A model for gravity changes induced by lava fountaining at Mt Etna

2021 ◽  
Author(s):  
Luigi Passarelli ◽  
Mehdi Nikkhoo ◽  
Eleonora Rivalta ◽  
Corine Frischknecht ◽  
Costanza Bonadonna ◽  
...  
Keyword(s):  
Magma Chamber ◽  
Foam Layer ◽  
Lava Fountain ◽  
Gas Accumulation ◽  
Lava Fountaining ◽  
Gravity Changes ◽  
Gravity Measurements ◽  
Mt Etna ◽  
Lava Fountains ◽  
Gravity Signal

<div> <p><span>Lava fountains represent a common eruptive phenomenon at basaltic volcanoes, which consist of jets of fluid lava ejected into the atmosphere from active vents or fissures. They are driven by rapid formation and expansion of gas bubbles during magma ascent. The dynamics of lava fountains is thought to be controlled by the gas accumulation in the foam layer at the top of a shallow magmatic reservoir, which eventually collapses triggering the lava fountaining. Gravity measurements taken from a location close to summit of Mt. Etna during the 2011 lava fountain episodes showed a pre-fountaining decrease of the gravity signal. The interplay between gas accumulation in the foam layer and its subsequent exsolution in the conduit has been interpreted as the mechanism producing the gravity decrease and eventually leading to the foam collapse and onset of the lava fountaining activity. Gravity measurements have proved helpful in recording the earliest phases anticipating the lava fountain episodes and inferring the amount of gas involved. However, more accurate estimates of the accumulating and ascending gas volume and total magma mass require considering the possible effect of non-spherical magma chamber geometries and magma compressibility. </span></p> </div><div> <p><span>Under task 4.4 of the H2020 NEWTON-g project, we are accomplishing a detailed study aimed to simulate the gravity signal produced in the stage prior to a lava fountain episode, through a magma chamber - conduit model. We use a prolate ellipsoidal chamber matching the inferred shape of the shallow chamber active at Mt. Etna during the lava fountain episodes, and calculate the surface gravity changes induced by inflow of new magma into the chamber-conduit system. We use a two-phase magma with fixed amount of gas mass fraction and account for magma compressibility. We find that a realistic chamber shape and magma compressibility play a key role and must be considered to produce realistic gravity changes simulations. We combine our physical model with empirical distributions of recurrence time and eruption size of the past lava fountains at Mt. Etna to stochastically simulate realistic time series of gravity changes. The final goal of this study is to develop a prediction model for the amount of magma and duration of lava fountains at Mt. Etna.</span></p> </div>

scholarly journals Balancing bulk gas accumulation and gas output before and during lava fountaining episodes at Mt. Etna

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Daniele Carbone ◽  
Luciano Zuccarello ◽  
Alfio Messina ◽  
Simona Scollo ◽  
Hazel Rymer
Keyword(s):  
Gas Accumulation ◽  
Lava Fountaining ◽  
Mt Etna

scholarly journals Anatomy of a Paroxysmal Lava Fountain at Etna Volcano: The Case of the 12 March 2021, Episode

2021 ◽  
Vol 13 (15) ◽  
pp. 3052
Author(s):  
Sonia Calvari ◽  
Alessandro Bonaccorso ◽  
Gaetana Ganci
Keyword(s):  
Lava Flow ◽  
Ground Deformation ◽  
Monitoring Network ◽  
Lava Flows ◽  
Etna Volcano ◽  
Lava Fountain ◽  
Eruptive Episode ◽  
Lava Fountains ◽  
Borehole Strainmeter ◽  
Ash Plume

On 13 December 2020, Etna volcano entered a new eruptive phase, giving rise to a number of paroxysmal episodes involving increased Strombolian activity from the summit craters, lava fountains feeding several-km high eruptive columns and ash plumes, as well as lava flows. As of 2 August 2021, 57 such episodes have occurred in 2021, all of them from the New Southeast Crater (NSEC). Each paroxysmal episode lasted a few hours and was sometimes preceded (but more often followed) by lava flow output from the crater rim lasting a few hours. In this paper, we use remote sensing data from the ground and satellite, integrated with ground deformation data recorded by a high precision borehole strainmeter to characterize the 12 March 2021 eruptive episode, which was one of the most powerful (and best recorded) among that occurred since 13 December 2020. We describe the formation and growth of the lava fountains, and the way they feed the eruptive column and the ash plume, using data gathered from the INGV visible and thermal camera monitoring network, compared with satellite images. We show the growth of the lava flow field associated with the explosive phase obtained from a fixed thermal monitoring camera. We estimate the erupted volume of pyroclasts from the heights of the lava fountains measured by the cameras, and the erupted lava flow volume from the satellite-derived radiant heat flux. We compare all erupted volumes (pyroclasts plus lava flows) with the total erupted volume inferred from the volcano deflation recorded by the borehole strainmeter, obtaining a total erupted volume of ~3 × 106 m3 of magma constrained by the strainmeter. This volume comprises ~1.6 × 106 m3 of pyroclasts erupted during the lava fountain and 2.4 × 106 m3 of lava flow, with ~30% of the erupted pyroclasts being remobilized as rootless lava to feed the lava flows. The episode lasted 130 min and resulted in an eruption rate of ~385 m3 s−1 and caused the formation of an ash plume rising from the margins of the lava fountain that rose up to 12.6 km a.s.l. in ~1 h. The maximum elevation of the ash plume was well constrained by an empirical formula that can be used for prompt hazard assessment.

Monitoring aquifer recharge using repeated high-precision gravity measurements: A pilot study in South Weber, Utah

Geophysics ◽  
2008 ◽  
Vol 73 (6) ◽  
pp. WA83-WA93 ◽  
Author(s):  
D. S. Chapman ◽  
E. Sahm ◽  
P. Gettings
Keyword(s):  
High Precision ◽  
Gravity Anomalies ◽  
Pilot Project ◽  
Alluvial Fan ◽  
Aquifer Recharge ◽  
Aquifer System ◽  
Aquifer Storage ◽  
Gravity Measurements ◽  
Groundwater Mound ◽  
Gravity Signal

Repeated high-precision gravity surveys were conducted over two infiltration cycles on an alluvial-fan aquifer system at the mouth of Weber Canyon in northern Utah as part of the Weber River Basin Aquifer Storage and Recovery Pilot Project (WRBASR). Gravity measurements collected before, during, and after infiltration events indicate that a perched groundwater mound formed during infiltration events and decayed smoothly following infiltration. Data also suggest the groundwater mound migrated gradually south-southwest from the surface infiltration site. Maximum measured gravity changes associated with the infiltration were [Formula: see text] during the first event (2004) and a net [Formula: see text] increase during the second event (2005). Gaussian in-tegration of the spatial gravity anomaly yields an anomalouscausative mass within 10% of the [Formula: see text] [Formula: see text] of infiltrated water measured in 2004. The spatial gravity field is consistent with a groundwater mound at the end of the infiltration cycle approximately equivalent to a cylindrical disc of height [Formula: see text] and a radius between [Formula: see text]. After infiltration ceased, gravity anomalies decreased to approximately 50% of their original amplitude over a characteristic time of three to four months. The reduction of the gravity signal is simulated by analytical solutions for the decay of a groundwater mound through a saturated porous media. This comparison places relatively tight bounds on the hydraulic conductivity of the alluvial-fan material below the infiltration site with a preferred value of [Formula: see text] on a length scale of a few hundred meters.

scholarly journals Research on absolute gravity variations in geodynamic laboratory in Książ in the period of 2007- 2011

2012 ◽  
Vol 47 (4) ◽  
pp. 169-176 ◽  
Author(s):  
Marek Kaczorowski ◽  
Tomasz Olszak ◽  
Janusz Walo ◽  
Marcin Barlik
Keyword(s):  
Extreme Values ◽  
Absolute Gravity ◽  
Absolute Gravimeter ◽  
Gravimetric Measurements ◽  
Gravity Changes ◽  
University Of Technology ◽  
Gravity Measurements ◽  
Water Level Variations ◽  
Gravimetric System ◽  
Absolute Measurements

ABSTRACT In 2006 a gravimetric pavilion was installed inside the Geodynamic Laboratory (LG) in Książ. The pavilion was equipped with two pillars intended to serve relative and absolute gravimetric measurements. Installation of measurement platform for absolute gravity measurements inside gravimetric pavilion of LG made it possible to perform four sessions of absolute gravity measurements: two of them in 2007 (June 10-12 and Nov. 21-22), one in 2008 (Apr. 21-22) and one in 2011 (June 19-21). In 2007 the absolute measurements were performed using two FG5 ballistic gravimeters. In April 2007 the measurements were performed by Dr Makinen from Geodetic Institute of Finnish Academy of Science with application of FG5 No. 221 absolute gravimeter. In June 2007 and in the years 2008 and 2011 such gravimetric measurements were performed by the team from Department of Geodesy and Astronomical Geodesy of Warsaw University of Technology using FG5 No. 230 absolute gravimeter. Elaboration of observation sessions from both gravimeters was performed in the Department of Higher Geodesy following the procedures used in constituting of uniform gravimetric system of geodynamic polygons reference. This constituting of gravimetric system comprised inter alia application of identical models of lithospheric tides (global model by Wenzel, 1997) and ocean tides (Schwiderski, 1980) (reduction of absolute measurements with tidal signals). Observations performed during summer of 2007, autumn of 2007, and spring of 2008 and 2011 indicated existence of small changes of absolute gravity of the order of 1 Gal. Maxima of accelerations appear in the spring period, and minima in the autumn period. This effect is connected with the influence of global hydrological factors the annual amplitude of which is ca 1,5 Gal and achieve extreme values in the spring-autumn interval. Very small value of observed amplitude of gravity changes in the period of extreme variability suggests that the observed gravity changes in LG are caused only by global phenomenon. This proves high degree of „independence” of gravimetric measurement base in LG from the local environmental factors such as ground water level variations, ground humidity, impact of snow cover, etc. At this moment the instrumental environment of absolute measurements obtains particular value, especially in the case of the tiltmeters and relative the gravimeter Lacoste& Romberg (LR-648). The relative gravity measurements as performed simultaneously with absolute gravity measurements enable us to determine the local tidal ephemeredes which makes it possible to replace the global tidal modal with ocean tidal model with the more realistic, locally determined tidal parameters (the local tidal ephemeredes).

scholarly journals Minimum Detectable Mass and Volume Fluxes During Magmatic Recharge at High Prominence Volcanoes: An Application to Erciyes Dağ Volcano (Turkey)

2021 ◽  
Vol 9 ◽  
Author(s):  
Katie Males ◽  
Jo Gottsmann
Keyword(s):  
Surface Deformation ◽  
Ground Deformation ◽  
Element Analysis ◽  
Mechanical Heterogeneity ◽  
Reservoir Volume ◽  
Gravity Changes ◽  
Mt Etna ◽  
Vertical Displacements ◽  
Magma Recharge ◽  
Ground Displacements

Magma reservoir recharge is widely recognised as a precursor of eruptive activity. However, the causative relationships between reservoir rejuvenation and surface observables such as gravitational potential field changes and ground deformation are still poorly understood. At intermediate and silicic intra-plate volcanoes where crustal mechanical heterogeneity combined with high-prominence are expected to fundamentally affect the crustal stress and strain relationship, protracted period of repose and absence of monitoring data raise questions about the detectability of magma recharge. Here we report results from integrated geodetic forward modelling of ground displacements and gravity changes from reservoir recharge at Erciyes Dağ, a large prominence (∼2,800 m), yet poorly studied, stratovolcano of the Central Anatolian Volcanic Province in Turkey. The most recent eruption at ∼7000 BC, close proximity to the Kayseri Metropolitan Area and absence of dedicated volcano monitoring set a precedent to explore stealth magmatic processes at the volcano. Using finite element analysis we systematically explore the influence of subsurface mechanical heterogeneities and topography on surface deformation and gravity changes from magmatic recharge of Erciyes Dağ’s reservoir. We show that whilst crustal heterogeneity amplifies ground displacements and gravity variations, the volcano’s substantial prominence has the opposite effect. For generic reservoir pressure and density changes of 10 MPa and 10 kg m−3 predicted vertical displacements vary by a factor of 5 while residual gravity changes vary by a factor of 12 between models ignoring topography or mechanical heterogeneity and those that do not. We deduce reservoir volume and mass changes of order 10–3 km3 and 1010 kg, respectively, at the detectability limit of conventional surveying techniques at the volcano. Though dependent on model assumptions, all results indicate that magma recharge at Erciyes Dağ may go undetected at fluxes 1) sufficient to maintain an active reservoir containing eruptable magma and 2) similar to those reported for intermediate/silicic volcanoes with repose times of 100–1,000s of years (e.g., Parinacota) and persistently active mafic volcanoes such as Mt. Etna and Stromboli. Our findings may be utilised to inform integrated geodetic and gravimetric monitoring at Erciyes Dağ and other large prominence silicic volcanoes and could provide early insights into reservoir rejuvenation with implications for the development of disaster risk reduction initiatives.

scholarly journals Magma Budget From Lava and Tephra Volumes Erupted During the 25-26 October 2013 Lava Fountain at Mt Etna

2018 ◽  
Vol 6 ◽  
Author(s):  
Daniele Andronico ◽  
Boris Behncke ◽  
Emanuela De Beni ◽  
Antonino Cristaldi ◽  
Simona Scollo ◽  
...  
Keyword(s):  
Lava Fountain ◽  
Mt Etna

GRAVITY INVESTIGATIONS IN THE HOCKLEY SALT DOME, HARRIS COUNTY, TEXAS

Geophysics ◽  
1955 ◽  
Vol 20 (4) ◽  
pp. 829-840 ◽  
Author(s):  
W. E. Allen ◽  
H. J. Caillouet ◽  
L. Stanley
Keyword(s):  
Salt Dome ◽  
Salt Rock ◽  
Harris County ◽  
Near Surface ◽  
Gravity Changes ◽  
Clastic Sediments ◽  
Gravity Measurements ◽  
Density Values ◽  
Cap Rock ◽  
Gypsum Rock

Gravity measurements at the surface, in the shaft, and in the drifts of the United Salt Company’s mine at the Hockley salt dome have been analyzed to determine densities of sediments, cap rock, and salt rock. The curve derived from the gravity changes indicates the presence of lithologic breaks that correspond with the known geology of the shaft. The density values computed from this curve correspond closely with acceded values for near‐surface clastic sediments, limestone, gypsum rock, anhydrite rock, and salt rock.

Optical readout design for a MEMS semi-absolute pendulum gravimeter

2021 ◽  
Author(s):  
Phoebe Utting ◽  
Giles Hammond ◽  
Abhinav Prasad ◽  
Richard Middlemiss
Keyword(s):  
Microelectromechanical Systems ◽  
Gravity Data ◽  
Oscillation Period ◽  
Mems Sensor ◽  
Optical Readout ◽  
Gravity Measurements ◽  
Gravity Sensor ◽  
Mt Etna ◽  
Current Design ◽  
Set Up

<p>Gravimetry has many useful applications from volcanology to oil exploration; being a method able to infer density variations beneath the ground. Therefore, it can be used to provide insight into subsurface processes such as those related to the hydrothermal and magmatic systems of volcanoes. Existing gravimeters are costly and heavy, but this is changing with the utilisation of a technology most notably used in mobile phone accelerometers: MEMS –(Microelectromechanical-systems). Glasgow University has already developed a relative MEMS gravimeter and is currently collaborating with multiple European institutions to make a gravity sensor network around Mt Etna - NEWTON-g. A second generation of the MEMS sensor is now being designed and fabricated in the form of a semi-absolute pendulum gravimeter. Gravity data for geodetic and geophysical use were provided by pendulum measurements from the 18<sup>th</sup> to the 20<sup>th</sup> century. However, scientists and engineers reached the limit of fabrication tolerances and readout accuracy approximately 100 years ago. With nanofabrication and modern electronics techniques, it is now possible to create a competitive pendulum gravimeter again. The pendulum method is used to determine gravity values from the oscillation period of a pendulum with known length. The current design couples two pendulums together. Here, an optical shadow-sensor pendulum readout technique is presented. This employs an LED and split photodiode set-up. This optical readout can provide measurements to sub-nanometre precision, which could enable gravitational sensitivities for useful geophysical surveying. If semi-absolute values of gravity can be measured, then instrumental drift concerns are reduced. Additionally, the need for calibration against commercial absolute gravimeters may not be necessary. This promotes improved accessibility of gravity measurements at an affordable cost.</p>

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