Physics of Volcanoes - Book of abstracts Thursday 01 March 2018 - Friday 02 March 2018 GEOMAR Helmholtz Centre for Ocean Research Kiel
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Physics of Volcanoes
Thursday 01 March 2018 - Friday 02 March 2018
GEOMAR Helmholtz Centre for Ocean Research Kiel
Book of abstracts
Physics of Volcanoes / Book of abstracts Monday 22 July 2019Table of contents
40Ar-39Ar age clustering in the active phonolitic Cadamosto Seamount (Cape Verdes): Indications for periodic
magmatic activity ....................................................................................................................... 1
A fingerprint of fragmentation in volcanic ash – phase distribution in natural and experimental pyroclasts ... 2
Age relations, mineral-chemical and isotopic investigations on basaltic gem stone zircons from Eastern
Germany – insights into melt evolution ........................................................................................... 3
AGPA @ Pangaea-X: remote sensing and geophysical investigation of lunar and planetary geology on
Lanzarote, Canary Islands (Spain) ................................................................................................... 4
Analysis of volcano-related seismicity around Fogo and Brava, Cape Verde, by (multi-)array techniques ...... 5
Annual BrO/SO2 variations in the volcanic gas plume of Nevado del Ruiz .............................................. 6
Constraining the electrification properties of weak volcanic plumes ...................................................... 7
Crustal Seismicity along the Southern Andes Volcanic Zone, Southcentral Chile ...................................... 8
Determination of Gas Exit Velocities Using Thermal Infrared Data Recorded at Stromboli Volcano, Italy ...... 8
Dr. One on Tour: Morphological features of Volcán de Colima's summit crater ........................................ 9
Earth Observation-based Monitoring of Volcanoes – the contribution of the International Charter ‘Space and
Major Disasters’ .......................................................................................................................... 9
Experimental H2O degassing of Vesuvius melt: porosity, bubble shrinkage and coalescence ....................... 10
First detailed bathymetric and sampling investigations of the Bathymetrists Seamounts ............................ 11
Flying around Volcanic Clouds ...................................................................................................... 11
Geogenic CO2-degassing at the banks of the Laacher See – the use of mofette-indicator plants ................... 12
Geyser geodesy: Detection of ground deformation at Strokkur Geyser, Iceland, by ground based InSAR and tilt
measurements ............................................................................................................................ 12
Gravitational collapse of Mount Etna's south-eastern flank .................................................................. 13
Hazard Forecasting and Estimation of Potential Loss and Damage Due to Volcanic Eruption: Case Study of
Sinabung Volcano – Indonesia ....................................................................................................... 13
How to preserve semi-consolidated, submarine tuff for structural analysis .............................................. 14
Implications of divergent vent geometry for volcanic jet dynamics and acoustics ..................................... 15
Insights on high temperature SO2 scavenging ................................................................................... 15
Inter-event times of volcanic earthquakes in comparison with gas emission events of Villarrica, Chile .......... 16
Lightning-induced melting and geochemical alteration of volcanic ash - first experimental insights ............. 17
Mapping water vapor contents in the volcanic gas plume of Láscar volcano, Northern Chile, by means of
satellite-based radar interferometry (InSAR) ..................................................................................... 18
iMicrotextures on grain surfaces from subaerial and submarine deposits of different eruptions of Soufriere
Hills, Montserrat – A study in progress ............................................................................................ 18
Modeling of trajectories of volcanic ballistic projectiles from Timanfaya Volcano, Lanzarote ...................... 19
Monitoring seafloor displacement offshore Mount Etna: Evidence for active deformation from acoustic
geodesy ..................................................................................................................................... 20
Monitoring the Explosive Activity of Turrialba Volcano, Costa Rica, using Doppler Radar ......................... 20
Pre-eruptive conditions of phonotephrites of the East Eifel volcanic system, Germany - preliminary
experimental results .................................................................................................................... 21
Precision timing in the field .......................................................................................................... 21
Pressure and chemistry dependence of vapor/melt partition coefficients for boron in silicate melts .............. 22
Retrieval advances of BrO/SO2 molar ratios from NOVAC .................................................................. 22
ROBEX Summer School at Vulcano: A natural laboratory for marine, terrestrial and planetary science and
technology ................................................................................................................................. 23
Seismic and infrasound measurements at Santiaguito volcano, Guatemala .............................................. 23
Seismic imaging of the Klyuchevskoy Volcanic System, Kamchatka ....................................................... 24
Seismicity at Villarrica Volcano (Chile): Characteristics, origin and implications on wave propagation ......... 25
Statistical analysis of the repose intervals during an increase in volcanic activity at Volcán de Colima
(2014-2015) ................................................................................................................................ 26
Sulphur and Bromine monoxide emission inside Reventador’s volcanic plume ......................................... 26
The Dynamics of Submarine Hydrothermal Systems—Insights from Numerical Models ............................. 27
The geodynamics of plume-ridge interaction at fast spreading rates ....................................................... 28
The impact of topographic unloading on dyke intrusions: Modelling magma propagating under calderas. ..... 29
The new HH SO2Cam .................................................................................................................. 30
The Origin of Researcher Ridge (Central Atlantic Ocean) .................................................................... 31
The relationship between thermal infrared and acoustic signals of Strombolian explosions ......................... 32
The use of light aircraft for volcano monitoring – capabilities and examples of application ........................ 33
Three-Dimensional Modeling of Transient Electromagnetics at Stromboli Volcano ................................... 34
Time series of a volcano crater morphology: Insights from aerial photogrammetry at Volcán de Colima,
Mexico ...................................................................................................................................... 35
U-Th zircon dating and geochemistry of Santa Maria-Santiaguito volcanic complex ................................. 36
Vesiculation processes in rhyolitic magma as a response to heating and slow decompression ...................... 37
Volcanoes up close - Rapid evolution of vent and crater morphology at Stromboli volcano as seen by UAV ... 38
Volcanology at sea – unravelling the eruption history of the Azores ...................................................... 39
Young Volcanism on old Oceanic Crust: The Balerion Lava Fields, NW Atlantic ...................................... 40
iiPhysics of Volcanoes / Book of abstracts
15
40Ar-39Ar age clustering in the active phonolitic Cadamosto Seamount
(Cape Verdes): Indications for periodic magmatic activity
Author: SAMROCK, Lisa 1
Co-Authors: Dr. HANSTEEN, Thor 2; Dr. WARTHO, Jo-Anne 1
1
GEOMAR Helmholtz Centre for Ocean Research Kiel
2
GEOMAR Helmhohltz Centre for Ocean Research Kiel
The Cape Verde archipelago is situated ~400-800 km off the west coast of Africa and is comprised of a
northern and southern chain of islands and seamounts. Morphological observations and previous radiometric
dating of the islands indicate a slow age progression, over ~22 Ma, from east to west (Holm et al. 2008). We
present the first radiometric ages for Cadamosto Seamount, which is composed of complex evolved volcanics
and is situated at the southwestern tip of the Cape Verde archipelago (e.g. Barker et al. 2012).
We analyzed five different submarine phonolites that were sampled by remotely operated vehicles (ROV)
Kiel6000 and dredging during the RV Meteor (M80/3) and RV Poseidon (POS320/2) cruises. Fresh sanidine and
nepheline grains were selected and carefully prepared for 40Ar-39Ar single grain total fusion analysis.
Sanidine single grain 40Ar-39Ar ages from 5 samples range from 11.5 ± 6.5 ka to 349.0 ± 20.4 ka (2σ errors),
and cluster in several age groupings (using the decay constant and atmospheric air ratio of Steiger & Jäger
(1977), and age standard TCS2 (27.87 ± 0.04 Ma; 1σ; M.A. Lanphere, pers. comm.)). Three age groups can be
identified within the youngest (0-170 ka) sanidines, which are separated by periods of ~52-54 ka. These age
groups can be correlated to global relative sea level changes. Nepheline grains from one sample yielded much
older ages of 169.5 ± 16.5 ka to 1521.5 ± 8.3 ka (2σ).
Our data suggests young ages for the Cadamosto Seamount, which is in accordance with recorded seismic
activity (Grevemeyer et al. 2010), and its position adjacent to the active islands of Fogo (last eruption in
2014/2015) and Brava (current seismic activity). The different sub-groups of sanidine 40Ar-39Ar ages can be
used to identify different activity maxima corresponding to cycles of magmatic productivity in a long-lived
magmatic system.
References:
Barker A.K. et al. (2012) Contrib. Mineral. Petrol. 163, 949–965.
Grevemeyer I. et al. (2010) Geophys. J. Int. 180, 552–558.
Holm P.M. et al. (2008) J. Geophys. Res. 113, doi:10.1029/2007JB005339, 2008.
Steiger R.H., Jäger E. (1977) Earth Planet. Sci. Lett. 36, 359–362.
1Physics of Volcanoes / Book of abstracts
29
A fingerprint of fragmentation in volcanic ash – phase distribution in
natural and experimental pyroclasts
Author: Dr. HORNBY, Adrian 1
Co-Authors: Dr. KENDRICK, Jackie 2; Prof. LAVALLÉE, Yan 2; Dr. KUEPPERS, Ulrich 3; Prof. BUTCHER, Alan 4; Dr. AYRIS, Paul 3; Dr.
ROLLINSON, Gavyn 5
1
LMU-München
2
University of Liverpool
3
Ludwig-Maximilians-Universität (LMU)
4
Geological Survey of Finland (GTK)
5
Camborne School of Mines
The physical and chemical properties of volcanic ash are a fingerprint for fragmentation processes in volcanic
eruptions. However, detailed ash particle analyses are typically labor-intensive and limited by particle number
and particle size range. Here, we show that QEMSCAN® PMA, an automated mineralogy technique, can
rapidly discriminate thousands of ash particles and constituent phases at a micron scale, dramatically
improving the efficiency of subsequent image analysis. We compare particle characteristics from natural ash
samples collected at Santiaguito, Guatemala and pyroclasts generated from shock tube experiments using rock
cores from Tungurahua, Ecuador. We use image analysis to measure size-dependent variation in ash particle
properties. Here, we present novel analysis showing a disparity between the bulk and boundary distribution of
plagioclase and groundmass glass in ash particles lofted from pyroclastic flows and the ash produced by shock
tube experiments, but not in ash particles deposited from a Vulcanian explosion plume. Ash deposited
following pyroclastic flows shows a preferential distribution of glass and depletion of plagioclase at particle
boundaries. Plagioclase depletion is also characteristic of the pyroclast surfaces produced by shock tube
experiments, together with an increased cpx-microlite fraction. These observations may represent fracturing
focused in differing phases under varying fragmentation regimes (e.g. abrasion, overpressure, faulting) and
provide important constraints on the fragmentation processes during explosions at dome-forming volcanoes.
Changes in surface componentry affect a range hazards to health, the environment, aviation and
infrastructure, in addition to providing a new tool to diagnose fragmentation modes and we encourage further
development of this technique within the community.
2Physics of Volcanoes / Book of abstracts
0
Age relations, mineral-chemical and isotopic investigations on basaltic
gem stone zircons from Eastern Germany – insights into melt evolution
Author: BÜCHNER, Jörg 1
Co-Authors: Dr. TIETZ, Olaf 1; Prof. VIERECK, Lothar 2; Dr. GERDES, Axel 3
1
Senckenberg Museum Görlitz
2
3Institut für Geowissenschaften, Friedrich-Schiller-Universität Jena
3
Geozentrum der Universität Frankfurt
In alkali basaltic rocks scarcely appear accessory minerals such as zircon and corundum. The origin of these
mostly gem stone like mega-crystals is unknown and discussed controversial. Host magmas of the zircon
mega-crystals are normally SiO2 undersaturated (basanites and nephelinites). In several localities we could
observe some zircon megacrystals and in a quarry in Saxony (eastern Germany) we collected about 40 crystals
up to 15 mm in size in situ from the basanitic rock [1]. Zircons occur in agglutinates of lower crater facies of a
scoria cone. The related lava flows are almost free of zircons and their Zr contents reaches up to 900 ppm [2].
There is a good correlation between Ar/Ar data of the basanites (30 to 31 Ma) and the zircon U/Pb data which
show ages about 30.5 Ma.
First investigations indicate an alkaline source for zircons which origin possibly from intermediate alkaline
melts. This is evidenced by zircon-typology, mineral
chemistry and analyses of mineral inclusions and mineral paragenesis [3]. Preliminary in situ Hf-isotopic
analyses of zircons indicate an origin from mantle melts. The crystals show an intensive magmatic corrosion
in alkali basaltic rocks (including nephelinites), whereas zircons out of phonolites are mostly euhedral. Zircons
in basaltic rocks have more or less evolved reaction rims, composed mostly of baddeyleit. Zr-contents in the
rims of clinopyroxene phenocrystals decreases rapidly with the distance from the zircon inclusions. This
indicates late entrainment of zircon crystals into the basanitic melt.
The age data of the zircons in relation to that of the host rocks as well as the mineral chemical and isotopic
data imply a cogenetic development of both.
[1] Tietz & Büchner (2007) ZdGG 158, 201-206. [2] Büchner
et al. (2006) Z. geol. Wiss. 34, 121-141. [3] Seifert et al.
(2008) N. Jb. Mineral., Abh. 184, 299-313.
3Physics of Volcanoes / Book of abstracts
27
AGPA @ Pangaea-X: remote sensing and geophysical investigation of
lunar and planetary geology on Lanzarote, Canary Islands (Spain)
Author: Mr. ORTENZI, Gianluigi 1
Co-Authors: Dr. ROSSI, Angelo Pio 2; Prof. UNNITHAN, Vikram 2; Dr. TORRESE, Patrizio 3; Dr. BORRMANN, Dorit 4; Prof.
NUECHTER, Andreas 4; Mr. LAUTERBACH, Helge 4; Mr. JAEHRIG, Tim 2; Dr. SOHL, Frank 1
1
DLR, Institute for Planetary Research, Rutherfordstraße 2, 12489 Berlin, Germany
2
Jacobs University Bremen, Physics and Earth Sciences, Bremen, Germany
3
Università di Pavia, Via Ferrata 1, 27100, Pavia, Italy
4
Julius-Maximilians-Universität Würzburg, D-97074 Würzburg, Germany
The investigation of Earth planetary analogues is a key point to test future experiments for planetary surface
and subsurface exploration. In this context, the ESA (European Space Agency) astronaut training campaign
extension PANGAEA-X held in November 2017 on Lanzarote, gave the opportunity to different research
teams to perform a set of geological and geophysical experiments on an Earth analogue terrain for Mars and
Moon. One of these projects was: “Augmented field Geology and Geophysics for Planetary Analogues
(AGPA)”.
The aims of AGPA were to combine geophysical and field geology analytical techniques to improve the
geological characterization of the surface and the subsurface of the investigated area and moreover, to test
their potential for future planetary missions. The remote sensing was performed through drone
stereogrammetry and ground-based or mobile LIDAR systems. The combination of aerial and ground-based
remote sensing provides detailed geological and geomorphological information of the surface that could be
relevant to characterise future Lunar and Mars landing sites and their human and/or robotic exploration. The
geophysical survey was carried out with geo-electrics and seismics experiments. The main aim of the
geophysical analysis was to identify and characterise buried lava tunnel which are of great interest for the
Martian subsurface investigation.
In conclusion, due to its volcanic features the island of Lanzarote was an excellent terrain to test and combine
the different analytical techniques in order to improve geological and geomorphological analysis with a
planetary analogue perspective.
4Physics of Volcanoes / Book of abstracts
8
Analysis of volcano-related seismicity around Fogo and Brava, Cape
Verde, by (multi-)array techniques
Author: LEVA, Carola 1
Co-Authors: LINK, Frederik 1; RÜMPKER, Georg 1; WÖLBERN, Ingo 1; FARIA, Bruno 2
1
Institute of Geosciences, Goethe-University Frankfurt, Germany
2
National Institute of Meteorology and Geophysics, Cape Verde
The Cape Verde archipelago is believed to originate from a mantle plume beneath an almost stationary
tectonic plate. Fogo and Brava are located in the south-western part of the archipelago, about 18 km apart
from each other and belong to the younger islands. Only Fogo experienced historic eruptions and has an
eruption interval of about 20 years, with the last eruption from November 2014 to February 2015.
Previous studies, using seismic stations distributed on the islands, have indicated relatively high seismic
activity in the vicinity of Brava. Based on these findings, a possible link of the plumbing system of Fogo to a
magmatic source near Brava has been proposed. More recently, a “seismic crisis” on Brava led to the
evacuation of a village during August 2016.
We aim to investigate the magmatic system of Fogo and to characterize the seismic activity of this region. As
the majority of the seismic events are located offshore, we decided to use multi-array techniques to perform
the investigations. Furthermore, many volcano-related seismic signals lack a clear onset of phases, such that
array methods may be more suitable to locate their origin.
In October 2015 we first deployed a seismic array on Fogo. The circular array consists of 10 stations with an
aperture of 700m. Additionally, we set up three broadband-stations across the island in January 2016. Since
January 2017 we operate three similar arrays, two on Fogo and one on Brava, complemented by 7 single
short-period stations on both islands.
To localize earthquakes, we apply a time-domain array analysis, combined with a distance estimation from
travel-time differences between S- and P-wave arrivals. With this method, 276 earthquakes were located near
Brava in 2016. 25 of the events occurred during the “seismic crisis” on Brava from August 1-2, 2016. The
seismicity beneath Brava remained at a high level in the following months. The temporal evolution of these
earthquakes, as well as their locations and magnitudes will be presented.
Additionally, we recorded a swarm of earthquakes beneath Fogo. We analyzed 13 events of this cluster located
beneath southern Fogo at a depth of about 40 km. Results from our receiver-function analysis show that the
Moho discontinuity is located at a depth of about 11 km. This indicates that the deep earthquakes occur well
within the upper mantle. We ascribe these events to a magma related origin, which in turn questions the
hypothesis of a link between the magma supply systems of Fogo and Brava.
5Physics of Volcanoes / Book of abstracts
5
Annual BrO/SO2 variations in the volcanic gas plume of Nevado del Ruiz
Author: Mr. DINGER, Florian 1
Co-Authors: Prof. PLATT, Ulrich 2; Prof. WAGNER, Thomas 1; Dr. BOBROWSKI, Nicole 3; Ms. CHACON, Zoraida 4; Dr. GARZON,
Gustavo 5
1
Max-Planck Institute for Chemistry, Mainz, Germany
2
Institute for Environmental Physics, University of Heidelberg, Germany
3
Insitute for Environmental Physics, University of Heidelberg
4
Servico Geologico Colombiano, Manizales, Colombia
5
Servico Geologico Colombiano, Cali, Colombia
Nevado del Ruiz volcano (4°53'N,75°19'W, Colombia) has become infamous for its eruption in 1985 which
caused 25000 causalities. Since 2010, Nevado del Ruiz exhibits a new and still ongoing period of activity
accompanied by strong gas emissions. On June 30 2012, major phreatomagmatic explosions occurred. Since
2009, Nevado del Ruiz is part of the Network for Observation of Volcanic and Atmospheric Change (NOVAC).
The NOVAC data provides the possibility for deriving semicontinuous (at daytime only) time-series of the
slant column densities (SCD) of SO2 and BrO in the volcanic gas plume. We present and discuss the BrO to
SO2 molar ratios in the volcanic gas plume of Nevado del Ruiz from December 2009 until late 2017. Variation
of the BrO/SO2 ratio can be caused by atmospheric chemistry and/or by volcanic activity changes.
The SO2-SCDs have been below 1*10^18 molec/cm^2 after the NOVAC instruments had been installed until
September 2010, have been up to 3*10^18 molec/cm^2 between September 2010 and early 2012, have increased
in the first half of 2012 to extreme values of up to 24*10^18 molec/cm^2 prior to the explosions on June 30
2012, and vary at still extreme levels of 8-16*10^18 molec/cm^2 since July 2012. The BrO-SCDs have been up
to 2*10^14 molec/cm^2 after the NOVAC instruments had been installed until early 2012, have increased to
3*10^14 molec/cm^2 prior to the explosions on June 30 2012, and varies between 3-7*10^14 molec/cm^2 since
July 2012.
Despite the large changes in SO2-SCDs and BrO-SCDs, the time series of the BrO/SO2 molar ratios shows
only few discontinuities but a linear trend and a periodic pattern. The mean BrO/SO2 molar ratio increased
with a linear trend of 0.4*10^-5 per year from 2*10^-5 in late 2010 to 5*10^-5 in late 2017. The trend has been
superimposed by a periodic pattern which has been identified as an interference of an annual cyclicity and a
semi-annual cyclicity. This pattern has a minimum every year in July and a maximum every year in October,
each with amplitudes of 1.5*10^-5. For comparison, the residual (after subtracting trend and periodic pattern)
time series has a standard deviation of 1.8*10^-5. Furthermore, the residual time series has a drop of 2*10^-5
between January and May 2012. This drop has been discussed by Lübcke et al. (2014) as a possible precursor of
the magmatic crisis in June 2012. Another drop by 3*10^-5 has been observed between May and October 2014.
This drop has been followed by enhanced seismic activity and thermal anomalies in November 2014. A drop
in mid 2013 and a peak in mid 2017, both with an amplitude of 2*10^-5, have not yet been assigned to a
possible volcanic origin.
6Physics of Volcanoes / Book of abstracts
46
Constraining the electrification properties of weak volcanic plumes
Author: Dr. CIMARELLI, Corrado 1
Co-Authors: GAUDIN, Damien 2; KNUEVER, Marco 2; NICOLL, Keri 3; AIREY, Martin 4; KOH, Kuang Liang 5; BENNETT, Alec 6
1
Department of Earth and Environmental Sciences, Ludwig Maximilians Universität München, Germany
2
LMU München
3
Department of Meteorology, University of Reading, UK; Department of Electronic and Electrical Engineering, University of Bath, UK
4
Department of Meteorology, University of Reading, UK
5
Department of Electronic and Electrical Engineering, University of Bath, UK
6
BIRAL, Bristol Industrial Research Associates Ltd, Portishead, UK
Electrification of volcanic plumes is often observed by the occurrence of lightning discharges during vigorous
explosive eruptions. It is generally agreed that electric charge is carried by the ash and that plume
electrification depends on the way the ash is generated, ejected and subsequently processed in the plume. This
conceptual model is built on the observation of lightning discharges produced by ash-rich, mid- to
highly-explosive eruptions (Vulcanian to Plinian). Very little is known about the electrification of mild
explosive eruptions (e.g. Strombolian style) where less ash and gas are erupted, leading to smaller plumes
rising to a few hundred of meters only, and bearing a lower ash concentration containing a range of
proportions of gas and ash containing . Studying these eruptions has a two-fold interest. First, they are very
frequent, making the instrumentation set-up easier and allowing statistical analysis. Second, being at the
lower end of the spectrum of explosivity, they represent the best opportunity to derive basic information
about the charge distribution and charge carriers in volcanic plumes containing a range of proportions of gas
and ash.
In this scope, we carried out a multi-parametric monitoring campaign at Stromboli volcano (Italy) during
October 2017. The instrumental array at the ground was composed of a wideband radio receiver, a high-speed
electrostatic sensor, a thermal imaging camera, a high-speed camera, and two infrasound sensors. With the
exception of the high-speed camera, which was triggered manually at the occurrence of the explosions, the
other instruments were recording continuously thus allowing correlations between the variation in explosive
activity and the electrical signals recorded. Additionally, an airborne miniature sensing package measuring
electrostatic charge, aerosol concentration and SO2 concentration was deployed for the first time for in-situ
measurement inside the volcanic plume.
Preliminary results show that ash is not the only charge carrier, since SO2-rich ash-poor portions of the
plumes can also be substantially charged. Our results further extend the spectrum of electrical activity
observations in relation to volcanic explosive activity and open a new scenario for the interpretation of the
role of gas and solid aerosol in carrying electrostatic charges in the plume.
7Physics of Volcanoes / Book of abstracts
7
Crustal Seismicity along the Southern Andes Volcanic Zone, Southcentral
Chile
Author: LANGE, Dietrich 1
Co-Authors: SIELFELD, Gerd 2; CEMBRANO, Jose 2
1
GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel
2
Pontificia Universidad Católica de Chile
We examine the crustal seismicity of the volcanic arc of the Southern Andes, focussing on the nature and
kinematics of deformation in an active magmatic arc dominated by the margin-parallel Liquiñe-Ofqui fault
system (LOFS) and margin transverse faults (ATF). Intra-arc crustal seismicity, provides information about
current faulting processes, delineating the geometry and kinematics of high strain domains driven by
oblique-subduction, and subsequent, transpressional regime. Here, we present high-resolution local seismicity
based on 16-months data collected from 34 seismometers monitoring a ~200 km long section of the Chilean
magmatic arc covering the stratovolcanoes Lonquimay and Villarrica. We located 356 crustal events with
moment magnitudes between 0.6 and 3.6. Local seismicity occurs at all depths down to 40 km. Maximal depth
of seismicity increases away from the magmatic arc most likely related to lower temperature gradients. Focal
mechanisms indicate strike-slip faulting consistent with ENE-WSW shortening in line with the long-term
deformation history revealed by structural geology studies. However, we find regional to local-scale variations
in the shortening axes orientation as revealed by the nature and spatial distribution of microseismicity, within
three distinctive latitudinal domains. In the northern domain (37.9˚S-38.8˚S), seismicity is localized within a
transtensional domain demarking the northern termination of the LOFS; in the central domain (38.8˚-39.3˚S),
seismicity distributes along ENE- and WNW-striking discrete faults, indicating active faulting of the ATF. The
southern domain (39.3°-40°S) is characterized by seismicity focused along a N15˚E striking master branch of
the LOFS. The seismicity provides for the first time detailed information of current faulting along the northern
part of the LOFS.
38
Determination of Gas Exit Velocities Using Thermal Infrared Data
Recorded at Stromboli Volcano, Italy
Author: RÖH, Franziska 1
Co-Authors: VON DER LIETH, Jost 1; Prof. HORT, Matthias 1
1
University of Hamburg
The exit velocity of gas and particles during an eruption is an important parameter for volcanic hazard
mitigation as well as eruption modelling. Thermal infrared measurements provide an important tool for
remote observations of eruptive processes as it does not rely on daylight. In previous studies using thermal
infrared data, often only one method is used for the velocity estimation. Here, three different approaches are
tested and compared to investigate the advantages and disadvantages of each of them: manual picking (MP),
time-height diagram (THD) and area-based velocimetry (ABV).
For MP, the upper boundary of the plume (i.e. largest temperature gradient) was picked in a vertical
temperature profile for each frame in the IR video (see Harris and Ripepe, 2007, doi: 10.1029/2006JB004393). For
constructing the THD (see Gaudin et al., 2017, doi: 10.1002/2016JB013707) the temperatures along a vertical
line above the vent are plotted side by side. Velocities appear as slopes marking changes in temperature in the
diagram. A novel approach is ABV that counts the amount of pixels above certain defined temperatures.
Assuming the plume exits the vent approximately in the form of a spherical sector for at least the first two
seconds, the velocity can be determined using the normalised change of areas above the temperatures.
Since normalised area changes are considered, this method is insensitive to bombs uncoupling from the main
plume. Furthermore, while the first two approaches rely on subjective manual picking, ABV provides an
objective and accurate way to quantify the eruption velocities. Preliminary results already show that the three
methods produce different results. Therefore, the velocities will be compared to independent velocity
estimates from Doppler radar recorded simultaneously to the thermal infrared data. Further approaches to
improve the performance of the above-mentioned techniques will also be discussed.
8Physics of Volcanoes / Book of abstracts
45
Dr. One on Tour: Morphological features of Volcán de Colima's summit
crater
Author: Mr. JUCHEM, Marlin 1
Co-Authors: Dr. KUEPPERS, Ulrich 2; Dr. HORNBY, Adrian 3; Dr. VARLEY, Nick 4
1
Earth Environmental Sciences, Ludwig-Maximilians-Universität (LMU), Munich, Germany
2
Ludwig-Maximilians-Universität (LMU)
3
LMU-München
4
CIIV, Faculty of Science, University of Colima, Mexico
Volcán de Colima's ongoing eruptive cycle has started 20 years ago and is ongoing. It is characterised by
intermittent explosive activity, separated by periods of quiescence or dome growth. Between January 2015 to
January 2017, several highly energetic Vulcanian explosions took place, sending impulsive ash plumes several
kilometres into the air and generating pyroclastic density currents in valleys of the drainage network.
Monitoring the eruptive activity is essential for a detailed understanding of the explosions but also the signals
leading to them. Here we present aerial and drone data acquired in 2017. Ongoing subsidence inside the
summit crater is clearly visible based on images take in June and November. This is apparently localised to the
NW sector whereas several explosion craters are still visible in the central and SW part. We discuss
morphological features and try to link them to videos of the eruptions. We compare the precision of digital
elevation models based on photos or still frames acquired from videos.
Today's off-the-shelf drones have become an increasingly powerful and reliable tool. Flying at 4.000 m asl or
at wind velocities of 20 m/s did not categorically impede data acquisition. Used to support volcano
monitoring, they can deliver high-resolution images and movies and allow for increasing temporal resolution
at low cost.
23
Earth Observation-based Monitoring of Volcanoes – the contribution of
the International Charter ‘Space and Major Disasters’
Author: Dr. PLANK, Simon 1
Co-Author: Dr. MARTINIS, Sandro 1
1
DLR
The International Charter ‘Space and Major Disasters’ is an international consortium of space agencies and
satellite operators that aims at providing a unified system of space data acquisition and delivery to those
affected by natural or man-made disasters. The Charter was founded by the European, the French and the
Canadian space agencies (ESA, CNES and CSA) in the year 2000. Following countries subsequently joined the
Charter: the USA, India, Argentina, Japan, UK, China, Germany, Korea, Brazil, Russia, Bolivia and the Arab
Emirates. Also the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) is a
Charter member. This article presents the activities of the Charter in the context of Earth Observation-based
disaster monitoring of large volcanic eruptions. In the last 18 years the Charter has been activated 34 times
due to larger volcanic events, starting with the eruption of Mount Etna, Sicily, Italy in 2001 to the currently
on-going eruptions on Papua New Guinea’s Kadovar Island and of Philippines' most active volcano, Mount
Mayon. Since 2010 the German Aerospace Center (DLR) is member of the Charter and contributes RADAR
imagery of the TerraSAR-X mission, RapidEye optical imagery as well as Value Adding, i.e. the extraction of
relevant crisis information from satellite data and the transfer of this information into geo-information
products, such as maps. Focus of this article is the 16 volcano-related Charter activations where DLR was
actively involved.
9Physics of Volcanoes / Book of abstracts
52
Experimental H2O degassing of Vesuvius melt: porosity, bubble shrinkage
and coalescence
Author: ALLABAR, Anja 1
Co-Author: NOWAK, Marcus 1
1
Eberhard Karls Universität Tübingen, Fachbereich Geowissenschaften
Bubble nucleation and growth are the fundamental mechanisms that control melt degassing and thus the
magma ascent just prior and during volcanic eruptions. In order to investigate bubble nucleation, growth and
potential coalescence, combined hydration and decompression experiments were performed in an internally
heated argon pressure vessel. Phonolitic VAD79 melts were hydrated at 200 MPa and 1523 K for 96 and
subsequently decompressed at super-liquidus conditions of 1323 K with 0.17 MPa•s-1 to final pressures (Pfinal)
between 110 MPa and 60 MPa. At Pfinal the samples were quenched isobarically. H2Ot contents of the
partially degassed samples were measured with FTIR spectroscopy. Bubble number densities (BND) and
porosities were determined with both, transmitted light microscopy (TLM) and quantitative BSE image
analysis using a stereological 2D to 3D transformation.
Homogeneously distributed bubbles are observed in experiments decompressed to P ≤ 100 MPa with a BND of
~105 mm-3. BNDs are constant down to 60 MPa with narrow size distributions in all experiments. Coalescence
is not observed in the investigated pressure range. Glass porosity increases up to 20 %. However, glass porosity
does not equal melt porosity due to bubble shrinkage induced by the decrease of molar volume (Vm) of H2O
during isobaric cooling (Marxer et al. 2015). H2O diffusivity calculations indicate that near-equilibrium H2O
contents must have been adjusted prior to quench and thus equilibrium porosity at 60 MPa is 40 %, not
sufficient for coalescence.
Bubble (volume-) shrinkage factors, linking equilibrium melt porosity to glass porosity, decrease from 26 to 2.5
with decreasing Pfinal from 100 to 60 MPa. Further calculations show that bubble shrinkage cannot solely be
explained by the decrease in molar volume of H2O (EOS) (down to Tg) in samples quenched at Pfinal > 70
MPa. Additionally required cooling induced bubble shrinkage is attributed to resorption of H2O from fluid
bubbles into the melt during cooling, driven by increasing H2O solubility with decreasing temperature at P <
300 MPa (McIntosh et al. 2014, Schmidt et al. 2008). To quantify the contribution of both, EOS- and
resorption-shrinkage, the fictive temperature Tf EOS, where EOS driven bubble shrinkage stops due to
viscosity increase, needs to be known. However, under the assumption of near-equilibrioum H2O contents at
Pfinal, the critical porosity at which coalescence occurs can be studied by performing additional experiments
at lower Pfinal.
Bubble shrinkage processes need to be modeled and experimentally investigated by in-situ studies to clarify
the role of EOS- and resorption driven shrinkage during cooling. This is especially important for “post
mortem” analyzed decompression experiments where equilibrium porosity is not achieved and thus, melt
porosity is not known.
Marxer H, Bellucci P, Nowak M (2015) J Volc Geotherm Res 297: 109-124
McIntosh et al. (2014) EPSL 401: 1-11
Schmidt & Behrens (2008) Chem.Geol. 256: 259-268
10Physics of Volcanoes / Book of abstracts
42
First detailed bathymetric and sampling investigations of the
Bathymetrists Seamounts
Author: Dr. VAN DER ZWAN, Froukje Marieke 1
Co-Authors: Dr. AUGUSTIN, Nico 2; MILUCH, Jakub Mateusz 3; SCHADE, Martin 1; SCHÖNBERG, Janto 1; GARBE-SCHÖNBERG,
Dieter 1; Dr. LE SAOUT, Morgane 2; Dr. WÖLFL, Anne-Cathrin 2; ANTONIO, Richard Jason 4; FOLLMANN, Jörg 1; HEINATH, Verena 1;
KÖSE, Mehmet Can 1; KRACH, Louisa 1; LONG, Xiaojun 2
1
Christian Albrechts Universität Kiel
2
GEOMAR Kiel
3
Ernst Moritz Arndt Universität Greifswald
4
Universität Bremen
Intraplate volcanism, in contrast to mid-ocean-ridge basalts, is formed by low degrees of mantle melting under
thick lithosphere and thus has a unique and distinct major element, trace element and isotopic composition.
Magmatism associated with the emplacement of intraplate seamount provinces therefore can significantly
alter the composition of the underlying lithosphere and in addition, magmatism may trigger local structural
changes and fluid flow causing large-scale hydrothermal activity, which would also modify the original
composition of the lithosphere. Nevertheless the origin of some of these intraplate volcanic provinces is not
entirely clear.
The BATHYCHEM expedition (MSM70, Dec 2017-Feb 2018) aimed to study one of these, so far poorly
researched, intraplate volcanic provinces: the Bathymetrists Seamount Chain (located in between the Cape
Verde Rise and the Sierra Leone Rise) and its corresponding fault zones; Cape Verde Ridge and Kane Gap that
border the Seamounts to the north. The formation of the Bathymetrists Seamounts may have affected the
composition of oceanic crust that has a wide range of ages from 30 to >100 Ma and thus has been exposed to
variable degrees of alteration during the evolution of the seafloor. This project aims at characterizing the
structure, age and composition of the Bathymetrists Seamounts and adjacent areas to understand their origin
and formation mechanism, which will allow a better assessment of how intraplate volcanism modifies the
structure and composition of oceanic lithosphere through time.
Here we present the first results of the expedition MSM70 based on high-resolution bathymetric mapping and
dense rock sampling of the Bathymetrists Seamounts and the adjacent fracture zone(s). Most of the seamounts
(62%) resemble flat-topped seamounts or guyots capped by carbonated platforms, manganese-iron or
phosphorite crusts as has been observed in the Pacific. Samples from the volcano flanks reveal dense basaltic
samples and vesicular volcanoclastic material of mafic origin containing pyroxenes, amphiboles and biotite.
The morphology of the seamounts indicate a structural control for volcano formation, potentially related to
the local fault patterns and reorganisation of the African plate movement.
53
Flying around Volcanic Clouds
SIEVERS, Klaus 1
1
VC - German Airline Pilots´ Association
Eyjafjallajökull - Bardarbunga - Puyehue: words that stand for more than nature plays. Each of these volcanic
eruptions had its peculiarities, and influenced air traffic. What was common to all was that there was a degree
of uncertainty about dealing with the concrete impact: pilots were surprised by a flood of information or were
not given important information. Furthermore, instruments that detect volcanic ash or gas are presently not
installed in operational aircraft. This paper presents a pilots´ view of volcanic clouds, and presents suggestions
for more efficient as well as safer flights when volcanic clouds are presented.
11Physics of Volcanoes / Book of abstracts
2
Geogenic CO2-degassing at the banks of the Laacher See – the use of
mofette-indicator plants
Author: Prof. PFANZ, Hardy 1
Co-Author: Dr. THOMALLA, Annika 2
1
Lehrstuhl für Vulkanbiologie Universität Duisburg-Essen
2
Lehrstuhl für Vulkanbiologie
Hardy Pfanz and Annika Thomalla; Chair of Applied Botany and Volcano Biology, University of
Duisburg-Essen, 45117 Essen, Germany. hardy.pfanz@uni-due.de
A geogenic CO2 emitting site (mofette U1) at the banks of the Laacher See/Eifel Mountains was selected to
study the relationship between heavy geogenic soil degassing and vegetation. A rectangle of 54 x 7 m was
identified within a forested area and laid out with a 1m grid. Soil as well as vegetation analysis was performed
each meter. Soil parameters like degassing patterns of carbon dioxide and oxygen showed an inhomogeneous
degassing pattern which centered at the inner part of the research area. CO2 concentrations ranged from zero
to 100%. CO2 concentrations increased with soil depth (0 to 60cm). Soil CO2 fluxes nicely correlated with soil
CO2 concentrations; oxygen concentration linearly decreased with increasing CO2. Soil permeability as
measured with a penetrologger correlated quite well with the soil skeleton and with CO2 gas emission. Soil
pH and conductivity followed the pattern of CO2 emission. From 69 species found within the area, only one
proved to be mofettophilic (Carex acutiformis) and exclusively grew on strong CO2 emitting sites, whereas all
other species within the area avoided CO2 emission (mofettophobic species) and grew on control plots or only
slightly degassing soil. Strictly high soil-CO2 avoiding species were Symphoricarpos albus, Stellaria holostea,
Ranunculus ficaria, Corydalis solida, and Poa nemoralis. Total number of growing species was highest in low
CO2 soils (max. 17 species per m2) and lowest at high CO2 emitting sites (one species per m2). Plant coverage
followed the same pattern. Total plant coverage reached values of up to 84% under control or slightly
degassing soils and 5-6% and CO2 venting sites.
51
Geyser geodesy: Detection of ground deformation at Strokkur Geyser,
Iceland, by ground based InSAR and tilt measurements
Author: ALLAHBAKHSI, Masoud 1
Co-Authors: WITT, Tanja 1; WALTER, Thomas 1; JOUSSET, Philippe 1
1
GFZ Potsdam
Ground deformation at volcanoes is a fundamental part of volcano monitoring as it can indicate whether a
volcano is showing signs of unrest, or is potentially building towards an eruption. Furthermore, it gives
important information for better understand of magmatic processes. Based on the mechanism technique, we
are able to detect both spatial (e.g., by InSAR etc) and temporal patterns of ground deformation (e.g., by GPS,
tiltmeters) for volcano monitoring the ground deformation measurements are combined with other
techniques, as measurements of seismicity, gas emissions or hydrological changes. Geysers, which are springs
producing discrete eruptions of steam, liquid water, and non-condensable gases, provide a natural laboratory
to study eruptive processes. Their eruptions are smaller and typically more frequent than volcanoes and
hydrothermal eruptions. Most data used to study geysers comes from observation made at the surface, because
measurements in site are limited due to their complexity. To better understand the fluid path in the crust and
to learn more about the conduit, further investigations are needed. In this project, we investigate detailed,
continuous surface deformation monitoring during many eruption cycles, i.d. we will measure the ground
deformation geyser before, during and after an eruption.
12Physics of Volcanoes / Book of abstracts
3
Gravitational collapse of Mount Etna's south-eastern flank
Author: Ms. URLAUB, Morelia 1
Co-Authors: Mr. PETERSEN, Florian 1; GROSS, Felix 2; BONFORTE, Alessandro 3; PUGLISI, Giuseppe 3; GUGLIELMINO, Francesco 3;
Prof. KRASTEL, Sebastian 4; LANGE, Dietrich 5; KOPP, Heidrun 5
1
GEOMAR Helmholtz Centre for Ocean Research
2
Institut für Geowissenschaften, Christian-Albrechts-Universität zu Kiel
3
INGV Catania
4
Institute of Geosciences, Christian-Albrechts-Universität zu Kiel
5
GEOMAR
Mount Etna’s southeastern flank is densely populated and hosts numerous world heritage sites. It has long
been known that it slides into the Ionian Sea at rates of centimetres per year with highest displacement rates
at the coast. The prevailing understanding is that pressurization of the feeding system and magmatic
intrusions control Mount Etna’s flank movement and not gravitational forces acting on the flank of the
volcano, although this has also been proposed. So far, it has not been possible to distinguish between these
processes, because no data on the offshore deformation were available until we conducted the first long-term
seafloor displacement monitoring campaign from April 2016 until July 2017. Combining our data with onshore
ground deformation data shows that deformation increases away from the magmatic system. We suggest that
the bulk of Mount Etna’s flank movement is driven by gravity and that inflation and magma overpressure
cause episodic accelerations in addition to gravitational sliding.
35
Hazard Forecasting and Estimation of Potential Loss and Damage Due to
Volcanic Eruption: Case Study of Sinabung Volcano – Indonesia
Author: Mr. YUDHISTIKA, Andre 1
Co-Authors: Dr. SULE, Rachmat 1; Dr. GOTTSCHAEMMER, Ellen 2; Dr. KRISWATI, Estu 3; Dr. PRAMBADA, Oktory 3
1
Institut Teknologi Bandung -Indonesia
2
Karlsruhe Institute of Technology
3
Center of Volcanology and geological Hazard Mitigation – Indonesia
Mapping of tephra distribution is very important for hazard mitigation. It could be used for determining
evacuation strategies, and estimation of potential loss and damage. This is important, especially for a country
like Indonesia, which it situated at a plate boundary and is therefore exposed to a variety of natural hazards.
Sinabung Volcano, which is situated in North Sumatra Province (Indonesia) showed its first activity in August
28th 2010, and until now its eruption is still ongoing, with periods of eruption one month up to three years.
The determination of the tephra distribution from ash cloud eruptions from Sinabung Volcano is presented in
this work. We could estimated the tephra distribution by an indirect method, i.e. simulating the ash fall using
the Fall3d program. The input data for the simulation is grain size, wind direction and wind speed, and also
other eruption parameters. Samples of volcanic ash were collected from Simpang Empat Sub-district and
Sinabung volcano observatory, which is about 5 km and 10 km from the eruption point of Sinabung Volcano,
respectively. From the granulometry measurement, the grain size is found to be about 2380 micrometer to 52
micrometer. The wind data used in the simulation was taken from the Australian Bureau of Meteorology
(BOM), which is accessible through internet. Further eruption parameters must also be determined, especially
duration of eruption, column height, and volume of erupted materials. The simulation results are displayed as
contours of ash thickness in the vicinity of that volcano from which an estimation of potential loss and
damage is conducted. The thickness of ash fall varies from 7.4 cm to 0.1 cm. The contours of ash fall are
asymmetric circles to the South with a maximum radius of the minimum thickness is 12 km. The potential loss
and damage estimation is divided into two parts :(1) loss related to the settlement, and (2) loss for the
agriculture sector. The loss estimation for settlement is about 36 Mio. €, whereas for agriculture sector we
compute about 120,000 €. By knowing the typical distributions of ash fall and typical values of potential loss
and damage, we hope that the mitigation strategy could be designed in a better way.
13Physics of Volcanoes / Book of abstracts
26
How to preserve semi-consolidated, submarine tuff for structural analysis
Author: Mr. STERN, Sönke 1
Co-Authors: Dr. KUEPPERS, Ulrich 1; Dr. BEIER, Christoph 2
1
Ludwig-Maximilians-Universität (LMU)
2
Friedrich-Alexander Universität Erlangen-Nürnberg
Explosive volcanic eruptions generate gas particle jets that are ejected into the atmosphere. If too heavy, these
jets can collapse and form density currents. The sedimentary and stratigraphy information contained in the
related deposits allows information of transport and sedimentation processes. During the M128 research cruise
of RV Meteor in July 2016 on the Azores plateau, semi-consolidated tuff samples were taken at Capelinhos
volcano, Faial island, and at the seamount João de Castro, approximately half way between the islands of
Terceira and São Miguel. The deposits belong to the 1957 and 1958 Capelinhos and 1720 João de Castro
eruptions and have been sampled with a TV grab. Immediate visual observations showed planar and
cross-bedded strata of ash-sized material, resulting from constructive deposition interrupted by erosional
events. Samples were found to be loosely consolidated. To allow for detailed sedimentological analysis, the
samples were dried and then impregnated with a two-component epoxy in a vacuum chamber in a step-wise
manner. Different problems occurred: 1) Low permeability prevented a complete impregnation even for 1 cm
vertical filling steps. 2) The high salt content (causing crystallisation of the salt) and reacting of water-bearing
minerals to the exothermic glue frequently led to sample cracking preferentially along bedding planes. Further
work is intended to go into the preparation to produce thin sections showing the sedimentary structures of the
samples, enabling insights into the eruptive processes and depositional environment.
14Physics of Volcanoes / Book of abstracts
24
Implications of divergent vent geometry for volcanic jet dynamics and
acoustics
Author: Dr. PENA FERNANDEZ, Juan Jose 1
Co-Authors: Dr. CIGALA, Valeria 2; Prof. SESTERHENN, Jörn 1; Dr. KUEPPERS, Ulrich 3; Prof. DINGWELL, Donald Bruce 2
1
Department of Fluid Mechanics and Technical Acoustics, Berlin Institute of Technology, Berlin, Germany.
2
Department of Earth and Environmental Sciences. Ludwig-Maximilians-Universität (LMU). Munich, Germany.
3
Ludwig-Maximilians-Universität (LMU)
Explosive volcanic eruptions are impulsive and highly dynamic events that eject tephra into the atmosphere.
Commonly, tephra ejection takes place through a vent with a complex geometry. This plays a crucial role in
both fluid mechanics and acoustics of volcanic jets. To date, a quantitative understanding of the physical
processes during explosive eruptions as well as the influence of boundary conditions (especially the vent
geometry) is still lacking.
We focus here on the influence of the vent geometry on volcanic jet dynamics and acoustics. For this purpose,
we choose a multidisciplinary approach coupling large-scale numerical simulations and experimental
acoustics. We study impulsively starting gas jets (with ratios of reservoir total pressure p_0r to ambient
pressure p_∞ of up to 80) to evaluate the changes in the acoustics and the properties of the fluid flow when
being ejected through different vent geometries. We focus on three geometries: (i) one straight vent and two
divergent vents (ii) and (iii). The respective exit to throat area ratios are: (i) 1, (ii) 2.36 and (iii) 4. The
corresponding adapted pressure ratio (i.e., the pressure ratio for which the jet is perfectly expanded, delivering
supersonic flow without shocks; (p_0r/p_∞)_a) for geometries (i), (ii) and (iii) are 1, 20.31 and 54.74,
respectively. As it can be seen, there is a positive correlation between the exit to throat area ratio and the
adapted pressure ratio. For pressure ratios over the adapted pressure ratio, the exit Mach number remains
constant to the adapted value, but for lower pressure ratios, the exit Mach number decreases drastically, even
in the subsonic regime. This affects the entire fluid flow of the jets and the acoustics related. Although we
have not introduced particles in the investigation yet, which might further affect the jet dynamics and related
acoustic signature, the results obtained offer a better understanding of the consequences of a divergent vent in
both the fluid flow and the acoustics of volcanic jets. By establishing a robust link between the fluid flow and
the acoustics of volcanic jets, we would be able to better predict the governing parameters of explosive
volcanic eruptions. As a direct consequence, it will be possible to implement the monitoring systems based on
volcanic jet acoustics, which already have been deployed with success and hold promises to be very sensitive
and very cost efficient compared to current volcanic monitoring methods.
6
Insights on high temperature SO2 scavenging
Author: Ms. CASAS, Ana 1
Co-Authors: Dr. WADSWORTH, Fabian 2; Dr. AYRIS, Paul 2; Dr. DELMELLE, Pierre 3; Dr. VASSEUR, Jeremie 2; Prof. DONALD,
Dingwell 2
1
Ludwig-Maximilians-Universität
2
LMU
3
Université catholique de Louvain
The fate of gases and volatiles exolved during large volcanic eruptions can be better assessed, if ash-gas
interactions are considered. Such interactions can remove considerable amounts of gases by adsorption onto
the ash surface and posterior mineral growth. We have confirmed previous assumptions that SO2-scavenging
is temperature dependent, and sustained by Ca2+ diffusion toward the particle surface. We also evaluated the
effect of grain size distribution, humidity, SO2 concentrations and exposure time on gas scavenging. Finally,
we applied and scaled our findings to model and predict how much SO2 could be scavenged at an in-dome
scenario (20008 rhyolitic dome at Volcán Chaitén). Our results show for the first time that scavenging at
fractured, permeable flow rhyolitic domes is feasible and can be more effective than in-plume or in-conduit
scavenging.
15Physics of Volcanoes / Book of abstracts
13
Inter-event times of volcanic earthquakes in comparison with gas
emission events of Villarrica, Chile
Author: LEHR, Johanna 1
Co-Authors: BREDEMEYER, Stefan 2; RABBEL, Wolfgang 1; THORWARTT, Martin 1
1
Institute of Geosciences, Kiel University
2
GEOMAR Helmholtz Centre for Ocean Research Kiel
Frequency distributions of inter-event times (iets) – the time between two consecutive earthquakes – allow for
a statistical analysis of earthquake occurrences without the need of identifying fore-, main-, or aftershocks.
The distribution of iets implies an underlying stochastic process which, in turn, may be explained by a
physical process. Moreover, when scaled with the mean occurrence rate, the frequency distributions of quakes
occurring on different time scales, regions, etc. can easily be compared. This makes iets an ideal observable for
comparing the different types of seismicity encountered at volcanoes.
We analyzed volcano-tectonic (VT) and low-frequency (LF) seismicity at Villarrica Volcano during nine days
of early March 2012. VT-events were identified using an STA/LTA trigger. LF-events, recorded near the active
vent, were triggered when the envelope of the signal exceeded the low-pass filtered envelope. By the same
means, we identified ‘gas emission events’, i.e. a short-term elevation of sulfur dioxide fluxes, which were
measured in the downwind portion of the volcanic gas plume (at ~6km distance from the vent) by three
scan-DOAS stations between January and April 2012. Iets of VT-events are well represented by the right
skewed universal Gamma distribution for tectonic earthquakes, as proposed by Corrall et al., 2004. In contrast,
iets of LF-events, although asymmetric, show a clearly unimodal distribution which can be fitted e.g. by
another Gamma distribution with significantly different shape parameters. Our result for the LF-seismicity is
in good agreement with similar analyses at Stromboli and Etna, where LF-activity originates from outgassing
magma.
In order to verify such a relationship for Villarrica, we applied the iet analysis to the ‘gas emission events’.
Despite the significant differences between the two data sets, both iets collapse into almost identical frequency
distributions after rescaling. This requires at least a similar stochastic process of event occurrence, but strongly
suggests a common physical process as well.
We suggest interpreting the sulfur dioxide variations in the gas plume as a low-pass filtered response of a
discrete degassing process: assuming that LF-events are eventually caused by frequent escapes of relatively
small amounts of gas, the material accumulates in the plume resulting in a slower fluctuation of the gas flux,
but involving larger quantities. The scale-invariance of the Gamma distribution in case of proportional rate
parameters would then allow for our observation. The atmospheric mixing processes in the equilibrating
plume which cause a homogenization of gas distribution inside the plume act as the filter.
We have no means to verify the emission of discrete gas parcels at the vent opening for our observation
period. However, Villarrica is well-known for its infrasonic signals, which accompany coinciding seismic LF-
and outgassing events during small strombolian eruptions – a mechanism that was 1) most likely active
during our campaign and 2) supports the idea of a degassing process by frequent discharge of small amounts
of gas.
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