Geologist posts animated video explainer on volcanic eruptions

A University of the Philippines geologist used original animations to help explain the different types of volcanic eruptions after the Taal Volcano spewed a huge cloud of ash into the sky on Sunday.

Thousands of residents in the Batangas and Cavite areas evacuated from their homes as the volcano remains on Alert Level 4, which means that a hazardous eruption is possible within hours to days.

In a series of videos posted on Facebook, UP Nationwide Operational Assessment of Hazards (NOAH) Executive Director Dr. Mahar Lagmay broke down the dynamics of the phreatic, magmatic, and phreato-magmatic eruptions.

A phreatic eruption is a steam-driven explosion caused by magma that rises near the surface of the volcano and heats up the lake.

In steam-driven eruptions, however, the magma does not come in contact with the groundwater or Taal Lake.

According to Lagmay's animation, the components of a phreatic eruption include steam, rocks and ash.

The geologist also noted that phreatic eruptions are difficult to predict.

A magmatic eruption, meanwhile, happens when magma reaches the Earth's surface and shoots out of the volcano through lava fountains and lava bombs.

The resulting lava flow from a magmatic eruption would be "very hot and fast-moving."

On Monday, the PHIVOLCS said that Taal Volcano had a magmatic eruption "characterized by weak lava fountaining accompanied by thunder and flashes of lightning."

The components of a magmatic eruption include fragmented lava or pyroclastic ash, crystals, rocks and glass, according to Lagmay's animation.

A magmatic eruption from Taal Volcano would also contribute to the drying of its lake.

There is another type of eruption—the phreato-magmatic—when magma reaches the lake, but it does not turn into fast-moving lava flows.

In Lagmay's animation, a phreato-magmatic eruption is defined by an explosion of magma and water. Components of this eruption are crushed lava bits, rocks, crystals, ash and steam.

A phreato-magmatic eruption is described as "extremely violent" and the resulting explosion would pulverize magma into ash.

Taal Volcano's last major eruption occurred in October 3, 1977. —MGP, GMA News