Analysis of the 2020 Taal Volcano tephra fall deposits from crowdsourced information and field data

Abstract

After 43 years of dormancy, Taal Volcano violently erupted in January 2020 forming a towering eruption plume. The fall deposits covered an area of 8605 km2, which includes Metro Manila of the National Capital Region of the Philippines. The tephra fall caused damage to crops, traffic congestion, roof collapse, and changes in air quality in the affected areas. In a tropical region where heavy rains are frequent, immediate collection of data is crucial in order to preserve the tephra fall deposit record, which is readily washed away by surface water runoff and prevailing winds. Crowdsourcing, field surveys, and laboratory analysis of the tephra fall deposits were conducted to document and characterize the tephra fall deposits of the 2020 Taal Volcano eruption and their impacts. Results show that the tephra fall deposit thins downwind exponentially with a thickness half distance of about 1.40 km and 9.49 km for the proximal and distal exponential segments, respectively. The total calculated volume of erupted fallout deposit is 0.057 km3, 0.042 km3, or 0.090 km3 using the exponential, power-law, and Weibull models, respectively, and all translate to a VEI of 3. However, using a probabilistic approach (Weibull method) with 90% confidence interval, the volume estimate is as high as 0.097 km3. With the addition of the base surge deposits amounting to 0.019 km3, the volume translates to a VEI of 4, consistent with the classification for the observed height and umbrella radius of the 2020 main eruption plume. VEI 4 is also consistent with the calculated median eruption plume height of 17.8 km and sub-plinian classification based on combined analysis of isopleth and isopach data. Phreatomagmatic activity originated from a vent located in Taal Volcano’s Main Crater Lake (MCL), which contained 42 million m3 of water. This eruptive style is further supported by the characteristics of the ash grain components of the distal 12 January 2020 tephra fall deposits, consisting dominantly of andesitic vitric fragments (83–90%). Other components of the fall deposits are lithic (7–11%) and crystal (less than 6%) grains. Further textural and geochemical analysis of these tephra fall deposits contributes to better understand the volcanic processes that occurred at Taal Volcano, one of the 16 Decade Volcanoes identified by the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) because of its destructive nature and proximity to densely populated areas. The crowdsourcing initiative provided a significant portion of the data used for this study while at the same time educating and empowering the community to build resilience.

Perspectives on the 12 January 2020 Taal Volcano eruption: An analysis of residents’ narrative accounts

“…frontiersin.org the initial reports of the phreatomagmatic nature of the event starting at 4:00 p.m. (Balangue-Tarriela et al, 2022). Stratigraphic and component analyses of deposits collected during fieldwork on TVI, conducted a year after the January 2020 eruption, provide confirmation of the sequence of events starting from the phreatic nature of the first few hours of the event (Lagmay et al, 2021).…”

“…At around 7:30 p.m., the activity produced an eruption column of more than 15 km and volcanic lightning. Wet, heavy ashfall was experienced in most of the northeastern Taal municipalities surrounding Taal Caldera and the neighboring provinces of Cavite, Laguna, and Quezon (PHIVOLCS, 2020) (Figure 1B) The prevailing northward wind direction brought light ashfall to Metro Manila and as far as the province of Bulacan to the north (PHIVOLCS, 2020;Balangue-Tarriela et al, 2022). Concurrently, the alert level was raised to alert level 4 (PHIVOLCS 2020c) and expanded evacuation was recommended to include areas identified to be within the base surge hazard zone and 14-km radius (Figure 3) (Supplementary Table S4).…”

Sediment Transport Modeling in the Pasig River, Philippines Post Taal Volcano Eruption

“…During the 2020 eruption, ashfall from the volcano was experienced in Cavite and Laguna and reached as far as Metro Manila, Bulacan, and Pam-panga (more than 100 km from the source). According to Lagmay et al [21], initially, the tephra released from the volcano moved southwest before shifting its direction north-northeastward after a few hours [22]. The following day, the smoke and ash from Taal Volcano moved in a southwestward direction [1,3,22].…”

“…According to Lagmay et al [21], initially, the tephra released from the volcano moved southwest before shifting its direction north-northeastward after a few hours [22]. The following day, the smoke and ash from Taal Volcano moved in a southwestward direction [1,3,22]. Dispersed tephra particles with a thickness of < 1 mm were measured in Rizal, Bulacan, and Pampanga, while thicker deposits measuring ≥ 1 mm were reported in southern Metropolitan Manila and some portions of the provinces of Rizal, Cavite, and Laguna [22].…”

Diffuse CO2 degassing precursors of the January 2020 eruption of Taal volcano, Philippines

“…The eruption was characterized first by a phreatic-phreatomagmatic style, producing a giant plume of volcanic ash up to ~ 15 km in the atmosphere 45 , and ended with a less explosive eruption characterized by the occurrence of lava fountains. The eruption ejected juvenile products, with evidence of magma mingling 46 and represented a great impact to the Philippines, as around half a million people were directly affected by the event, producing the loss of ~ 69 M$ worth of damage to infrastructure and agriculture 47 . The acidity of the TMLC waters (pH ~ 3) allows the emission of big amounts of CO 2 to the atmosphere, as at low pH values, the water of the lake reduces dramatically its ability to dissolve acid gas species as CO 2 .…”