Constraining recent Shiveluch volcano eruptions (Kamchatka, Russia) by means of dendrochronology

Abstract

Abstract. Shiveluch (N 56°38´, E 161°19´; elevation: active dome ~2500 m, summit of Old Shiveluch 3283 m) is one of the most active volcanoes in Kamchatka. The eruptions of Shiveluch commonly result in major environmental damage caused by debris avalanches, hot pyroclastic flows, tephra falls and lahars. Constraining these events in time and space is important for the understanding and prediction of these natural hazards. The last major eruption of Shiveluch occurred in 2005; earlier ones, dated by instrumental, historical, 14C and tephrochronological methods, occurred in the last millennium around AD 1030, 1430, 1650, 1739, 1790–1810, 1854, 1879–1883, 1897–1898, 1905, 1927–1929, 1944–1950, and 1964. A lava dome has been growing in the 1964 crater since 1980, occasionally producing tephra falls and pyroclastic flows. Several Shiveluch eruptions (~AD 1050, 1650, 1854, 1964) may have been climatically effective and are probably recorded in the Greenland ice cores. Previously, most dates for eruptions before AD 1854 were obtained by tephrochronology and constrained by radiocarbon dating with an accuracy of several decades or centuries. In this paper we report tree-ring dates for a recent pyroclastic flow in Baidarnaia valley. Though the wood buried in these deposits is carbonized, fragile and poorly preserved, we were able to measure ring-width using standard tree-ring equipment or photographs and to cross-date these samples against the regional Kamchatka larch ring-width chronology. The dates of the outer rings indicate the date of the eruptions. In the Baidarnaia valley the eruption occurred shortly after AD 1756, but not later than AD 1758. This date coincides with the decrease of ring-width in trees growing near Shiveluch volcano in 1758–1763 in comparison with the control "non-volcanic" chronology. The pyroclastic flow in Kamenskaia valley, although similar in appearance to the one in Baidarnaia valley, definitively yielded a different age. Due to the age limit of the reference chronology (AD 1632–2005) and its short overlap with the sample chronology in Kamenskaia valley the dates of these deposits are very preliminary. The deposits probably date back to approximately AD 1649 or a few years later. This date is in close agreement with the previously obtained radiocarbon date of these sediments to AD 1641(1652)1663. Our data agree well with the tephrochronological findings, and further constrain the chronology of volcanic events in this remote area.