Major explosive eruption of Bezymianny volcano, ash to 12.2 km (40 000 ft) a.s.l.

A major explosive eruption took place at Russia's Bezymianny volcano 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 of the volcano, according to the Tokyo VAAC. This is the strongest eruption of this volcano since September 2012.

At 05:43 UTC, KVERT said they raised the Aviation Color Code from Orange to Red. "Ash cloud as big as 28 x 25 km (17.4 x 15.5 miles) drifts to the northeast of the volcano," the Observatory said, adding that ash explosions up to 10 – 15 km (32 800 – 49 200 feet) a.s.l. could occur at any time. "Ongoing activity could affect international and low-flying aircraft.

This is the strongest eruption of Bezymianny volcano since September 1/2, 2012. It comes just two days after a powerful eruption of nearby Sheveluch volcano ejected ash to an altitude 12 km (39 360 feet) a.s.l. Sheveluch is located 90 km (56 miles) NE of Bezymianny.

The last significant eruption of Bezymianny volcano, although nowhere near today's, took place on March 9, 2017. Based on webcam observations, an ash plume rose to altitudes of 6 – 7 km (20 000 – 23 000 feet) a.s.l. and drifted 20 km (12.4 miles) northeast. The Aviation Color Code was raised from Yellow to Orange. About 30 minutes later, an ash plume rose to altitudes of 7 – 8 km (23 000 – 26 200 feet) a.s.l. and drifted 60 km (37 miles) northwest. Later that day a 274-km-long (170 miles) ash plume identified in satellite images drifted NW at altitudes of 4 – 4.5 km (13 100 – 14 800 feet) a.s.l.; the majority of the leading part of the plume contained a significant amount of ash. A lava flow traveled down the NW part of the lava dome.

Bezymianny is one the most active volcanoes in the world. In 1955, for the first time in history, it started to erupt, and 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.

Featured image: Eruption at Bezymianny volcano on March 9, 2017. Credit: KB GS RAS