KVERT reported that thermal anomalies at Sheveluch, over both the “300 years of RAS” dome on the SW flank of Old Sheveluch and the lava dome in the crater of Young Sheveluch, were identified in satellite images during 8-15 August.

An explosive eruption at the “300 years of RAS” dome began at 1145 on 17 August and generated ash plumes that rose as high as 9 km (30,000 ft) a.s.l. by 1200, about 5.7 km above the summit. Both the Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS) and the Kamchatka Volcanological Station reported that two vents on the W flank were active and producing ash plumes. Lightning strikes occurred within the ash plumes. Ashfall was reported in Ust'-Kamchatsk (100 km SE) and by 1550 the plumes had drifted 492 km SE. KVERT raised the Aviation Color Code to Red (the highest level on a four-color scale) at 2040. Incandescence from the vents was visible at night.

Explosive activity persisted, producing ash plumes to lower altitudes, or as high as 5 km (16,400 ft) a.s.l., at least through 0553 on 18 August. The plumes drifted SE and ESE and had drifted as far as 1,520 km. By 1920 the leading edge of a 1,900-km-long ash cloud was 2,400 km from the volcano. At 2033 the Aviation Color Code was lowered to Orange. KVERT noted that although the explosive phase had likely ended, extrusion from two vents near the “300 years of RAS” dome was ongoing; one of the vents was likely new.

Geological Summary. The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1,300 km3 andesitic volcano is one of Kamchatka's largest and most active volcanic structures, with at least 60 large eruptions during the Holocene. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes occur on its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large open caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT), Kamchatka Volcanological Station, Institute of Volcanology and Seismology (IVS) of the Far Eastern Branch of the Russian Academy of Sciences (FEB RAS)