Bezymianny is one of the most active volcanoes in Kamchatka and in the world. In December 2016, activity of the volcano began to intensify after four years of silence during 2012–2016. In 2017, three, and in 2019, two paroxysmal explosive eruptions of the volcano occurred. The work describes the eruption that occurred on March 15, 2019, as well as the events preceding it, based on the study of video and various satellite data. The volcano was monitored using the information system (IS) “Remote monitoring of the activity of Kamchatka and Kurile volcanoes” (VolSatView). The eruption had been predicted by KVERT (Kamchatkan Volcanic Eruption Response Team) staff 6.5 hours before it began. Explosions raised ash up to 15 km above sea level, the eruptive cloud moved northeast and east of the volcano, the main area of the territory where ashfalls were observed was about 210,410 km2 , including 15,000 km2 on land. An animated image of the ash cloud movement from the volcano is shown, made according to a series of images of Himawari-8 in the IS VolSatView (http://kamchatka.volcanoes.smislab.ru/animation/1584509687.gif). After the eruption, aerosol clouds were recorded in the atmosphere at a distance of up to 4000 km in the northeast of the volcano until March 18, 2019. As a result of the eruption, deposits of pyroclastic flows and pyroclastic surges formed on all slopes of the volcano
(mainly on the eastern and southeastern), the area of which reached about 30 km2.

Deep long-period (DLP) earthquakes observed beneath active volcanoes are sometimes considered as precursors to eruptions. Their origin remains, however, unclear. Here, we present a possible DLP generating mechanism related to the rapid growth of gas bubbles in response to the slow decompression of over-saturated magma. For certain values of the gas and bubble content, the elastic deformation of surrounding rocks forced by the expanding bubbly magma can be fast enough to generate seismic waves. We show that amplitudes and frequencies of DLP earthquakes observed beneath the Klyuchevskoy volcano (Kamchatka, Russia) can be predicted by our model when considering pressure changes of ~107 Pa in a volume of ~103–104 m3 and realistic magma compositions. Our results show importance of the deep degassing in the generation of volcanic seismicity and suggest that the DLP swarms beneath active volcanoes might be related to the pulses of volatile-rich basaltic magmas rising from the mantle.