RESUMEN
The scale of volcanic eruptions influences the effects of wide-ranging disasters involving ashfall, such as the disruption of lifelines and paralysis of urban functions. This highlights the importance of vehicle availability on ash-covered roads for disaster management personnel involved in rescue and recovery efforts and for citizens who must evacuate or continue their social lives. We conducted tests to scientifically verify the running ability of vehicles on ash-covered roads. Results revealed that all-wheel-drive vehicles showed better running performance than two-wheel-drive vehicles, which get stuck when ashfall thickness exceeds 10 cm. Most of the vehicle's drive power is consumed as energy to scrape ash grains from under the tires, hindering sufficient propulsion. In addition, the tires sink into the ash layer, which increases driving resistance and causes the vehicle to get stuck. Running ability on ash-covered roads is mainly determined by the relation between the "drive system" of the vehicle and the "thickness of ash" on the roads. In addition, road surface conditions, including ash thickness, could change in time and space because of traffic volume and weather conditions.
RESUMEN
The Kamchatka Peninsula is a prominent and wide volcanic arc located near the northern edge of the Pacific Plate. It has highly active volcanic chains and groups, and characteristic lavas that include adakitic rocks. In the north of the peninsula adjacent to the triple junction, some additional processes such as hot asthenospheric injection around the slab edge and seamount subduction operate, which might enhance local magmatism. In the forearc area of the northeastern part of the peninsula, monogenetic volcanic cones dated at <1 Ma were found. Despite their limited spatiotemporal occurrence, remarkable variations were observed, including primitive basalt and high-Mg andesite containing high-Ni (up to 6300 ppm) olivine. The melting and crystallization conditions of these lavas indicate a locally warm slab, facilitating dehydration beneath the forearc region, and a relatively cold overlying mantle wedge fluxed heterogeneously by slab-derived fluids. It is suggested that the collapse of a subducted seamount triggered the ascent of Si-rich fluids to vein the wedge peridotite and formed a peridotite-pyroxenite source, causing the temporal evolution of local magmatism with wide compositional range.