Forecasting eruptions from long-quiescent volcanoes

Forecasts of eruption are uncertain. The uncertainty is amplified when volcanoes reawaken after several generations in repose, because direct evidence of previous behaviour is rarely available. It fosters scepticism about warnings of volcanic activity and may compromise the success of emergency procedures. The quality of forecasts has improved over the past 50 years, owing mainly to a growing sophistication in statistical analyses of unrest. Physics-based analyses have yet to achieve the same level of maturity. Their application has been delayed by a view that volcanoes are too complex to share patterns of behaviour that can be described in a deterministic manner. This view is being increasingly challenged and an emerging line of inquiry is to understand how forecasts can be further improved by integrating statistical approaches with new constraints on possible outcomes from physics-based criteria. The introduction of deterministic reasoning yields rational explanations of why forecasts are not perfect and, as a result, offers new opportunities for increasing public confidence in warnings of eruption

Forecasting Volcanic Eruptions: Beyond the Failure Forecast Method

Volcano-tectonic seismicity and ground movement are the most reliable precursors to eruptions after extended intervals of repose, as well as to flank eruptions from frequently active volcanoes. Their behavior is consistent with elastic-brittle failure of the crust before a new pathway is opened to allow magma ascent. A modified physical model shows that precursory time series are governed by a parent relation between faulting and elastic deformation in extension, subject to independent constraints on the rate of crustal loading with time. The results yield deterministic criteria that can be incorporated into existing operational procedures for evaluating the probability of crustal failure and, hence, levels of alert during an emergency. They also suggest that the popular failure forecast method for using precursory time series to forecast eruptions is a particular form of the parent elastic-brittle model when rates of stress supply are constant, and that magma transport and crustal fracturing during unrest tend toward conditions for minimizing rates of energy loss

Controls on explosive-effusive volcanic eruption styles

One of the biggest challenges in volcanic hazard assessment is to understand how and why eruptive style changes within the same eruptive period or even from one eruption to the next at a given volcano. This review evaluates the competing processes that lead to explosive and effusive eruptions of silicic magmas. Eruptive style depends on a set of feedbacks involving interrelated magmatic properties and processes. Foremost of these are magma viscosity, gas loss, and external properties such as conduit geometry. Ultimately, these parameters control the speed at which magmas ascend, decompress and outgas en route to the surface, and thus determine eruptive style and evolution

The 1831 eruption of Babuyan Claro that never happened: has the source of one of the largest volcanic climate forcing events of the nineteenth century been misattributed?

Abstract The 1831 eruption of Babuyan Claro in the Philippines is regarded as one of the most significant volcanic climate forcing events of the nineteenth century. Modern databases have assigned the eruption a VEI of 4? and Magnitude of 4.7. Our analysis of historical sources, however, suggests that there was no such eruption in 1831 and that this date is the result of a misinterpretation of a traveller’s account which had been taken to be the primary source. We therefore suggest that the 1831 eruption is a false event. In this case, one or more eruptions elsewhere must have been responsible for producing the climate-impacting stratospheric sulphate aerosol in 1831. Our results reveal the need to re-evaluate the hazard assessment of Babuyan Claro volcano and also, potentially, the quantitative treatment of the 1831 stratospheric sulphate aerosol in climate models. The Babuyan Claro example discussed in this paper therefore reinforces a call for the careful analysis of primary historical sources in volcanology

U-series disequilibria in young (A.D.1944) Vesuvius rocks : preliminary implications for magma residence times and volatile addition.

The results of a preliminary U-series study of the timescale of magmatic processes at Vesuvius are presented. Phonotephrites of the 1944 eruption of Vesuvius show 0–15% 230Th–238U and 350–1150% 226Ra–230Th disequilibria. Apparent U–Th internal isochrons for a lava and a cumulate nodule suggest crystal residence times of 12 and 39 ka, respectively. A tephra sample shows isotopic heterogeneity, possibly related to mixing of younger crystal-laden melt and older crystals giving apparent U–Th ages of 0.4 and 18 ka, respectively. Mineral 226Ra–230Th disequilibria on Ba-normalised internal isochron diagrams suggest Ra–Th ages of 1730–3300 years for the same rocks and phenocrysts. Minor 226Ra/230Th heterogeneity between minerals and groundmass (or whole rock) is evidence of open-system Ra–Th behaviour. This heterogeneity suggests that there have been recent, post-crystallisation changes in melt composition that affected 226Ra more than 230Th. Continued crystallisation in a Ra-enriched magma has subsequently resulted in Ra–Th disequilibria probably as a result of addition via a fluid-rich phase. Magma differentiation, residence time, transport, and pervasive gas addition at Vesuvius apparently occur over geologically short periods

Understanding volcanic hazard at the most populated caldera in the world: Campi Flegrei, Southern Italy

Naples and its hinterland in Southern Italy are one of the most urbanized areas in the world under threat from volcanic activity. The region lies within range of three active volcanic centers: Vesuvius, Campi Flegrei, and Ischia. The Campi Flegrei caldera, in particular, has been in unrest for six decades. The unrest followed four centuries of quiescence and has heightened concern about an increased potential for eruption. Innovative modeling and scientific drilling are being used to investigate Campi Flegrei, and the results highlight key directions for better understanding the mechanisms of caldera formation and the roles of magma intrusion and geothermal activity in determining the volcano's behavior. They also provide a framework for evaluating and mitigating the risk from this caldera and other large ones worldwide