First Historical Eruption of Krasheninnikov Volcano (Eastern Kamchatka): Field Observations and Composition of Lavas Erupted in August‒September 2025

Abstract On August 3, 2025, a few days after a major Mw 8.8 earthquake struck southern Kamchatka, the first historically documented eruption of Krasheninnikov volcano began in the central part of the Eastern Kamchatkan Volcanic Front. During August and September 2025, we carried out three weeks of field observations of the ongoing activity. The eruption was dominated by lava effusion from three vents aligned along a submeridional fissure zone in the summit area of the Northern Cone and was accompanied only by moderate explosive activity. Based on field observations, we identified and characterized the extent and volumes of four distinct lava flows. Drone-based imagery and video allowed determination of the vent locations feeding each flow. By the end of September, the total area of lava flows was estimated at ∼2.5 km2, with an eruptive volume of minimum 0.025 km3. Analyses of 11 samples of lava and volcanic bombs erupted during the first two months show that the products are moderate-K dacites (SiO2 = 64.9–65.7 wt %; K2O = 1.9–2.0 wt %) belonging to a high-Fe tholeiitic series.