KVERT reported that activity at Bezymianny increased on 21 July and then escalated on 24 July. Lava-dome extrusion significantly increased on 21 July, causing collapses of the E part of the lava dome and subsequent hot avalanches of material. Activity continued and on 22 July the Aviation Color Code was raised to Orange (the third level on a four-color scale). Extrusion and collapses continued through 24 July with ash plumes continuing to rise 2-3 km a.s.l. and drift at least 70 km SW. A strong explosive eruption began at 1510 on 24 July, prompting KVERT to raise the Aviation Color Code to Red at 2002. The explosions produced a large ash plume that initially rose to 9.6 km (31,500 ft) a.s.l. and then to 12 km (39,400 ft) a.s.l.; the plume drifted 300 km ESE. Pyroclastic flows descended the flanks. By 0035 on 25 July the explosive phase had ended so the Aviation Color Code was lowered to Orange. Effusion at the lava dome continued and viscous lava extruded onto the dome’s flanks. The activity was accompanied by notable steam-and-gas emissions and the descent of hot avalanches. Ash clouds generated on 24 July were visible in satellite images drifting 2,500 km SE until 25 July and 1,800 km SW until 27 July. The Aviation Color Code was lowered to Yellow at 2317 on 28 July. Dates are based on UTC times; specific events are in local time where noted.

Geological Summary. The modern Bezymianny, much smaller than its massive neighbors Kamen and Kliuchevskoi on the Kamchatka Peninsula, was formed about 4,700 years ago over a late-Pleistocene lava-dome complex and an edifice built about 11,000-7,000 years ago. Three periods of intensified activity have occurred during the past 3,000 years. The latest period, which was preceded by a 1,000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of St. Helens in 1980, produced a large open crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)