A major eruption started at Bezymianni volcano, Kamchatka, Russia at 03:41 UTC on December 20, 2017. According to Tokyo VAAC, volcanic ash plume is reaching 15.2 km (50 000 feet) above sea level and drifting NE. In terms of ash cloud height, this is the strongest eruption anywhere on the planet this year.

The activity at the volcano started gradually increasing on Monday, December 18. According to video data by RAS, hot avalanches at the southeastern flank of the lava dome were observed for several hours, probably as a result of the extrusive eruption.

This activity, accompanied by strong gas-steam activity continued through early December 20 when strong ash explosions started at 03:41 UTC. Ash plume rose to about 8 km (26 000 feet) a.s.l., forcing authorities to raise the Aviation Color Code from Orange to Red.

At 04:09 UTC, ash plume/cloud was extending 20 km (12 miles) NE of the crater. By 04:20 UTC, it was already 85 km (53 miles) NE of the crater.

"Strong ash explosions up to 15 km (49 000 feet) a.s.l. occur at this time," KVERT said 04:47 UTC. "Ongoing activity could affect international and low-flying aircraft," they warned.

Webcam located in Kozyrervsk, approximately 50 km (31 miles) west of Bezymianny volcano. Credit: Kamchatka Branch of the Geophysical Survey RAS

Webcam located in seismic station, approximately 7 km (4.3 miles) East of Bezymianny volcano. Credit: Kamchatka Branch of the Geophysical Survey RAS

The activity of the volcano decreased, KVERT said 10:59 UTC, lowering the Aviation Color Code back to Orange. Strong ash emission is no longer coming out of the volcano, but separate ash clouds continue drifting to the northeast. Gas-steam activity continues and and there is a danger of ash explosions up to to 10 km (32 800 feet) a.s.l., it said.

The last major explosive eruption at Bezymianny volcano started at 04:53 UTC on Friday, June 16, 2017. By 05:10 UTC, ash plume from the eruption reached an altitude of 12.2 km (40 000 feet) above sea level and a distance of 40 km (25 miles) NE.

Bezymianny is one the most active volcanoes in the world. It started erupting, for the first time in known history, in 1955. After six months, it produced a catastrophic eruption with the total volume of eruptive products over 3 km3.

The lava dome began to grow in the explosive caldera immediately after the catastrophe and still continues. At least 44 Vulcanian-type strong explosive eruptions of Bezymianny occurred between 1965 - 2012.

Geological summary

Prior to its noted 1955-56 eruption, Bezymianny had been considered extinct. The modern volcano, much smaller in size than its massive neighbors Kamen and Kliuchevskoi, was formed about 4700 years ago over a late-Pleistocene lava-dome complex and an ancestral edifice built about 11000 - 7000 years ago. Three periods of intensified activity have occurred during the past 3000 years.

The latest period, which was preceded by a 1000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of St. Helens in 1980, produced a large horseshoe-shaped 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. (GVP)

Featured image: Eruption of Bezymianni volcano on December 20, 2017. Credit: Kamchatka Branch of the Geophysical Survey RAS