Ground deformation reveals the scale-invariant conduit dynamics driving explosive basaltic eruptions

The mild activity of basaltic volcanoes is punctuated by violent explosive eruptions that occur without obvious precursors. Modelling the source processes of these sudden blasts is challenging. Here, we use two decades of ground deformation (tilt) records from Stromboli volcano to shed light, with unprecedented detail, on the short-term (minute-scale) conduit processes that drive such violent volcanic eruptions. We find that explosive eruptions, with source parameters spanning seven orders of magnitude, all share a common pre-blast ground inflation trend. We explain this exponential inflation using a model in which pressure build-up is caused by the rapid expansion of volatile-rich magma rising from depth into a shallow (<400 m) resident magma conduit. We show that the duration and amplitude of this inflation trend scales with the eruption magnitude, indicating that the explosive dynamics obey the same (scale-invariant) conduit process. This scale-invariance of pre-explosion ground deformation may usher in a new era of short-term eruption forecasting.

CO2 favours the accumulation of excess fluids in felsic magmas

&lt;p&gt;Volcano deformation and gas emissions provide insights into subsurface magmatic systems. Large discrepancies are observed between the volumes calculated from deformation data, mass of emitted gases, and volumes of erupted magmas. Such discrepancies hinder our capacity to predict the magnitude and intensity of imminent eruptions and are ascribed to the amount of excess fluids stored in magma reservoirs. High-pressure (1240 bar) and high-temperature (1200 &amp;#176;C) hot isostatic press experiments show that the amount of trapped excess fluids in haplogranitic magmas with variable crystal contents (30, 50, 60, and 70 vol.%) depends strongly on fluid composition. Magmas with CO&lt;sub&gt;2&lt;/sub&gt; excess fluids become permeable at much larger porosities (44% higher) with respect to the H&lt;sub&gt;2&lt;/sub&gt;O-rich counterparts at equivalent crystallinity. Available excess gas geochemistry data calculated from volatile-saturated melt inclusion record, syn-eruptive SO&lt;sub&gt;2&lt;/sub&gt; emission, and erupted juvenile porosity data collected for crystal-rich andesite and crystal-poor dacite/rhyolite volcanoes with known eruption magnitude and intensity (Mt St Helens 1980, Pinatubo 1991, Soufri&amp;#232;re Hills 1996, and Merapi 2010) reveal that the discrepancy between erupted magma volume and SO&lt;sub&gt;2&lt;/sub&gt; released during the eruption increases with CO&lt;sub&gt;2&lt;/sub&gt; excess in magmas. In agreement with our experiments, these data highlight that CO&lt;sub&gt;2&lt;/sub&gt;-rich fluids enhance magma&amp;#8217;s capacity to store excess volatiles and shed light on the largest discrepancies between pre-eruptive deformation, gas emissions, and eruption intensity and magnitude.&lt;/p&gt;

The magnitude and impact of the 431 CE Tierra Blanca Joven eruption of Ilopango, El Salvador

The Tierra Blanca Joven (TBJ) eruption from Ilopango volcano deposited thick ash over much of El Salvador when it was inhabited by the Maya, and rendered all areas within at least 80 km of the volcano uninhabitable for years to decades after the eruption. Nonetheless, the more widespread environmental and climatic impacts of this large eruption are not well known because the eruption magnitude and date are not well constrained. In this multifaceted study we have resolved the date of the eruption to 431 ± 2 CE by identifying the ash layer in a well-dated, high-resolution Greenland ice-core record that is >7,000 km from Ilopango; and calculated that between 37 and 82 km3of magma was dispersed from an eruption coignimbrite column that rose to ∼45 km by modeling the deposit thickness using state-of-the-art tephra dispersal methods. Sulfate records from an array of ice cores suggest stratospheric injection of 14 ± 2 Tg S associated with the TBJ eruption, exceeding those of the historic eruption of Pinatubo in 1991. Based on these estimates it is likely that the TBJ eruption produced a cooling of around 0.5 °C for a few years after the eruption. The modeled dispersal and higher sulfate concentrations recorded in Antarctic ice cores imply that the cooling would have been more pronounced in the Southern Hemisphere. The new date confirms the eruption occurred within the Early Classic phase when Maya expanded across Central America.

ENSO sensitivity to radiative forcing

&lt;p&gt;To improve El Ni&amp;#241;o / Southern Oscillation (ENSO) predictions and projections in a changing climate, it is essential to better understand ENSO&amp;#8217;s sensitivities to external radiative forcings. Strong volcanic eruptions can help to clarify ENSO&amp;#8217;s sensitivities, mechanisms, and feedbacks. Strong explosive volcanic eruptions inject millions of tons of sulfur dioxide into the stratosphere, where they are converted into sulfate aerosols. For equatorial volcanoes, these aerosols can spread globally, scattering and absorbing incoming sunlight, and inducing a global-mean surface cooling. Despite this global-mean cooling effect, paleo data confirm remarkable warming of the eastern equatorial Pacific in the two years after a tropical eruption, with a shift towards an El Ni&amp;#241;o-like state. To illuminate this response and explain why it tends to occur during particular seasons and ENSO phases, we present a unified framework that includes the roles of the seasonal cycle, stochastic wind forcing, eruption magnitude, and various tropical Pacific climate feedbacks. Analyzing over 20,000 years of large-ensemble simulations from the GFDL-CM2.1 climate model forced by volcanic eruptions, we find that the ENSO response comprises both stochastic and deterministic components, which vary depending on the perturbation season and the ocean preconditioning. For boreal winter eruptions, stochastic dispersion largely obscures the deterministic response, being the largest for the strong El Ni&amp;#241;o preconditioning. Deterministic El Ni&amp;#241;o-like responses to summer eruptions are well seen on neutral ENSO and weak to moderate El Ni&amp;#241;o preconditioning and grow with the eruption magnitude. The relative balance of these components determines the predictability and strength of the ENSO response. The results clarify why previous studies obtained seemingly conflicting results.&lt;/p&gt;

4. The enemy within

‘The Enemy Within’ begins with volcanic super-eruptions and their devastating consequences such as the 1815 eruption of volcano Tambora in Indonesia, and ancient eruptions in Yellowstone, USA, and Toba, northern Sumatra. Volcanic explositivity index, eruption magnitude, and eruption intensity are explained. Volcanic landslides in Hawaii and the Canary Islands will, in the future, result in giant tsunamis wreaking havoc around the Pacific and Atlantic Ocean rims. But when will they happen? Finally, the fate of industrial cities, such as Tokyo, located near active fault-lines and in earthquake zone, and the resultant effects on the world economy are considered.

The influence of eruption season on the global aerosol evolution and radiative impact of tropical volcanic eruptions

Simulations of tropical volcanic eruptions using a general circulation model with coupled aerosol microphysics are used to assess the influence of season of eruption on the aerosol evolution and radiative impacts at the Earth's surface. This analysis is presented for eruptions with SO2 injection magnitudes of 17 and 700 Tg, the former consistent with estimates of the 1991 Mt. Pinatubo eruption, the later a near-"super eruption". For each eruption magnitude, simulations are performed with eruptions at 15° N, at four equally spaced times of year. Sensitivity to eruption season of aerosol optical depth (AOD), clear-sky and all-sky shortwave (SW) radiative flux is quantified by first integrating each field for four years after the eruption, then calculating for each cumulative field the absolute or percent difference between the maximum and minimum response from the four eruption seasons. Eruption season has a significant influence on AOD and clear-sky SW radiative flux anomalies for both eruption magnitudes. The sensitivity to eruption season for both fields is generally weak in the tropics, but increases in the mid- and high latitudes, reaching maximum values of ~75 %. Global mean AOD and clear-sky SW anomalies show sensitivity to eruption season on the order of 15–20 %, which results from differences in aerosol effective radius for the different eruption seasons. Smallest aerosol size and largest cumulative impact result from a January eruption for Pinatubo-magnitude eruption, and from a July eruption for the near-super eruption. In contrast to AOD and clear-sky SW anomalies, all-sky SW anomalies are found to be insensitive to season of eruption for the Pinatubo-magnitude eruption experiment, due to the reflection of solar radiation by clouds in the mid- to high latitudes. However, differences in all-sky SW anomalies between eruptions in different seasons are significant for the larger eruption magnitude, and the ~15 % sensitivity to eruption season of the global mean all-sky SW anomalies is comparable to the sensitivity of global mean AOD and clear-sky SW anomalies. Our estimates of sensitivity to eruption season are larger than previously reported estimates: implications regarding volcanic AOD timeseries reconstructions and their use in climate models are discussed.