David Budd

Persistent multitiered magma plumbing beneath Katla volcano, Iceland

Recent seismic unrest and a persistent Holocene eruption record at Katla volcano, Iceland indicate that a near-future eruption is possible. Previous petrological investigations suggest that Katla is supplied by a simple plumbing system that delivers magma directly from depth, while seismic and geodetic data also point toward the existence of upper-crustal magma storage. To characterize Katlas recent plumbing system, we established mineral-melt equilibrium crystallization pressures from four age-constrained Katla tephras spanning from 8 kyr BP to 1918. The results point to persistent shallow- (≤8 km depth) as well as deep-crustal (ca. 10 – 25 km depth) magma storage beneath Katla throughout the last 8 kyr. The presence of multiple magma storage regions implies that mafic magma from the deeper reservoir system may become gas-rich during ascent and storage in the shallow crust and erupt explosively. Alternatively, it might intersect evolved magma pockets in the shallow-level storage region, and so increase the potential for explosive mixed-magma ash eruptions.

Ancient Oral Tradition Describes Volcano–Earthquake Interaction at Merapi Volcano, Indonesia

Abstract erapi volcano is among the most hazardous volcanoes on the planet. Ancient avanese folklore describes erapis activity as the interaction between the pirit Kings that inhabit the volcano and the ueen of the South ea, who resides at arangtritis beach, 50 km of erapi. The royal palace in ogyakarta is located half‐way along the hypothetical line between erapi and arangtritis (the erapi–raton–outh ea axis) to bring balance between these mystical forces. In 2006 and 2010, erapi erupted explosively and on both occasions, earthquakes shook the region and the eruptions grew more violent in response. These earthquakes appear to influence the sub‐volcanic magma supply of erapi and a positive feedback loop has recently been postulated between the volcano and local earthquake patterns. The 2006 earthquakes clustered along the pak iver fault to the south of the volcano, which trends –, and reaches the southern sea at arangtritis beach, the fabled residence of the ueen of the South ea. Our interpretation of the erapi–raton–outh ea axis is that local folklore was used by ancient people to describe and rationalize the complex interplay between geological processes. We suggest that erapi displayed volcano–earthquake interaction many times in the past, and not only during its most recent eruptive cycle. Although now shrouded in mystery, these oral traditions can be thought of as an ancient hazard mitigation tool, which makes them likely useful in helping to foster effective dialogues with a variety of target parties and interest groups around the volcanos slopes.

Magma reservoir dynamics at Toba caldera, Indonesia, recorded by oxygen isotope zoning in quartz

Quartz is a common phase in high-silica igneous rocks and is resistant to post-eruptive alteration, thus offering a reliable record of magmatic processes in silicic magma systems. Here we employ the 75 ka Toba super-eruption as a case study to show that quartz can resolve late-stage temporal changes in magmatic δ18O values. Overall, Toba quartz crystals exhibit comparatively high δ18O values, up to 10.2‰, due to magma residence within, and assimilation of, local granite basement. However, some 40% of the analysed quartz crystals display a decrease in δ18O values in outermost growth zones compared to their cores, with values as low as 6.7‰ (maximum ∆core−rim = 1.8‰). These lower values are consistent with the limited zircon record available for Toba, and the crystallisation history of Toba quartz traces an influx of a low-δ18O component into the magma reservoir just prior to eruption. Here we argue that this late-stage low-δ18O component is derived from hydrothermally-altered roof material. Our study demonstrates that quartz isotope stratigraphy can resolve magmatic events that may remain undetected by whole-rock or zircon isotope studies, and that assimilation of altered roof material may represent a viable eruption trigger in large Toba-style magmatic systems.