During 16-23 August, seismicity remained above background levels at Shiveluch, although only three earthquakes with magnitudes of 1.7-1.9 occurred. A number of smaller 0- to 6-km-deep earthquakes were registered, as well as many other local shallow seismic signals. The signals were possibly indicative of avalanches and ash-and-gas explosions (one to three per day reached heights of 1-1.5 km above the dome). Volcanic tremor continued at previous levels. Ash-and-gas plumes rose to a maximum height of 4 km above the dome. Thermal anomalies were visible on satellite imagery, but ash was not. Shiveluch remained at Concern Color Code Yellow ("volcano is restless").

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.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)