Fundamentals of physical volcanology

Intrusive Magmatism Strongly Contributed to the Volatile Release Into the Atmosphere of Early Earth

Article

Full-text available

Nov 2022
GEOCHEM GEOPHY GEOSY

Magmatic volatile release was crucial for the build‐up and composition of the early atmosphere and thus for the origin and evolution of life. Even though the rate of intrusive to extrusive magma production on Earth is high, intrusive volatile release is commonly neglected in studies modeling the composition of the early atmosphere. This can mainly be attributed to the solubility of volatiles like H2O and CO2. The solubility is increasing with depth and thus is thought to prevent the release of these volatiles. However, due to the accumulation of H2O and CO2 within the melt during fractional crystallization, the solubility can be exceeded even at greater depths. In our study, we developed a novel numeric model to quantify the amount of H2O and CO2 that can be released from an intrusive system if we consider the process of fractional crystallization. Additionally, we take the possibility of melt ascent and the formation of hydrous minerals into account. According to our simulations, the release of H2O and CO2 from an intrusive magma body is possible within the whole lithosphere. However, the release strongly depends on the initial volatile budget, the formation of hydrous phases, the depth of the intrusion and the buoyancy of the melt. Considering all these factors, our study suggests that about 0%–85% H2O and 100% CO2 can be released from mafic intrusions. This renders the incorporation of the intrusive volatile release mandatory in order to determine the volatile fluxes and the composition of early Earth's atmosphere.

Gediz Vadisinde Erken Pleistosen Dönemi Sualtı Volkanizması: Kavtepe - Kula Volkanik Yöresi

Article

Full-text available

Oct 2020

Dünya üzerinde volkanizmanın oldukça önemli bir kısmı okyanus diplerinde meydana gelmesine rağmen sualtı volkanizma araştırmaları oldukça sınırlı kalmıştır. Bununla birlikte özellikle son dönemlerde deniz dibi jeomorfolojisi ile ilgili araştırmalarda önemli gelişmeler kaydedilmesi bu gizemli alanın önceden tahmin edilemeyen özelliklerinin de belirlenmesine yardımcı olmuştur. Gerçekten de bugün için okyanus ortası sırtlarında bulunan volkanların yeryüzündeki volkanların yaklaşık olarak %75 ini oluşturduğu bilinmektedir. Hernekadar su altı volkanlarının önemli bir kısmı derin deniz ve okyanus tabanların yer alsalar da bunların bazıları ise sığ deniz alanları ile göl ortamlarında da yer almaktadırlar. Dünya üzerinde karasal volkanizmanın oluşum süreçleri, ürünleri ve ortaya çıkan şekiller çok iyi bilinmesine rağmen denizaltı veya sualtı volkanizmasına ilişkin bilgilerimiz oldukça yenidir. Bu durumun temel nedeni sualtı volkanizmasına ilişkin birçok sürecin kolaylıkla gözlemlenememesidir. Yakın bir zamana kadar, sualtı volkanizmasına ilişkin bilgilerimizin önemli bir kısmı geçmiş volkanizmaların izleri üzerine yorumlama ile elde edilmektedir. Bu yönüyle Kula yöresi gerek karasal volkanizma gerekse sınırlı bir alanda gerçeklemiş olsa bile su altı volkanizması açısından yer tarihinin önemli delillerini barındırmaktadır. Bu çalışmada Erken Pleistosen döneminde Kula’da paleo-Gediz nehri üzerinde oluşan lav seti gölü (paleo-göl) içerisinde meydana gelen su altı volkanizması ve buna bağlı oluşan volkanik şekillerin oluşumunun jeomorfolojik delillerinin ortaya konulması amaçlanmıştır. Araştırmada uzun yıllardan beri yörede yürütülmekte olan projelerimizin arazi bulgularından yararlanılmıştır. Çeşitli stratigrafik birimlerin yaş bilgileri ise söz konusu projelerin yaşlandırma analizlerinden veya alana ilişkin literatürden temin edilmiştir. Araştırma kapsamında Kavtepe’nin yörede yaygın görülen Miyosen yaşlı sedimanter birimleri kesip çıkan bir volkanik çıkış merkezi, volkan bacası olduğu; Kavtepe volkanizmasının iki evrede gerçekleştiği, başlangıçta volkanizmanın Paleo-Gediz vadisine yakın bir yerde başladığı ve açığa çıkan lavların Paleo-Gediz’in VI. taraçasını kısmen örttüğü belirlenmiştir. Volkanizmanın ikinci evresinin ise Akçeme volkanının Gediz Nehrini bloke ettikten sonra oluşan paleogöl içerisinde gerçekleştiği ve ikinci evrede açığa çıkan lavların, doğrudan su ile temas ederek yastık lava dönüştüğü tespit edilmiştir.

A Physical Model for Volcanic Eruption Tremor

Article

Full-text available

Oct 2020

Seismic waves are commonly used to monitor unrest before, during, and after volcanic eruptions. The source of seismic tremor during a sustained explosive volcanic eruption is not well understood. Recent observations of the 2016 eruption of Pavlof Volcano, Alaska, revealed a change in the relationship (hysteresis) between ash plume height and seismic amplitude over time. Based on similarities in physical processes and observed seismic tremor in rivers, we explore two key sources of seismic energy in the volcanic conduit: (1) forces exerted by particle impacts and (2) dynamic pressure changes by the turbulent flow. We develop a physical model calculating the seismic power spectral density (PSD), where forces on the conduit wall are convolved with the Green's function for Rayleigh waves. Using reasonable eruption parameters, the model is able to reproduce the frequency spectrum from the Pavlof eruption, although the modeled amplitudes are generally lower. We test the relative importance of different eruption parameters, including grain size, velocity, and conduit dimensions. We find that turbulence generally dominates over particle impacts. However, to reach the PSD amplitude during the Pavlof eruption, large grain sizes are required, as they have the greatest relative influence on the modeled amplitude. The hysteresis between plume height and seismic amplitude can then potentially be explained by grain size changes. The PSD shape is mostly determined by the Rayleigh‐wave quality factor Q, and substantial variations in seismic amplitude can be modeled assuming a constant mass eruption rate.

Numerical Modeling of Magma Ocean Solidification and Concurrent Atmosphere Formation

Thesis

Full-text available

May 2020

Athanasia Nikolaou

Magma ocean is a crucial stage in the build-up of terrestrial planets. Its solidification and the accompanying outgassing of volatiles set the conditions for important processes that occur later or even simultane-ously, such as solid state mantle convection and atmospheric escape. In order to constrain the duration of a global scale magma ocean on Earth I have built and applied a 1D interior model coupled alternatively with either a grey H2O/CO2 atmosphere or with a pure H2O atmosphere treated with a line-by-line radiative transfer approach. This study examines the effects of several factors affecting the magma ocean lifetime, such as the initial abundance of H2O and CO2 , the convection regime, the viscosity, the mantle’s melting temperature, and the longwave radiation absorption from the atmosphere. In this specifically multi-variable system I assess the impact of each factor with respect to a reference setting commonly assumed in the literature. This setting is intended to be a benchmark and it is deliberately kept low in complexity. Such approach helps emphasize the potential role of each additional modeled process in the solidification time.It is found that the magma ocean stage can last from a few thousand to several million years for a rocky planet of terrestrial size and composition. By coupling the interior model with the line-byline radiative transfer treatment in the atmosphere, I identify the conditions that determine whether the planet experiences a transient magma ocean or it ceases to cool and maintains a magma ocean,conditional on the assumption that atmospheric mass is conserved. I find a dependence of this distinction simultaneously on the mass of outgassed H2O atmosphere and on the magma ocean surface melting temperature. The present work discusses their combined impact on the magma ocean lifetime in addition to the known dependence on albedo, orbital distance and stellar luminosity and notes observational degeneracies that arise thereby for target exoplanets. A potential magma ocean case for Venus and Mars is shortly discussed and is put in perspective with the study findings.

Volumetric changes of mud on Mars: evidence from laboratory simulations

Preprint

Full-text available

Jun 2023

Subtle mounds have been discovered in the source areas of martian kilometer-sized flows and on top of summit areas of domes. These features have been suggested to be related to subsurface sediment mobilization, opening questions regarding their formation mechanisms. Previous studies hypothesized that they mark the position of feeder vents through which mud was brought to the surface. Two theories have been proposed: a) ascent of more viscous mud during the late stage of eruption and b) expansion of mud within the conduit due to the instability of water under martian conditions. Here we present experiments performed inside a low-pressure chamber, designed to investigate whether the volume of mud changes when exposed to a reduced atmospheric pressure. Depending on the mud viscosity, we observe volumetric increase of up to 30% at the martian average pressure of ~6 mbar. This is because the low pressure causes instability of the water within the mud, leading to the formation of bubbles that increase the volume of the mixture. This mechanism bears resemblance to the volumetric changes associated with the degassing of terrestrial lavas or mud volcano eruptions caused by a rapid pressure drop. We conclude that the mounds associated with putative martian sedimentary volcanoes might indeed be explained by volumetric changes of the mud. We also show that mud flows on Mars and elsewhere in the Solar System could behave differently to those found on Earth, because mud dynamics are affected by the formation of bubbles in response to the low atmospheric pressure.

Morphological and textural analysis of basaltic pyroclasts (Atexcac maar, central Mexico): Implications for fragmentation and conduit processes

Article

Feb 2022
J S AM EARTH SCI

Atexcac is a maar volcano, which forms part of the monogenetic volcanic field of the Serdán-Oriental Basin, in the eastern sector of the Mexican Volcanic Belt. This volcanic landform was originated by a combination of phreatic, magmatic and phreatomagmatic explosive eruptions. During the formation of the distinct depositional facies, fluctuations in the water availability of the local aquifer, as well as in the magma flux, were probably responsible for the different mechanisms of magmatic and phreatomagmatic fragmentation and the production of the two main populations of fragments (breccia and cross-bedded deposits particles), whose morphological features, allow us to infer the dominant regime (brittle or ductile), fragmentation mechanism (magmatic or phreatomagmatic) and conditions of bubble growth dynamics and fragmentation processes during the ascent of magma through the conduit. We conclude that the breccia particles were derived from dominant magmatic explosions while the cross-bedded deposits particles are thought to be generated from explosive phreatomagmatic events. 3D imaging based on high-precision X-ray microtomography was used to determine the vesicularity of juvenile fragments of the Atexcac maar. Calculated vesicularity index, vesicle number density (VND) and vesicle morphology indicate important processes of coalescence of gas bubbles, during the ascent of the magma. VND's Atexcac clasts suggests vesicle mechanisms similar to medium-intensity eruptions, reported in the literature. The elongated and polylobular vesicle morphology of the Atexcac clasts reveals early acceleration of magma and subsequent coalescence events at most stages of gas bubble growth.

Explosive volcanism in Noctis Fossae on Mars

Article

Dec 2021

Based on theoretical considerations, basaltic volcanism of explosive character should be common on Mars. Although the record of explosive volcanic fields on Mars continues to grow, many unexplored volcanic fields remain. In this research, we identified a group of 25 volcanic cones and associated lava flows emplaced in the Noctis Fossae region on Mars. To analyze this volcanic field, we used images from the Context Camera (CTX) and High Resolution Imaging Science Experiment (HiRISE) of Mars Reconnaissance Orbiter (MRO). We interpreted those volcanic cones and their geological history by (1) analyzing their spatial distribution, (2) determining the morphometric parameters, (3) measuring orientations of their summit alignments, and (4) dating these cones along with surrounding lava flows. The identified cones are characterized by various states of preservation from almost fully eroded vent relicts to well-preserved edifices of conical shapes accompanied by short-distance lava flows. Morphological data suggest that the whole set of identified cones likely represent explosive scoria cones. Using the crater count dating method coupled with the structural relationship between the lava flows and volcanic cones, we found that the southern and central cones likely formed >300 Ma, while the northernmost cones between 200 and 50 Ma. These results suggest long-lived volcanism in the studied area active until the latest Amazonian period. In addition, to the present state of knowledge, these cones represent the youngest explosive volcanism in Tharsis and support other findings of young explosive-origin features on Mars. This might shed new light on the magmatic plumbing system of the Tharsis region, although magma sources from Syria Planum, or less likely Valles Marineris, are not excluded. Such magmas of explosive nature are probably rich in volatiles, which might derive from water and/or hydroxyl bearing minerals' or subsurface permafrost deposits. In addition, these magmas might be associated with intensive hydrothermal activity in the region.

Resistivity Data Modeling for Subsurface Volcanostratigraphy Construction of Cibadak Sub-Watershed, Bogor, West Java, Indonesia.

Article

Full-text available

Jun 2021

In Mt. Salak, there are six volcanic facies divided by eruption time seen from geomorphology data analysis and to identified the subsurface layer DC Resistivity method is applied. Beside resistivity, geostatistical parameters also influence the result model interpretation, so for obtain best model correlation parameters such as tilting, surfacing, variogram, grid method, and logarithmic distribution is applied. Using 18 points of acquisition data subsurface model is produce and then section model made to describe vertical resistivity distribution then correlated with facies lithology model. Based on that, produce three facies resistivity type namely: 0 – 100 Ohm.m (Low Resistivity Value) Interpreted as pyroclastic material composed as tuff and breccia that lies under lava. 100 – 300 Ohm.m (Medium Resistivity Value) Interpreted as breccia lithology type. Harder that pyroclastic material due to by this product is avalanches of lava. And >300 Ohm.m (High Resistivity Value) Interpreted as lava lithology that lies at high elevation and the hardest lithology in this area. From the model, pyroclastic layer that is modeled found at low elevation and based on the direction it described as oldest facies layer, but at the bottom of this layer lies high resistivity value that unknown product. It can be Mt. Pangrango product due to at low elevation predicted as combine area product from product of Mt. Salak and Pangrango. High resistivity value show lava lithology and lava facies located in high elevation and medium resistivity describe breccia lithology as avalanche product of lava (youngest pyroclastic facies) and found at 500 – 100 meters msl.

Tracking secondary lahar flow paths and characterizing pulses and surges using infrasound array networks at Volcán de Fuego, Guatemala

Article

Full-text available

Oct 2021

Lahars are one of the greatest hazards at many volcanoes, including Volcán de Fuego (Guatemala). On 1 December 2018 at 8:00pm local Guatemala time (2:00:00 UTC), an hour-long lahar event was detected at Volcán de Fuego by two permanent seismo-acoustic stations along the Las Lajas channel on the southeast side. To establish the timing, duration, and speed of the lahar, infrasound array records were examined to identify both the source direction(s) and the correlated energy fluctuations at the two stations. Co-located seismic and acoustic signals were also examined, which indicated at least 5 distinct energy pulses within the lahar record. We infer that varying sediment load and/or changes in flow velocity is shown by clear fluctuations in the acoustic and seismic power recorded at one of the stations. This particular event studied with infrasound provides insight into how lahars occur around Volcán de Fuego.

An overview of explosive volcanism on Mars

Article

Nov 2020
J VOLCANOL GEOTH RES

Decades of space exploration reveal that Mars has been reshaped by volcanism throughout its history. The range of observed volcanic landforms shows that effusive and explosive eruptions have occurred, albeit unevenly in time and space. Evidence for explosive volcanism—characterized as eruptions in which magma is disrupted by the expansion of dissolved gases or by an interaction of magma with external volatiles—is less common than evidence for effusive activity. Nonetheless, indications of explosive volcanism have been identified. Examples include old, rimless depressions, termed paterae, often on the summits of broad topographic rises with very gentle flanks, which are located mainly around the Hellas impact basin. Fields of kilometre-sized cones are interpreted as scoria cones, tuff rings and tuff cones. Also, extensive clusters of sub-kilometre pitted cones in the northern lowlands are proposed to be rootless cones, i.e. constructional features caused by accumulation of volcanic fragments. Finally, layered deposits widely spread in equatorial areas (e.g., the Medusae Fossae Formation), and layered stacks of ash and a putative volcanic bomb observed by rover, also point to a protracted history of explosive volcanism on Mars. Yet some of these interpretations remain a matter of scientific debate. The discovery of evidence for explosive volcanism on Mars triggered an interest in the theoretical aspects of such volcanism under gravitational and atmospheric conditions different from those on Earth. These studies indicate that explosive eruptions on Mars would behave differently from their terrestrial counterparts. This is because a lower atmospheric pressure and gravity can affect all stages of the eruption including the ascent of magma, the process of degassing and magma fragmentation, the transport and deposition of the pyroclasts, and, in some cases, the formation of explosive volcanoes themselves. On Earth, explosive eruptions are responsible for the formation of most volcanoes on land, and so the relatively sparse occurrence of explosive volcanism on Mars is surprising, especially considering the martian environmental conditions as well as wide occurrence of external volatiles on Mars. This is because the lower atmospheric pressure than on Earth ought to favour magma fragmentation and hence the formation of pyroclasts and associated explosive volcanic edifices, even if lower volumes of dissolved gases were present in martian magma than is usual on Earth. The relative dearth of explosive activity on Mars therefore represents a gap in our understanding of martian volcanism, suggesting that there may be considerable compositional differences between Mars and Earth or that evidence of explosive volcanism on Mars manifests differently than on Earth. Understanding these differences is important, as explosive volcanism provides insight into the planet’s composition and plays a crucial role in the evolution of a planet’s atmosphere by the release of magmatic gases, which have the ability to affect geological and even biological processes operating on the surface. In this paper, we present an overview of explosive volcanism on Mars—from both observational and theoretical perspectives—and discuss the implications of explosive eruptions for the evolution of the Red Planet.

The large Rupelian Rhodope Massif eruptions as the source of airfall tuffs in SE, S and Central Europe: 40Ar/39Ar and U–Pb age constraints

Article

Sep 2024
INT J EARTH SCI

Numerous Priabonian and Oligocene tuff layers within the Eastern and Central Europe Paratethys and Tethyan sedimentary basins attest for extensive volcanic activity during that period. However, the sources of these eruptions are completely unknown. Using precise radioisotopic dating, along with their stratigraphic relationships, we correlate some of these tuff layers with Rupelian eruptions from the Rhodope Massif, South Bulgaria. Three major silicic eruptions of ignimbrites and ash falls, namely Dazhdovnitsa, Borovitsa and Perelik, with ages of 33.2 Ma, 32.8 Ma and 31.6 Ma, respectively, have been identified in the Rhodope Massif. The ejected tephra was dispersed over more than 1,000,000 km2 and the combined estimated volume of thousands cubic kilometers, which marks this period as one of the most voluminous sequence of volcanic eruptions/explosions in Europe in the Rupelian Stage. The areal coverage and estimated volumes meet the requirements for volcanic supereruptions and the wide geographic occurrence of the products can be used as stratigraphic isochronous marker horizons for correlating, dating, and synchronizing deposits and events in geologic and paleoenvironmental studies. Further, the volcanic products were deposited during the early Rupelian anoxic Paratethys events and we explore the possible influence of volcanic eruptions on the process of anoxia.

Degradation of the 2014–2015 Holuhraun vent-proximal edifice in Iceland

Article

Full-text available

Mar 2024
B VOLCANOL

The earliest stages of volcanic vent degradation are rarely measured, leaving a gap in the knowledge that informs landform degradation models of cinder cones and other monogenetic vent structures. We documented the initial degradation of a 500-m-long spatter rampart at the primary vent of the 2014–2015 Holuhraun eruption in northern Iceland with high-resolution topographic change maps derived from terrestrial laser scanning (TLS) and photogrammetric surveys using an unoccupied aircraft system (UAS). Topographic differencing shows a total negative volume change of 42,637 m ³ , and a total positive volume change (basal deposition) of 10,304 m ³ (primarily as deposition at the base of steeply sloping surfaces). Two distinct styles of volume changes were observed on the interior and exterior of the spatter rampart. Material on the interior of the vent was removed from oversteepened slopes by discrete rockfalls, while diffusive processes were qualitatively evident on the exterior slopes. We propose a novel conceptual landform evolution model for spatter ramparts that combines rockfall processes on the interior walls, diffusive gravitational sliding on the exterior slopes, and incorporates cooling contraction and compaction over the entire edifice to describe the observed modes of topographic change during the onset of degradation. Potential hazards at fresh spatter ramparts are rockfalls at high slope areas of the vent interior walls where contacts between spatter clasts are prone to weakening by fumarolic activity, weathering, and settling. To capture such hazards, our data suggest a cadence for monitoring changes yearly for the first few years post-eruption, and at longer intervals thereafter.

Characterizing Volcanic Ash Density and Its Implications on Settling Dynamics

Article

Full-text available

Jan 2024

Volcanic ash clouds are carefully monitored as they present a significant hazard to humans and aircraft. The primary tool for forecasting the transport of ash from a volcano is dispersion modeling. These models make a number of assumptions about the size, sphericity and density of the ash particles. Few studies have measured the density of ash particles or explored the impact that the assumption of ash density might have on the settling dynamics of ash particles. In this paper, the raw apparent density of 23 samples taken from 15 volcanoes are measured with gas pycnometry, and a negative linear relationship is found between the density and the silica content. For the basaltic ash samples, densities were measured for different particle sizes, showing that the density is approximately constant for particles smaller than 100 μm, beyond which it decreases with size. While this supports the current dispersion model used by the London Volcanic Ash Advisory Centre (VAAC), where the density is held at a constant (2.3 g cm⁻³), inputting the measured densities into a numerical simulation of settling velocity reveals a primary effect from the silica content changing this constant. The VAAC density overestimates ash removal times by up to 18%. These density variations, including those varying with size beyond 100 μm, also impact short‐range particle‐size distribution measurements and satellite retrievals of ash.

Characterizing Volcanic Ash Density and its Effects on Dispersion Forecasts

Preprint

Sep 2023

Volcanic ash clouds are carefully monitored as they present a significant hazard to humans and aircraft. The primary tool for forecasting the transport of ash from a volcano is dispersion modelling. These models make a number of assumptions about the size, sphericity and density of the ash particles. Few studies have measured the density of ash particles or explored the impact that the assumption of ash density might have on the output of a dispersion model. In this paper, the raw apparent density of 23 samples taken from 15 volcanoes are measured with gas pycnometry, and a negative linear relationship is found between the density and the silica content. For the basaltic ash samples, densities were measured for different particle sizes, showing that the density is approximately constant for particles smaller than 100 μm. There is a deviation in density of up to 25% from the operational model currently used by the London Volcanic Ash Advisory Centre (VAAC); by inputting the measured density-size relationship into a numerical simulation, up to 18% difference in ash fallout time was found, with the VAAC model overestimating ash removal times.

Dolomitisation of carbonate platform margins by fault‐controlled geothermal convection: Insights from coupling stratigraphic and reactive transport models

Article

Full-text available

May 2023

Abstract Reactive transport modelling is increasingly deployed to quantitatively evaluate conceptual models of diagenetic processes. However, construction of models of complex systems involves trade‐offs between accuracy and simplification. This tension is explored for models of fault‐associated dolomitisation by sea water convection in a syn‐rift carbonate platform, evaluating the contribution of incorporating stratigraphic growth and fault propagation. Simulations of the high heat flux southern margin of the Derbyshire Platform (Northern England), with heterogeneous matrix permeability that reflects the evolving stratal architecture and burial compaction focusses dolomitisation in more permeable units at all depths. A permeable platform margin fault zone enhances dolomitisation in a broad area on the upper slope and margin, and to a lesser but significant extent, across the interior as platform top waters are entrained and discharge via the fault. Stepwise simulation of flow and reactions during stratigraphic growth suggests that static models over‐predict dolomite abundance in younger sediments and show how regions optimally supplied with reactants and heat to drive dolomite formation migrate vertically and laterally during platform growth. Dolomitisation intensity increases with depth due to greater time for reactions and kinetically favourable temperatures. Adding the fault zone to this model focusses and accelerates flow, giving a more spatially restricted dolostone body and reducing dolomitisation temperature. Changes in fault connectivity with the surface of the evolving platform shift fluid flow pathways and change the rate and temperature of dolomite formation. Results concur with petrographic, isotopic and geochemical observations of the early dolomite on the Derbyshire Platform. This work demonstrates the importance of understanding diagenesis as the product of an evolving set of processes that respond to geological and palaeoenvironmental changes rather than as a sequence of individual diagenetic events. This is particularly critical for reactions, such as dolomitisation by geothermal convection of sea water, which occur over timescales synchronous with platform development.

Liquid jet breakup regimes in lava fountains

Article

Full-text available

Jun 2022
J VOLCANOL GEOTH RES

Primary magma fragmentation in “fluid-dominated” (as opposed to “ash-dominated”) lava fountains involves the hydrodynamic breakup of a jet of magma. Lava fountains partly resemble industrial liquid jets issued from a nozzle into a quiescent atmosphere, on which there is a vast literature. Depending on the internal liquid properties, nozzle diameter and ejection velocity, liquid jet breakup in industrial applications occurs in four regimes: (I) coarse laminar breakup (Rayleigh regime); (II) transition region between laminar and turbulent breakup (first wind-induced regime); (III) turbulent breakup at the jet surface and unstable but intact liquid core (second windinduced regime); (IV) fully turbulent fine spray (atomization regime). Ductile magma breakup associated with regimes II, III and IV have been reproduced during the initial expansion of experimental magma fragmentation pulses as part of this study. In each experiment, volcanic rocks were re-melted at 1200 ◦C, then fragmented through the injection of compressed argon gas within a few tens of milliseconds. Three compositions were used: olivine-melilitite, alkali basalt, and basaltic trachy-andesite. Each composition was ejected at 3 and 10 MPa gas driving pressure, yielding exit velocities between 11–13 and 33–44 m/s, respectively. The ultramafic magma ejected at high speed developed quickly into a fully developed spray (regime IV), whereas the basaltic trachy-andesite ejected at low-speed initially expanded as a coherent magma mass before breaking into coarse domains (regime II). The observed variability among the experiments is linked to the relative balance among surface tension, viscosity, density, jet diameter and ejection velocity of the magma versus external aerodynamic effects acting on the jet surface. These factors, particularly viscosity and exit velocity, are also likely to control jet breakup regimes in natural lava fountains and some Strombolian pulses.

Multiyear temporal variation of b-values at Alaskan volcanoes: The synergetic influence of stress and material heterogeneity

Article

May 2022
J VOLCANOL GEOTH RES

K. I. Konstantinou

Changes in seismicity parameters is often utilized as a tool for forecasting eruptive activity at volcanoes world-wide. One of these parameters is the slope of the Gutenberg-Richter law, known as the b-value, whose temporal variation is studied here as an indicator of volcanic activity. Four Alaskan volcanoes (Makushin, Martin, Redoubt, Spurr) were selected in order to reconstruct the b-value variation over a multiyear period (≥ 25 years). The magnitude of completeness and the b-value were estimated using a sliding window for each earthquake catalog, while bootstrap uncertainties were estimated for each window. The size of the analysis window was selected by applying the Magnitude Bandwidth Criterion (MBC) that maximizes the number of windows with magnitude bandwidth larger than 2.0 in the complete part of the catalog. All four volcanoes exhibit decreasing b-values before unrest and eruptions, while maximum b-values exceed 1.0 only at Redoubt and Spurr. Previously published laboratory experiments on volcanic rock deformation and failure suggest that the decrease in b-value is a result of increased stress that may stem either from magma intrusions or from exsolution of volatiles. On the other hand, whether the b-value at each volcano will exceed 1.0 or not, is also determined by the degree of material heterogeneity.

Introduction to the Volcanology

Chapter

Full-text available

Apr 2022

The main volcanological concept is shown and expressed so that any volcano can be understood easily. Volcanic products are listed and explained in plain language from lava flow to various pyroclastic products. The volcanic products have been explained schematically and their textural, field relationships characteristics are highlighted. The origin of magma within the interior of the Earth is also explained and the link between mantle and crust has been shown. The relationship among crust, mantle, and core has been highlighted embracing the source-to-surface model. An updated explanation of the Pyroclastic Density Currents (PDC) has been done to perceive their danger. Some of the most successful Volcanology books have been used. This will help the students, with a passion for Volcanology, to understand the principles of Volcanology.

The physical and chemical evolution of magmatic fluids in near-solidus silicic magma reservoirs: Implications for the formation of pegmatites

Article

Full-text available

Feb 2022

As ascending magmas undergo cooling and crystallization, water and fluid-mobile elements (e.g., Li, B, C, F, S, Cl) become increasingly enriched in the residual melt until fluid saturation is reached. The consequential exsolution of a fluid phase dominated by H2O (magmatic volatile phase or MVP) is predicted to occur early in the evolution of long-lived crystal-rich "mushy" magma reservoirs and can be simulated by tracking the chemical and physical evolution of these reservoirs in thermome-chanical numerical models. Pegmatites are commonly interpreted as the products of crystallization of late-stage volatile-rich liquids sourced from granitic igneous bodies. However, little is known about the timing and mechanism of extraction of pegmatitic liquids from their source. In this study, we review findings from thermomechanical models on the physical and chemical evolution of melt and MVP in near-solidus magma reservoirs and apply these to textural and chemical observations from pegmatites. As an example, we use a three-phase compaction model of a section of a mushy reservoir and couple this to fluid-melt and mineral-melt partition coefficients of volatile trace elements (Li, Cl, S, F, B). We track various physical parameters of melt, crystals, and MVP, such as volume fractions, densities, velocities, as well as the content in the volatile trace elements mentioned above. The results suggest that typical pegmatite-like compositions (i.e., enriched in incompatible elements) require high crystallinities (>70-75 vol% crystals) in the magma reservoir, at which MVP is efficiently trapped in the crystal network. Fluid-mobile trace elements can become enriched beyond contents expected from closed-system equilibrium crystallization by transport of MVP from more-evolved mush domains. From a thermomechanical perspective, these observations indicate that, rather than from melt, pegmatites may more likely be generated from pressurized, solute-rich MVP with high concentrations of dissolved silicate melt and fluid-mobile elements. Hydraulic fracturing provides a mechanism for the extraction and emplacement of such pegmatite-generating liquids in and around the main parental near-solidus mush as pockets, dikes, and small intrusive bodies. This thermomechanical framework for the extraction of MVP from mushes and associated formation of pegmatites integrates both igneous and hydrothermal realms into the concept of transcrustal magmatic distillation columns.

Evidence of Regionally Distributed Tectono‐Volcanism in a Floor Fractured Crater of North‐Central Arabia Terra, Mars

Article

Full-text available

Nov 2021

Arabia Terra features many tectonic structures, which have been correlated to episodes of incipient tectonics, massive impacts, and controls on fluvial systems. However, the extent of regionally distributed tectono‐volcanism and its effects on local structures remains unknown. To characterize the prevalence of volcanically driven processes in this region, we investigate the geomorphic features of an unnamed ∼85‐km diameter and 3.6 Ga old floor‐fractured crater (FFC) in North‐Central Arabia Terra. Widespread crater floor rocks resemble layered sedimentary deposits. Nevertheless, the central crater floor hosts mounds and linear ridges, which have higher thermal inertia than the surroundings, indicating a provenance distinct from the sedimentary units. Crosscutting relationships suggest that the mounds and ridges are stratigraphically overlying the layered sedimentary rocks. Morphologically and morphometrically, the mounds and ridges resemble known Martian and terrestrial volcanic cone and dike systems. Unlike other FFCs of Arabia Terra, the dikes and cone azimuths consistently orient in the NW‐SE direction, implying that regional tectonic controls on their formation overrode localized effects of the crater‐forming impact. Our observations collectively support magma intruding and erupting along regionally controlled tectonic structures; the migration of magma was perhaps facilitated by the impact that formed the host crater. Consequently, the studied FFC may represent a category of hitherto unrecognized numerous, small‐scale volcanic centers controlled by regional tectono‐volcanism within Arabia Terra. This is also consistent with regionally distributed magmatic systems in the late Noachian to early Hesperian, associated with a thermally eroded crust.

Rheological evolution of eruptible Basaltic-Andesite Magmas under dynamic conditions: The importance of plagioclase growth rates

Article

Oct 2021
J VOLCANOL GEOTH RES

The effects of crystal nucleation and growth on the viscosity of andesitic magmas are investigated at 1 atm. Pressure. The data are used to describe the rheological evolution of andesitic magmas and to derive empirical equations to model the crystallization dynamics. Viscosity experiments were performed at temperatures of 1473, 1483, and 1493 K with shear rates of 0.5 s⁻¹ by using wide-gap concentric cylinder viscometry. We focused on eruptible magmas (i.e., crystal contents well-below ~50%) by following the time evolution of crystal nucleation and growth of a natural andesitic magma, while continuously monitoring the changes in viscosity. At near-equilibrium conditions, the basaltic-andesite contains 6, 13, and 25 area % crystals at 1493, 1483, and 1473 K, respectively, resulting in a viscosity increase of ca. 1 log unit. We show that the timescale of viscosity increase is mainly dictated by the delay time preceding crystallization and markedly decreases with increasing undercooling (from 22 to 42 K) and shear rates (from 0.1 to 1 s⁻¹). The plagioclase growth rates estimated from our data are in the order of ~3–5 × 10⁻⁶ cm/s, which is much faster than the rates estimated for crystallization in static conditions. We conclude that the effect of the shear rate must be taken into account in modelling magmatic and volcanic processes, especially when transient changes in viscosity need to be estimated. Our results are important for understanding the dynamics of lava flows where deformation plays a significant role in promoting crystallization.

Análisis de la dinámica y productos balísticos durante la erupción del Poás (Costa Rica) en el 2017

Article

Full-text available

Jan 2020

Alvarado Induni Guillermo

The 1845–46 and 1766–68 eruptions at Hekla volcano: new lava volume estimates, historical accounts and emplacement dynamics

Article

Full-text available

Apr 2021
JOKULL

We use new remote sensing data, historical reports, petrology and estimates of viscosity based on geochemical data to illuminate the lava emplacement flow-lines and vent structure changes of the summit ridge of Hekla during the large eruptions of 1845–46 and 1766–68. Based on the planimetric method we estimate the bulk volumes of these eruptions close to 0.4 km3 and 0.7 km3, respectively. However, comparison with volume estimates from the well-recorded 1947–48 eruption, indicates that the planimetric method appears to underestimate the lava bulk volumes by 40–60%. Hence, the true bulk volumes are more likely 0.5–0.6 km3 and 1.0–1.2 km3, respectively. Estimated melt viscosity averages for the 1766–68 eruption amount to 2.5 x10^2 Pa s (pre-eruptive) and 2.5x10^3 Pa s (degassed), and for the 1845–46 eruption 2.2x10^2 Pa s (pre-eruptive) and 1.9x10^3 Pa s (degassed). Pre-eruptive magmas are about one order of magnitude more fluid than degassed magmas. In the 1845–46 and 1947–48 eruptions, SiO2 decreased from 58–57 to 55–54 wt% agreeing with a conventional model that Hekla erupts from a large, layered magma chamber with the most evolved (silica-rich) magmas at the top. In contrast, the lava-flows from 1766–68 reveal a more complicated SiO2 trend. The lava fields emplaced in 1766 to the south have SiO2 values 54.9–56.5%, while the Hringlandahraun lava-flow that erupted from younger vents on the NE end of the Hekla ridge in March 1767 has higher SiO2 of 57.8%. This shows that the layered magma chamber model is not suitable for all lava-flows emplaced during Hekla eruptions.

Analyzing Low Frequency Seismic Events at Cerberus Fossae as Long Period Volcanic Quakes

Article

Full-text available

Mar 2021

The InSight Mission began acquiring the first seismic data on Mars in early 2019 and has detected hundreds of events. The largest events recorded to date originate at Cerberus Fossae, a young volcanic region characterized by high volume, low viscosity lava flows. A handful of Low Frequency (LF) quakes that share key attributes of Long Period quakes recorded on Earth's volcanoes are also traced to Cerberus Fossae. This study explores whether a traditional volcanic source model that simulates the generation of tremor as pressurized fluid makes its way through a channel at depth, can explain these atypical LF events. We consider a wide range of physical parameters including fluid viscosity, the ratio of driving pressure to lithostatic pressure, aspect ratio of the channel, and the equilibrium channel opening. We find that the model can produce the observed seismic signature, with a combination of low‐viscosity magma and high volume flux of ∼10⁴ − 10⁵ m³/s that are within an order‐of‐magnitude agreement with Cerberus Fossae lava flow properties deduced from analysis of lava flow dimensions. It is impossible, however, at this stage to conclude whether or not this is a likely explanation for Mars, as the model results in fluxes that are extreme for Earth yet are just within bounds of what has been inferred for Cerberus Fossae. We therefore conclude that we cannot rule out active magma flow as the mechanism responsible for the atypical LF events that likely originate from Cerberus Fossae.

Holocene variability of East Asian summer monsoon as viewed from the speleothem δ 18 O records in central China

Article

Mar 2021
EARTH PLANET SC LETT

Monsoon precipitation in East China shows distinct spatial distribution and its variability is closely linked with the changes of the East Asian summer monsoon (EASM). Located in the transition zone between the southern subtropical humid climate and the northern warm temperate semi-humid climate, central China is a core region for recognizing and understanding the spatio-temporal variability of the EASM. Using U-series dating and stable isotope analysis on five stalagmites (MG-1, MG-2, MG-7, MG-40 and MG-64) from Magou Cave, Henan Province, Central China, we construct a high-resolution and precisely dated composite stalagmite δ18O time series covering most of the Holocene. This composite record reveals variations in precipitation δ18O between 11.7 and 1.1 ka BP with average resolution of ∼4 yrs. The Magou composite record demonstrates that EASM intensity dominates long-term changes in precipitation δ18O, which generally follows the northern hemisphere summer insolation (NHSI) trend. Both, Ensemble Empirical Mode Decomposition (EEMD) and wavelet filtering analyses real that the amplitudes of long-term (100-500 and 500-3000 yrs) components were slightly reduced between 8.5 and 4.9 ka BP, implying a weakened influence of climatic forcings on centennial and even millennial timescales during this warm period. Variance on 1-30-yr timescales is relatively low and ascribed to sampling resolution. Fourteen weak EASM intervals, including the 8.2 ka event, were identified within the period corresponding broadly with the Holocene Megathermal. Since no cold excursions other than the 8.2 ka event are found in the Greenland ice core records, we tentatively propose that oscillations in tropical sea surface temperature (SST) likely play an important role in steering other weak monsoon events. Aligning the Magou composite record and other moisture records with archaeological records from the study region, it seems that climate change influenced both the spatial distribution and agricultural practices of ancient cultures. However, overall moderate climatic changes in this region, most likely characterized by shifts between subtropical humid climate and warm temperate semi-humid climate, supported a generally consecutive development of ancient cultures without major hiatuses.

(Geo)demografie nejen pro ekonomy

Book

Full-text available

Nov 2020

Publikace (Geo)demografie nejen pro ekonomy se zaměřuje na analýzu a výklad informací a dat o lidských populacích a lidské společnosti. Reflektuje nejen demografickou reprodukci a strukturální změny v prostoru a čase, ale i aktuální globální problémy jako jsou mezinárodní migrace a stárnutí populací. Je určena primárně k výuce předmětu Demografie, která probíhá v bakalářském studiu na Ekonomicko-správní fakultě Masarykovy univerzity. Její uplatnění je ovšem možné nalézt i u dalších programů a oborů ekonomicky, společensky či přírodovědně zaměřených fakult, škol či institucí. Forma knihy je koncipována jako podoba vysokoškolského učebního textu, obsah kombinuje prvky demografické analýzy a regionální demografie s důrazem na studium populací, resp. obyvatel státních útvarů, regionů a makroregionů a interpretace jejich prostorových, ekonomických a sociokulturních podobností a rozdílů.

The Magnitude of the 39.8 ka Campanian Ignimbrite Eruption, Italy: Method, Uncertainties and Errors

Article

Full-text available

Oct 2020

The calculation of the magnitude of an eruption needs the accurate estimate of its deposit volume. This is particularly critical for ignimbrites as no methods for their volume calculations and associated errors and uncertainties are consolidated in the literature, although invariably the largest magnitude eruptions on Earth are made of ignimbrites. The 39.8 ka Campanian Ignimbrite (CI) eruption is the largest of the Campi Flegrei caldera (Italy). The global cooling following the CI eruption and its widespread tephra affected the paleoenvironment and the migration of hominids in Europe at that time. Despite the large number of studies, the estimates of the Dense Rock Equivalent volume of the CI range between 60 and 300 km³, because of the lack of clear and reproducible methods for its calculation. Here we present a new calculation of the volume of the CI, grounded on a clear and reproducible method that can be applied universally and which provides an accurate estimation of the volume of the deposits on ground and their uncertainties and errors, allowing a strong base for further estimates of the amount of deposits eroded, covered, elutriated, which are essential for the final computation of the eruption magnitude. In order to calculate the CI volume, we reconstructed the first total isopach map of the pyroclastic density current deposit preserved on land, developed through a method that reconstructs the paleo-topography during the eruption, which is reproducible for all topographically controlled ignimbrites and allows the calculation of well-defined uncertainties in the on-land ignimbrite deposits. The preserved total extra-caldera bulk volume of the ignimbrite is estimated at 68.2 ± 6.6 km³. The total pyroclastic density current deposit volume is then corrected for erosion, ash elutriation, the intracaldera deposit volume, and the volume of tephra deposited in the sea, whereas volumes of the basal fallout deposits are taken from other studies. The total Dense Rock Equivalent volume of the eruption is 181–265 km³, whose range accounts for errors and uncertainties. This value corresponds to a mass of 4.7–6.9 × 10¹⁴ kg, a magnitude (M) of 7.7–7.8 and a volcanic Explosivity Index (VEI) of 7.

Analysis of the dynamic and the ballistic products of the 2017 eruption of Poas Volcano (Costa Rica)

Article

Full-text available

Dec 2019

From April 12 until April 22 2017 Poás volcano experienced a new explosive phase with ballistic fragments reaching up to ~2,2 km. At its final phase non juvenile bocks predominated, product both of a 1953 lava body destruction and a lacustrine floor, followed by an increment of juvenile fragments (glassy bread crust blocks, scoriaceous bombs and, rarely, fusiform bombs). The largest ones measured up to 20 m in diameter and 1,5 m in thickness, reaching up to 200 m from the crater. The juvenile fragments showed a varied vesiculation (15-50% vesicles) with a basaltic andesitic composition (phenocrysts of plag 20- 22%, cpx 6-8%, opx 3-5%, lo 1-3%, mt 0-1%) within an intersertal matrix. The juvenile phreatomagmatic ash content increased from approximated 9% to 85% at the end, consisting of a strombolian activity. When hitting the floor, the bombs generated perpendicular cooling joints and shear stress conjugate pairs. While cooling, the joints were parallel to impact surface generating a symmetric conjugated rectangular pattern. When fallon surfaces with a slope the pattern was more complex due to viscous flow. The ballistic initial velocity was estimated in the 100-300 ms-1 range, the final velocity was estimated in the 36-120 ms-1 range, and a terminal velocity (defined in the text) in the 124-250 ms-1 range. Flight time from bottom of Main crater to the visitor area (View point) was estimated in the 8-15 secs range. At the end, a set of recommendations for future volcanic ballistic studies is included based on a totally new physics model using actual range and impact angle. It is here recommended that more shelters be built on the path between the active and Botos craters.

Temporal and spatial evolution of the Somún Curá Magmatic Province, Northern Extra-Andean Patagonia, Argentina

Article

Dec 2020
J S AM EARTH SCI

The Somún Curá Magmatic Province (SCMP) is a Cenozoic volcanic region comprised by several basaltic fields and large central volcanoes located at the Northern Extra-Andean Patagonia, Argentina. The principal volcanic sequences were erupted between the late Eocene and late Miocene, forming the Meseta de Somún Curá, which covers ~30,000 km2 between 40°30′-43°20′S and 65°50′-69°20′W, involving around 1 to 2 × 103 km3 of mafic lavas, and about half that volume of intermediate to silicic lava-pyroclastic associations. The SCMP developed in a back-arc to intraplate tectonic setting over the North Patagonian Massif (NPM), at the time of two major geodynamic events at the western margin of South America: the consumption of the Aluk and the break-up of the Farallón oceanic plates. The magmatism at the studied area is represented by eight volcanic complexes, the Somún Curá Formation flood basalts, and other units related to minor volcanic fields or polygenetic centres. These sequences share intricate stratigraphic relations, which hinder the evolution of the SCMP. To address this issue, an updated compilation of geochronological determinations for the Meseta de Somún Curá region is provided. Its integrated analysis, together with stratigraphic information, allowed the identification of periods of preferential volcanic emission, after which seven constructional phases between late Eocene and late Miocene are proposed. Within these phases, seven pulses of magmatic activity are interpreted for the volcanic complexes emplaced in this area (~38-37 Ma, ~32.5–31 Ma, ~29.5–28 Ma, ~26-24 Ma, ~21–18.5, ~18-15 Ma and ~10.5 Ma), together with four pulses of effusion of flood basalts, represented by the Somún Curá Formation (~32 Ma, ~27-26 Ma, ~26-25 Ma, and ~21.5 Ma). The superposition and recurrence of the magmatic pulses associated with the volcanic complexes and the Somún Curá Formation argue against the application of a "pre-plateau", "plateau" and "post-plateau" scheme, which is revised. The largest volumes of magma associated with the Somún Curá Formation and the volcanic complexes were extruded during the late Oligocene and the early Miocene, respectively. The area of emplacement of the Somún Curá Formation changed over time, defining a roughly counter-clockwise spatial and temporal pattern, starting from the southwest. The magmatic activity recorded by the volcanic complexes from late Eocene to middle Oligocene seems to have concentrated alternatively along NW-SE and NE-SW corridors, and along a N–S belt to the west during the early Miocene. This systematic organization could be related to the reactivation of previous structures, triggered by the kinematic changes in the convergence vector between the Farallón-Nazca Plates and the South American Plate.

Mt. Etna Feeding System and Sliding Flank: A New 3D Image From Earthquakes Distribution in a Customisable GIS

Article

Full-text available

Oct 2020

High-resolution seismic imaging enables the reconstruction of ascending paths of magma and fluids, shallow molten accumulation and flank collapse areas, all crucial information for developing an efficient eruption forecasting strategy. Here, the Marching Cubes algorithm (MC - generally applied to medical visualization and three-dimensional (3D) modeling) is applied to 16 years of earthquake location data at Mt. Etna (Italy). The algorithm defines three-dimensional seismic clusters that take into account seismic location uncertainties and are embedded in a novel volcano-oriented Geographyc Information Systems (VolGIS) offering an interpretational environment comprising tomographic images and alternative geophysical models. The results show that a volume of very-low-seismicity is embedded in a high-velocity body, and acts as a zone of transition between transient magmatic events (west) and eastern deep seismicity related to the sliding eastern flank. The eastern cluster represents the 3D seismic signature of a deep (2–8 km below sea level) instability, affecting the portion of the eastern flank nearest to the feeding systems. This instability is likely caused by a combination of gravitational spreading and magmatic intrusions.

Effusive-explosive transitions of water-undersaturated magmas. The case study of Methana Volcano, South Aegean Arc

Article

May 2020
J VOLCANOL GEOTH RES

Most arc volcanoes erupt intermediate to silicic magmas that have sufficient volatile contents to behave explosively. Despite this explosive potential, low-energy effusive eruptions of such viscous water-rich magmas are common occurrences. Hence, predicting the style of the next eruption, with its obvious importance on hazard mitigation, remains one of the main challenges of volcanology. Here, we investigate the changes in eruptive styles at Methana volcano, from the South Aegean Arc. This volcano has generated multiple andesite-to-dacite eruptions, with the last event occurring in historical times (~2250 BP). We focus on 14 eruptive events, 3 being explosive. We compare the petrology and geochemistry of the deposits to reconstruct the magma chamber events that preceded both types of eruptions. We estimate the thermo-chemical conditions that characterized each eruptive event, and highlight the causes that promoted or inhibited magma fragmentation: temperature, pressure, composition, relative volumes of different magma batches, dissolved water content, crystallinity, melt and bulk viscosities. The results indicate that Methana harbors an upper crustal silicic reservoir stored at ~2 kbar (likely dacitic to rhyodacitic in composition) that is in a highly crystalline state (>50 vol% crystals, mostly uneruptible). All the eruptions are triggered by deeper magma recharge ascending from storage pressures of ~4–5 kbar, leading to some rejuvenation of the shallow silicic mush. The most mafic recharges (~55 wt% SiO2, ~1000 °C, >3 wt% H2O) promote effusive eruptions after mixing and hybridizing the upper crustal reservoir (~57–64 wt% SiO2, ~900–950 °C, generally 3–4 wt% H2O). Slightly colder, wetter and more differentiated recharges (~62 wt% SiO2; ~900 °C, ~4 wt% H2O) trigger explosive events after having minimal interaction with the upper crustal reservoir. However, the dissolved water content is not the only factor influencing explosivity, as some of the wettest magmas (>4.5 wt% H2O) generate lava flows. Our data indicate that a key control on effusive-explosive transitions at Methana is the crystallinity of the erupted material. A high-crystallinity (40–55 vol%) increases the bulk-viscosity, which results in the magma having a slower ascent velocity. In addition, crystallinity enhances the formation of permeable pathways for the gas. Longer ascent timescales and enhanced permeability in the conduit improve the outgassing potential of the magmas and lead to effusive behavior. The opposite occurs for explosive events. Here, the lower-crystallinity of the magmas (30 vol%) translates into lower bulk-viscosities and faster ascent rates, which inhibit outgassing. This case study highlights the importance of obtaining better constraints on the state of subvolcanic magma reservoirs, in particular concerning crystallinity and volatile concentrations, which has to become a priority in the years to come.

Tectonomagmatic evolution of Pune – Nasik Deccan Dykes: Insights from structure and dimension scaling

Article

Oct 2024
TECTONOPHYSICS

The Deccan Continental Flood Basalt of the Indian Peninsula is characterized by extensive basaltic eruptions ornamented with three spectacular distinct dyke swarms: the Pune – Nasik, Narmada – Tapi, and Western Coastal dyke swarms. Our study area is the Pune – Nasik dyke swarm, which has ~ 465 mappable dykes. These dykes exhibit different orientations with a predominant trend of N101° and vary in length from less than 1 km to ~64 km. These dykes are massively jointed and occasionally contain vesicles filled with secondary minerals like quartz and calcite. The host rock is weathered basalt of various older Deccan flows. In this study, we have calculated magmatic overpressures and magma chamber depths using the aspect ratios (length/thickness) of the dykes. The average estimated source depth is ~ 13 km, based on an average Young’s modulus for the host rock basalt (Eavg, 7.5 GPa). Additionally, we compared the inferred magma source depths of the Pune – Nasik, and Narmada-Tapi dyke swarms which include the Nandurbar – Dhule, and Pachmarhi dykes of the Deccan Flood Basalt Province. Our findings indicate that the magma chamber source depth is greater in the Pune – Nasik dyke swarm compared with other dyke swarms. The variation in strike distribution of the Pune-Nasik dyke swarm may be attributed to several factors, including a larger magma chamber, local stress fields generated by shallow magma chamber, or the superimposition of tectonic stress fields (N-S and E-W extension) during the emplacement of dykes. This contrasts with the commonly held belief that the dykes are solely connected to a central edifice of the Reunion hotspot.

Flow dynamics and thermal effects in the ejecta of the multiple-layered Kotka crater on Mars

Article

Sep 2024
PLANET SPACE SCI

Gas and Thermal Emissions of Volcanoes

Chapter

Jul 2024

Remote sensing techniques have greatly enhanced our understanding of volcanic processes and hazards by providing valuable data on volcanic activity from a safe distance. This chapter provides a comprehensive overview of current remote sensing techniques, state-of-the art instrumentation and challenges in remote sensing of volcanoes. Both ultraviolet (UV), mid-wave and thermal infrared (IR) gas monitoring techniques to track changes in volcanic behavior are reviewed for both ground-based and space-borne sensors. Current challenges in remote sensing of volcanoes, such as atmospheric interference, data processing complexities and instrument limitations are also addressed and discussed. Finally, this chapter explores the practical applications of remote sensing in both effusive and explosive volcanic eruption scenarios as well as in geothermal and hydrothermal volcanic activity.

Explosive Eruption Styles, Columns, and Pyroclastic Fallout Deposits: Subaerial and Subaqueous, Dynamics, Deposit Characteristics and Classification

Chapter

Jun 2024

In this chapter, we consider the range of volcanic explosive eruption styles, from the smallest and least intense to the largest and most intense that produce pyroclastic fallout deposits. At the small-scale end of the spectrum of subaerial explosive eruptions, we include strombolian sensu stricto, halema’ma’uan and small-scale vulcanian and hydrothermal explosions. At the next level, there are small-scale hawai’ian magma/fire fountaining and larger scale vulcanian and hydrothermal explosions, followed by large-scale hawai’ian magma/fire fountaining, large vulcanian, and violent strombolian eruptions. We consider the eruptions that produce basaltic scoria through to rhyolitic pumice cones to be micro-plinian, at the small end of the spectrum of sub-plinian, plinian, and ultra-plinian explosive styles. We suggest that violent strombolian eruption style, which also produces cones, represents a transition between open-system degassing and closed-system degassing processes, and also that all the magmatic explosive eruption styles can transition into phreatomagmatic equivalents, irrespective of the scale, as demonstrated by the 2022 Hunga Tonga-Hunga Ha’apai eruption. The dynamics of the explosive eruption columns for all these styles are discussed, as are characteristic erupted masses and mass eruption rates. The characteristics of the deposits from each eruption style are described and comprehensively illustrated, particularly the field facies characteristics. Close to the vent, some proximal fallout deposits are welded, or pass into agglutinated spatter. We also review what is known about pyroclastic fallout processes in aqueous environments, and highlight how eruption dynamics, columns, and dispersal processes are different from subaerial processes. Several new proposed subaqueous eruption styles have recently emerged from recent research, including yalian, poseidic, neptunian, tangaroan-havre, and now hunga tongan. Although not enough is presently known about the fragmentation processes, intensity, and dispersal extent of these subaqueous eruption styles, it is important that they be acknowledged as a basis for driving future research. Finally, we consider how fit for purpose existing classification schemes for pyroclastic fallout deposits are. We suggest modifications to these, including recalibration of the logarithmic VEI, Eruption Magnitude and Explosive Intensity scales that have been applied for several decades, to accommodate smaller scale events that could previously not be included, but can be lethal in their impact, and therefore, need to be included in all schemes that reflect eruption scale and intensity.

Ebeko Volcano Activity in 2022: Mechanism and Products of Eruption

Article

Full-text available

Jul 2023

The paper provides information about the eruptive activity of the Ebeko volcano in 2022. From January 22 to June 13, phreatic explosions occurred in the crater lake caused by water seeping through the plug formed in the upper part of the magma channel and its boiling. On June 14, Vulcanian explosions began, destroying the lake. The granulometric composition of the ashes has changed in the direction of reducing the particle size. Petrographic and mineralogical-geochemical studies of tephra allow us to define this period as a phreatomagmatic eruption by the presence of fresh juvenile material. It is established that the interaction of magma with the waters of the hydrothermal system of the Ebeko volcano leads to its depletion with alkali metals and enrichment with silica. It is suggested that the formation of amorphous water-containing silica in the form of numerous separations and its subsequent dehydration may contribute to the explosive activity of the volcano.

Degradation of the 2014–2015 Holuhraun vent-proximal edifice in Iceland

Preprint

Full-text available

Sep 2023

The earliest stages of volcanic vent degradation are rarely measured, leaving a gap in the knowledge that informs landform degradation models of cinder cones and other monogenetic vent structures. We documented the initial degradation of a 500 m long spatter rampart at the primary vent of the 2014–2015 Holuhraun eruption in northern Iceland with high resolution topographic change maps derived from terrestrial laser scanning (TLS) and photogrammetric surveys using an unoccupied aircraft system (UAS). Topographic differencing shows a total negative volume change of 55,687 m ³ , and a total positive volume change (basal deposition) of 9,640 m ³ . Two distinct styles of volume changes were observed on the interior and exterior of the spatter rampart. Material on the interior of the vent was removed from oversteepened slopes by discrete rockfalls, while diffusive processes were qualitatively evident on the exterior slopes. We propose a novel conceptual landform evolution model for spatter ramparts that combines rockfall processes on the interior walls, diffusive gravitational sliding on the exterior slopes, and incorporates cooling contraction and compaction over the entire edifice to describe the observed modes of topographic change during the onset of degradation. Potential hazards at fresh spatter ramparts are rockfalls at high slope areas of the vent interior walls where contacts between spatter clasts are prone to weakening by fumarolic activity, weathering, and settling. To capture such hazards, our data suggest a cadence for monitoring changes yearly for the first few years post-eruption, and at longer intervals thereafter.

Magma Ocean, Water, and the Early Atmosphere of Venus

Article

Full-text available

Sep 2023
SPACE SCI REV

The current state and surface conditions of the Earth and its twin planet Venus are drastically different. Whether these differences are directly inherited from the earliest stages of planetary evolution, when the interior was molten, or arose later during the long-term evolution is still unclear. Yet, it is clear that water, its abundance, state, and distribution between the different planetary reservoirs, which are intimately related to the solidification and outgassing of the early magma ocean, are key components regarding past and present-day habitability, planetary evolution, and the different pathways leading to various surface conditions. In this chapter we start by reviewing the outcomes of the accretion sequence, with particular emphasis on the sources and timing of water delivery in light of available constraints, and the initial thermal state of Venus at the end of the main accretion. Then, we detail the processes at play during the early thermo-chemical evolution of molten terrestrial planets, and how they can affect the abundance and distribution of water within the different planetary reservoirs. Namely, we focus on the magma ocean cooling, solidification, and concurrent formation of the outgassed atmosphere. Accounting for the possible range of parameters for early Venus and based on the mechanisms and feedbacks described, we provide an overview of the likely evolutionary pathways leading to diverse surface conditions, from a temperate to a hellish early Venus. The implications of the resulting surface conditions and habitability are discussed in the context of the subsequent long-term interior and atmospheric evolution. Future research directions and observations are proposed to constrain the different scenarios in order to reconcile Venus’ early evolution with its current state, while deciphering which path it followed.

The continuation of the Mull Dyke Swarm into the Southern North Sea

Article

Aug 2023

We present new geophysical observations of the Mull Dyke Swarm in the Southern North Sea. 2D and 3D reflection seismic and aeromagnetic data were used to map the dykes. The three main dyke groups recognised onshore (Cleveland, Blyth and Hawick-Acklington) are found to extend to varying distances into the North Sea, crossing a number of major crustal-scale fault zones and domain boundaries, with almost no re-orientation. The Blyth Dyke Group extends furthest, for a distance of 672km from the source on Mull. The seismic data shows extensive development of pit chain craters above the upper tips of these dykes, which can be approximately dated to the late Palaeocene from the ages of crater fills. Volumetric estimates are made of the intrusive volumes associated with each group, ranging from 90km 3 to 202km ³ . These three main axes of intrusion probably formed in different intrusive events within a c. 1 million year period, from 59 to 58Ma, during magnetic chron C26R.

The 2022 Activity of Ebeko Volcano: The Mechanism and Ejecta

Article

Full-text available

Aug 2023

Interior Degassing

Chapter

Jul 2023

3D geothermal system modeling Songa - Wayaua, Bacan, Maluku Utara, Indonesia

Conference Paper

Jan 2023

An overview of sedimentary volcanism on Mars

Preprint

Full-text available

Jan 2023

Extensive fields of sub-kilometre-to kilometre-scale mounds, cones, domes, shields, and flow-like edifices cover large parts of the martian lowlands. These features have been compared to structures on Earth produced by sedimentary volcanism – a process that involves subsurface sediment/fluid mobilization and commonly releases methane to the atmosphere. It was proposed that such process might help to explain the presence of methane in martian atmosphere and also may have additionally produced habitable, subsurface settings of potential astrobiological relevance. However, it remains unclear whether sedimentary volcanism on Earth and Mars share genetic similarities; hence whether methane, or other gases were released on Mars during this process. The aim of this review is to summarize the current knowledge about mud-volcano-like structures on Mars, address the critical aspects of this process, identify key open questions, and point to areas where further research is needed to understand this phenomenon and its importance for the red planet’s geological evolution. We show here that after several decades of exploration, the amount of evidence supporting a martian sedimentary volcanism scenario has increased significantly, but as critical ground truth is still lacking, alternative explanations cannot always be ruled out. We also highlight that the lower gravity and temperatures on Mars compared to Earth control the dynamics of clastic eruptions as well as surface emplacement and resulting morphologies of erupted material. This implies that shapes and triggering mechanisms of mud-volcano-like structures may be different from those observed on Earth. Therefore comparative studies should be done with caution. To provide a better understanding of the significance of these abundant features on Mars, we argue for follow-up studies targeting putative sedimentary volcanic features identified on the planet’s surface and, if possible, for in situ investigations by landed missions such as that currently in progress by the Zhurong rover.

Estándar geográfico para mapas geológicos de volcanes colombianos

Book

Full-text available

Dec 2022

Se presentan las pautas para unificar la representación de los mapas geológicos de volcanes compuestos en Colombia como resultado de los avances del Servicio Geológico Colombiano (SGC) en la representación efectiva para el mapeo de unidades volcanogénicas en los Andes del norte, a partir de la búsqueda y análisis de diversas estrategias cartográficas implementadas en otros lugares del mundo, e identificadas en la literatura científica y en sitios web de otros servicios geológicos. El principal objetivo de este estándar es brindar una guía para la presentación digital de los mapas geológicos de volcanes compuestos del Plioceno-Holoceno, que proporcione una exposición integral de la cartografía y la estratigrafía, con base en una geodatabase dinámica, y que integre mejores prácticas en la representación y organización digital sistemática de mapas temáticos de volcanes compuestos para establecer un lenguaje común que facilite la comunicación y el entendimiento entre diferentes usuarios. En esta publicación se presentan los lineamientos para el manejo de la información geográfica asociada a la cartografía geológica de volcanes colombianos, como parte de las políticas y lineamientos de la Infraestructura Colombiana de Datos Espaciales del SGC, que busca optimizar la interoperabilidad y la normalización de la información geoespacial, con procesos de generación y actualización de los datos y herramientas para la evaluación de calidad, que faciliten el intercambio de información.

New Evidence for Sedimentary Volcanism on Chryse Planitia, Mars

Article

Apr 2022
ICARUS

Kilometre-sized flows (KSFs) have been observed in many regions on Mars and have been typically interpreted as lava flows. However, sedimentary volcanism has been proposed as an alternative origin for some KSFs. Remarkable examples of such hypothesized sedimentary KSFs are located at the southern margin of Chryse Planitia. There, the flows are associated with conical and dome-shaped edifices; however their formation mechanism remains enigmatic due to the absence of ground truth. Previous studies revealed that these KSFs consist of three morphological elements: a central depression, leveed central channels, and a distal portion of the fading channel(s). Here, we present new morphological results obtained on these KSFs using seven newly available Digital Elevation Models computed from HiRISE stereo pairs. Our investigation confirms that these features are aggradational and formed by the transport of a liquid. This material emerged from identified depressions and the presence of subtle mounds inside them is interpreted to mark the position of feeder vents. We also observe that the margins surrounding the central large channels are not continuous. They are cut by meter-sized troughs linking the central channels to units which have distinctive albedo and roughness compared to their surroundings. These bright units do not have a clear topographical expression, suggesting that the effused material originally flowing away from the central channel was easily removed after its emplacement. Such surface features are unlikely to be related to igneous deposits, since once lava is released from a main channel, it would rapidly solidify due to the heat loss and hence result in topographically distinct features. In contrast, such morphological expressions are more likely related to sedimentary volcanism and the emplacement of low viscosity water-rich mud. Sublimation, evaporation, infiltration or a combination of these processes should lead to water loss from the flows without leaving a detectable topographic expression but changing the roughness and hence albedo of the surface. The southern part of Chryse Planitia is a region on Mars where subsurface sediment mobilization could have operated in the past and hence represents a promising site for future exploration where deeper-sourced sedimentary deposits are exposed at the surface.

Volcanic Eruptions, Explosive: Experimental Insights

Chapter

Jan 2009

The effects of Damavand volcanic ash on some morphological and physiological characteristics of Phaseolus vulgaris

Article

Nov 2020

Srážky v ČR v období 1961–2019

Preprint

Full-text available

Jan 1961

Miloslav Šír, Pavel Kalenda V posledním období sucha v ČR v letech 2014-2019 celkový srážkový deficit vůči dlouhodobému srážkovému normálu 674 mm (1961-1990) činil 379 mm a roční územní teplota vzrostla vůči dlouhodobému normálu teploty vzduchu 7,5 °C o asi 2 °C (ČHMÚ 2020). Na jaře 2020 klimatologové vydávali zprávy, ve kterých varovali před pokračujícím katastrofálním 500letým suchem (Trnka, 2020). A to navzdory skutečnosti, že průměrné roční srážkové úhrny se v posledním padesátiletí zvyšovaly o asi 2 % za desetiletí (MŽP 2015). Pokud by se prognózy setrvalého vysušování ČR naplnily, pak by vodní hospodářství ČR stálo na prahu kolapsu, neboť je plně závislé na zdroji vody ze srážek. Na překlenutí dlouhých suchých období je totiž k dispozici jen vcelku málo podzemních a povrchových vod. Proto se v koncích víceletého sucha vyskytuje výrazné hydrologické sucho, které přetrvává i po několik počátečních let následujícího mokrého období. I při dlouhotrvajícím hydrologickém suchu je zásobování pitnou vodou v ČR spolehlivě zajištěno, neboť zásoby vody ve vodárenských nádržích mají velkou rezervu na pokrytí víceletých suchých období. Odběry vody z toků však zaručeny nejsou (Punčochář 2019). Z hlediska spolehlivé funkce vodního hospodářství je proto zásadní otázkou: Lze doložit nějaký trend k soustavnému vysušování ČR nebo se jedná o několikaleté oscilace srážkové činnosti? Odpověď naznačuje studium historických pramenů, podle kterých na našem území dochází až k nápadně pravidelnému střídání období sucha a mokra v cca 5-7letých intervalech (Svoboda el al. 2003) a v periodě 179 let dochází ke katastrofálním srážkám a povodním (Elleder 2016). A to v podmínkách nepravidelného kolísání teplot ovzduší, kdy periody významných změn mají délku mnoha desetiletí až staletí. Občas se však vyskytne výjimečné sucho, jako tomu bylo v letech 1944-1957, a větší sucho s odstupem 60-70 let v období 2014-2019. Oscilace srážkové činnosti, kdy se střídají několikaletá suchá (interpluviály) a mokrá (pluviály) období, je generálně podřízena vývoji sluneční aktivity (Kalenda, Šír 2020). Pro naše přírodní podmínky přitom převládá vztah, kdy vzestupné větve sluneční aktivity odpovídají srážkově bohatším obdobím a sestupné větve sluneční aktivity obdobím útlumu srážkové činnosti. V některých časových úsecích, a to jak v historické řadě klementinských pozorování, tak v obdobích před přístrojovým měřením srážkových úhrnů, však platí závislost zcela opačná, a vyskytují se i úseky bez jakékoliv vzájemné korelace těchto dvou jevů (Vašků 1997). Což napovídá, že do vztahu mezi sluneční aktivitou a srážkovou činností vstupují další faktory, které ovlivňují zemské klima. Obvykle se uvažuje o vlivu globálního oteplování na cirkulaci atmosféry a velkých sopečných výbuchů na průzračnost a odrazivost atmosféry vůči sluneční radiaci. Příspěvek se věnuje mechanismům, které způsobují střídání období sucha a mokra na území ČR. Odpovíme na otázku, zda očekávání katastrofického sucha je v souladu s dosud poznanými mechanismy, vysvětlíme náhlý konec období sucha 2014-2019 a zdůvodníme katastrofální srážky v srpnu 2002.

Morphologic Evidence for Volcanic Craters Near Titan's North Polar Region

Article

Full-text available

Aug 2020

Cassini Radar observations of Titan have revealed diverse landforms resulting from a variety of geologic processes. Many landforms can be unambiguously interpreted as resulting from atmospheric processes (dunes, rivers, and lakes) or impact cratering. Here we argue from morphological evidence such as nested collapses, elevated ramparts, halos, and islands or floor mountains that some of the abundant small depressions in the north polar region of Titan are volcanic collapse craters. A few similar depressions occur near the south pole; the restriction of this volcanism to polar regions is possibly related to predicted warmer and thinner‐than‐normal ice crust at the low‐elevation poles. The close association of the proposed volcanic craters with polar lakes is consistent with a volcanic origin through explosive eruptions, as either maars or calderas. The apparent freshness of some craters may mean that volcanism has been relatively recently active on Titan or even continues today.

Strombolian eruptions and dynamics of magma degassing at Yasur Volcano (Vanuatu)

Article

Apr 2020
J VOLCANOL GEOTH RES

Open vent basaltic volcanoes account for a substantial portion of the global atmospheric outgassing flux, largely through passive degassing and mild explosive activity. We present volcanic gas flux and composition data from Yasur Volcano, Vanuatu collected in July 2018. The average volcanic plume chemistry is characterised by a mean molar CO2/SO2 ratio of 2.14, H2O/SO2 of 148 and SO2/HCl of 1.02. The measured mean SO2 flux in the period of 6th to 9th July is 4.9 kg s⁻¹. Therefore, the mean fluxes of the other species are 7.5 kg∙s⁻¹ CO2, 208 kg∙s⁻¹ H2O and 4.8 kg∙s⁻¹ HCl. The degassing regime at Yasur volcano ranges from ‘passive’ to ‘active’ styles, with the latter including Strombolian activity and spattering. Gases emitted during active degassing are enriched in SO2 over HCl and CO2 over SO2 relative to passive degassing, with CO2/SO2 ratios of 2.85 ± 0.17, SO2/HCl of 1.6 ± 0.22, and H2O/SO2 of 315 ± 78.8. Gases emitted during passive degassing have CO2/SO2 ratios of 1.96 ± 0.12, SO2/HCl of 0.50 ± 0.07 and H2O/SO2 of 174 ± 43.5. We use a model of volatile degassing derived from melt inclusion studies (Metrich et al., 2011), combined with our observations of chemical variations in the outgassing bubbles to propose a mechanism for magma degassing in the conduit at Yasur. We envisage a shallow conduit filled with crystal-rich magma, forming a viscous and mobile plug that develops an effective yield strength from the surface to a depth of at least 2000 m, in which bubbles are trapped, grow, ascend towards the surface and burst in a typical Strombolian eruption. Deeper bubbles released during active degassing are enriched in CO2 and SO2 compared to bubbles released during ‘passive degassing’, which are sourced from close to the surface, and are, consequently, HCl-rich.

Fundamentals of physical volcanology

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