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Taal Volcano is a complex volcano on the island of Luzonmarker in the Philippinesmarker. It is situated between the towns of Talisaymarker and San Nicolasmarker in Batangasmarker. It consists of an island in Lake Taalmarker, which is situated within a caldera formed by an earlier, very powerful eruption. It is located about 50 km (31 Miles) from the capital, Manilamarker. 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 to 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 Manilamarker 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. Forty-seven 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 shores of 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 rumblings. 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 artificial 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 explosion. In particular, the 1965 eruption led to the recognition of base surge 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.

Images

Image:Taal Volcano 2007.jpg|Taal VolcanoImage:Taal lake.jpg|Taal Lakemarker and Taal Volcano taken from a boatImage:Taal_volcano.jpg|Taal volcano's crater lake in 2005Image:Taal volcano crater.jpg|A cinder cone in an acidic lake on Taal VolcanoImage:Taal Caldera.jpg|Taal Caldera 2005Image:Taal Volcano satellite image.gif|Satellite image showing Taal Lake with Volcano island within itImage:Taal_Crater.JPG|Taal crater panorama in October 2007


See also



Notes

Bibliography

  • Lowry A.R., Hamburger M.W., Meertens C.M., Ramos E.G. (2001), GPS monitoring of crustal deformation at Taal Volcano, Journal of Volcanology and Geothermal Research, v.105, p.35-47
  • Richon P., Sabroux J.-C., Halbwachs M., Vandemeulebrouck J., Poussielgue N., Tabbagh J., Punongbayan R. (2003), Radon anomaly in the soil of Taal volcano, the Philippines: A likely precursor of the M 7.1 Mindoro earthquake (1994), Geophysical Research Letters, Volume 30, Issue 9, pp. 34-1


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