eruptions in recorded history. The first recorded eruption was in 1616, the last major eruption ceased on 1 October 2006, although a devastating lahar followed on 30 November 2006. A further summit eruption occurred on 10 August 2008.

Mayon Volcano on September 23, 1984

The most destructive eruption of Mayon occurred on February 1, 1814. Lava flowed but not as much compared to the 1766 eruption. Instead, the volcano was belching dark ash and eventually bombarding the town with tephra that buried the town of Cagsawa—only the bell tower of the town's church remained above the new surface. Trees were burned; rivers were certainly damaged. Proximate areas were also devastated by the eruption with ash accumulating to 9 m (30 ft) in depth. 2,200 Albay locals perished in what is considered to be the most lethal eruption in Mayon's history.

Mayon Volcano's longest uninterrupted eruption occurred on June 23, 1897 which lasted for seven days of raining fire. Lava once again flowed down to civilization. Seven miles eastward, the village of Bacacay was buried 15 m (49 ft) beneath the lava. In Libog, 100 people were declared dead—incinerated by steam and falling debris or hot rocks. Other villages like San Roque, Misericordia and Santo Niño became deathtraps. Ash was carried in black clouds as far as 160 km (100 mi) from the catastrophic event. More than 400 persons were killed.

Samuel Kneeland, a professor and a geologist had observed the volcanic activity five months before the eruption. Kneeland was amazed with the beauty of Mayon:

“

At night the scene was truly magnificent and unique. At the date of my visit the volcano had poured out...a stream of lava on the Legaspi side from the very summit. The viscid mass bubbled quietly but grandly, and overran the border of the crater, descending several hundred feet in a glowing wave, like red-hot iron. Gradually, fading as the upper surface cooled, it changed to a thousand sparkling rills among the crevices, and, as it passed beyond the line of complete vision behind the woods near the base, the fires twinkled like stars, or the scintillions of a dying conflagration. More than half of the mountain height was thus illuminated.

”

Mayon Volcano overlooks a peaceful pastoral scene approximately five months before the volcano's violent eruption in September 1984.

No casualties were recorded from the 1984 eruption after more than 73,000 people were evacuated from the danger zones as recommended by scientists of the Philippine Institute of Volcanology and Seismology.^[5]

Pyroclastic flows killed 77 people, mainly farmers, in Mayon’s fatal eruption of 1993.

2006 activity

Mayon erupted again from July to October 2006, with no apparent loss of life during the actual eruption period.

On July 18, 2006: The number and size of incandescent rockfalls from the active lava dome, as well as sulfur oxide emissions, increased, according to the Philippines Institute of Volcanology and Seismology (Phivolcs), which warned that pyroclastic flows or an explosive eruption could occur any time.

On August 7, 2006: The Philippine government ordered the evacuation of about 20,000 people living near the volcano, stating that an eruption was feared soon. Volcanologists have detected 21 low-frequency volcanic earthquakes since early Sunday morning.

On August 8, 2006: The government expected to move some 34,276 people to 31 state-run shelters and warned that the mountain could explode at any time.

Mayon Volcano as seen from space.

On August 9, 2006: Volcanologists warned that Mount Mayon could explode at any time but that the gravitational pull of a full moon could provide the final push. A full moon coincided with at least three of Mayon’s nearly 50 explosions over the last four centuries, including the two most recent in 2000 and 2001. Nearly 40,000 people have been moved from an 8 km (5 mi) danger zone on the southeast flank of the volcano, which has been quaking and spitting plumes of ash since July.

On August 10, 2006: Scientists in the Philippines renewed warnings of a major explosion at the Mount Mayon volcano, describing a sudden period of quiet as "ominous". A drop in gas emissions and earthquakes sparked fears that the crater had plugged itself, increasing the likelihood of an explosive eruption.

On August 11, 2006: Scientists said ground surveys showed Mayon was still "swollen" and registered a high number of volcanic earthquakes, emitted large amounts of sulfur dioxide gas and continued to eject lava down its slope nearly four weeks after it came to life in a "quiet" eruption on July 14. Phivolcs maintained threat level at Alert Level 4 for the next month due to the continued extrusion of lava, ash explosions, steam and smoke plumes, seismic activity, and threat of further eruption.

On September 11, 2006 Phivolcs downgraded threat level to Alert Level 3. "After the ash explosion of 01 September, a general decline in the overall activity of Mayon has been established. The decrease in key parameters such as seismicity, gas (Sulfur Dioxide) emission rates and ground inflation all indicate a waning condition. The slowdown in the eruptive activity is also evident from the decrease in intensity of crater glow and the diminishing volume of lava being extruded from the summit".

On October 3, 2006 Phivolcs downgraded threat level to Alert Level 2. "All monitored key parameters such as earthquake levels, ground deformation and gas outputs further declined. In addition, lava extrusion apparently ceased on 01 October 2006 as reported by Ligñon Hill Observatory. The above observations indicate the absence of an intruding new mass of magma."

On October 25, 2006 Phivolcs downgraded threat level to Alert Level 1 (no hazardous eruption imminent).

Phivolcs did not issue any further alerts or updates for Mayon in November or December 2006.

Devastating aftermath

On November 30, 2006, Typhoon Durian caused mudslides of volcanic ash and boulders from the slopes of Mayon Volcano, killing an estimated 1,000 and covering a large portion of the village of Padang (an outer suburb of Legazpi City) in mud up to the houses' roofs.

The number of dead was estimated at around 1000, about half the death toll of the 1814 eruption. The precise figure may never be known since many people were buried under the lahars, and entire villages disappeared.

Parts of Daraga were also devastated, including the Cagsawa area, where the ruins from the eruption of 1814 were partially buried once again. Large areas of Guinobatan were destroyed, particularly Maipon.

Students from Aquinas University in Barangay Rawis of Legazpi City were among those killed as mudslides engulfed their dormitory. Central Legazpi escaped the mudslide but suffered from severe flooding and power cuts.

2008 Eruption

On 10 August 2008, a summit explosion ejected ash 200 metres above the summit, with the ash drifting ENE. In the weeks prior to the eruption, there was a visible glow within the crater, and increased seismicity.

Current activity

On 10 July 2009, PHIVOLCS issued the following bulletin:

This is a notice for the raising of Mayon Volcano’s status from Alert Level 1 (low level unrest) to Alert Level 2 (moderate unrest).

Beginning June 2009 monitored parameters indicated an increase in the current activity of Mayon Volcano. The number of recorded low frequency volcanic earthquakes rose to a higher level signifying possible movement of magma beneath the volcano edifice at shallow depth. The present seismic count is at the same level when a phreatic explosion occurred last August 2008. Ground uplift of about one centimeter was measured by Precise Leveling Survey conducted last June 15-22, 2009 and the uplift was sustained during a re-survey yesterday, July 9, 2009. Glow at the summit crater has intensified and could now be observed at Lignon Hill Observatory without the aid of telescopes. Steam emission was at moderate level.

Aerial survey conducted last July 08, 2009, showed a cone-shaped pile of hot, steaming old rocks, possibly remnants from previous eruptions which could be the source of the glow at the crater. The low frequency volcanic earthquakes and ground uplift could indicate that fresh volcanic materials are moving upward at depth, causing the formation of the cone-shaped pile of materials at the crater.

Because of the above observations, PHIVOLCS is now raising the Alert status of Mayon Volcano from Alert Level 1 to Alert Level 2. This alert condition signifies, a state of unrest which could lead to ash explosions or eventually to hazardous magmatic eruption. Thus, at Alert Level 2, PHIVOLCS strongly recommends that the 6-km radius Permanent Danger Zone (PDZ) around the volcano and the 7-km Extended Danger Zone (EDZ) on the southeast flank of the volcano are off-limits due to the threat from sudden explosions and rockfalls from the upper slopes. Active river channels and those areas perennially identified as lahar prone in the southeast sector should also be avoided especially during bad weather conditions or when there is heavy and prolonged rainfall.

On 20 July 2009 National Disaster Coordinating Council (NDCC) executive officer Glenn Rabonza issued a memorandum ordering regional and provincial disaster management agencies to closely monitor Mayon and Taal volcanoes.

"You are hereby directed to undertake monitoring and precautionary measures in your areas of responsibility. The public and the Disaster Coordinating Council concerned are advised to take appropriate actions and to be on alert for any development," the memorandum said.

Based on the Philippine Institute of Volcanology and Seismology (Phivolcs) alert levels chart for Mayon, Alert Level 1 is hoisted when there is a slight increase in seismicity and sulfur dioxide (SO2) gas output above the background level and when a very faint glow of the crater may occur but no conclusive evidence of magma ascent. At this stage, there is no danger of imminent eruption, but people are not allowed to enter the 6-km radius permanent danger zone (PDZ).

index

News flash on Mayon volcano's latest activity

Spending time with a rumbling GIANT (Mayon Volcano)

Taal Lake

Ecology

Fishkill

Tourism

Mount Pinatubo

Contents

Overview of the Mount Pinatubo area

Cultural history

Geological history

Ancestral Pinatubo

Modern Pinatubo

1991 awakening

Evacuation

Eruptions build to a climax

The climactic eruption

Aftermath

Local economic and social effects

Global environmental effects

Activity since 1991

Taal Volcano

Contents

Geological history

Eruption of 1754

Crater Lake & Vulcan Point

Recent activity

Current activity

Eruption precursors at Taal

Earthquake precursors in the Taal region

Mayon Volcano

Contents

Geomorphology

Location and formation

Recorded eruptions

2006 activity

Devastating aftermath

2008 Eruption

Current activity