Abstract
The Eldgjá lava flood is considered Iceland’s largest volcanic eruption of the Common Era. While it is well established that it occurred after the Settlement of Iceland (circa 874 CE), the date of this great event has remained uncertain. This has hampered investigation of the eruption’s impacts, if any, on climate and society. Here, we use high-temporal resolution glaciochemical records from Greenland to show that the eruption began in spring 939 CE and continued, at least episodically, until at least autumn 940 CE. Contemporary chronicles identify the spread of a remarkable haze in 939 CE, and tree ring-based reconstructions reveal pronounced northern hemisphere summer cooling in 940 CE, consistent with the eruption’s high yield of sulphur to the atmosphere. Consecutive severe winters and privations may also be associated with climatic effects of the volcanic aerosol veil. Iceland’s formal conversion to Christianity dates to 999/1000 CE, within two generations or so of the Eldgjá eruption. The end of the pagan pantheon is foretold in Iceland’s renowned medieval poem, Vǫluspá (‘the prophecy of the seeress’). Several lines of the poem describe dramatic eruptive activity and attendant meteorological effects in an allusion to the fiery terminus of the pagan gods. We suggest that they draw on first-hand experiences of the Eldgjá eruption and that this retrospection of harrowing volcanic events in the poem was intentional, with the purpose of stimulating Iceland’s Christianisation over the latter half of the tenth century.
Highlights
The Eldgjá (‘fire gorge’) eruption occurred along an approximately 75-km-long fissure system associated with Katla volcano, which lies beneath the Mýrdalsjökull ice cap (Fig. 1)
We have focused on a section of the core that contains the signatures of both the Eldgjá eruption and the Millennium Eruption of Changbaishan
Far more striking is a pronounced non-sea-salt sulphur (nssS) signal that begins 7.5 years earlier, i.e. in 939 CE (Fig. 2). This can be firmly attributed to Eldgjá because the prominent horizon is present in the GISP2 ice core, from which glass shards have been extracted and matched geochemically to Eldgjá compositions (Zielinski et al 1995)
Summary
The Eldgjá (‘fire gorge’) eruption occurred along an approximately 75-km-long fissure system associated with Katla volcano, which lies beneath the Mýrdalsjökull ice cap (Fig. 1) It is the largest known lava flood eruption of the Common Era—an estimated 19.6 km of magma (dense-rock equivalent) were erupted, mostly effusively, accompanied by the emission of 30– 70 Tg of SO2 into the atmosphere (Thordarson et al 2001). Ásbj rn is noted as a particular devotee of the pagan god Thor, to whom he dedicated his part of the settled land, by designating it Þórsm rk (‘Thor’s wood’) This area seems later to have been abandoned, likely as a result of the eruption. It is explicitly described as a ‘wasteland’ in other twelfth-century sources (the Icelandic word is eyði and is referred to by Benediktsson 1968)
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