By Aaron Recuenco STO. DOMINGO, Albay — Signs that the Mayon Volcano is slowing down were monitored for the past three days but volcanologists here still want to make sure of the consistency of the data feed from their instruments before making a conclusion — if the situation is normalizing or a prelude to the feared "big bang." Residents play on a makeshift basketball court as Mayon volcano spews ash in Camalig, Albay, January 31,2018. (Czar Dancel) Today, the Philippine Institute of Volcanology and Seismology (Phivolcs) sent its field scientists to conduct confirmatory tests and collect new data from the instruments installed near Mayon. Ed Laguerta, Phivolcs resident volcanologist, said among the data they observed is the decrease in the emission of sulfur dioxide from the volcano crater — from 3,066 tons a day on February 1 to an average of 1,500 tons a day in the past two days. But the most significant data collected was from geologists that reported a one-millimeter deflation on the edifice of Mayon on its northern side. The defllation in the volcano edifice means a decrease in the pressure inside the volcano as there may not be much resupply of magma to the Mayon's chamber. "If this trend continues, then it would be better because this means a gradual slowing down of volcanic activities," said Laguerta. "But again, this could just be a pause so, to make sure, we will reconfirm our data." Prior to the January 22 hazardous eruption that prompted volcanologists here to hoist Alert Level 4 over Mayon, a decrease in Mayon activities were also monitored. Laguerta said the decrease in volcanic activities does not necessarily translate to normalization. Phivolcs still needs to confirm the consistency of the downtrend in the deflation of Mayon edifice. The deflation should also be supported by a decrease in emission of sulfur dioxide and other pyroclastic materials. The continuous deflation and decrease in the materials being spewed by Mayon would mean that there is not much magma supply, and what could be left are the old supply that remain in the two-kilometer passage outlet of the volcano heading towards the crater. Mayon is some 2.4 kilometer high. This is the reason why there is a continuous lava flow despite a possible decrease in the supply of magma. "If there will be no additional intrusion, the lava flow will eventually stop," said Laguerta. The crater of the volcano, however, was not visible yesterday due to thick clouds that covered Mayon the whole day. But near the Phivolcs station in Sto. Domingo town which is within the five kilometer distance from the crater, burning vegetation, as a result of the lava flow, was noticeable. The sudden stop in the lava flow and degassing of Mayon that results in the ejection of pyroclastic density materials (composed of lava, ash and gas) also needs to be continuously monitored. If there is an abrupt stop in the spewing of volcanic materials but monitoring instruments read an increasing activity such as inflation of the edifice and volcanic quakes, there is a high possibility of a "big bang" as this would mean that something is blocking the outlet of the volcano. If the data would indicate a consistency in the decrease of Mayon's activity, Laguerta said, they would still need one week to decide whether or not the alert status--which is currently at Level 4--over Mayon would be downgraded.