First Findings of Late Pleistocene Tephras of Avachinsky Volcano (Southern Kamchatka)

In the Nikolaevka-1 quarry (53°05′17.45″ N, 158°21′26.28″ E), in lake sediments formed about 100 000 years ago, we found buried ash layers. Geochemical analysis of the volcanic glass from these ash layers allowed, for the first time, the identification of three Late Pleistocene tephras from the Avachinsky volcano labeled 21/23, 21/4, and 21/10. In addition, we found a tephra labeled DS7 from one of the centers of the Karymsky volcanic area, dated to ∼107 ka. The stratigraphic position of Avachinsky ash relative to the DS7 tephra suggests that tephra 21/10 is slightly younger than 100 ka, whereas the other two (21/4 and 21/23) are older than 100 ka. Estimates of the minimum volumes of material ejected during these eruptions make them comparable to most historical eruptive events at this volcano, and eruption 21/4 to the 1945 eruption – the most powerful eruption of the 20th century.