A geological hazard investigation was conducted on July 28, 2021 by the technical personnel of the Mines and Geosciences Bureau IV-CALABARZON (MGB IV-CALABARZON) on the reported Sinkholes and Fissuring in Barangays of Laguile, Apacay and Latag in Taal, Batangas. The investigation was conducted as per request of the Office of Civil Defense IV-CALABARZON (OCD IV-CALABARZON).

The “sinkholes” being referred are indeed “fissures” formed as a result of the Taal Volcano Eruption and the effects of the July 24, 2021 magnitude 2021 earthquake. The site visited are generally underlain by tuff and tuffaceous sandstone which covers the area within the 17-kilometer radius of Taal Volcano. Sinkholes are only common in areas where the rock layer below the surface contain carbonate rocks especially Limestone, which can be easily dissolved by groundwater percolating and circulating around. Therefore, occurrence of sinkhole in the proximity is very unlikely.

A total of six (6) fissure openings trending Northeast-Southwest were identified in three Barangays (one (1) in Barangay Latag, two (2)  in Barangay Apacay, and three (3) in Barangay Laguile. Most of the fissures have been in existence even before the occurrence of July 24, 2021 magnitude 6.6 earthquake in Calatagan, Batangas. The map plotting revealed that the fissures in Barangay Apacay and Laguile seemed to be interconnected. The most notable among the fissure openings is the one of the three fissures in Barangay Laguile which created a huge opening where two (2) houses were severely damaged including other five (5) more structures within the designated buffer zone.

It is concluded that the main factor to influence the expansion, deepening, and opening of these fissures is the soil erosion caused by the oversaturation of soil due to continuous rainfall. The oversaturated soil can no longer hold more water that when the earthquake occurred, collapse was triggered and aggravated the soil erosion.

Due to profound depth of the pit in Barangay Laguile, the residents within 5-meter buffer zone especially the two (2) households are recommended to relocate as the area is no longer safe for occupancy. The public are also encouraged to closely observe and report exposure/s or any occurences of fissures in their respective areas.

MGB CALABARZON team assess the fissure in Barangay Latag, Calatagan Batangas.
MGB CALABARZON team assess the fissure in Barangay Latag, Calatagan Batangas.

The fissure in Brgy. Latag, Taal, Batangas. The opening of the said fissure is approximately 1.45 meters wide and 2.4 meters deep and leads down to a cavern-like opening that stretches further in the direction of around S 40°W. According to an individual inside the school premises who claims to witness the occurrence of the said fissure, it appeared on July 27, 2021.  Photo on the left shows the proximity of the school building from the fissure being few meters away.

The first fissure opening in Brgy. Apacay, Taal, Batangas. The opening of the fissure is 3.2 meters wide horizontally, 2.1 meters vertically, and 4.1 meters deep and has two openings further below where one is oriented at a direction at approximately N 30° E and one that is oriented at around S 25° W.

The second fissure opening in Brgy. Apacay, Taal, Batangas. The opening of the fissure is 2.5 meters wide 2.7 meters deep. This opening is approximately 30 meters away from the first fissure and is interconnected following the trace oriented S 25° W from the first fissure.

The first fissure opening in Brgy. Laguile, Taal, Batangas. Two (2) houses were severely damaged by the huge opening as shown in the photo with five (5) more within the 5-meter previously designated buffer zone. The massive depression is 10.3 meters wide and 7 meters deep that might be possibly deeper as the personal possession of the occupants like motorcycles, doors, and others also piled up into the pit together with the soil debris and cannot be retrieved as of the time of visit.

The second fissure opening in Barangay Laguile, Taal, Batangas. The opening is 6 meters long, 4 meters wide and 2.1 meters deep. It is approximately 11 meters away from the first opening.

The third fissure opening in Barangay Laguile, Taal, Batangas. The opening is 4.9 meters wide and 4.2 meters deep. It is approximately 8 meters away from the second opening. According to a resident, the fissure above was only a small crack after the Taal Volcano Eruption last year. After the event of Typhoon “Ulysses”, it collapsed and start to form a trace oriented N 40° E.


By: Chester A. Sta. Maria                        |              13 September 2021