The Structural Features and Development of the Marine Accumulative Terrace in Avachinsky Gulf near the Prilivnaya River (Kamchatka)

The structure of a marine accumulative terrace has been studied and the stages of its Holocene development have been reconstructed. The approximate age of the beach ridges and their average rates of accumulation (progradation) in the Prilivnaya River valley have been determined. The tephrochronological scale for the study area has been refined: tephra layers were identified and correlated within the peat-pyroclastic cover. In addition to regional marker horizons (KSht3, OP, and KS1), layers associated with eruptions of Avachinsky Volcano were identified based on chemical analysis. The oldest tephra layer is approximately 5400 years old. Geological evidence of an ancient strong subduction earthquake was discovered, manifested as a buried erosional scarp no older than 1400 years. Mathematical models of the morpholithodynamics of the Avachinsky Gulf coast were developed. The modern sedimentation parameters of the coastal zone were established. The proximity to Petropavlovsk-Kamchatsky, the area’s popularity, and the presence of a tsunami hazard zone underscore the relevance of this study.