How many volcanoes are there in Bicol? Let us learn about the volcanic centers and complexes in the Bicol region.

The Bicol Volcanic Arc is one of the prominent volcanic arcs that form the Philippine Mobile Belt (PMB). This 260 km. volcanic arc runs across the central-eastern margin of the PMB, from Camarines Norte to Sorsogon in the Bicol Peninsula. The arc hosts at least 12 volcanic centers in Bicol, four of which are categorized as active by the Philippine Institute of Volcanology and Seismology (PHIVOLCS): Mt. Isarog and Mt. Iriga in Camarines Sur; Mt. Bulusan in Sorsogon; and Mt. Mayon in Albay. Other volcanic centers in Bicol Arc include Mt. Labo, Mt. Culasi, Mt. Cone, Mt. Sagñay, Mt. Malinao, Mt. Masaraga, Mt. Bintacan, and the Bacon-Manito Complex.

While active volcanism in Bicol puts lives and properties in danger, volcanic deposits from past eruptions make the soil fertile, and well-suited for agriculture. Its highlands covered by rich vegetation suggest a favorable impact of the volcanoes in the region.

Per the Philippine Association of Geology Students, the Bicol arc is an NW-SW chain of Pleistocene to Quaternary volcanoes and complexes which stretches from Camarines Norte to Sorsogon. This is a product of the westward subduction of the Philippine Sea Plate along the Philippine Trench. Subduction happens when a denser plate slides under a less dense plate whenever these tectonic plates collide. The thick sediments of the converging plates accumulate in the trench. On the other hand, the denser subducting plate releases fluids due to higher pressure and temperature. The fluids released, like seawater and carbon dioxide, cause partial melting. This creates magma, which eventually rises to the surface, forming volcanoes.

Mount Bulusan

Located in the southern tip of the Bicol peninsula, Mount Bulusan is a volcano with four craters and three lakes. In the country, it is with the most recent eruption. The young stratovolcano covers an area of 900 sq. km. Known for its hot and cold springs, geothermal fields, rich biodiversity, and natural sights, Bulusan Volcano is shared by Casiguran, Barcelona, Irosin, and Juban in the Sorsogon province.

Mt Bulusan is the country’s fourth active volcano. It recently spewed ash and steam during a phreatic eruption last 2022 June 5, prompting Philippine Institute of Volcanology and Seismology (PHIVOLCS) to raise Bulusan Volcano’s alert level status from 0 to 1, which means that it is currently at low-level unrest (per PHILVOLCS Bulusan Volcano Bulletin, January 18, 2023.)

Phreatic, strombolian, and caldera-forming eruptions characterize the common eruption types of Bulusan volcano. Its last known eruption was recorded last 12 June 2022, and explosive activity with ash ejection occurred in 2006-2007, 2010, and 2011. Many moderate explosive eruptions have also been recorded since the mid-19th century. Heavy rains often trigger mudflows from loose deposits on the flank.

Bulusan volcano lies in the so-called Bulusan Volcanic Complex (BVC), along with the 11-km wide Irosin caldera and older dissected volcanic centers that include the Gate Mountains at the southern tip of the peninsula and Mt. Bintacan to the west. Bulusan is an andesitic volcano built upon the northeast rim of the older Irosin Caldera, formed about 41,000 years ago during the post-caldera stage. Rising to 1,565 meters above the low-lying floor of Irosin Caldera, Bulusan Volcano is the youngest of several cones and lava domes within the caldera. The rocks found in Bulusan Volcano vary from basalt to dacite but are dominated by andesites.

Its summit is unvegetated and contains a 300-m wide, 50-m-deep crater, along with several vents and fissures. Three other small craters are located on Bulusan’s southeast flank. Within Bulusan also lies three lakes, namely—Bulusan Lake, which is found at the foot of the volcano; Lake Aguingay, which is located at the middle of the volcano; and Blackbirds’ Lake, which is near the summit of the volcano,

During the post-caldera period, the heat subsided, aided by a vent which is the Bulusan Volcano. As a result, lush vegetation grew and developed in the area. Much of Bulusan Volcano’s vegetation is composed of forested areas, including lowland forest on its flanks and montane forest around its peak. Other habitats include secondary grassland, freshwater lakes and pools, small settlements and rural gardens, abandoned farmland, and disturbed ground. Bulusan Volcano, with its extensive forests, likely supports faunal species like white-spotted cat snake (Boiga drapiezii) and some near-threatened and vulnerable birds such as the Luzon bleeding-heart (Gallicolumba luzonica) and the Philippine hawk-eagle (Spizaetus philippensis). It is also a habitat of some endemic flora like an aquatic plant (Schefflera bulusanicum), a fern (Prenephrium bulusanicum) and a tree (Palaquium sorsogonense).

The government in 2000 declared the Bulusan Volcano as a protected area and designated it as a Natural Park in 1935. The Bulusan Volcano Natural Park covering 3,672 hectares, has three main peaks, the active Bulusan Volcano, Sharp Peak, and Mt Jormahan. Similarly, it was also declared as an Eco-Tourism Zone by the Department of Tourism (DOT). The Bulusan Volcano Natural Park is one of the last remaining intact forests in the Bicol region and in the country that serves as a vital watershed supplying the water needs of Sorsogon province.

Mount Isarog

Rising at 1,966 meters, Mt. Isarog is part of the Bicol Volcanic Arc occupying the narrow strip of land between Lagonoy Gulf and San Miguel Bay. It is likewise surrounded by different towns of Naga City, Pili, Ocampo, Tigaon, Goa, Tinambac, and Calabanga.

Many might believe that Isarog is an inactive volcano. However, the latest known eruption of Mt. Isarog occurred sometime between 1050 and 1200 AD (TJ Daita et al, ongoing research). Philippine Institute of Volcanology and Seismology (PHIVOLCS) has classified Isarog volcano as active, meaning it has erupted within historical times (within the last 600 years), accounts of these eruptions were documented by man erupted within the last 10,000 years based on the analyses of material from young volcanic deposits.

Mt. Isarog was declared a Natural Park through Proclamation No. 214, s. 2002 consisting of 10,112 hectares of a protected area and home to diverse species of plants and animals.

Prior to the arrival of the Spaniards in Bicol, Isarog became home to the ethnolinguistic group Agta, who were its first inhabitants. They were also the first devotees of Our Lady of Peñafrancia but resisted Spanish colonization and sought refuge here.

Mount Labo

Mt. Labo is an andesitic stratovolcano sitting at the northwestern end of the Bicol Volcanic Arc. It rises 1,544 meters above sea level, with its base measuring around 24,000 meters in diameter. Numerous andesite and dacite domes exist around the central volcanic edifice. Aside from lava domes, this volcano is composed of lava flows and a prominent central cone.

Its eruptions starting around 580,000 years ago developed the lava domes on its northern side. The present edifice was formed about 270,000 years ago, and flank lava dome emplacement took place from about 200,000 to about 40,000 years ago (determined using thermoluminescence dating as per Ramos et al., 2000)

Mt. Labo is one of the two potentially active volcanoes in Bicol, and its latest eruption produced pyroclastic that flowed from the summit cone about 27,000 years ago. Thermal activity in the form of hot and warm springs continues, and this volcano has been the object of extensive geothermal explorations for the last 25 years. Eight wells have been drilled in Mt. Labo from 1990 to 1997, but all intersected acidic geothermal fluids (DOE, 2009; Maturgo et al., 2000).

On the other hand, Mt. Labo is a protected area. Its thick forest has been the habitat of this endemic small animal species like the Labo shrew-rat (Rhynchomys labo). It also is a significant source of water for Camarines Norte, considering it an important watershed.

Mount Malinao

Mt. Malinao is a stratovolcano located in the central part of the Bicol Volcanic Arc rising at 1,548 meters with a base diameter of ~22.5 kilometers. This Quaternary volcano contains a large summit crater that is breached to the east. Its active neighbor, Mayon Volcano, is 20 aerial kilometers of Malinao.

As per Nielson et al., 1996, Mt. Malinao was active 0.5 to 0.06 Ma. Its rock type is andesitic according to Philippine Institute of Volcanology and Seismology (PHIVOLCS). Located on its eastern flank is the site of Luzon’s largest solfataras and hot springs, some of which deposit silicious sinter.

Like Mt. Labo in Camarines Norte, the PHIVOLCS classified Mt. Malinao as a potentially active volcano. Its current activity is fumarolic, where steam and volcanic gases are emitted from the openings in the earth’s surface.

Mount Masaraga

Standing northwest of the famous Mayon is Mt. Masaraga, a forested inactive volcano. It is a stratovolcano rising 1,328 meters surrounded by four (4) towns in the province of Albay, namely, Polangui, Oas, Ligao City, and Tabaco City. Mt. Masaraga’s flanks have thick lava flows, but there has been no data about its eruption history.

A critical watershed for the Bicol River Basin, the 810-hectare Mt. Masaraga Watershed Forest Reserve, was declared as Watershed Forest Reserve last October 27, 1992. This isolated mountain is inhabited by diverse species of flora and fauna, including the world’s largest flower—the Rafflesia.

Mt. Masaraga is part of the Bicol Volcanic Arc, a chain of volcanoes resulted from the subduction of the Philippine Sea Plate along the Philippine Trench.

Mount Mayon

Majestic at a height of 2,462 meters, Mayon’s almost perfectly shaped cone resulted from centuries of explosions and erosions. It is a stratovolcano composed of layers of hardened lava, volcanic ash, and other eruptive materials.

Mayon sits on the Pacific Ring of Fire with more than 450 volcanoes that stretch about 40,000 km between the boundaries of the Philippine Sea plate, the Pacific Plate, Juan de Fuca and Cocos plates, and the Nazca Plate. It is also part of the Bicol Volcanic Arc, which consists of at least 12 older volcanoes.

Mayon is one of the country’s most active volcanoes. It has erupted 52 times since its first reported eruption in 1616. The most destructive was a Plinian eruption in 1814 that affected Camalig, Cagsaua, Budiao, Guinobatan, and half of Albay. About 1,200 people died in lahar and pyroclastic flow. The next was on June 4 to July 23, 1897, with casualties reaching 350.

UPDATE: On January 13, 2018, Mayon Volcano reported an increase in its activities, generating phreatic or steam-driven eruption. The next day, the Volcano Alert Level was raised from 1 (abnormal) to 2 (increasing unrest). Three days after, Alert Level 3 (high level of unrest) was in effect. On January 22, Alert Level 4 (hazardous eruption imminent) was raised. Strombolian eruption (magmatic activity) was recorded at 2:25 AM, which generated 200 to 500-meter-high lava fountains, and ash plumes that rose 1,300 meters above the summit. The plumes were drifted southwest and ashfall was experienced in Oas and Guinobatan in Albay Province. On March 6, with the diminishing trend in the monitored parameters, Alert Level 4 was lowered to Alert Level 3. Subsequently, Alert Level 2 took effect after 23 days. (reference: Phil. Institute of Volcanology and Seismology)