Taal Volcano (; ), also known as Taal Caldera, is a large caldera filled by Taal Lake in the Philippines. Located in the province of Batangas about south of Manila, the volcano is the second most active volcano in the country, with 39 confirmed historical eruptions, concentrated on Volcano Island, near the middle of Taal Lake. The caldera was formed by prehistoric eruptions between less than 670,000 and less than 6,000 years ago. The cones Batulao, Macolod, and Sungay are remnants of the early pre-caldera Taal system, with Batulao being the earliest known cone.
Taal Volcano has had several violent eruptions in the past, causing deaths on the island and the populated areas surrounding the lake, with an overall recorded death toll of about 6,000. Because of its proximity to populated areas and its eruptive history, the volcano was designated a Decade Volcano, worthy of close study to prevent future natural disasters. The site was declared National Geological Monument in 1998 and a national park in 2018.
Etymology Taal Volcano was known as Pulo, Bombou or Bombon in the 1800s.
The municipality of Taal and the Taa-lan River (now known as Pansipit River) were named after the Taa-lan tree, which grows along the river. The tree also grew along the shore of Bombon Lake (now known as Taal Lake). The Taa-lan River was a narrow channel that connects the present-day Taal Lake and Balayan Bay to each other.
Taal is a Tagalog word in the Batangueño dialect that means true, genuine, and pure.
Geography
Taal Volcano is part of a chain of volcanoes lining the western edge of the island of Luzon. They were formed by the subduction of the Eurasian Plate underneath the Philippine Mobile Belt. Taal Lake lies within a caldera formed by explosive eruptions between less than 670 (Sampaga Formation) and less than 3 ka to 1000CE (Buco Formation). Each of these eruptions created extensive ignimbrite deposits reaching as far away as present-day Manila.
Taal Volcano is primarily located in the province of Batangas however, the northern caldera rim and the northern segment of its massive ignimbrite shield is located on Tagaytay which is in Cavite. The northern half of Volcano Island falls under the jurisdiction of the lake shore town of Talisay, and the southern half in San Nicolas. The other communities that encircle Taal Lake include the cities of Tanauan and Lipa, and the municipalities of Talisay, Laurel, Agoncillo, Santa Teresita, San Nicolas, Alitagtag, Cuenca, Balete, and Mataasnakahoy.
Surrounding the caldera is a large ignimbrite shield which extends in all directions. It is composed of the ignimbrites and other tephra deposits from prehistoric events. Since the formation of the caldera, subsequent eruptions have created a volcanic island within the caldera, known as Volcano Island. This island covers an area of about with the center of the island occupied by the Main Crater with a single crater lake formed from the 1911 eruption. The island is a resurgent dome consisting of overlapping cones and craters, of which forty-seven have been identified. Twenty six of these are tuff cones, five are cinder cones, and four are maars. The Main Crater Lake on Volcano Island has one of the largest third order islands in the world. This lake contains Vulcan Point, a small rocky island inside the lake. After the 2020 eruption, the Main Crater Lake temporarily disappeared due to an eruption, but had returned by March 2020 and in due course filled up to make Vulcan Point an island again.
Permanent settlement on the island is prohibited by the Philippine Institute of Volcanology and Seismology (PHIVOLCS), declaring the whole Volcano Island as a high-risk area and a Permanent Danger Zone (PDZ). Despite the warnings, some appear to continue to reside on the island, mainly caretakers of fish cages.
Eruptive history Prehistoric eruptions The prehistoric eruptions of Taal were either large caldera forming events or minor eruptions similar to what is observed today. The major eruptions helped create the present Taal Lake, with a large eruption termed "The Pasong Fluidal Juvenile Bomb-Rich Ignimbrite Formation" ejecting of material, shaping the immediate landscape with pyroclastic flows and thick ash deposits across southern Luzon. Prehistoric eruptions left significant deposits of pumice and pyroclastic material across southern Luzon, with thicknesses up to in some areas, impacting vast regions. All major eruption deposits show evidence of plagioclase, pyroxene and magnetite fractionation, although magma evolution for the youngest three of the several eruption units was dominated by magma mixing. Over time, major eruption-units have been becoming more mafic from 63 wt.% SiO2 for the Alitagtag Formation to 58 wt.% SiO2 for the Buco Formation.
Comparing Taal's prehistoric "major" eruption volumes to better studied calderas, the DRE of the VEI 6 Buco eruption may compare to the 41 ka eruption of Irosin caldera which produced a caldera. The VEI 6 Alitagtag eruption, being of similar volume to the 1425 eruption of Kuwae caldera in Vanuatu which may have formed a caldera. The VEI 6 Indang eruption has a dense rock eruptive volume equivalent to that of the eruption of Mt. Mazama around 7,700 years ago, which formed a caldera. The VEI 7 Pasong eruption produced DRE more material than the Akahoya eruption that formed Kikai Caldera 7.3 ka. An estimated size for the Pasong caldera may have been larger than .
There is a very limited age data available for Taal's prehistoric deposits, therefore most estimates for the exact age of Taal Caldera are based on dates of deposits from other volcanoes or of a rather unknown origin. The most commonly published estimate for the age of Taal Caldera is 140 ka. This date is based on a lava of unknown origin on Laurel Island and hence, is not considered accurate.
An alternate age of about 30 ka has been suggested for Taal Caldera, however, this is a Carbon-14 date from the Cubao pumice flow-unit, which belongs to the Diliman Tuff Formation. There is currently no clear source volcano for the Diliman Tuff Formation because the chemistry does not match either published chemistry of the Taal Caldera but shares similarities with the Laguna Caldera with it being more primitive.
The Taal Group The Taal Group denotes the pre-historic pyroclastic sequence of the Taal Caldera Volcano. It has ten named formations and three unofficial units. Each formation consists of one eruption unit, which is separated from the surrounding formations by a paleosoil or modified deposits. Informal 'units' consist of a bundle of multiple narrow layers containing many ancient soils without the distinctiveness needed for correlation into a formation.
The Taal Group is up to approximately thick and is exposed around Taal Lake, Tagaytay Ridge and its surrounding ignimbrite plains to the coast. Outcrops are found along the river valleys, recent road-cuts and quarries. Historical deposits from Volcano Island overlay the Taal Group which covers older scoria cones and Miocene to Paleocene sedimentary and intrusive rocks. Multiple ignimbrites extend below the level of the lake and the contacts with the pre-Taal basement are not usually exposed. Where they are exposed, deposits of the Taal Group are above the lava from Mt. Sungay, the Lipa and Saimsim scoria cones, the Upper Miocene Dingle Limestone and the Lower Miocene Tolos Batholith. Some of the Taal group could be redeposited either as lahar deposits or fluvial.
The Sampaga Tuff Formation The Sampaga Tuff Formation of unknown age is the oldest recognized eruption unit in the Taal Group and resulted from a VEI 5 eruption with DRE of . It is a poorly fused, dark grey to white tuff approximately thick, featuring coarse dark pumices and fragmented accretionary lapilli within a fine ash matrix. Its basal section, thick, features a low-angle cross-bedding with aligned lithic clasts. A white accretionary lapilli-tuff, thick, overlies the lithic clasts. The Sampaga Formation's extent is characterized by erosion and features a thin upper palaeosol superimposed by multiple younger layers believed to consist of the Buco Formation. The upper tuff features strata of nearly horizontal white concretions resembling bedding, transitioning into an orange palaeosol that includes white calcrete-like concretions, showing signs of vegetation in thin section. The Batangas Formation is above this palaeosol. The type locality of the Sampaga Formation is situated along a newly constructed southern road-cut from Antonio Carpio Road, close to the Sampaga Barangay Hall, and it is consistent with an explosive eruption that generated at least one dilute, potentially hydrovolcanic, pyroclastic density current (PDC}.
The Batangas Tuff Formation The undated Batangas Tuff Formation also has an unkcharacterised composition and consists of a layer of non-lithified, clast-supported, dark, subrounded pumice lapilli covered by a delicate layer of pellets and substantial accretionary lapilli-tuff. It resulted from a VEI 6 eruption with DRE of . At its type locality it has a thickness of , but it is thicker than in other locations. It has an upper calcrete rich orange palaeosol and is consistently covered by the Alitagtag Formation. It is consistent with a violent eruption with at least two volcanic flows of dense ash. The initial current contained a high amount of pumice along with a co-ignimbrite column that laid down fine ash in pellet form; this stratum therefore represents a boundary of flow units. Subsequently, a less concentrated pyroclastic density current occurred, prior to the end of the eruption.
The Alitagtag Banded Pumice Ignimbrite Formation The undated Alitagtag Banded Pumice Ignimbrite Formation is also known as the 'Alitagtag Pumice Flow'. It is a non-lithified mainly dacitic to andesitic ignimbrite, in thickness, featuring typical highly vesicular, striped or dark – white gradational pumice fragments, and a thin, lithic-dense, dacitic pumice fall layer at its foundation. An uncommon black dacitic pumice is found solely as bombs featuring fluidal forms that are somewhat less vesicular compared to the white and banded pumice. Both pumice varieties might exhibit uncommon andesitic compositions. The Alitagtag Formation is characterized at a type locality northeast of Batangas City, to the south of the Southern Tagalog Arterial Road toll road. The recently created road section is close to the Calumpang River, over which a bridge was built in February 2020. In this location, the Alitagtag Formation is situated above the upper palaeosol of the Batangas Formation and is separated from the overlying Calumpang Formation by a palaeosol that is orange, thick, and contains calcrete. Each contact is aligned and nearly horizontal. In the northwest, a slender orange palaeosol extends. through an erosive interface between the Alitagtag and the Pasong Formation, which locally truncates the Alitagtag Formation. The formation is found in two other places, including as a veneer deposit where there is no black pumice observed. An exposure discovered to the north of Lake Taal, is tentatively recognized as Alitagtag Formation.
Alitagtag Distribution