Manila, Jan. 6 -- The level of unrest in Mayon Volcano has increased, particularly at its summit or surface level, the Philippine Institute of Volcanology and Seismology (Phivolcs) reported on Tuesday.

In an interview with the Philippine News Agency, Phivolcs Director Teresito Bacolcol said the near-doubling of rockfall events-from 44 recorded between Jan. 4 and 5 to 85 between Jan. 5 and 6-indicates increasing instability at the volcano's summit, a condition commonly associated with magma rising from below.

The Phivolcs recorded incandescent rockfall from the summit lava dome on Monday night.

An incandescent rockfall involves hot material that appears glowing, especially at night. This indicates that the rocks came from the hot portio...