But more steam-driven eruptions seen
THE Philippine Institute of Volcanology and Seismology (Phivolcs) yesterday warned of more phreatic eruptions in the coming days after Bulusan Volcano in Sorsogon spewed an ash column on Sunday morning.
But there is no need to raise the volcano’s alert to Level 2 despite the possibility of similar steam-driven eruptions occurring in the coming days, weeks, or months, said Phivolcs Director Renato Solidum.
Solidum explained that a phreatic eruption occurs when the passage of steam accumulated under the volcano is blocked, thus creating pressure which results in a sudden eruption.
Based on Bulusan’s history, phreatic eruptions occurred in intervals of days, weeks, or months, he said.
“Posibleng magkaroon pa ng mga pagsabog na kahalintulad nang kahapon na phreatic or steam-driven explosion diyan sa Bulusan. Sa mga nakaraang eruptions, minsan ang pagitan ng mga pagsabog ay araw, linggo, minsan ay buwan. So dapat dito ay maging masunurin tayo sa mga pinagbabawal na permanent danger zone. (It is possible that similar phreatic or steam-driven explosions will occur in Bulusan. The intervals of eruptions in the past are sometimes days, weeks, and even months. So, people should not enter the [4-kilometer] permanent danger zone),” Solidum told the “Laging Handa” media briefing.
Bulusan Volcano spewed an ash column of about a kilometer on Sunday, prompting Phivolcs to raise the alert to Level 1. Ashfall reached several barangays in Juban and Irosin towns.
Solidum said there is no need to raise the alert level because Level 2 would mean there is magma involved in the volcanic activity, or there is gas coming from magma due to the rising water temperature.
Solidum said the source of Bulusan’s phreatic eruption last Sunday was shallow. He said it is different from eruptions of other volcanoes, which involve magma or melted rocks reaching the summit.
Under Level 1, which means the volcano is in an “abnormal condition” or on a low level of volcanic unrest, there is a slight increase in volcanic earthquake and steam or gas activity, sporadic explosions from existing or new vents, a notable increase in the temperature of hot springs, and a slight inflation or swelling of the edifice. Phivolcs said this means the “source of activity is shallow, near crater or in the vicinity of Irosin Caldera.”
Under Level 2 (moderate level of volcanic unrest), there are elevated levels of volcanic earthquake, steam/gas emission, ground deformation and hot spring temperature. There are also intermittent steam/ash explosions, above baseline sulfur dioxide2 emission rates, and increased swelling of volcanic edifice. This means “probable intrusion of magma at depth, which can lead to magmatic eruption.”
Solidum said the last time Bulusan Volcano spewed magma was in the 1900s.
Bulusan was relatively quiet yesterday, with only 29 volcanic earthquakes recorded. Before the phreatic eruption last Sunday, 77 quakes were recorded in the vicinity.
Solidum said phreatic explosions can happen anytime in the country’s active volcanoes, including Kanlaon Volcano in Negros Island which is under Alert Level 1.
“There is no escalation of activity in Kanlaon Volcano but I repeat that just like Bulusan, there is a possibility of a sudden explosion. Its permanent danger zone is also four kilometers,” he said in Filipino.
Solidum reminded residents to keep a safe distance from Bulusan Volcano so they can easily evacuate once phreatic eruptions and heavy ashfalls occur anew.
EVACUATION
Solidum said Phivolcs has not recommended evacuation but the local governments can implement “temporary evacuation” in case of heavy ashfall.
The National Disaster Risk Reduction Management Council (NDRRMC) said 50 families consisting of 180 individuals coming from Barangay Putting Sapa in Juban town, Sorsogon were evacuated due to heavy ashfall and pungent odor in the affected area.
“Most of the evacuees are the vulnerable sector such as children, pregnant women and senior citizens,” the NDRRMC said.
It said classes in three schools in Juban town– Puting Sapa Elementary School, Sangkayon Elementary School, and Añog Elementary School — have been suspended due to heavy ashfall.
Police Brig. Gen. Roderick Alba, chief of the PNP Public Information Office, said the Bicol Police Regional Office has been placed on full alert following Bulusan Volcano’s eruption on Sunday morning.
Alba said policemen from the Bulusan Municipal Police Station, in coordination with nearby police stations, are continuously monitoring the activity of Bulusan Volcano for possible evacuation, search and rescue operations of affected residents.
Police Major Gen. Valeriano de Leon, the PNP director for operations, said policemen were sent to affected areas to prevent looting.
He also said policemen are convincing residents to stay away from the 4-kilometer permanent danger zone.
ASSISTANCE
The Diocese of Sorsogon is seeking assistance for the affected families.
“Beddings, masks, food packs, bottled water are the immediate needs in the evacuation centers plus respiratory meds/interventions,” said Caritas Sorsogon director Fr. George Fajardo.
“The immediate danger is in inhaling the ash. Hopefully, rain will come so that the ashes in the roofs and roads will be washed away,” he also said.
Residents in affected areas, especially those who have medical conditions, were immediately evacuated by the local government units.
Health Secretary Francisco Duque III said he has ordered the prepositioning of medicines and medical supplies while also putting on alert healthcare workers in Sorsogon.
“I also already instructed the distribution of N-95 masks and N-88 surgical masks to protect our people from the ashfall and its impact on eyes,” he added.
He said this is vital amid the COVID-19 pandemic.
“Our local healthcare frontliners are monitoring the health situation there, more especially in evacuation centers, where evacuees are staying close to each other,” he said. — With Gerard Naval
