Taal volcano, situated in Tagaytay, is a vibrant green island abundant with vegetation. However, it also contains areas that resemble a “desert” due to the ash and cinder from the Kaygabok Lava Flow in 1969. Located about 2 hours south of Manila (Figure 1), Taal Volcano Island resides in the midst of Taal Lake. Considered as a decade volcano, Taal holds significance as it serves as a prototype for predicting and researching volcanic eruptions. This report aims to outline the tectonic setting of Taal volcano, its land formations and vegetation, the dangers associated with residing near an active volcano, as well as provide a brief account of my personal encounter on Taal Island.
Taal volcano is situated in Batangas, with precise coordinates of 14°0’7″N 120°59’34″E. It is located within the western area of the Pacific Ring of Fire, renowned for its abundant volcanic activity. The formation of Taal Volcano Island occurred as a result of the collision between the Philippine plate (Oceanic plate) and the Eurasian plate, leading to the creation of a subduction zone beneath the Philippines Mobile Belt. In the western portion, the oceanic segment of the Eurasian plate (South China Sea basin) is being subducted beneath the Manila and Sulu trenches, spanning a length of 560 miles.
The small islands north of Luzon have a scattered line of active volcanoes stretching from Taal to Iraya. Within this area, there are four microplates being squeezed together between two gigantic plates. Taal volcano is located on the smallest microplate and is experiencing pressure from the Eurasian plate on its western boundary. Its southern and eastern boundaries are transform margins. Taal volcano is situated on a conservative margin known as the Philippine Fault, which connects two subduction zones. This configuration makes the plate margin destructive according to Figure 2.
The landforms and vegetation of Taal Volcano were dramatically altered by a series of catastrophic events. It was once an enormous prehistoric volcano towering at a height of approximately 18,000 feet. However, about 500,000-100,000 years ago, the volcano experienced four massive explosions that ultimately caused its collapse into a caldera. This caldera now stretches across 25-30 kilometers and includes Taal Lake. Originally, the lake was connected to the sea, but in 1754, a powerful eruption from Taal Volcano reshaped its outlet. This eruption gave rise to the present-day Pansipit River and transformed the lake’s water into freshwater. This river became the sole outflow for Taal Lake.
Taal Lake has an area of 234.4 km2. The Main Crater Lake, used for eruption prediction tests, has a width of 2 km and a depth of 80 meters. Taal Volcano is a post-caldera feature covering 23 sq km with multiple eruption centers. Taal is home to around 35 volcanic cones and 47 craters or depressions caused by eruptions or ground subsidence. Out of Taal’s eruptions, 12 took place in the Main Crater Lake, while the five main eruption centers are Binintiang Malaki, Binintiang Munti, Pira-piraso, Calauit, and Mt. Tabaro.
There are various landforms in Taal, such as Mt. Tabaro, where the 1968 eruption occurred. This eruption resulted in the formation of the Kaygabok Lava flow and the Main Crater Lake. Tephra, which refers to airborne ejecta from a volcano, can be found all over the island. The tephra on the island includes ash, which consists of fine rock and mineral particles, and cinder, a fragment of cooled pyroclastic material.
The presence of these tephra in this location is attributed to both pryoclastic flows and ash cloud eruptions that occurred from the volcano. The region near Mt. Tabaro lacks vegetation and is characterized by high temperatures and a dense environment. In contrast, the Kaygabok Lava flow area is abundant in vegetation thanks to its mineral-rich fertile soil that facilitates healthy plant growth.
The large rock structures found in the Kaygabok Lava flow area are hardened lava, specifically olivine basalt. The more commonly used term for this type of rock is scoria, which is composed of iron magnesium silicate (FeMgSiD4). Scoria is formed when lava solidifies, resulting in the presence of small holes called vesicles, making the rock lightweight and porous. The Main Crater Lake is located in the central area of Volcano Island, where concentrated vegetation can be found due to the presence of tephra. Additionally, swimming in the lake is possible as long as there are currently no alert levels (Figure 3.1).
Additionally, Taal houses a diverse array of vegetation (Figure 2.1) as a result of its mineral-rich soil derived from past ejecta. Consequently, various forms of plant life have thrived within the volcano’s vicinity. Some examples of plant life in Taal consist of Acacia bushes, Wild Mint, Cogon grass, and Malunggay trees. Notably, the Acacia bush exhibits remarkable resilience, thriving in relatively arid conditions. This tenacity can be attributed to their long roots that extend deep underground in search of moisture to sustain themselves. Moreover, the Acacia bush is situated near the main crater and is part of the older vegetation surrounding it.
In Taal, there are two prominent plants: the wild mint and the cogon grass. The wild mint emits a distinct aroma when someone passes by it, and it can be found near the main crater. On the other hand, the cogon grass appears as clumps of long, reed-like plants growing out of the ash on Volcano Island. It is also located near the main crater and the Kaygabok lava flow. Similar to the acacia bush, the cogon grass has long roots that grow underground to reach the water table. However, during the dry season, the grass tends to turn brown.
In conclusion, the Malunggay trees in Taal are believed to have originated from other parts of the Philippines after the 1911 eruption of the main crater. It is interesting to note that these trees, along with acacia, cogon, and wild mint, are located near the main crater and mainly grow in older areas of vegetation with a thin layer of soil. The history of Taal Volcano is marked by its devastating eruptions, including the great volcanic eruption that occurred 500,000-100,000 years ago. These eruptions led to the formation of a caldera, which is now occupied by Taal Lake.
There have been 33 recorded eruptions since 1572, one of which resulted in the loss of over 1000 lives. The most recent period of activity occurred between 1965 and 1977 and was attributed to the interaction of magma with the lake, causing explosive phreatic events with steam, ash, and magma bombs. The eruption in 1965 led to the discovery of base surges (ash and steam clouds) that moved swiftly along the ground, as well as cold pyroclastic flows that crossed the lake and devastated multiple villages, resulting in the deaths of hundreds of people. Unfortunately, correct interpretation of warning signs prior to the eruption was hindered.
On the other hand, in 1968 and 1969, volcanic eruptions at Taal were characterized by Strombolian activity, resulting in low-level eruptions. These eruptions also led to a significant lava flow that reached the shores of the lake. Additionally, the 1977 eruption resulted in the formation of a small cider cone within the main crater. The most recent report from PHIVOLCS in 2007 noted that seismic activity at the volcano was notably higher than usual. Despite there being no immediate threat of eruption, alert level one remained in place since September 2004, resulting in restricted access to the main crater. Taal is also recognized as one of the 16 decade volcanoes.
The International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) has identified 16 volcanoes as Decade Volcanoes. These volcanoes are considered worthy of specific study due to their history of large, destructive eruptions and their proximity to populated areas. The reason for their designation as decade volcanoes is that the IAVCEI has deemed them deserving of study based on their destructive eruptions and their closeness to populated areas.
Taal Volcano is associated with various volcanic hazards such as base surges, lava flows, ballistic fallout, ash and scoria fallout, toxic gases, acidic flashes from the crater lake, lake tsunamis and seiches, lakeshore flooding, earthquakes, ground fissuring and subsidence, landslides and sectoral collapse, turbulent ashflows, and lahars. These hazards have been extensively documented from Taal Volcano and the volcanic cones in its vicinity.
The danger of Taal is the reason behind the existence of multiple PHIVOLCS monitoring stations. These stations include the volcano itself, Buco, and Talisay. The Central Receiving and Processing Stations consist of these three stations, while the remaining 7 stations are divided into two groups: Seismic stations and Repeater stations. The Seismic stations can be found in Binintiang Munti, Calauit, the Main Crater, and Pira-piraso (Figure 3.1). On the other hand, the Repeater stations are located in Tagbakin, Napayung, and Daang Kastila.
PHIVOLCS monitors the volcanoes through various methods, including seismic monitoring for volcanic quakes and tremors, visual observations, ground deformations such as EDM, precise leveling, and tilt measurements. Additionally, they test the chemistry, temperature, and water level in the Main Crater Lake.
Despite the inherent dangers, many small settlements continue to exist on the island. This is primarily due to the economic benefits derived from tourists visiting the island. The residents can provide tours and services to these visitors. Furthermore, the presence of residents on Taal has resulted in the surrounding areas gaining Barangay status. This designation grants them monetary benefits for running local government and assisting with services such as garbage collection, healthcare, water supply, and infrastructure maintenance.
In addition to living in a volcanic area with fertile soil and abundant minerals from the volcano’s ejecta, the residents of the island grow coffee, cocoa, and cassava. The fishermen, who reside in small houses on Taal Lake, have fish farms that primarily consist of clupeid species, which they utilize for both consumption and sale. To ensure public safety, PHIVLOCS has developed a comprehensive 6-level warning system for Taal, ranging from a calm level 0 to the most destructive level 5. This system aims to inform people about the safety conditions on Taal Island, allowing them to either visit the main crater and swim or evacuate if necessary.
Currently, Taal is at level 1, indicating a low level of seismicity and other activity. There is no imminent eruption. However, if Taal were to reach level 2, it would mean a low to moderate level of seismicity with unfelt earthquakes, ground deformation, increased water temperature, and increased bubbling in Crater Lake. This would make an eruption possible.
Level 3 is characterized by an increasing occurrence of low frequency and/or harmonic tremors (some felt), sudden or increasing temperature changes, bubbling, radon gas emission, changes in Crater Lake pH, bulging of the volcano, and fissuring. An eruption could occur within days to weeks.
At level 4, there is extreme unrest with continuous seismic activity including harmonic tremor and/or “low frequency earthquakes” which can usually be felt. There is profuse steaming along existing and new vents and fissures. A hazardous and explosive eruption could happen within days.
Finally, in level 5, there are base surges accompanied by lava flows or eruption columns. Reflection: The boat ride to the mountain was unexpectedly wet and rough, with waves rocking the boat and spraying water everywhere. Consequently, I ended up drenched from head to toe, including my pants. Upon disembarking, I discovered that my bag had also become wet.
We received a briefing on land and then began our trek. The word “trekking” invokes a sense of exhaustion as my calves pleaded for rest. We trekked to the Kaygabok Lava flow, a magnificent sight where vegetation sprouted from black rocks, creating a serene and cool image. After observing the lava flow, we continued our trek towards the source of it, Mt. Tabaro.
During the journey, I stumbled upon a piece of scoria that tore through my pants and caused two cuts, causing me pain. Upon reaching the summit of Mt. Tabaro, our group witnessed a panoramic view of everything on this side of the island, from the Lake to the Lava flow. Following this, we continued our trek to a resting spot where we enjoyed a meal. Afterwards, my recollection becomes hazy, but I do remember stopping at a designated area before being forced to turn back due to an approaching storm.
When we emerged from the bushes and vegetation, we hurriedly boarded the boats and set out towards the shore. I believed that the ordeal was finally finished, but it turned out I was mistaken. Leaving behind the village and fisheries, our boat began to sway in response to small waves. As the rain began to pour and larger waves grew in intensity, water splashed into our boat with each collision. In that moment, I felt a surge of fear that we might be tossed overboard by the powerful waves. However, thanks to the presence of outriggers, our only consequence was getting drenched.
Upon reaching the shore, I quickly ascended the stairs to change my drenched attire. Torn between bidding farewell and feeling a sense of attachment, I realized I would miss this memorable encounter. In conclusion, these experiences have left an indelible mark on both my physical and mental being, fostering a deeper understanding and appreciation for perilous wonders such as Taal Volcano Island.
