Eruption Source Parameters for Recent Icelandic Eruptions and Their Implications for Duration and Termination of Events

Abstract:

Since 1947, Iceland has featured 26 volcanic eruptions (2.5 eruptions/year). These include events at the central volcanoes Hekla, Eyjafjallajökull, Grímsvötn and Askja and the fissure eruptions of Surtsey 1963-67 and Nornahraun 2014-15. Of these, 11 are effusive, 8 are mixed (explosive to effusive) and 6 are within-glacier events. Surtsey is the only emergent submarine event (1309 days; 1 km³). Duration of effusive eruptions spans 0.3 to 181 days, with volume, average and peak magma discharge ranging from 10^-5–1.6 km³, 0.5–123 m³/s and 1–370 m³/s. Similarly, the mixed events have durations spanning 2.8 to 393 days with volume, average and peak magma discharge ranging from 0.03–0.87 km³, 14–617 m³/s and 50–35600 m³/s. Duration of within-glacier events spans 4.4 to 14 days with volume, average and peak magma discharge ranging from 0.05–0.27 km³, 9–440 m³/s and 400–14000 m³/s. The discharge profiles for these eruptions are highly variable. Mixed eruptions often feature intense discharge (1500 to 40000 m³/s) at the onset of eruption (lasting hours), but some start in a much more subdued manner (500-1000 m³/s). This initial phase is followed by low (3-20 m³/s) magma discharge lasting for weeks to months that normally terminates abruptly. The onset of effusive eruptions is typified by modest discharge (10’s to 100’s m³/s). They can be very abrupt (<1 day), or drawn out for weeks to months with discharge dropping steadily throughout. The within-glacier events are short-lived explosive events, although with highly varied intensity (see above), and appear to terminate rather abruptly. Plots of eruption duration against size or discharge exhibits no systematic correlation suggesting that none of the eruption source parameters exert principal control on eruption duration or termination. However, these parameters may play a role in conjunction with other factors such as the nature of the lithostratigraphic succession and the local stress field at the eruption site.