We all know that the Philippines sits on the Pacific Ring of Fire. We have volcanoes for neighbors in our communities. The beautiful Mayon Volcano in Albay, with its world-famous perfect cone. Mt. Pinatubo,which exploded in 1991, the world’s largest explosion in living memory that caused global temperature to dip half a degree (celcius).
There’s another volcano that plays home to locals and tourists who seem oblivious to its status as an active volcano — Taal volcano. I used to think that identifying Taal Volcano is a simple matter: there’s the crater and there’s the lake. Then I learned that Taal Volcano has 47 craters and 4 maars (shallow, flat-floored craters).
The Main Crater Lake, which is obviously inside the Main Crater, is 1.9 kilometers in diameter. The conical crater which we prominent from the Tagaytay ridge is not the main crater. It’s an extinct crater. The Main Crater is inside the Taal Caldera (25 kms across). Inside the Taal Caldera, surrounding the Main Crater, is the Taal Lake (267 square kilometers). This is why it’s also referred to as the lake within a lake. [See map and directions. Rate and review Taal Volcano and Taal Lake.]
The Tagaytay Ridge, with its numerous establishments catering to travelers and tourists, offers a good view of Taal Volcano and the Taal Lake. Lakeshore towns, or those which border on Taal Lake, include Talisay, Tanauan, Agoncillo, Balete, San Nicolas and Laurel.
There were 33 historical eruptions, the last one in 1977. The Volcano Island is a permanent danger zone.
The government agency specifically tasked to keep an eye on volcanoes, the PHIVOLCS, declared a Alert Level 2 in June of 2010, which alert was downgraded to Level 1 in August. Based on PHIVOLCS information, the alert levels for Taal Volcano (Mayon Volcano has separate alert level descriptions) are as follows:
No alert (Normal)
Criteria: Background, quiet.
Interpretation: No eruption in foreseeable future.
Alert Level 1 (Abnormal)
Criteria: Low level seismicity, fumarolic, other activity.
Interpretation: Magmatic, tectonic or hydrothermal disturbance; no eruption imminent.
Alert Level 2 (Alarming)
Criteria: Low to moderate level of seismicity, persistence of local but unfelt earthquakes. Ground deformation measurements above baseline levels. Increased water and/or ground probe hole temperatures, increased bubbling at Crater Lake
Interpretation: A) Probable magmatic intrusion; could eventually lead to an eruption.
B) If trend shows further decline, volcano may soon go to level 1
Alert Level 3 (Critical)
Criteria: Relatively high unrest manifested by seismic swarms including increasing occurrence of low frequency earthquakes and/or harmonic tremor (some events felt). Sudden or increasing changes in temperature or bubbling activity or radon gas emission or Crater Lake pH. Bulging of the edifice and fissuring may accompany seismicity.
Interpretation: A) If trend is one of increasing unrest, eruption is possible within days to weeks.
B) If trend is one of decreasing unrest, volcano may soon go to level 2
Alert Level 4 (Eruption Imminent)
Criteria: Intense unrest, continuing seismic swarms, including harmonic tremor and/or “low frequency earthquakes” which are usually felt, profuse steaming along existing and perhaps new vents and fissures.
Interpretation: Hazardous explosive eruption is possible within days.
Alert Level 5 (Eruption)
Criteria: Base surges accompanied by eruption columns or lava fountaining or lava flows.
Interpretation: Hazardous eruption in progress. Extreme hazards to communities west of the volcano and ashfalls on downwind sectors.