Rittmann volcano, Antarctica as the source of a widespread 1252 ± 2 CE tephra layer in Antarctica ice

Abstract

Tephra occur in many ice cores from Antarctica and are important time markers that assist in correlations between cores and in dating their valuable climate records. Major element compositions of glass shards in a trachytic tephra found in ice cores drilled at WAIS Divide, Roosevelt Island and Styx Glacier, and blue ice patches at Brimstone Peak and the Rennick Glacier in Victoria Land, are similar and suggest they are the same tephra. The composition of the tephra is also similar to tephra layers reported in 3 others ice cores from the East and West Antarctica Ice Sheets. In the WAIS Divide WDC06A ice core the tephra is dated as 1252±2 CE. The distribution of the tephra implies a source in northern Victoria Land, Antarctica. The Pleiades, Mt. Melbourne and Rittmann volcano in northern Victoria Land all have evidence of recent eruptive activity which has resulted in the occurrence of trachytic tephra in ice cores, blue ice/snow areas and as surficial tephra layers. Although there is a significant area of geothermal activity at Mt. Rittmann, until now there has been no evidence of any recent eruptive activity. A pyroclastic breccia, with glassy fiamme-like clasts was formed by an explosive eruption from Rittmann volcano. Analyses of the glass clasts and whole rock analyses of some lava samples have trachytic compositions very similar to the 1252 CE tephra. Rittmann volcano is now considered the source of this tephra, which is here named the Rittmann tephra. Rittmann tephra is spread over 2000 km and the 8 known occurrences makes it the most widely correlated tephra layer in Antarctic ice and a valuable marker layer. The wide distribution implies a large possibly Plinian eruption which makes it the largest known eruptions from any Holocene volcano in the western Ross Sea area. This discovery of young explosive eruptions from Rittmann volcano and other northern Victoria Land volcanoes show that there is a significant volcanic hazard from these volcanoes especially to aircraft operations.