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Low-frequency harmonic quakes rocked Mount Mayon accompanied
by a sudden drop in its steam emission caused by a partial
"blockade" of fresh magma at a portion of the volcano's conduit,
indicating a high probability of an explosive eruption,
scientists said Thursday.
According to the Philippine Institute of Volcanology and
Seismology, seismic instruments detected 51 low frequency quakes
compared to the 16 quakes recorded on Wednesday. PHIVOLCS said
the tremors were brought by the active degassing process by the
volcano for the past days, indicating that "viscous" magma is
ascending toward the crater summit.
Instruments also recorded 343 tremors caused by lava tumbling
down the volcano's slopes.
PHIVOLCS resident volcanologist Ed Laguerta, said the rate of
sulfuric steam disgorged by the volcano continues to fluctuate
from high to low levels, signifying an active degassing is
taking place as a new batch of magma enters the volcano's vent.
"The presence of low-frequency volcanic earthquakes triggered
by the active degassing and the partial "blockade" of viscous
magma would either lead to a continued lava flow or an explosive
The PHIVOLCS advisory said the drop in the sulfur dioxide
(SO2) on Thursday at 4,760 tons a day compared to the 12,548
rate the previous day still shows active degassing.
"The sudden drop in gas emission due to the ‘blockade’ in
Mayon's conduit cause a significant slowdown of degassing magma
at the summit," Laguerta said.
He added the fast and slow degassing rate suggests that the
volcano is building up pressure that may eventually lead to an
Lava oozing from the volcano crater since its mild eruption
last July 14, had accumulated to about 18 million cubic meters.
The bulk of the lava was first funneled into the Mabinit channel
south-southeast of the crater while the subsequent flows have
entered the gullies at the southeast upper and middle slopes
from Miisi channel in Daraga to Buyoan channel.
The lava front that is as big as a four-story building is
reaching the six-km Permanent Danger Zone (PDZ) and destroying
hectares of coconut plantation and other farm lots in Barangay
Farmers in the village have cut hundreds of coconut trees
planted along the pathways of the lava so that they can make use
Alert Level 3 is still up, meaning sudden explosion and lava
avalanche may occur anytime.
Disaster authorities are maintaining the "off limits" policy
at the six-km PDZ and the seven-km extended PDZ at the southeast
flank of the volcano to all residents and visitors.