Bulusan's last phreatic eruption
was recorded in June 2017.
"This phreatic eruption
is at Alert Level 2, but it's still under the volcano and we think we have to go under the bench," Phivolcs officer-in-charge Renato Solidum reportedly said.
On January 14, Phivolcs raised the volcano eruption alert level to 3 after Mayon spewed ash (phreatic eruption
) on January 13.
Almost 17,500 people living within Mayon's six-to-seven-kilometer danger zone have been evacuated since the volcano started to spew steam and ash clouds during a phreatic eruption
- a steam-driven explosion - on Saturday.
However, on Saturday the mountain sent smoke up into the air for the second time in a week in what volcanologists call a phreatic eruption
-- caused by the heating and expansion of groundwater.
A magmatic-hydrothermal eruption meanwhile differs from an ordinary phreatic eruption
in that it is caused by extrusion of hydrothermal fluids (vapor and liquid) from a hydrothermal reservoir, without the need for substantial energy or mass input from magma.
Sometimes this was low in energy and in number of events but it was related with a posterior phreatic eruption
It warned pilots to avoid flying close to the volcano's summit, as ash from any sudden phreatic eruption
can be hazardous to aircraft.
Disaster mitigation officials have called it a phreatic eruption
which is caused due to heating and expansion of groundwater.
at Mayon Volcano at 8:49am, ashfall should be expected on the southwest and west slopes.