Description: From Riehle and others (1987): "To summarize, our data indicate that most of the pyroclastic flows were emplaced after a debris avalanche of cone material from the northeast sector of Yantarni cone. Blocks of cone material as much as tens of meters across are incorporated in the lowermost pyroclastic-flow deposits, suggesting that the initial pyroclastic flows were partly contemporaneous with avalanching. Debris avalanches are commonly but not necessarily accompanied by directed explosions (Siebert, 1984). We have found a possible but ambiguous candidate for a directed-blast deposit at one site 8 km southeast of the cone. Thus, we conclude that the debris avalanche was caused or at least closely followed by magmatic eruptive activity, but we cannot prove that the avalanche was accompanied by a directed blast."
"Deposits of the debris avalanche and ensuing pyroclastic flows are certainly no older than Holocene by virtue of the absence of glacial erosion. The pyroclastic bed at site 58 that is provisionally correlated with the catastrophic eruption overlies silt with a radiocarbon age of about 2 ka (fig. 12 [in original text]). The radiocarbon age is a minimum, due to the presence of a trace amount of modern rootlets. Moreover, the pyroclastic bed lies atop silt (loess) that contains disseminated ash sized clasts of white, gray, and honey-colored pumice and black obsidian. Such disseminated ash closely resembles, in its proportions of colors, proximal tephra deposits of the caldera- forming eruptions of Aniakchak Caldera collected at a site 30 km southwest of Yantarni Volcano (Riehle, unpublished data). The age of the Aniakchak eruption is between 3.3 and 3.7 ka (Miller and Smith, 1977), and if the correlation with site 58 is valid, then the coarse pyroclastic bed is no more than about 3,500 yr old. Thus, we provisionally consider the catastrophic eruption to be no more than 3,500 yr old and possibly as young as 2,000 yr."
The Global database on large magnitude explosive volcanic eruptions (LaMEVE; 2017) reports a magnitude of 5, bulk eruptive volume of 1 cubic km and a dense rock equivalent eruptive volume of 0.4 cubic km for the eruption.