Constraints on climate forcing by sulphate aerosols from seasonal changes in Earth's spin

Angular momentum exchanges between atmosphere and solid Earth are strongly modulated by variations in global atmospheric circulation. Geodetically determined length-of-day (LOD) fluctuations provide an independent resource to investigate climate changes. Here, I evaluate the effects of volcanic and anthropogenic sulphate aerosols on Earth’s rotational energy variations. The period analysed, 1980–2002, shows that the strongest seasonal LOD variations are related to sulphate peak concentrations from the El-Chichon 1982, and Pinatubo and Cerro ´ Hudson 1991 volcanic eruptions. The Earth’s rotational energy budget implies that radiative forcing alone cannot produce the observed LOD anomalies. Rather, the required amount of atmospheric kinetic energy can be explained only by a strong influence of sulphate aerosols on energy partitioning into the atmosphere, for example, as sulphate aerosols affect latent heat release and transport during condensation–evaporation–freezing cycles. Overall, the effects of sulphate aerosols on Earth’s spin changes are faster than those produced by greenhouse gases

Volcanic eruptions from ghost magma chambers

Recent studies have proposed that magma reservoirs crystallized to a virtually rigid crystal-mush can be partially remelted by diffusion of hot fluids. We show that for a crystal mush with the composition of a K-trachyte from the Campanian Ignimbrite (CI) Eruption, remelting can occur without a significant increase of the magma temperature, but simply by diffusion of H2O by the magmatic gases feeding the system. The CI origin is not the issue here, but rather the chemical and physical behavior of an almost solidified magma mass left over in a reservoir after a major eruption. To test our hypothesis, we run high pressure/high temperature laboratory experiments to study the kinetics of water diffusion, together with thermodynamics and fluid diffusion modelling. For small diffusivities, or large diffusion time, the remelting mechanism proposed above needs to be replaced by other processes as gas percolation or intrusion of a magmatic mass

Earth's rotation variability triggers explosive eruptions in subduction zones

The uneven Earth’s spinning has been reported to affect geological processes, i.e. tectonism, seismicity and volcanism, on a planetary scale. Here, we show that changes of the length of day (LOD) influence eruptive activity at subduction margins. Statistical analysis indicates that eruptions with volcanic explosivity index (VEI) ≥3 alternate along oppositely directed subduction zones as a function of whether the LOD increases or decreases. In particular, eruptions in volcanic arcs along contractional subduction zones, which are mostly E- or NE-directed, occur when LOD increases, whereas they are more frequent when LOD decreases along the opposite W- or SW-directed subduction zones that are rather characterized by upper plate extension and back-arc spreading. We find that the LOD variability determines a modulation of the horizontal shear stresses acting on the crust up to 0.4 MPa. An increase of the horizontal maximum stress in compressive regimes during LOD increment may favour the rupture of the magma feeder system wall rocks. Similarly, a decrease of the minimum horizontal stress in extensional settings during LOD lowering generates a larger differential stress, which may enhance failure of the magma-confining rocks. This asymmetric behaviour of magmatism sheds new light on the role of astronomical forces in the dynamics of the solid Earth

Corrigendum. Maars to calderas: end-members on a spectrum of explosive volcanic depressions

A corrigendum on Maars to calderas: end-members on a spectrum of explosive volcanic depressions by Palladino, D. M., Valentine, G. A., Sottili, G., and Taddeucci, J. (2015). Front. Earth Sci. 3:36. doi: 10.3389/feart.2015.00036 Reason for Corrigendum: In the original article (Palladino et al., 2015), there was an error in Figure 1. The vertical axis of the qualitative plot reported erroneously “ratio of juvenile to lithic materials in deposits outside of depression”. The correct wording is as follows: “ratio of juvenile to total (i.e., juvenile+lithic) materials in deposits outside of depression”. In fact, as it was reported correctly in the text, the amount of juvenilematerial (i.e., scoria or pumice) deposited ouside the different types of explosive volcanic depressions increases from zero (i.e., no juvenile, all lithic products), as is the case of hydrothermal (phreatic) explosion craters, to become largely dominant over the lithic component in the case of ash flow deposits associated with large overpressure collapse calderas. The corrected Figure 1 appears below. The authors apologize for this error and state that this does not change the scientific conclusions of the article in any way

Maars to calderas. End-members on a spectrum of explosive volcanic depressions

We discuss maar-diatremes and calderas as end-members on a spectrum of negative volcanic landforms (depressions) produced by explosive eruptions (note—we focus on calderas formed during explosive eruptions, recognizing that some caldera types are not related to such activity). The former are dominated by ejection of material during numerous discrete phreatomagmatic explosions, brecciation, and subsidence of diatreme fill, while the latter are dominated by subsidence over a partly evacuated magma chamber during sustained, magmatic volatile-driven discharge. Many examples share characteristics of both, including landforms that are identified as maars but preserve deposits from non-phreatomagmatic explosive activity, and ambiguous structures that appear to be coalesced maars but that also produced sustained explosive eruptions with likely magma reservoir subsidence. A convergence of research directions on issues related to magma-water interaction and shallow reservoir mechanics is an important avenue toward developing a unified picture of the maar-diatreme-caldera spectrum

CO2-crystal wettability in potassic magmas. Implications for eruptive dynamics in light of experimental evidence for heterogeneous nucleation.

The volatile content in magmas is fundamental for the triggering and style of volcanic eruptions. Carbon dioxide, the second most abundant volatile component in magmas after H2O, is the first to reach saturation upon ascent and depressurization. We investigate experimentally CO2-bubble nucleation in trachybasalt and trachyte melts at high temperature and high pressure (HT and HP) through wetting-angle measurements on different (sialic, mafic or oxide) phenocryst phases. The presence of crystals lowers the supersaturation required for CO2- bubble nucleation up to 37 per cent (heterogeneous nucleation, HeN), with a minor role of mineral chemistry. Different from H2O-rich systems, feldspar crystals are effective in reducing required supersaturation for bubble nucleation. Our data suggest that leucite, the dominant liquidus phase in ultrapotassic systems at shallow depth (i.e. <100 MPa), facilitates late-stage, extensive magma vesiculation through CO2 HeN, which may explain the shifting of CO2-rich eruptive systems towards an apparently anomalous explosive behaviour

Geological constraints for a conceptual evolutionary model of the slope deformations affecting Mt. Nuovo at Ischia (Italy)

ischia island was the scenario of several Holocene slope in- stability events occurred at different scales, from shallow mass movements, triggered by meteo-climatic forcing, up to massive rock slope failures such as large debris avalanches these last ones related to the volcano-tectonic dynamics of a resurgent caldera. the present study focuses on the gravitational deformation that in- volves Mt. nuovo, located in the western portion of Mt. epomeo resurgent block. a high-resolution engineering-geological model was reconstructed according to a multi-modelling approach sup- ported by field geo-structural evidences and constrained by pas- sive seismic investigations. it revealed a complex morpho-struc- tural setting and led to the identification of a multiple compound mechanism, involving a rock mass volume of about 190 million of cubic meters. the obtained geological model shows a partial structural control of the pre-existing tectonic pattern on slope deformation mechanisms, highlighting geometric and volumetric similarities between the Mt. nuovo ongoing deformation and an already oc- curred rock avalanche. the defined conceptual evolutionary mod- el allows to hypothesize the role of inner pressures constraining the shear zone initiation and propagation and making reliable a future scenario of generalized collapse. Starting from these new field and laboratory data, numerical models will be reconstructed in order to depict the evolution of the gravitational slope deformation, evaluate its sensitivity and constrain future evolutionary instability scenarios

A IRRITAÇÃO DO SISTEMA DA ECONOMIA SOBRE O SISTEMA DO DIREITO: UMA ANÁLISE EMPÍRICA ACERCA DA REFORMA DA PREVIDÊNCIA

Resumo: O direito previdenciário é um direito de segunda geração e, indiscutivelmente, fundamental para atingir os objetivos do Estado, previstos no art. 3, III da Constituição Federal. Por isso, analisar o paradoxo da irritação causada pelo sistema da economia no sistema do direito previdenciário é o escopo principal deste artigo, através de um viés teórico e científico. Busca-se, ainda, verificar quais seriam os limites da influência – se essa é possível e aceitável – do ambiente nos direitos dos trabalhadores, qual a possível solução, advinda do direito comparado, a ser adotada para evitar o prejuízo irreversível para o bem-estar social, a afetação do meio no direito previdenciário. Como resultado da pesquisa teórica e empírica notou-se que existe um exemplo prático de Reforma Previdenciária no Chile, que pode ser utilizado como parâmetro para o Brasil