Abstract
ABSTRACTSeveral cryptotephra layers that originate from Icelandic volcanic eruptions with a volcanic explosivity index (VEI) of ≤ 4 and tephra volumes of < 1 km3 have previously been identified in Northern Europe, albeit within a restricted geographical area. One of these is the Hekla 1947 tephra that formed a visible fall‐out in southern Finland. We searched for the Hekla 1947 tephra from peat archives within the previously inferred fall‐out zone but found no evidence of its presence. Instead, we report the first identification of Hekla 1845 and Hekla 1510 cryptotephra layers outside of Iceland, the Faroe Islands, Ireland and the UK. Additionally, Hekla 1158 tephra was found in Finland for the first time. Our results confirm that Icelandic eruptions of moderate size can form cryptotephra deposits that are extensive enough to be used in inter‐regional correlations of environmental archives and carry a great potential for refining regional tephrochronological frameworks. Our results also reveal that Icelandic tephra has been dispersed into Finnish airspace at least seven times during the past millennium and in addition to a direct eastward route the ash clouds can travel either via a northerly or a southerly transport pathway.
Highlights
Cryptotephra layers produced by very large (VEI ≥ 5: Newhall and Self, 1982) silicic explosive eruptions of Icelandic volcanoes form the backbone of the North European tephrochronological frameworks and provide powerful tools for dating and correlating palaeoenvironmental archives such as peat sequences and lake sediment records from the Last Glacial–Interglacial transition (LGIT) and the Holocene (e.g. Wastegård and Davies, 2009; Lawson et al, 2012; Davies et al, 2012; Timms et al, 2019)
In addition to these major marker layers, cryptotephra horizons from Icelandic smaller scale (VEI ≤ 4) eruptions (e.g. Dugmore et al, 1996; Rea et al, 2012; Watson et al, 2015), as well as ultra‐distal cryptotephra deposits that are sourced from other continents and volcanic centres, have been detected across Northern Europe (e.g. Jensen et al, 2014; van der Bilt et al, 2017; Plunkett and Pilcher, 2018; Jones et al, 2019)
Despite careful inspection of 47 surface peat cores and monoliths, no cryptotephra deposits could be attributed to the Hekla 1947 eruption
Summary
Cryptotephra layers produced by very large (VEI ≥ 5: Newhall and Self, 1982) silicic explosive eruptions of Icelandic volcanoes form the backbone of the North European tephrochronological frameworks and provide powerful tools for dating and correlating palaeoenvironmental archives such as peat sequences and lake sediment records from the Last Glacial–Interglacial transition (LGIT) and the Holocene (e.g. Wastegård and Davies, 2009; Lawson et al, 2012; Davies et al, 2012; Timms et al, 2019). Wastegård and Davies, 2009; Lawson et al, 2012; Davies et al, 2012; Timms et al, 2019) In addition to these major marker layers, cryptotephra horizons from Icelandic smaller scale (VEI ≤ 4) eruptions Icelandic eruptions of VEI ≤ 4 have generally produced tephra isochrones with restricted dispersal areas in the distal field (Lawson et al, 2012) and most of the ultra‐distal cryptotephras have been identified at single sites far As all the 18 historical Hekla eruptions have started with an explosive phase during which a sustained tephra plume has reached a height of 12–36 km (Thorarinsson, 1967; Janebo et al, 2016), each of these eruptions, independent of size, carries the potential to form distally transported cryptotephra deposits in the North European palaeoenvironmental records
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