FAST FACTS: Taal Volcano alert levels

A phreatomagmatic eruption in the Taal Volcano on July 1, 2021, prompted the Phivolcs to place the volcano under Alert Level 3. A phreatomagmatic eruption involves both magma and water.

The Taal Volcano may be placed from Alert Level 0 to 5, depending on its volcanic activity. Here's what you should know about volcano alert levels for Taal, according to Phivolcs:

Alert Level 0: Quiet or no alert
  • All monitored parameters are within background levels
  • Volcano is quiet

At Alert Level 0, there is no eruption in the foreseeable future.

Alert Level 1: Low level of volcanic unrest
  • Low-level seismicity, fumarolic (smoke), or other activity
  • Disturbance in magma, earth surface, and hydrothermal activities (magmatic sources associated with heated water in the volcanic area)

No eruption is imminent. 

Alert Level 2: Increasing unrest
  • Low to moderate level of seismicity, persistence of local but unfelt earthquakes
  • Ground deformation measurements are above baseline levels
  • Increased water and/or temperatures of ground probe holes
  • Increased bubbling at Crater Lake

Magmatic intrusion is probable, which may lead to an eruption. However, if trend shows a decline, alert may go down to Level 1.

Taal Volcano was previously placed under Alert Level 2 on March 9 due to increasing unrest.

Alert Level 3: Magmatic unrest
  • Relatively high unrest
  • Seismic swarms, including increasing occurrence of low-frequency earthquakes and/or harmonic tremor
  • Sudden or increasing changes in temperature, bubbling activity, radon gas emission, or pH levels of Crater Lake
  • Bulging of the volcanic edifice and fissuring (cracks) may occur

Now that the volcano is under Alert Level 3, Phivolcs recommended that Taal Volcano Island and high-risk barangays in the towns of Agoncillo and Laurel in Batangas be evacuated "due to the possible hazards of pyroclastic density currents and volcanic tsunami."

Alert Level 4: Hazardous eruption imminent
  • Intense unrest
  • Continuing seismic swarms, including harmonic tremor and/or earthquakes which are usually felt

At this level, hazardous eruption is possible within days.

The last time Phivolcs placed Taal Volcano under Alert 4 was in January 2020. At the time, the Civil Aviation Authority of the Philippines was instructed to advise aircrafts to avoid airspace around Taal Volcano due to airborne ash and ballistic fragments that could cause hazards to an aircraft.

Alert Level 5: Hazardous eruption in progress
  • Base surges accompanied by eruption columns
  • Lava fountaining or lava flows

Eruptions at this final alert level pose extreme hazards to communities west of the volcano (such as Agoncillo) and ashfalls on downwind sectors. – Rappler.com

Read Rappler explainers on Taal Volcano: