Abstract
Large explosive eruptions inject volcanic gases and fine ash to stratospheric altitudes, contributing to global cooling at the Earth’s surface and occasionally to ozone depletion. The modelling of the climate response to these strong injections of volatiles commonly relies on ice-core records of volcanic sulphate aerosols. Here we use an independent geochemical approach which demonstrates that the great 1257 eruption of Samalas (Lombok, Indonesia) released enough sulphur and halogen gases into the stratosphere to produce the reported global cooling during the second half of the 13th century, as well as potential substantial ozone destruction. Major, trace and volatile element compositions of eruptive products recording the magmatic differentiation processes leading to the 1257 eruption indicate that Mt Samalas released 158 ± 12 Tg of sulphur dioxide, 227 ± 18 Tg of chlorine and a maximum of 1.3 ± 0.3 Tg of bromine. These emissions stand as the greatest volcanogenic gas injection of the Common Era. Our findings not only provide robust constraints for the modelling of the combined impact of sulphur and halogens on stratosphere chemistry of the largest eruption of the last millennium, but also develop a methodology to better quantify the degassing budgets of explosive eruptions of all magnitudes.
Highlights
Sulphur (S) gases injected into the stratosphere during plinian eruptions are converted into sulphate aerosols that travel around the globe and backscatter solar radiation, resulting in a net cooling of the troposphere and the Earth’s surface[1]
Archaeologists recently determined a date of 1258 for mass burial of thousands of medieval skeletons in London[10], that could be linked in some respect to climatic perturbations in the Northern Hemisphere by the 1257 Samalas eruption
The recent re-evaluation of the record of volcanic sulphate deposition based on an extensive array of Antarctic ice cores suggested that a total of 170 Mt of SO2 (85 Tg of S) would have been released to produce the observed sulphate spikes, greater than the 45 Mt of SO2 estimated for the 1815 Tambora eruption[16]
Summary
Sulphur (S) gases injected into the stratosphere during plinian eruptions are converted into sulphate aerosols that travel around the globe and backscatter solar radiation, resulting in a net cooling of the troposphere and the Earth’s surface[1]. We further quantify the distribution of sulphur and halogens between the pre-eruptive silicate melt (melt inclusions), the volatile-bearing mineral phases (sulphide (S), apatite (SO2, Cl) and amphibole (Cl)), and the vapour phase (Fig. 3) consisting of gas species exsolved during in-situ crystallization of the trachydacite in the shallow crust, with possible incremental influx of deeper-derived vapour phase[20].
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