KVERT reported that during 25 February-4 March seismic activity at Koryaksky was at background levels. Observers reported that during 3-4 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 more than 200 km ENE. Ash deposits were seen at the summit. Ash deposits 1-2 mm thick accumulated in an area between Koryaksky and Avachinsky volcanoes. The Level of Concern Color Code was raised to Orange.

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.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)