KVERT reported that seismic activity at Koryaksky was above background levels on 3 March and at background levels on the other days during 27 February-6 March. Observers reported that during 3-5 March gas plumes containing a small amount of ash rose to an altitude of 3.7 km (12,100 ft) a.s.l. and drifted ENE, E, and SE. The plumes were also seen on satellite imagery. Ash deposits were seen at the summit, and on the N flank at a thickness of about 4 cm. Ash deposits 1-2 mm thick had accumulated in an area between Koryaksky and Avachinsky volcanoes. A weak new fumarole was seen in the crater. The Level of Concern Color Code remained Orange.

Based on information from the Yelizovo Airport, the Tokyo VAAC reported ash on 8 March. On 10 March, an ash plume rose to an altitude of 3.7 km (12,000 ft) a.s.l. and drifted SE.

Geological Summary. The large symmetrical Koryaksky stratovolcano is the most prominent landmark of the NW-trending Avachinskaya volcano group, which towers above Kamchatka's largest city, Petropavlovsk. Erosion has produced a ribbed surface on the eastern flanks of the 3430-m-high volcano; the youngest lava flows are found on the upper W flank and below SE-flank cinder cones. Extensive Holocene lava fields on the western flank were primarily fed by summit vents; those on the SW flank originated from flank vents. Lahars associated with a period of lava effusion from south- and SW-flank fissure vents about 3900-3500 years ago reached Avacha Bay. Only a few moderate explosive eruptions have occurred during historical time, but no strong explosive eruptions have been documented during the Holocene. Koryaksky's first historical eruption, in 1895, also produced a lava flow.

Sources: Tokyo Volcanic Ash Advisory Center (VAAC), Kamchatkan Volcanic Eruption Response Team (KVERT)