Taal volcano is a lush green island, with lots of vegetation but also, with some “desert” areas, created by ash and cinder from the Kaygabok Lava Flow (1969). It is in Tagaytay which is about 2 hours south of Manila (Figure 1). Taal Volcano Island is in the middle of Taal Lake. Taal is an important volcano because it is what is known as a decade volcano, which is a volcano used as a model to predict and study eruptions. In this report I will describe the tectonic setting of Taal volcano, its land formations and vegetation, the hazards of living near an active volcano and a brief description of my experience on Taal Island.
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Taal volcano is found in Batangas, its precise latitude and longitude are 14ï¿½0ï¿½7″N 120ï¿½59ï¿½34″E. It is located along the western region of the Pacific Ring of Fire which is named for its high volcanic activity. Taal Volcano Island was created by the Philippine plate (Oceanic plate) crashing into and going under the Eurasian plate, which formed a subduction zone underneath the Philippines Mobile Belt. In the west, the oceanic part of the Eurasian plate (South China Sea basin) is being subducted under the 560-mile length of the Manila and Sulu trenches.
This produces a scattered line of active volcanoes from Taal to Iraya in the small islands north of Luzon. However, between the two gigantic plates are 4 microplates being squeezed together, with Taal being on the smallest micro plate, it’s western boundary being pushed by the Eurasian plat while it’s southern boundary and eastern boundary are transform margins (Figure1.1). This means that Taal volcano lies on a conservative margin known as the Philippine Fault but there are two subduction zones and the fault connects the two subduction zones, which makes the plate margin destructive (Figure 2).
Landforms and vegetation:
Before Taal Volcano erupted, it was believed to be an immense pre-historic volcano, standing an estimated 18,000 feet high, and then 500,000-100,000 years ago, 4 giant explosions destroyed the volcano and it collapsed into a caldera, with a channel opening towards Balayan Bay. This destructive eruption created Taal Lake, which lies within the 25-30 km caldera. Originally, Taal Lake was connected to the sea but in 1754 a powerful eruption from Taal Volcano reshaped the outlet, to form the present day Pansipit River, this diluted the water, turning it into fresh water, now this is the lake’s only outflow. Taal Lake is 234.4 km2, the Main Crater Lake, where tests are taken to predict eruptions, is 2 km wide and 80 meters deep and Taal Volcano which is a 23 sq km post-caldera feature with, numerous eruption centers.
In Taal there are about 35 volcanic cones, and 47 craters or depressions caused by direct eruptions or ground subsidence. However, the Main Crater Lake is where 12 of Taal’s eruptions took place, while the five major eruption centers are namely Binintiang Malaki, Binintiang Munti, Pira-piraso, Calauit and Mt. Tabaro (Figure 3.1). There are many different landforms in Taal but the more recognizable features include, Mt. Tabaro, where the 1968 eruption took place, the 1968 eruption created the Kaygabok Lava flow and the Main Crater Lake. All over the island, there is lots of tephra, tephra is airborne ejecta from a volcano, the types of tephra that we found on the island were ash, a very fine rock and mineral particles, and cinder which is a fragment of cooled pryoclastic material.
The reason these tephra are found here is because of the pryoclastic flows and ash cloud eruptions from the volcano. Towards the area of Mt. Tabaro, there is very little vegetation, which makes the area very hot and dense. In contrast, the Kaygabok Lava flow area contains lots of vegetation, because of the fertile soil it produces due to the minerals, which make the plants, grow well. The reason there are large rock like structures in the Kaygabok Lava flow area is because they are hardened lava. The proper term for this rock is olivine basalt, while it’s generic term is scoria, scoria is made of iron magnesium silicate (FeMgSiD4), it’s formed when lava solidifies, leaving little holes known as vesicles, this makes the rock both light and porous. The Main Crater Lake is in the central area of the Volcano Island, here there is concentrated vegetation because of the tephra, and you can also swim in the lake, if there are currently no alert levels (Figure 3.1).
As well, Taal is full of vegetation (Figure 2.1), due to the mineral rich soil from past ejecta, because of this many forms of plant life have grown and prospered in areas in the Volcano. The plant life in Taal include: Acacia bushes, Wild Mint, Cogon grass and Malunggay trees. The acacia bush is a very hardy plant, capable of growing in relatively dry conditions, this is due to the fact that their long roots can bury deep underground where the moisture is, and they can survive on that; also the acacia is near the main crater and is part of the older vegetation. Another plant, that grows in Taal is the wild mint, it can be recognized by the distinctive aroma it gives off if a person were to walk by it; it is near the main crater.
A more, recognizable plant in Taal is, the cogon grass, which appears as clumps of long grassy, reed like plants growing out of the ash on Volcano Island, it is also near the main crater and the Kaygabok lava flow. Just like the “acacia bush”, the cogon grass has long roots; however, they grow underground to the water table. However, the grass becomes browner in the dry season. To finish with, another plant in Taal is the Malunggay trees, the Malunggay trees got into Taal, because their spores were blown from other areas of the Philippines following the 1911 eruption of the main crater, coincidentally the Malunggay trees are near the main crater just like, the acacia, cogon and wild mint. Interestingly, the trees grow in the more established (older) areas of vegetation, where there is a thin layer of soil.
Hazards and management:
Taal volcano has an incredibly destructive history, from the great volcanic eruption 500,000-100,000 years ago to 2007. In prehistory, Taal Volcano destroyed itself with 4 gigantic eruptions and created a caldera where Taal Lake now lies. There have 33 recorded eruptions since 1572; this includes a devastating eruption that claimed for than 1000 lives. The most recent period of activity was from 1965-1977 and was caused by the interaction of magma with the lake, producing powerful phreatic explosions (steam, ash and magma bombs).
The 1965 eruption led to the notion that base surges (clouds of ash and steam moving along the ground a high speeds) and cold pyroclastic flows, which traveled across the lake and destroyed several villages on shore, killing hundreds of people. Unfortunately, this was because precursory signs were interpreted correctly after the eruption. On the other hand, eruptions from 1968 and 1969 were characterized by Strombolian activity (low-level volcanic eruptions) and produced a major lava flow that reached the shores of the lake.
The 1977 eruption produced a minor cider cone within the main crater. In the most recent report (2007), PHIVOLCS has reported that the seismic activity in the volcano is notably higher than usual, and even though no eruption is imminent, alert level one was continued from September 2004, which meant that the main crater was off-limits to anyone.
Taal has been named as one of the 16 decade volcanoes. Decade Volcanoes are 16 volcanoes identified by the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) as being worthy of particular study in light of their history of large, destructive eruptions and proximity to populated areas. The reason it was named a decade volcano was, because the IAVCEI had decided that it was worthy of study due to its destructive eruptions and closeness to populated areas.
The major volcanic hazards of Taal Volcano are base surges, were documented during an eruption at Taal in 1965, lava flows, ballistic fallout, ash and scoria fallout, toxic gases, acidic flashes from crater lake, lake tsunamis and seiches, lakeshore flooding, earthquakes, ground fissuring and subsidence, landslides and sectoral collapse, turbulent ashflows, and lahars. These are most of the volcanic hazards recorded from Taal and volcanic cones near it.
Thus, because Taal is so dangerous, there are numerous PHIVOLCS monitoring stations, in: the volcano itself, Buco and Talisay, these three stations, are the Central Receiving and Processing Stations, while the other 7 stations are divided up into 2 groups Seismic stations and Repeater stations. The Seismic stations are in: Binintiang Munti, Calauit, the Main Crater and Pira-piraso (Figure 3.1). Meanwhile, the Repeater stations are in: Tagbakin, Napayung and Daang Kastila. The ways PHIVOLCS monitors the volcanoes are, seismic monitoring (number of volcanic quakes and tremors), visual observations, ground deformations (EDM, precise leveling, tilt) and testing the chemistry, temperature and level of water in the Main Crater Lake.
However, even though there are all these dangers, there are many small settlements on the island, this is because the inhabitants of the island benefit from the tourists, coming to visit the island, and they can take them on tours. Also, because there are residents living on Taal, the surrounding areas have gained Barangay status, which means that they receive monetary benefits for running local government and help in the services (garbage collection, health, water etc.) and infrastructure (buildings, roads, bridges etc.). In addition, because they live in a volcanic area, the soil is fertile and full of minerals from the ejecta that came out of the volcano; this allows them to grow coffee, cocoa and cassava. As well, the fishermen, who live in Taal Lake on small houses in the water, are subsistent and have fish farms that contain many fish mostly clupeid, which are used for eating and selling.
In addition, to let people know either that Taal is “safe, go to the main crater and swim” or to evacuate the entire island; PHIVLOCS has made a 6 level warning system, for Taal, with 0 being calm and 5 at its most destructive. As of now, Taal is currently at a level 1 which means that there is a low level of seismicity and other activity; no eruption imminent. However, if Taal were to go to level 2, that would mean low-moderate level seismicity, many unfelt earthquakes, ground deformation above baseline, increased water temperature, increased bubbling in Crater Lake; eruption possible.
At level 3, increasing occurrence of low frequency and/or harmonic tremors (some felt), sudden or increasing temperature changes/ bubbling/ radon gas emission/ Crater Lake pH, bulging of edifice and fissuring may accompany seismicity; eruption possible within days to weeks. Then, at level 4 extreme unrest, continuous seismic activity, including harmonic tremor and/or “low frequency earthquakes” which are usually felt, profuse steaming along existing and perhaps new vents and fissures; hazardous, explosive eruption possible within days. Finally, in level 5, there are base surges accompanied by lava flows or eruption columns.
Nothing could have prepared me for what we were about to do when we went to that mountain. Firstly, the boat ride was wet, there were actually waves! They rocked the boat and sprayed water all over the place. Before long, I was wet from my face to my pants and when we got off of the boat, I found out that my bag was wet as well. On land we were briefed on what we had to do and then we started Trekking. Trekking, now that word brings me nothing but the pleading of my calves to stop walking and rest, we trekked to the Kaygabok Lava flow, an incredible site in itself, vegetation sticking out of black rocks gave a calming and cool picture. Then after observing the Lava Flow we trekked up to where it came out of, Mt. Tabaro.
Along the way I fell over a piece of scoria, which cut through my pants and gave me two cuts, ow. At the top of Mt. Tabaro we could see everything on this side of the island, from the Lake to the Lava flow. After this we trekked to an area where we sat down and ate, after this, well all I can remember is that we went to a sort of “pit-stop” and then had to go back, because a storm was blowing in. When we finally broke through out of the bushes and vegetation, we jumped on the boats and headed out toward shore, I thought at last it’s over.
It wasn’t. As we left the village and fisheries behind, we were rocked up and down by small waves. Then the rain started and bigger waves hit our boat, and every time we crashed into them water was sent everywhere in large proportions and suddenly, I was afraid that we were going to be thrown overboard by the waves but thanks to the outriggers we only got wet. When we finally got on to shore, I rushed up the stairs and changed my wet clothes. Then, all too soon we were leaving and I was actually gonna miss the experience. To conclude, thanks to this experience I have gained memories that have been imprinted onto my body and my mind and I believe I have gained a better appreciation for dangerous hazards like Taal Volcano Island.