IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4A1_2I-O1

Room A5

Date/Time: July 24 8:45-9:10

Erebus volcano: an open-vent archetype
Mount Erebus Volcano Observatory
NMT, USA
E-mail: co200@cam.ac.uk

Erebus is well known for its lava lake, alkaline intraplate character, and, of course, its southerly latitude. It also
serves as a paradigm of open–vent volcanism, with persistent degassing and sporadic Strombolian eruptions
associated with the long–lived lava lake. Its proximity to the largest station in Antarctica (McMurdo), and thecomprehensive logistical support from the US Antarctic Program, provide an exceptional research infrastructuresuch that Erebus ranks among the world’s outstanding laboratory volcanoes. On one level, the behaviour of
Erebus simple, stable and sustained but the magma differentiation (basanite, through intermediate terms, tophonolite), mantle–to–surface degassing (and associated redox changes), and the moderate viscosity of thesurficial (phonolitic) magma, superimpose fascinating complexity on the long–lived lava lake. The gases emitted
from the lava lake are dominated by carbon dioxide (by mass), symptomatic of the important role played by carbon
dioxide in magmatic evolution beneath the volcano. In addition to the signature of deeper magmatic processes
evident in the surface gas signature, cyclic changes in gas composition and lava lake height and velocity highlight
aspects of magma convection and degassing in the uppermost parts of the magma conduit and the lava lake
itself. This presentation will provide an overview of recent research findings form Erebus and link to several othercontributions on Erebus being given at the IAVCEI meeting.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

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IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4A1_2I-O2

Room A5

Date/Time: July 24 9:10-9:25

Zonation in anorthoclase feldspar megacrystals reveals dynamics of the magma conduit
feeding the lava lake at Erebus volcano, Antarctica
Yves Moussallam1 , Clive Oppenheimer1 , Bruno Scaillet2 , Phil Kyle3 , Iris Buisman4 , Alain Burgisser3
1

Department of Geography, University of Cambridge, Downing Place, Cambridge, CB2 3EN, UK,
ISTO, UMR 6113 Universite d’Orleans-CNRS, 1A rue de la Ferollerie, 45071 Orleans cedex 2, France,
3
Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, USA,
4
Department of Earth Sciences, University of Cambridge, Downing Place, Cambridge, CB2 3EQ, UK
2E-mail: ym286@cam.ac.uk

Anorthoclase megacrysts are a striking feature of many peralkaline trachyte and phonolite lavas. At Mt Erebus
volcano (Antarctica) they reach up to 7 cm long, and display two interesting properties: perfect oscillatory zoning
and large melt inclusions. By combining experimental and analytical approaches we can recreate the P-T-H2 O-fO2
history of these crystals and illuminate the magma dynamics of the plumbing system feeding Erebus’ lava lake.
Phase equilibrium experiments indicate a correlation between the anorthoclase composition and both pressure
and temperature. After imaging the melt inclusion by X-ray tomography to assure they are fully enclosed, melt
inclusions confined within anorthoclase zones of known composition were analyzed by electron probe, ion probe
and Fe K-edge micro-x-ray absorption near-edge structure spectroscopy (XANES). We found a correlation between
the CO2 content in melt inclusions and the chemistry of their host zone suggesting that oscillatory zoning in thesemegacrystals reflects crystallization at different depths within the conduit. This finding allows us to decode eachcrystal and track its history of circulation up and down the magmatic conduit.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

616

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4A1_2I-O3

Room A5

Date/Time: July 24 9:25-9:40

Tracking the hydraulic connection between Kilauea’s summit and rift zones using lava
level
Matthew Patrick, Tim Orr
US Geological Survey - Hawaiian Volcano Observatory, USA
E-mail: mpatrick@usgs.gov

A magmatic connection between Kilauea Volcano’s summit and rift zones has been inferred for decades, evencenturies, based on the temporal relationship of changes during discrete events in these two areas of the volcano,but continuous tracking of the fluid connection has not been possible in modern times until just recently. We track
the fluid lava levels at Halema’uma’u and Pu’u ’O’o craters and demonstrate that a state of dynamic hydraulicequilibrium exists between Kilauea’s summit and east rift zone. The hydraulic head loss in the system was usedwith the Darcy-Weisbach equation to infer that the conduit feeding the east rift zone eruption is <5 m in diameter,
and the rate of draining of the summit lava lake in March 2011 was modeled with the Poiseuille equation to infer thatthe conduit supplying lava to Halema’uma’u is also <5 m wide. During 2011, rising lava levels at both Halema’uma’uand Pu’u ’O’o, inflation of the summit and east rift zone and increasing numbers of earthquakes along the upper east
rift zone presaged several rift zone eruptive events, consistent with rising hydraulic head pressure in the summit-riftmagmatic system that triggered the rift activity and draining of the summit magma reservoir. The summit lava
level closely tracked tiltmeter and GPS measurements of summit deformation (during both inflation and deflation),
indicating that the lava level within Halema’uma’u Crater is a reasonable proxy for pressurization of the magmatic
system. The Halema’uma’u lava lake level therefore serves as a convenient gauge for judging the likelihood of
future eruptive or intrusive events along the rift zones. Historical summit lava level data from the 1800s and early
1900s confirms that rift eruptions were usually preceded by rising, elevated lava levels in the summit. The patterns
from 2011 reaffirm the usefulness of lava level in forecasting rift activity and provide an improved picture of howlava level relates to precursory trends observed in modern geophysical data. Forecasting eruptive potential fromlava level likely has value at other open-vent basaltic volcanoes around the world.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

617

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4A1_2I-O4

Room A5

Date/Time: July 24 9:40-9:55

Estimating the location and volume of shallow magma storage at Kīlauea Volcano fromobservations of episodic ground deformation
Kyle Anderson1 , Jessica Johnson2 , Michael Poland1 , Asta Miklius1 , Matthew Patrick1
1

USGS Hawaiian Volcano Observatory, USA, 2 Center for the Study of Active Volcanoes, University of
Hawaii at Hilo, USA
E-mail: kranderson@usgs.gov

A variety of geophysical observations suggest the presence of at least two long-lived magma reservoirs beneaththe summit of Kīlauea Volcano. Although the locations of the reservoirs are known generally, their volumes arepoorly constrained. Episodic pressure perturbations in the shallow magmatic system, however, generate cycles
of ground deformation that provide valuable constraint on the location and volume of the more shallow of thetwo reservoirs. These cycles of ground deformation, divided into three different classes based on their temporal
histories, have been labeled deflation-inflation (DI) events. Recorded by tilt, GPS, InSAR, and strain data, a typical
DI cycle consists of deflation of the summit region over a period of roughly 8 hours to 3 days, in many cases at
a quasi-exponentially decaying rate, followed by a recovery over hours to a few days to roughly the original level.
Since the opening of Kīlauea’s summit vent in 2008, the rate of DI event occurrence has increased, and DI-related
ground deformation has also closely tracked the level of the summit lava lake. Cyclic deformation at the summit isalso often reflected, after a pause of roughly one-half to three hours, at the Pu‘u ‘Ō‘ō eruptive vent 20 km from thesummit, suggesting that DI events reflect perturbations of magma flow and pressure conditions throughout muchof Kilauea’s interconnected shallow plumbing system.

We invert deformation data recorded during more than 400 individual DI events to estimate the location ofKīlauea’s shallow magma reservoir (the Halema‘uma‘u reservoir) and look for changes associated with eruptive
activity. We find that the three classes of DI events share a common source region, located near the east marginof Halema‘uma‘u Crater, which has moved little if at all in more than ten years (the time span of the most accurate
deformation records). The depth of this source is shallow but poorly resolved from the tilt data alone; however,GPS, InSAR, and strain data can provide additional constraint. The volume change associated with individual DI
events is probably less than one million cubic meters, although the estimate is correlated with source depth. Whilethe deformation data cannot constrain the total volume of the Halema‘uma‘u reservoir, we are able to estimate
volume by assuming that the summit lava lake is in magmastatic equilibrium with the reservoir such that its surface
height may be used as a manometer. Using probabilistic estimates of host rock rigidity and magma density
together with volume change obtained from inversion of the deformation data, we estimate that the Halema‘uma‘ureservoir has a volume of several cubic kilometers.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

618

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4A1_2I-O5

Room A5

Date/Time: July 24 9:55-10:10

Componentry of pyroclastic fall deposits from September and October 2008 weak
explosions at Kilauea summit crater: insights into the dynamics of an open basaltic
magma column
Julia Eychenne1 , Bruce Houghton1 , Don Swanson2 , Tim Orr2 , Rebecca Carey3
1

Geology and Geophysics, University of Hawaii, United States, 2 U.S. Geological Survey, Hawaiian
Volcano Observatory, United States, 3 University of Tasmania, Hobart, Australia
E-mail: eychenne@soest.hawaii.edu

On 19 March 2008 a small explosive event at Kilauea’s volcano summit opened a 35-m-wide vent on the south
wall of Halema’uma’u crater, initiating an eruptive period that extends to the time of writing. The activity of theopen basaltic magma column has been characterized by a vigorous outgassing and an unevenly intense spattering
at the free surface (permanent or background activity), and the occurrence of small explosive events consistently
triggered by conduit-wall and/or rim collapses. The componentry analyses of samples collected daily near the ventduring different sequences of events (including transitions from background activity to explosions and vice versa) in
September and October 2008 allow us to distinguish three main classes of juvenile particles by their vesicularity andbubble size distributions. The abundances of these classes vary from background- to explosion-samples, revealing
consistently contrasts in degassing and fragmentation processes before the disruption of the lava free surface by
the rockfalls, and during and soon after the explosive events. Textural and chemical analyses of particles fromdifferent componentry classes revealed mixing features and crystallinity variations. These results give insights into
the dynamics of the open lava column and particularly into the behavior of the top of the column during outgassing
and external disruption of the free surface-equilibrium state.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

619

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4A1_2I-O6

Room A5

Date/Time: July 24 10:10-10:25

An analysis of volcano inflation prior to an eruption at Stromboli volcano based on slug
flow and rising gas bubble models
Ryohei Kawaguchi, Takeshi Nishimura
Geophysics, Graduate School of Science, Tohoku University, Japan
E-mail: kawaguchi@zisin.gp.tohoku.ac.jp

Stromboli volcano is a small volcanic island located in the south of Italy, and its eruption is characterized byrepeated Strombolian type which is considered to be generated by a sudden release of a large gas slug at thecrater bottom. In this study, we examine the mechanism of magma flow in the conduit by comparing the tilt record
reported in Genco and Ripepe (2010) with two models: slug model and rising gas bubble model.
The tilt records associated with eruptions at Stromboli are observed at five stations located at about 300 -1100 m
distances from the vent. The observed tilt change prior to each eruption show volcano inflations with accelerated
rate from about 200 s before eruption and same temporal changes at the five stations.
We use slug flow model presented by James et al. (2008). Rising gas bubble model assume that plural gas
bubbles rise in melt without interaction of surrounding gas bubbles. Each bubble rise according to Stokes’ law.
Model parameters of the slug flow are the initial depth and size of slug, viscosity of melt. Model parameters of
rising gas bubbles are the initial radius and depth of gas bubbles. Number of the gas bubbles is also a model
parameter. Length and radius of the conduit and initial magma head depth are model parameters for both of thetwo models. We compare spatio-temporal changes of tilt caused by two models with the observed data. We use a
3-D boundary element method that can take into account the effects of topography of Stromboli volcano to calculate
volcano deformation.
First, we compare the changes of magma pressure in the conduit from the initial condition to just before an eruption
for the two models with the tilt changes observed at five stations. We estimate the model parameters that can fit
the observed tilt by using grid search methods. Subsequently, we compare temporal changes of tilt at each station
using the estimated model parameters with the observations. The results show that both models can explain thespatial changes of tilt at five stations with a variance reduction more than 98%. The pressure sources for the bothmodels are located at a shallow part (about a few hundred meter depths). Slug flow model, which are often used to
explain Strombolian eruptions, cannot explain the volcano inflation at a station located at 1000 m far from the vent.
This is because the tilt changes at such stations show down lift toward the vent due to depressurization of magma
where a slug locates at. On the other hand, the gas bubbles rise model can produce uplift toward the vent evenat stations far from the vent. We obtain model parameters of the rising gas bubble model: conduit length of 550 m
and radius of 5 m, initial gas bubbles radius of 0.6 m, the number of gas bubbles of 100, and initial magma head
depth of 170 m.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

620

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4A2_2I-O7

Room A5

Date/Time: July 24 10:45-11:00

Can passive degassing induce volcanic crisis?
Társilo Girona, Fidel Costa, Chris Newhall
Earth Observatory of Singapore, Nanyang Technological University, Singapore
E-mail: tarsilo.girona@gmail.com

Openly-degassing volcanoes (e.g. Asama, Japan; Mayon, Philippines; Etna, Italy) usually erupt every few months
or years. During quiescence, they passively emit several thousands of tonnes of gas per day (mainly water
vapour). Such gas mass withdrawal leads to a volume change of melt because the volatiles were previously
dissolved in it. On the other hand, there are evidences showing that openly-degassing volcanoes have welldeveloped conduits with the head of the magma column close to the summit. Thus, a volume decrease ofmagma could decrease the mean liquid level in the conduit and may, in turn, decrease significantly the pressure
at depth. This reasoning suggests that passive degassing may play an important role in the pressure evolutionof magma plumbing systems. However, the problem is much more complex when we consider a response of
the host-rock to pressure changes and hydraulic connection between deeper sources and shallow reservoirs. In
such a case, there is a feedback between degassing-induced underpressure, closure of the conduit and reservoir,
and magma replenishment. We have modelled these processes and we have found that underpressures up tosome tens of MPa may easily occur during the observed repose timescales. Continuous magma intrusions throughpermanent hydraulic connections are induced by passive degassing without the need of a pressurized magma
source. Intermittent replenishment can also be explained via passive degassing and successive openings andclosures of the feeding dykes. These pressure decreases may also cause physical destabilizations of the chamber
wall-rock and massive bubble nucleation and growth in the reservoir. The imbalance created by the large amount ofgas released during repose may incite the frequent volcanic unrest and eruptions of openly-degassing volcanoes.
This "top-down" process contrasts with the commonly proposed "bottom-up" processes of magma intrusions inshallow reservoirs driven by unspecified mechanisms occurring at depth. Coupling of top-down models with realtime monitoring of total gas fluxes may open new doors for anticipating volcanic crisis.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

621

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4A2_2I-O8

Room A5

Date/Time: July 24 11:00-11:15

The opening of vents like decompression valves of the hydrothermal system at Turrialba
volcano, Costa Rica
Geoffroy Avard1 , Javier Pacheco1 , Maria Martinez1 , Sebastian Miranda1 , Vladimir Conde2 , Bo Galle2
1

OVSICORI-UNA, Costa Rica, 2 Chalmers University of Technology, Sweden
E-mail: geoffroy.avard@una.cr

Between 1996 and 2009, Turrialba volcano, Costa Rica, reactivated, with the culmination on January 5th, 2010
with a phreatic (hydrothermal) explosion that opened a large vent. This vent has allowed since then to passively
decompress the volcanic system as suggested by the large increase in the SO2 flux observed between January2010 and May 2011, followed afterwards by a marked decrease on the SO2 flux, even when a small but noticeablesecond vent opened in early 2011. The opening of the 2010 vent has been attributed to movement of fluids fromdeep to shallow levels through cracks which allowed the migration of a hot magmatic volatile phase. On January
12th, 2012, a new vent opened possibly in response to the pressurization of a shallow hydrothermal system, assuggested by the absence of changes in the seismic patterns and the short-lived enhancement in the flux ofheat, CO2 and H2S that diffused through the soil. This event may have triggered a deeper decompression lateron January 18th which produced seismic tremor accompanied with the release of hot gases, water vapor, andnon juvenile ash through a confined conduit and with absence of CO2 and H2S diffuse flux anomaly. The nearmagmatic temperature of gas (around 800o C) suggests that this second degassing event opened the systemfurther.

These three vents are visually assumed to be the main contributors to the plume of Turrialba volcano evenif numerous low-temperature (<130o C) sulfur-rich fumarolic fields exist inside and outside the Central and West
Craters (about 25,000m2 ) in 2012, less than 5% of the summital area). Considering the stability and the rangeof temperature of the vents (around 600, 600 and 800o C for the 2010, 2011, and 2012 vents, respectively), it is
proposed that the 3 vents are an opening through the shallowest hydrothermal system of the volcano, while thelow temperature fumarolic fields are the surface manifestation of purely shallow-level hydrothermal activity.

The existence of these vents most likely combined with a decrease in the magmatic input prevented any
compression of the edifice in 2012 as suggested by the low seismic activity composed of mostly LPs, few screw
shape signals characteristic of gas-rich fluids motion and shallow VTs. Altogether, the decrease of seismicity,
SO2 flux, and of the acidity of the total deposition observed since mid 2011 support the hypothesis of the cooling
down of the magma body that probably intruded sometime in 2007-2008 or before. Thus, the opening of ventsin 2011 and 2012 while the system has been considered opened since the opening of the 2010 vent suggeststhat they are the manifestation of a saturation of the hydrothermal system capacity to transfer heat and volatiles tothe atmosphere. Testimonies prior to the 1864-66 eruption of Turrialba and prior to the 1963-65 eruption of Irazu
support this idea as many vents opened for both volcanoes prior to their magmatic eruptions.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

622

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4A2_2I-O9

Room A5

Date/Time: July 24 11:15-11:30

Open-system submarine volcanoes: dynamics and phase state
Richard Henley1 , Richard Arculus2 , Cornel de Ronde3
1

The Australian National University, Australia, 2 The Australian National University, Australia, 3 Dept
Marine Geosciences, GNS Science, New ZealandE-mail: r.143.henley@gmail.com

The discovery and subsequent exploration of active submarine volcanoes along convergent plate margins (deRonde et al., 2001) raises questions of the persistence of their eruptive activity and the phase state of gaseousdischarges from them. Several have been shown to host molten sulfur lakes (e.g. Macauley cone, Kermadec Arc,
Diakoku, Mariana Arc) while NW Rota-1 (Mariana Arc) has maintained Strombolian eruption activity for at least six
years. Some are known to discharge significant quantities of hydrothermal fluid (e.g., Brothers volcano, Kermadecarc), while others have sustained hydrothermal activity for up to 18,000 years, (e.g., Clark volcano, Kermadec arc)
while others, such as Giggenbach volcano (Kermadec arc), persistently discharge gases (especially CO2) morevigorously than others.
However, based on observations from spreading volcanic environments, it has been suggested that that drilling intosubmarine arc volcanoes could not penetrate beneath a two-phase fluid regime. Here, we show from first principles
that the normal state of magmatic gas discharge through an active volcanic system, whether submarine or
subaerial, is single phase, forming a low density, high enthalpy core regime Two phase conditions are constrained
to flank regimes with only surficial mixing and cooling in vent areas.

de Ronde, C.E.J.,et al., 2001, Intra-oceanic subduction-related hydrothermal venting, Kermadec volcanicarc, New Zealand:Earth Planet. Sci. Lett.193, 359-369.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

623

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4A2_2I-O10

Room A5

Date/Time: July 24 11:30-11:45

SO2 camera measurements at Popocatepetl Volcano (Mexico). Insights into the
dynamics of an atypical open vent volcano
Robin Campion1 , Matthias Fickel1 , Lucio Cardenas2 , Thomas Lecocq3 , Aurelie Damsin4 , Nathalie
Collard1 , Hugo Delgado-Granados1
1

Universidad Nacional Autonoma de Mexico, Mexico, 2 Centro Nacional para la Prevencion de losDesastres, Mexico, 3 Observatoire Royal de Belgique, Belgium, 4 Universite Libre de Bruxelles, Belgium
E-mail: robin@geofisica.unam.mx

Popocatepetl Volcano (Mexico) has been, since its reawakening in 1994, one of the strongest permanent emittersof sulfur dioxide in the world (e.g. Delgado, 2008). Its activity poses also a direct threat to the most populatedarea of Mexico including its capital city. Activity has so far consisted of cycles of dome building and destruction by
vulcanian explosions, alternating with periods of quiescent degassing. Average SO2 emission rate over the whole
eruption is about 50 kg/s but peaks of activity have released up to >1000 kg/s. Popocatepetl volcano is atypicalbecause other volcanoes capped by an active lava dome usually exhibit SO2 emission rates one or two ordersof magnitude lower. Volcanoes hosting lava domes and plugs are known to be subject to sealing processes that
precludes them from sustaining high SO2 emission for long periods.
We have used a UV camera to obtain high temporal resolution measurements of SO2 emission rates at
Popocatepetl volcano. The state-of-the-art UV camera technique was coupled with a coaligned mini-DOAS, andoften backed by ground-based DOAS traverses, in order to ensure the maximal accuracy of the results. Frequent
field campaigns, with durations of up to several weeks, were conducted during various states of volcanic activity.
This has allowed us to build a detailed picture of the sort-timescale variations of the degassing. Spikes of SO2
emissions are superimposed over a long term, slowly varying trend of 50-100 kg/s. We propose a model of gas
slugs bursting beneath a highly fractured dome to explain this degassing pattern. Strong fluxing of gas, provided
by unerupted mafic-intermediate magma, is suggested to hamper sealing processes from plugging the conduit.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

624

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4A2_2I-O11

Room A5

Date/Time: July 24 11:45-12:00

Open and closed system eruptive dynamics at Tungurahua volcano constrained by SO2
emission rate and seismo-acoustic intensity measurements
Silvana Hidalgo1 , Jean Battaglia2 , Alexander L. Steele1 , Santiago Arellano3 , Benjamin Bernard4 , Mario
Ruiz1 , Bo Galle3
1

Instituto Geofisico Escuela Politecnica Nacional, Ladron de Guevara E11-253 y Andalucia, Quito,
Ecuador, 2 Laboratoire Magmas et Volcans, CNRS UMR 6524, Univ. B. Pascal, IRD, Clermont-Ferrand,
France, 3 Chalmers University of Technology, Gothenburg, Sweden, 4 Universidad San Francisco de
Quito, Diego de Robles y Via Interoceanica, Quito, Ecuador
E-mail: shidalgo@igepn.edu.ec

The current eruptive period of Tungurahua volcano (Ecuador) began in 1999 with multiple episodes of explosive
activity that have threatened the local population. The monitoring network has been continuously improved in order
to better understand the eruptive behavior of Tungurahua and eventually provide early warning to the population.
We obtain SO2 gas emission measurements from a network of four permanent NOVAC stations located between
7 and 11 km from the volcano, covering the preferential directions of winds in the area. Seismic and acoustic
energies were calculated for explosions using a seismo-acoustic network composed of five broad band seismic
stations coupled to infrasonic sensors installed at distances between 5-7 km from the vent. Furthermore, we derive
tremor amplitudes from a short period seismic station, situated at about 2 km from the crater.
Since December 2009, five well-defined eruptive phases lasting from 21 to 70 days and following 82 to 181 daysof quiescence have been recognized. Besides, between November 2011 and September 2012 a succession ofshort explosive and/or ash emission phases also took place. Activity is characterized by strombolian and vulcanianeruptive styles. In five occasions, pyroclastic flows were generated by sustained lava fountains or triggered bydiscrete explosive events. Ash fallouts were common to these eruptions and had low to significant impact on the
nearby populations, depending on the duration and intensity of the eruptions.
During the eruptive phases no clear correlations were found between observed SO2 mass emission rates, seismic
and acoustic energy of the explosions and the tremor amplitude. However, in a few cases some patterns related todifferent eruptive dynamics can be identified. We identify and characterize two end-members, which correspond toopen and closed system degassing. In the first case, observed SO2 emission rates increase a few days before any
significant change in tremor amplitude and any explosive activity appear. A clear example of this behavior is theeruptive period between December 2009 and March 2010, where the SO2 measurements increased 4 days before
a change was evident in the seismic amplitude of tremor and 9 days before the occurrence of the first explosions.
This suggests open system dynamics where gases are easily released throughout the entire eruptive phase. In
the closed-system end member, the increase in SO2 degassing occurs simultaneously with the increase of tremor
and/or explosive activity. An example of this activity took place in May 2010, when almost no SO2 was detectedby the DOAS stations before a vulcanian explosion, with associated pyroclastic flows, partially opened the systemallowing gas escape.
In this work, we present observational evidence of these mechanisms which are used to identify possible patternsof evolution of the activity, contributing to a more effective volcanic hazard assessment.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

625

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4A2_2I-O12

Room A5

Date/Time: July 24 12:00-12:15

Degassing of Erebus lava lake, Antarctica
Tehnuka Ilanko1 , Clive Oppenheimer1 , Alain Burgisser2 , Philip Kyle3
1

Department of Geography, Cambridge University, UK, 2 Institut des Sciences de la Terre d’ Orleans,
CNRS, Universite d’ Orleans, France, 3 Department of Earth and Environmental Science, New Mexico
Institute of Mining and Technology, USA
E-mail: ti235@cam.ac.uk

Open system degassing was first observed at Erebus volcano, Antarctica, over a century ago, in the form ofa lava lake in its summit crater. The persistent activity of the lava lake provides an opportunity for continuous
measurements and observations of changes on a range of timescales. Gas emissions from Erebus lava lake
have been measured using open–path Fourier transform infrared spectroscopy, during each austral summer fieldseason from 2004 to 2012. The technique works particularly well at Erebus, thanks to the aridity of the Antarctic
atmosphere, and the availability of a permanent ‘infrared lamp’ in the form of the lava lake itself. At Erebus, it
is straightforward to measure both water and CO2 in the gas emissions, something that is challenging at most
volcanoes by OP–FTIR spectroscopy.

The sustained passive degassing and turnover of the lava lake is sporadically punctuated by Strombolian
explosions. Both types of activity have been captured in the gas measurements. The measurements also identify
longer–term changes to plume composition during and between field seasons (i.e. time scales of a few weeks tointerannual variability). While the connection between surface observations of the lake behaviour and the plumecomposition is fairly clear, measured gas ratios have also been used with the thermodynamic model ‘D–Compress’
to investigate deeper processes. The model simulates the equilibrium composition of melt and gas as a function ofpressure (depth). We report here on the application of ‘D–Compress’ in investigating magmatic source conditions
likely to generate the observed plume gas composition.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

626

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4A2_2I-O13

Room A5

Date/Time: July 24 12:15-12:30

Gas-driven lava lake fluctuations at Erta ’Ale volcano (Ethiopia) revealed by MODIS
measurements
Emmanuella Bouche1 , Sylvie Vergniolle2
1

CNRS UMR 6614 CORIA, UniversitÃl’ de Rouen, France, 2 Institut de Physique du Globe de Paris,
UMR7154 CNRS,75238 Paris Cedex 05, France
E-mail: vergniol@ipgp.fr

The permanent lava lake of Erta ’Ale volcano (Ethiopia) is remotely monitored by MODerate resolution Imaging
Spectroradiometers (MODIS) installed on satellites.

The Normalised Thermal Index (NTI) is shown to be

proportional to the volume of the lava lake based on visual observations. The lava lake’s variable level can be
related to a stable foam trapped at the top of the magma reservoir, whose thickness changes in response to thegas flux feeding the foam being successively turned on and off.
The temporal evolution of the foam thickness, and the resulting variation of the volume of the lava lake, is calculated
numerically by assuming that the gas flux feeding the foam, initially constant and homogeneous since December
9, 2002, is suddenly stopped on December 13, 2002 and not restarted before May 2003. The best fit between
the theoretical foam thickness and the level of the lava lake deduced from the NTI provides an estimate of both
the reservoir radius, 150-190 m, and the gas flux feeding the foam, 5.5x10-3-7.2x10-3 m3/s when existing. This
is in agreement with previous estimates from acoustic measurements. The very good agreement between thetheoretical foam thickness and that deduced from MODIS data shows for the first time the existence of a regime
based on the behaviour of a stable foam, whose spreading towards the conduit can explain the permanent activity.
The lava lake, when high, often shows regular rise and fall of its level. We have recognised a minimum of 26 very
well marked cycles between January 2001 and December 13, 2002, corresponding to a typical return time of 10.8+- 2.3 days and a gas volume of 8.3x105 +- 2.0x105 m3. This corresponds to a gas volume fraction in the reservoir
equal to 0.03–0.12 pourcent. The yearly gas flux, estimated between December 13, 2002 and September 27, 2004,
varies between 2.3x10-6 m3/s and 5.9x10-6 m3/s at the depth of the reservoir.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

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IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4P1_2I-O14

Room A5

Date/Time: July 24 15:00-15:15

What infrasound tells us about open-vent volcanic systems
Jeffrey B Johnson1 , David Fee2
1

Boise State University, USA, 2 University of Alaska Fairbanks, USA
E-mail: jeffreybjohnson@boisestate.edu

Open-vent volcanoes produce prodigious and intense infrasound that can be reliably recorded with arrays andnetworks of broadband microphones. The infrasound signals produced by volcanoes are as diverse as theireruptive processes and reflect both a wide range of conduit processes and degassing styles. This presentation
focuses on observations of volcanic activity made with cameras, thermal imagers, seismic, and tiltmeters, inconjunction with infrasound recordings. We highlight the relationship between sound intensity and explosive
degassing, which exists for a subset of volcano behaviors. We also explain the very energetic sounds produced bysome open-vent volcanoes with relatively minor levels of explosive activity. We conclude that while eruptive vigor
does not always scale well with radiated infrasound power, infrasound spectral content and envelope shape canhelp to constrain eruptive and degassing style.

We present comparative results from open-vent volcanoes with activity ranging from bubble bursts at lava
lakes (e.g., Erebus) to open-vent lava lakes (Halemaumau, Villarrica), to episodically erupting stratovolcanoes(e.g., Tungurahua, Karymksy, Santiaguito, and Sakurajima). We show how explosive gas outflux relates to thebimodal, or N-shaped, pulses that commonly accompany explosions. The various types of infrasonic tremors thatare routinely observed at open-vent systems will also be compared and contrasted. Responsible source processes
for tremor ranging from pulsating gas flow to crater/ vent resonances. In many cases these tremor signals rival
explosions pulses in terms of acoustic power, highlighting the diverse range of acoustic efficiencies capable ofopen vent systems.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

628

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4P1_2I-O15

Room A5

Date/Time: July 24 15:15-15:30

Effects of the atmospheric structure and topography on infrasound propagation around
Sakurajima
Giorgio Lacanna1 , Mie Ichihara2 , Makiko Iwakuni3 , Minoru Takeo2 , Masato Iguchi4 , Maurizio Ripepe1
1

University of Firenze, Italy, 2 Earthquake Research Institute, University of Tokyo, Japan, 3 Japan
Weather Association, Japan, 4 Disaster Prevention Research Institute, Kyoto University, Japan
E-mail: giorgio.lacanna@unifi.it

Detailed observations and numerical studies on infrasonic propagation reveal that effects of the atmosphere layers
and of the topography are more significant than it was thought. The topographic effect is more significant innear-source (less than 10 km) while the atmospheric structure has a strong effect at the regional scale (>100-1000
kilometers).
We use a dataset of infrasound generated by Vulcanian activity at Sakurajima and recorded by a dense network ofwell-calibrated infrasound sensors deployed around Sakurajima and at different distances <60 km from the crater.
The effect on wave propagation of atmosphere and topography with the distance is numerically investigated by a
2.5D finite difference (FDTD) method while a pure 3D FDTD modelling is used to analyse the azimuth distribution
around the crater.
We show how the amplitude ratio of individual stations with the reference station at 3 km from Sakurajima shows
remarkable seasonal differences. Amplitude ratio can vary 2 times at the same distance but different azimuth due
to topography and/or 5 times at the same station within one day by atmospheric changes.
Numerical results indicate that topography and atmospheric variations are the main factors affecting the acoustic
wave propagation.

Our work provide evidence that a detailed knowledge of the topography and of themeteorological conditions are needed for accurate analysis of the acoustic source.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

629

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4P1_2I-O16

Room A5

Date/Time: July 24 15:30-15:45

Seismic and geodetic precursors of small vulcanian eruptions at Suwanose-jima
volcano, Japan
Takeshi Nishimura1 , Masato Iguchi2 , Hiroshi Yakiwara3 , Jun Okiawa4 , Yu’ichi Hirai1 , Hiroshi Aoyama5 ,Haruhisa Nakamichi6 , Ryohei Kawaguchi1 , Yusaku Ohta1 , Takeshi Tamaguri2
1

Science, Tohoku Univ., Japan, 2 DPRI, Kyoto Univ., Japan, 3 Science and Engineering, Kagoshima
Univ., Japan, 4 ERI, Univ. of Tokyo, Japan, 5 Science, Hokkaido Univ., Japan, 6 Environmental Studies,
Nagoya Univ., Japan
E-mail: nishi@zisin.gp.tohoku.ac.jp

Suwanosejima is a small volcano island south of Kyushu on the Pacific Ocean. The volcanic eruption of theisland is characterized by small vulcanian explosions that repeatedly occur within a short interval of a few tens ofminutes every a few months. We deploy 4 broad-band seismometers, 3 short-period seismometers and 5 boreholetilt meters at distances of 0.4-1.5 km. In the present study, we summarize precursor signals that are caused bymagma behavior beneath active crater before explosions to understand the mechanism of vulcanian eruptions at
Suwanosejima volcano for the period from September 2009 to 2011. Vulcanian explosions often occur during
successive ash emissions for a few hours to days that generate continuous tremor. The explosions follow a sudden
stop for about one or two minutes of continuous tremor. Uplift toward the crater also start at the same time whencontinuous tremor amplitude stop. Such coincidence suggests that the pressurization in the shallow magma iscaused by accumulation of volcanic gas or ash due to a formation of a cap just beneath the active crater. It isnoted that the inflations and explosions are also observed during a quiet period when no ash emission is observed.
The cap is considered to be formed in a short time because the continuous tremor amplitude generally decreases
for a few tens of seconds. Amplitude and duration of the inflation signals tend to become larger and longer,
respectively, for explosion earthquakes with large maximum amplitude. The tilt signals are about a few tens of nanoradian, which are detected at only station located close the active crater. The inflation amplitude is attributed tothe pressurization at a depth of a few hundred kilometers beneath the active crater, and the maximum amplitude
of explosion earthquakes are also explained by a release of the pressure stored before explosion. About 0.5 to
1 s before the onset of explosions, a tiny deflation with duration of about 0.6 s is observed in the seismogram of
explosion earthquake. Our seismic waveform inversion shows that the tiny deflations are explained by contractionof volcanic conduit at a few hundred meter depth beneath the active crater. Pressure decreases are estimated to
be about 0.03-1 MPa for a cylindrical source with a length of 500 m and a radius of 10 m. The pressure decrease
may be a small leakage of gas, but no significant signal is detected by the acoustic sensors at stations: acoustic
signal gradually and slightly sometimes increase its amplitude just before an onset of explosion, but the duration is
not matched with that of the contraction seismic source. Although the mechanism of the contraction is still underinvestigation, it is noteworthy to mention that the maximum amplitude of explosion increases with the amplitude ofcontraction source.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

630

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4P1_2I-O17

Room A5

Date/Time: July 24 15:45-16:00

Long lived effusive activity on Arenal Volcano: Insight from a volcano-tectonic study
Cyril Muller1 , Rodrigo del Potro1 , Julliet Biggs1 , Mikel Diez1 , Gerardo Soto2 , Waldo Taylor2 , Joachim
Gottsmann1
1

Bristol University, United Kingdom, 2 OSIVAM-ICE, Costa Rica
E-mail: cyril.muller@bristol.ac.uk

Interactions between tectonic and volcanic systems are not well understood. Here we present the initial results ofa joint study combining several dozen UNAVCOs permanent GPS stations, a gravimetric campaign and geologicalfield results at Arenal volcano which showed more than four decades of relatively low-level continuous effusive
activity since its reawakening in 1968. Our results indicate that the magmatic system of Arenal volcano is being
built in an active extensional area, which may have promoted the low-level yet persistent activity.
Costa Rica is located in the western part of Caribbean Plate; the Cocos Plate subducts along the Middle America
Trench (MAT). Oblic subduction has generated a trench-parallel motion up to 10 mm yr-1 toward the North-West,which creates shear stresses between the MAT and the volcanic arc. Located in the volcanic arc, Arenal volcano, abasaltic-andesitic stratovolcano, grew within a comparable short timescale of a 7ka. The tectonic setting is complex
and active seismogenic faults surround the Arenal volcanic edifice. After 440 years of dormancy, Arenal erupted inJuly 1968. The eruptive period lasted until 2010, during which approximately 0.55 km3 (2 m3 s-1 in 1968 to 0.086
m3 s-1 between 2000 and 2004) of lava and pyroclasts have been erupted.
Gravimetric measurements detect an E-W negative anomaly with 10 mgal amplitude while the GPS velocities
shows a centimetric shear strain located within the volcanic arc. These geophysical techniques plus geologicalfield observations suggest the settlement of the volcanic complex on a pull-apart basin. We propose a hypothesis
in which the reported long-lived low effusion rate volcanic activity would be a consequence of local extensional
tectonics and relatively high heat fluxes typical of active volcanic arcs.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

631

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4P1_2I-O18

Room A5

Date/Time: July 24 16:00-16:15

Syneruptive deep magma transfer and shallow magma remobilization during the 2011
eruption of Shinmoe-dake, Japan-Constraints from melt inclusions and phase equilibria
experimentsYuki Suzuki, Atsushi Yasuda, Natsumi Hokanishi, Takayuki Kaneko, Setsuya Nakada, Toshitsugu Fujii
Earthquake Research Institute, Univ. of Tokyo, Japan
E-mail: ysuzuki@eri.u-tokyo.ac.jp

The 2011 Shinmoe–dake eruption started with a phreatomagmatic eruption (Jan 19), followed by climax sub-Plinian
events and subsequent explosions (Jan 26–28), lava accumulation in the crater (end of January), and vulcanianeruptions (February–April). In Suzuki et al. (resubmitted after revision, as of January 2013; JVGR), we havestudied a suite of ejecta to investigate the magmatic system beneath the volcano and remobilization processes inthe silicic magma mush. Most of the ejecta, including colored pumice blocks (Jan 26–28), ballistically ejected lava
(Feb 1), and juvenile particles in ash from the phreatomagmatic and vulcanian events are magma mixing products(SiO2 57–58 wt.%; 960–980C). Mixing occurred between silicic andesite (SA) and basaltic andesite (BA) magmas
at a fixed ratio (40%–30% SA and 60%–70% BA). The SA magma had SiO2 62–63 wt.% and a temperature of
870C, and contains 43 vol.% phenocrysts of pyroxene, plagioclase, and Fe–Ti oxide. The BA magma had SiO2 55
wt.% and a temperature of 1030C, and contains 9 vol.% phenocrysts of olivine and plagioclase. The SA magma
partly erupted without mixing as white parts of pumices and juvenile particles. The two magmatic end-members
crystallized at different depths, requiring the presence of two separate magma reservoirs; shallower SA reservoir
and deeper BA reservoir. An experimental study reveals that the SA magma had been stored at a pressure of 125
MPa, corresponding to a depth of 5 km. The textures and forms of phenocrysts from the BA magma indicate rapid
crystallization directly related to the 2011 eruptive activity. The wide range of H2O contents of olivine melt inclusions(5.5–1.6 wt.%) indicates that rapid crystallization was induced by decompression, with olivine crystallization first (≤250 MPa), followed by plagioclase addition. The limited occurrence of olivine melt inclusions trapped at depths of<5 km is consistent with the proposed magma system model, because olivine crystallization ceased after magma
mixing. Our petrological model is consistent with a geophysical model that explains whole crustal deformation
as being due to a single source located 7–8 km northwest of the Shinmoe-dake summit. However, even theshallowest estimated source of this deformation (7.5–6.2 km) is deeper than the SA reservoir, which thus requires
a contribution of deeper BA magmas to the observed deformation. Remobilization of mush-like SA magma occurredin two stages before the early sub-Plinian event. Firstly, precursor mixing with BA magma and associated heating
occurred (925–871C; stage-1 of ≥ 350h), followed by final mixing with BA magma (stage–2). MgO profiles ofmagnetite phenocrysts define timescales of 0.7–15.2h from this final mixing to eruption. The mixed and heatedmagmas, and stagnant mush that existed in the SA reservoir in the precursor stage, were finally erupted together.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

632

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4P1_2I-O19

Room A5

Date/Time: July 24 16:15-16:30

Magma mixing and degassing processes of the 2011 eruption series of Shinmoedake,
Kirishima volcano, based on petrological monitoring and melt inclusion analyses
Genji Saito
Geological Survey of Japan, National Institute of Advance Industrial Science and Technology, Japan
E-mail: saito-g@aist.go.jp

The 2011 eruption activity of Shinmoedake, Kirishima volcanic group, Japan, began with phreatomagmatic
eruptions on 19 January. The activity was culminated with the sub-Plinian eruptions on 26-27 January, followed
by lava effusion within the summit crater. Vulcanian explosions and minor ash discharges occurred intermittently
from February to September. Open system behavior was observed by geophysical, geological and geochemicalmonitoring; (1) Continuous inflation of the magma chamber in a year before the eruption (Kawamoto et al., 2011), (2)All tephra samples of the 2011 eruptions observed contained essential material (Oishi et al., 2012), (3) Continuous
degassing activity since January (Mori and Kagoshima Local Meteorological Observatory, 2012), (4) Inflation of themagma chamber from 2 February to November 2011 (Imakiire and Nishimura, 2012; Nakao et al., 2012). In thisstudy, petrological and melt inclusion studies of the 2011 eruption series in order to investigate the eruption anddegassing processes. The bimodal plagioclase core composition, relatively small rims of olivines and pyroxenes,
and diffusion profiles of the olivines in the eruptive products of the sub-Plinian eruptions indicate the mixing of mafic
magma and felsic magma in several days before the sub-Plinian eruption. The short time scale is consistent withestimation by diffusion profiles of the magnetite (Tomiya et al., 2012). Melt inclusion analyses indicated that theend members of the magma mixing were basaltic andesite and dacite magmas and its mixing ratio was estimatedto be 0.4 of the basaltic andesite. The eruptive products of the Vulcanian explosions and minor ash discharges in
February to August have similar mode composition, chemical compositions of phenocrysts, groundmass minerals
and groundmass and zoning profiles of olivines to those of the sub-Plinian eruptions. These results suggest thatthe same mixing process also occurred before each eruption. The amount of the degassed magma was estimatedbased on sulfur content of melt inclusions of the end member magmas and SO2 flux observation during January
2011 to September 2012. The amount of the degassed magma was larger than that of eruptive products in 2011,indicating the degassing of the magma in the chamber due to magma convection in a conduit. The amount of thedegassed magma during 2 February 2011 to September 2012 (31 Mm3 ) is larger than inflation of the chamber
observed by GPS after 2 February 2011 (10 Mm3 ). However, assuming that the mixing ratio of the magmas (0.4),
the amount of the degassed mafic magma was calculated to 12 Mm3 . This amount is similar to the inflation,suggesting that injection of the mafic magma from a deeper part into the chamber continued after February andcaused the eruptions and degassing activity.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

633

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4P1_2I-O20

Room A5

Date/Time: July 24 16:30-16:45

Characteristics of magma accumulation process of a basaltic volcano Izu-Oshima, Japanas revealed from integrated monitoring of deep low-frequency earthquakes, volcano
deformation and CO2 out-gassing
Hidefumi Watanabe
Disaster Prevention Division, Tokyo Metropolitan Government, Japan
E-mail: watanabe@eri.u-tokyo.ac.jp

In order to make successful mid-term eruption predictions, we need to detect particular precursory processes
operating in magma-plumbing system. Since 1989, Izu-Oshima volcano has continued its re-inflation, after the last
eruption in 1986, and further repeated deflation-inflation cycles, resulting a net inflation of the volcano. The rate of
secular inflation decreased exponentially until 2006, while the amplitudes of the deflation-inflation cycles increased.
Since 2007, the rate of secular inflation has kept a constant speed and has also increased the activity of deep
low-frequency (LF) earthquakes occurring at the depth range of 30-40 km beneath the volcano. Each episodic
LF earthquake activity was preceded by the volcano deflation and accompanied by the inflation. Based on theseevidences, we may suppose that the volcano inflation is caused by the supply of magma from a source region at thedepth range of 30-40 km beneath the volcano, and that an episodic out-gassing from the shallow magma reservoir
triggers each deflation-inflation cycle. To demonstrate the proposed mechanism, we need to combine the dataon magma accumulation and out-gassing processes. To monitor the out-gassing of basaltic magma accumulating
beneath the volcano, CO2 is most helpful. In September 2005, we started continuous monitoring of soil CO2
concentration at the summit of Izu-Oshima volcano, and obtained an evidence for the out-gassing process; thecorrelated increase of soil CO2 concentration during the periods of not only accelerated inflation but also deflationof the volcano. Integrating the observational data, we suppose that the rate of magma supply from the upper mantle
has increased since 2007 and that the increase in amplitude of deflation-inflation cycles might indicate a volume
increase of CO2 over-saturated region at the upper part of the magma reservoir beneath the volcano.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

634

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4W_2I-P1

Date/Time: July 24 Poster

Dissecting the August 2012 Paroxysmal Eruption: Advances and Challenges in
Monitoring Open System Activity at Tungurahua Volcano, Ecuador
John J Lyons1 , Mario C Ruiz2 , Benjamin Bernard3 , Hugo Ortiz2 , Silvana Hidalgo2
1

Alaska Volcano Observatory, US Geological Survey, USA, 2 Instituto Geofisico, Escuela Politecnica
Nacional, Ecuador, 3 Universidad San Francisco de Quito, Ecuador
E-mail: jlyons@usgs.gov

Tungurahua volcano (5023 m) is an andesitic stratovolcano that looms more than 3 km above the surrounding
population centers.

Since reactivation in 1999, Tungurahua has been in a relatively open system statecharacterized by low-level strombolian and vulcanian activity, short periods of repose (days to months), andmore violent paroxysmal eruptions capable of producing hazardous pyroclastic flows, subplinian columns, andvoluminous ash falls. Transitions from low-level to more hazardous activity can be abrupt and make monitoring
challenging.

Tungurahua is actively monitored by the Instituto Geofisico (IG) in Quito, in collaboration withnational and international partners, using data from broadband seismoacoustic stations, DOAS gas spectrometers,
tiltmeters, an ash fallout quantification network, satellite thermal and gas data, and reports from local observers.

Here, we highlight an example of the current open system activity with a multi-parameter analysis of theshort-lived paroxysmal eruption that occurred during August 2012. Based on ash fallout and seismoacoustic data,
the duration of the eruption was ~20 days, with just 11 days of continuous, elevated energy release. The gas(SO2 ), ash, and thermal emissions of the eruption were clearly seen from space, and although the estimated fallout
volume (0.3-0.45 x 106 m3 ) and explosive intensity (VEI=1) is low the ash fall significantly affected local air quality
and agricultural production. The seismoacoustic data and observations of the eruption indicate that the eruption
began with intermittent gas jetting and tremor that became strong and nearly continuous from 13-21 August,and was associated with strong ash fallouts and the highest SO2 emissions observed since a DOAS network
was installed in 2007. We compare correlation patterns between co-located seismic and infrasound sensors withgas emission and ash fallout data, and identify the patterns indicative of continuous emissions. Tremor and ash
emissions abruptly declined on the 21st and strong explosions began to occur, generating small pyroclastic flows
and ash columns to 4 km above the vent. The strongest explosive infrasound (>1000 Pa at 5.3 km from the vent)recorded since 2006 was generated on 21 August. Hundreds of explosions were recorded over 21-23 August,prior to a rapid decline in seismic and acoustic output and return to background activity within several days. Thiseruption sequence provides an example of the current open system activity at Tungurahua volcano, highlights
the methods and efforts currently in use to monitor and analyze the activity, and emphasizes the challenges andscientific opportunities provided by open system volcanoes.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

635

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4W_2I-P2

Date/Time: July 24 Poster

Precursors to explosive eruptions at the persistently restless Telica Volcano, Nicaragua.
Mel Rodgers1 , Halldor Geirsson2 , Molly Witter2 , Diana C. Roman3 , Peter LaFemina2 , Angelica Munoz4 ,Virginia Tenorio4
1

University of South Florida, USA, 2 The Pennsylvania State University, USA, 3 Carnegie Institution of
Washington, USA, 4 Instituto Nicaraguense de Estudios Territoriales (INETER)„ Nicaragua
E-mail: mjrodger@mail.usf.edu

Persistently restless volcanoes (PRVs) are characterised by consistently high levels of geophysical activity, suchas a high or variable seismicity rate, strong degassing and sporadic explosions. PRVs do not exhibit typical distinct’background’ and ’unrest’ states, but do experience non-eruptive and eruptive episodes. Traditional methods offorecasting volcanic activity based on seismicity patterns are not applicable to PRVs and the physical processes
behind the transition between non-eruptive and eruptive episodes are not well understood.

Telica Volcano,

Nicaragua, is a PRV that has experienced numerous VEI 1-2 eruptions over the last century, as well as historic
VEI 4 eruptions. We present geophysical data from the two most recent VEI 2 eruptions, in 1999 and in 2011. The
1999 eruptive episode started in May 1999 and consisted of ash emissions and discrete explosive activity, including
explosions in August and October 1999 and the most energetic explosions in December 1999. We observe asudden short-lived swarm of high-frequency (HF) (> 5 Hz) seismic events in September 1999, between the Augustand October 1999 explosions, coincident with the onset of many (22) short-lived long-period (LP) (< 5 Hz) seismic
event multiplets. This is followed by a reduction in the seismic event rate between the October 1999 explosions andthe large December 1999 explosions. In May 2011 an eruptive episode occurred at Telica with a five-week-longseries of explosions. Nine months before the eruption we observe a swarm of HF events followed one month later
by a significant drop in both LP and HF events. The event rate continued to decline until it reached a minimum six
weeks before the eruption. Seismic event locations between September 2010 and May 2011 suggest that all events
are shallow (< 2 km) and clustered beneath the active vent. Continuous GPS observations of the 2011 eruptionof Telica show no deformation that can be related to volcanic activity and precludes a large influx of magma. Boththe 1999 and 2011 eruptions show similar characteristics of a HF swarm followed by decreased seismicity before
the most energetic explosive episodes. We suggest that these patterns of seismicity relate to the sealing of themagmatic/hydrothermal system. This transition from open-system degassing to a closed system may have lead topressurisation of the system, resulting in explosions.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

636

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4W_2I-P3

Date/Time: July 24 Poster

Volcano deformation caused by magma recession during a vulcanian explosion at
Showa-crater of Sakurajima, Japan
Takashi Minowa, Ryohei Kawaguchi, Takeshi Nishimura
Geophysics, Science, Tohoku University, Japan
E-mail: minowa@zisin.gp.tohoku.ac.jp

It is necessary to investigate spatio-temporal changes of pressure source during the eruptions to understand the
dynamics of magma in volcanic conduit. In this study, we present a simple moving pressure source during avulcanian eruption and calculate volcano deformation. We compare the results with the observed data at Showa
crater of Sakurajima to understand the spatio-temporal change of magma recession.
We simplify the vulcanian eruption as follows. The explosion is triggered by a removal of a "cap" that pressurizes
magma in the conduit beforehand. The magma head propagates downward as volcanic ash ejects. During themagma head falls down, the normal stress that works on the conduit wall weaken. At the same time, the drag force
generated by magma flow is applied on the conduit wall, and its reaction force works on the bottom of conduit.
We calculate volcano deformation by using a 3-D boundary element method.

We duplicate topography of

Sakurajima by 10 m meshed DEM (GSI) and make a cylindrical conduit with a radius of 15 m under Showa crater.
Radial tilt and strain changes caused by the magma depression and drag force at the ground surfaces are calculated
at Arimura and Harutayama stations which are located at distances of 2.1 km and 3.2 km, respectively, from theShowa crater. The initial position of the magma head is set at 650 m altitude. We firstly explain deformation at
Arimura caused by the normal stress. The tilt does not change remarkably during the magma head is dropped from
650 m to 0 m. The tilt starts to subside toward the crater at about 0 m and turns to uplift at about -1300 m. The
radial strain shows extension at the beginning and turns to contract when the magma head reaches at about -950
m. The tilt caused by the drag force and its reaction force shows uplift toward the crater, and then turns to subsidewhen the magma head reaches at about -1300 m. The strain shows contraction at the beginning, and then turns
to show extension at about -950 m. Similar changes are shown at Harutayama station. These calculations indicatethat recession process of magma in the conduit can be quantified by the tilt and the strain data.
We compare the calculation results with observation records of a Showa crater eruption on Feb 6, 2008, which isreported in Iguchi (2008). The observed radial strain shows a change from extension to contraction about 10 min
after the start of eruption. The calculation indicates that the magma head downs to -950 to -1150 m at that time.
When the magma head becomes deeper than -2000 m, the tilt caused by normal stress shows uplift toward thecrater, while such a change is not observed. This fact suggests that the eruption stopped at the depth shallower
than -2000 m or that another deep deflation source exist.
The observed uplift toward the recorded just after the start of the eruption may be explained by upward drag force
due to magma ascent at shallower part of the conduit.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

637

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4W_2I-P4

Date/Time: July 24 Poster

Characteristics of precursory volcanic earthquakes to eruptions at the Showa crater of
Sakurajima volcano, Japan
Takeshi Tameguri, Masato Iguchi
Sakurajima Volcano Research Center, DPRI, Kyoto University, Japan
E-mail: tamekuri@svo.dpri.kyoto-u.ac.jp

Sakurajima is a post-caldera cone situated on the southern rim of Aira caldera, south Kyushu, Japan. Vulcanianeruptions have occurred at the Minamidake crater at the summit since 1955. Principal eruptive activity shifted to
the Showa crater at the eastern flank of the summit in 2006. The eruptions at the crater become active and minor
vulcanian eruptions occurred about 1,000 times per year in 2010-2012. Inflationary strain changes are observedby extensometers a few tens of minutes to several hours prior to the eruptions and are caused by pressure sources
located at depths of 0-1.5 km (Iguchi et al., 2013). The inflation rates decrease or sometimes suspend about 30
minutes before the eruptions. Small earthquakes dominated by high frequency components (5-6 Hz) swarm when
duration of inflation is longer than 1 hour. The earthquakes begin to occur a half hour to 1 hour after the start ofthe inflation. The amplitudes and number of the earthquakes further increase when the inflation rates decrease orsuspend. And, the occurrences of the earthquakes suddenly stop at the start of the eruptions. The occurrences ofthe earthquake swarms are related to the decrease of inflation rate and the long inflation. The hypocenters of theearthquakes are located at a depth of 0.5 km beneath the crater and are close to depth of the pressure source. The
precursory earthquakes may be generated by release of excess pressure accumulated by inflation of the pressuresource. The earthquakes are similar to BH-type earthquakes during the eruptive activity of the Minamidake craterin waveforms and relation of the inflationary deformation, however the earthquakes are different in amplitude, patterof occurrence and direct precursor of eruptions.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

638

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4W_2I-P5

Date/Time: July 24 Poster

Petrological monitoring of volcanic ash and evaluation of on-going eruptive activity of
Sakurajima volcano, Japan: Characterization of juvenile magma and its evolution since
2006
Akiko Matsumoto1 , Mitsuhiro Nakagawa1 , Mizuho Amma-Miyasaka1 , Masato Iguchi2
1

2

Department of Natural History Science, Graduate School of Science, Hokkaido University, Japan,
Sakurajima Volcano Research Center, Disaster Prevention Research Institute, Kyoto University, Japan
E-mail: a-matsu@mail.sci.hokudai.ac.jp

Sakurajima volcano restarted vulcanian eruptions in 2006 after a quiet period of nearly ten years. Recently, ourpetrological examination of juvenile materials of major eruptions during 20th century indicated that basaltic magma
had repeatedly input in silicic mixed magma and that the level of eruptive activity had corresponded to the scaleof basaltic injection (Ebihara et al., in this meeting). Here, we reveal the relationship between eruptive activity anderupted magma since 2006 to clarify whether magma plumbing system has changed or not. Based on the temporalchange of the magmatic system, we also evaluate the geophysical monitoring to forecast future activity. Collected
eruptive materials since 2006 consist mainly of volcanic ash, and sometimes lapilli. Lapilli usually have pyroxene
phenocrysts with reverse zoning, and sometimes olivine ones with normal zoning. Its whole-rock chemistry shows
the most mafic (SiO2 = 58.5-59.8 wt.%), being consistent with the compositional trends of the 20th century’s
juveniles. These features suggest that the 20th century’s magma plumbing system accompanied with basalt input
has continued until now. Based on microscopic and BEI observation, juveniles in ash samples can be identified andare subdivided into two types: Juvenile-A and -B. Juvenile-A are magmatic, essential materials with fresh matrix
in each eruption. On the other hand, Juvenile-B are similar to Juvenile-A, but usually contains dull colored matrix.
Thus, we recognized that Juvenile-B are slightly altered materials which were related to the previous eruptions
since 2006. We focus on Juvenile-A materials to investigate temporal change of magmatic materials. Juvenile-B
are occurred in all the samples since 2006, whereas juvenile-A has occurred since September, 2009. The matrix
glass compositions of Juvenile-A are wide (SiO2 = 65-73 wt.%) and become more mafic from Sep. 2009 to Apr.
2010. Then, those have become more silicic again until Sep. 2010. Although such compositional fluctuation has
repeated four times until now, those have gradually changed to be silicic as a whole.
If matrix glass compositions of juveniles could reflect the increase of the basaltic input, we can recognize four
periods with the increase of basaltic magma (Sep. 2009-Apr. 2010; Nov. 2010-Feb. 2011; Aug-Sep. 2011;
Dec. 2011-Feb. 2012). In these periods, the weight of volcanic ash as well as the volume of expansion of possiblepressure source beneath the volcano became larger. Thus, we conclude that the scale of the basalt input correlates
to the level of eruptive activity as in the case of activity during 20th century. Petrological and geophysical monitoringsuggests that the eruptive activity since 2006 reached maximum in the period from Sep. 2009 to Apr. 2010.
Although eruptive activity has continued since then, the temporal change of petrological features of volcanic ash
suggests that there exists no evidence indicating the increase of the level of eruptive activity.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

639

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4W_2I-P6

Date/Time: July 24 Poster

Seismic and tilt observation of vulcanian explosions at Lokon-Empung volcano,
Northern Sulawesi, Indonesia
Taishi Yamada1 , Hiroshi Aoyama1 , Takeshi Nishimura2 , Hiroshi Yakiwara3 , Haruhisa Nakamichi4 , Jun
Oikawa5 , Masato Iguchi6 , Muhamad Hendrasto7 , Yasa Suparman7
1

Hokkaido University, Japan, 2 Tohoku University, Japan, 3 Kagoshima University, Japan, 4 Nagoya
University, Japan, 5 the University of Tokyo, Japan, 6 Kyoto University, Japan, 7 Center for Volcanology andGeological Hazard Mitigation, Indonesia
E-mail: taishi@mail.sci.hokudai.ac.jp

Lokon-Empung located in the northern Sulawesi is one of the most active volcanoes in Indonesia. Vulcanianeruption activity is considerably high, so we began temporal seismic and tilt observation around the volcano since
September 2012, to understand the mechanism of vulcanian eruptions at Lokon-Empung.

Four broadband seismometers, Trillium 40, are deployed around the volcano in the distance range of 1.6 6.8 km from active Tompaluan crater. At the closest station WAILAN, a tilt meter (Pinnacle Denali) is also installed.
Each seismometer is connected to a data logger (HKS-9550) to record seismic data in a CF card with an A/D
resolution of 24 bit and a sampling rate 100 Hz with GPS time stamps. Tilt data digitized every 1 second within
the tilt meter are transmitted to a laptop PC at Kakaskasen Volcano Observatory (KKVO) through wireless LAN.
Seismic data of WAILAN is sent to Japan through the wireless network and global internet on a trial basis.

Explosion earthquakes on October 5 and November 11 have obvious onset with compressional P phase.
Ground velocity of the event on October 5 is in the order of 0.001 m/s at the station WAILAN. Visual report on
the height of ash column was about 1500 m above the crater.Before the eruption, small inflation phase (-80
nanoradian) around crater can be seen in tilt record. Duration of the inflation phase is about 40 minutes, which isalmost same order to those found in Semeru volcano (3 - 30 minutes). The height of ash column of the explosion
on November 11 is about 600 m. The velocity amplitude of the event on November 11 is about half of that on
October 5. Although the seismograms of these two explosions seem different in non-filtered traces, we can findvery similar waveforms in the lower frequency band below around 1 Hz. This similarity indicates that explosion
mechanism of these two events have common physical process. In the low-pass filtered seismograms, large
dilatational phase is identified after the compressional P wave and then clear retrograde motion representing
Rayleigh wave appears. These waveform characteristics are similar to the explosion earthquakes at Sakurajima,
Suwanosejima which often explode with Vulcanian styles. While small deflation phases appearing about a few
seconds before the initial compressional phase that are reported for the explosion of Suwanosejima and Semeru
volcanoes are not well recognized.

Although we have analyzed only a few events, several remarkable features have found in the obtained data,comparable to the other vulcanian eruptions. To analyze more events and compare them to the other eruptions are
effective ways to understand also the mechanism of vulcanian eruption itself, not only at Lokon-Empung.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

640

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4W_2I-P7

Date/Time: July 24 Poster

Variations in eruptive style and depositional processes of Neoproterozoic terrestrial
volcano-sedimentary successions in the Hamid area, North Eastern Desert, Egypt
Ezz El Din Abdel Hakim Khalaf
Associate professor, Egypt
E-mail: E.2012_khalaf@hotmail.com

Two contrasting Neoproterozoic volcano-sedimentary successions of ca. 600 m thickness were recognised in the
Hamid area, Northeastern Desert, Egypt. A lower Hamid succession consists of alluvial sediments, coherent lava
flows, pyroclastic fall and flow deposits. An upper Hamid succession includes deposits from pyroclastic density
currents, sills, and dykes. Sedimentological studies at different scales in the Hamid area show a very complex
interaction of fluvial, eruptive, and gravitational processes in time and space and thus provided meaningful insights
into the evolution of the rift sedimentary environments and the identification of different stages of effusive activity,
explosive activity, and relative quiescence, determining syn-eruptive and inter-eruptive rock units.
The volcano-sedimentary deposits of the study area can be ascribed to fourten facies and seven facies
associations: (1) basin-border alluvial fan, (2) mixed sandy fluvial braid plain, (3) bed-load-dominated ephemerallake, (4)lava flows and volcaniclastics,(5)pyroclastic fall deposits,(6) phreatomagmatic volcanic deposits, and(7)pyroclastic density current deposits.

These systems are in part coeval and in part succeed each other,

forming five phases of basin evolution: (i) an opening phase including alluvial fan and valley flooding together
with a lacustrine period, (ii) a phase of effusive and explosive volcanism (pulsatory phase), (iii) a phase of
predominant explosive and deposition from base surges (collapsing phase), and (iv) a phase of caldera eruption
and ignimbrite-forming processes (climactic phase). The facies architectures record a change in volcanic activity
from mainly phreatomagmatic eruptions, producing large volumes of lava flows and pyroclastics (pulsatory andcollapsing phase), to highly explosive, pumice-rich plinian-type pyroclastic density current deposits (climactic
phase).

Hamid area is a small-volume volcano, however, its magma compositions, eruption styles, andinter-eruptive breaks suggest, that it closely resembles a volcanic architecture commonly associated with large,
composite volcanoes.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

641

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4W_2I-P8

Date/Time: July 24 Poster

Lava dome structures and their significanceYan Lavallee1 , Jackie E. Kendrick2 , Adrian J. Hornby1 , Jeremie Vasseur2 , Emma Rhodes3 , Felix von
Aulock3 , Nick R. Varley4 , Ben Kennedy3 , Donald B. Dingwell2
1

University of Liverpool, UK, 2 Ludwig-Maximilians-University, Germany, 3 University of Canterbury, New
Zealand, 4 University of Colima, Mexico
E-mail: Yan.Lavallee@liverpool.ac.uk

Lava domes form by a combination of viscous, plastic and brittle deformation modes. During magma ascent, thecompetition between these deformation mechanisms controls the construction of the damage structure across thedomes and thus the degassing network with important repercussions on the eruptive style.

Here, we present an overview of signature structures developed during magma ascent, with a focus on
crystal-bearing lava domes (including Unzen, Santiaguito, Tarawera, Ceboruco, Colima, Soufriere Hills, and Mount
St. Helens). Our observations encompass features such as foam bands, tuffisites, thermal-stressing fractures,
unloading fractures, shear fractures, pseudotachylytes and cataclasites. We describe the relationships between
these structures and ultimately question the conditions underlying their origins as well as their influence on lava
dome eruption dynamics.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

642

IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4W_2I-P9

Date/Time: July 24 Poster

Frictional processes in glass and ash gouge
Yan Lavallee1 , Jackie E. Kendrick2 , Adrian J. Hornby1 , Takehiro Hirose3 , Kai-Uwe Hess2 , Donald B.
Dingwell2
1

University of Liverpool, UK, 2 Ludwig-Maximilians-University, Germany, 3 Kochi Institute for Core
Sample Research, JAMSTEC, Japan
E-mail: Yan.Lavallee@liverpool.ac.uk

The ascent of high-viscosity magma in upper conduits proceeds via the development of shear zones, which
commonly fracture, producing fault surfaces that control the last hundreds of meters of ascent by frictional slip.
Frictional slip in conduits may occur along magma-rock, rock-rock and magma-magma interfaces, with or without
the presence of gouge material. During slip, frictional work is converted to heat, which may result in strong
geochemical disequilibria as well as rheological variations, with important consequences on the dynamics ofmagma ascent.

Here, we present a thermo-mechanical study on the ability of glass and ash gouge (with different fractionsof glass and crystals) to sustain friction, and in some cases to melt, using a high-velocity rotary apparatus. The
friction experiments were conducted at a range of slip velocities (1.3 mm/s to 1.3 m/s) along a (fault) planesubjected to different normal stresses (0.5-5 MPa). We observe that the behaviour of volcanic rocks during slip
events varies remarkably, and unlike rocks which undergo comminution during slip, the inability of glass asperities
to comminute induces thermal stressing and commonly results in catastrophic failure within the elastic regime orupon the glass transition. Notably, samples heated at more than 400 K/s fully liquefied but subsequently failed
nonetheless. Thermo-mechanical analysis illustrates that beyond the calorimetric glass transition, slip continued
in the elastic regime before the samples relaxed and underwent viscous remobilization. We conclude that duringslip events, comminution, volumetric fluctuations and the viscous remobilisation temperature distinguish thefrictional behaviour of glass from that of crystalline rocks. Increasing damage along the slip zone contributes to thedevelopment of a cataclasite.

Slip in cataclastic ash gouge generally obeys Byerlee’s rule at low velocity, but shows an exponential decrease of
the friction coefficient with increasing slip velocity. An increase in slip velocity further increase the localisation of
deformation and development of shallow C/S fabrics in the gouge. The experiments do not produce significant heatcompared to glass-on-glass friction, and brings into question the capability for frictional melting when cataclasite ispresent along the fault zone. We discuss the implications of our findings to case studies of lava dome eruptions.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

643