Abstract
Widespread ash dispersal poses a significant natural hazard to society, particularly in relation to disruption to aviation. Assessing the extent of the threat of far-travelled ash clouds on flight paths is substantially hindered by an incomplete volcanic history and an underestimation of the potential reach of distant eruptive centres. The risk of extensive ash clouds to aviation is thus poorly quantified. New evidence is presented of explosive Late Pleistocene eruptions in the Pacific Arc, currently undocumented in the proximal geological record, which dispersed ash up to 8000 km from source. Twelve microscopic ash deposits or cryptotephra, invisible to the naked eye, discovered within Greenland ice-cores, and ranging in age between 11.1 and 83.7 ka b2k, are compositionally matched to northern Pacific Arc sources including Japan, Kamchatka, Cascades and Alaska. Only two cryptotephra deposits are correlated to known high-magnitude eruptions (Towada-H, Japan, ca 15 ka BP and Mount St Helens Set M, ca 28 ka BP). For the remaining 10 deposits, there is no evidence of age- and compositionally-equivalent eruptive events in regional volcanic stratigraphies. This highlights the inherent problem of under-reporting eruptions and the dangers of underestimating the long-term risk of widespread ash dispersal for trans-Pacific and trans-Atlantic flight routes.
Highlights
The ash-fall record preserved within the ice is swamped by recurrent local Icelandic basaltic eruptions[12], twelve cryptotephra deposits, ranging in age between 11.1 and 83.7 ka b2k, reveal major and trace-element signatures that are inconsistent with an Icelandic anorogenic magmatic setting (Figs 1b and 2, Table 1)
The discovery of several far-travelled volcanic ash clouds highlight the inherent problem of under-reporting eruptions and the under-representation of events from volcanoes with long repose times[2,9]
It is clear that many more eruptions in the past have deposited ash over much larger geographical areas than previously anticipated
Summary
The ash-fall record preserved within the ice is swamped by recurrent local Icelandic basaltic eruptions[12], twelve cryptotephra deposits (glass-shard concentrations insufficiently numerous to be visible to the naked eye), ranging in age between 11.1 and 83.7 ka b2k, reveal major and trace-element signatures that are inconsistent with an Icelandic anorogenic magmatic setting (Figs 1b and 2, Table 1). These cryptotephra deposits are only able to be detected by melting the ice and exploring the residual particulate material with light microscopy. Some of our suggested sources based on comparisons of available major element data include the Ata and Kutcharo (Japan) calderas to NEEM 2033.75 m and NGRIP 2441.28 m, respectively, but the ice-core ages for these events are mismatched with the local eruption stratigraphy and the proposed ages for the formation of these
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