Philippe Labazuy

Recurrent landslides events on the submarine flank of Piton de la Fournaise volcano (Reunion Island)

Abstract New studies confirm the existence of large landslide events related to both the Piton des Neiges and the Piton de la Fournaise volcanic systems. Like many other island basaltic shield volcanoes, Réunion Island has had a complex evolution combining construction processes and recurrent destructive events. Landslide deposits probably form an important part of its internal structure. Sliding events and related tsunamis are one of the major hazards of this kind of volcanic activity, in an intraplate oceanic context. The submarine flank of Piton de la Fournaise has been extensively studied using Seabeam bathymetry and high resolution side-scan sonar images. The eastern submarine flank is entirely covered by 550 km3 of landslide deposits, which are mainly subaerially erupted basaltic lavas, transported and fractured in large-scale mass wasting. Volumetric considerations imply recurrent partial destruction of the edifice, by landsliding, during its construction. For each sector collapse the fundamental process is the sliding of large blocks, up to several kilometres in length. Fractions of the slide blocks break up and evolve into debris avalanches. Analogue experiments have been carried out to tentatively explain the geometry of these periodic large landslides of the unbuttressed flank. The morphology and the deformation in the landslides of the model are compared to the natural system of Piton de la Fournaise.

Morphological analysis of active Mount Nemrut stratovolcano, eastern Turkey: evidences and possible impact areas of future eruption

Abstract Mount Nemrut, an active stratovolcano in eastern Turkey, is a great danger for its vicinity. The volcano possesses a summit caldera which cuts the volcano into two stages, i.e. pre- and post-caldera. Wisps of smoke and hot springs are to be found within the caldera. Although the last recorded volcanic activity is known to have been in 1441, we consider here that the last eruption of Nemrut occurred more recently, probably just before 1597. The present active tectonic regime, historical eruptions, occurrence of mantle-derived magmatic gases and the fumarole and hot spring activities on the caldera floor make Nemrut Volcano a real danger for its vicinity. According to the volcanological past of Nemrut, the styles of expected eruptions are well-focused on two types: (1) occurrence of water within the caldera leads to phreatomagmatic (highly energetic) eruptions, subsequently followed by lava extrusions, and (2) effusions–extrusions (non-explosive or weakly energetic eruptions) on the flanks from fissures. To predict the impact area of future eruptions, a series of morphological analyses based on field observations, Digital Elevation Model and satellite images were realized. Twenty-two valleys (main transport pathways) were classified according to their importance, and the physical parameters related to the valleys were determined. The slope values in each point of the flanks and the Heim parameters H/L were calculated. In the light of morphological analysis the possible impact areas around the volcano and danger zones were proposed. The possible transport pathways of the products of expected volcanic events are unified in three main directions: Bitlis, Guroymak, Tatvan and Ahlat cities, the about 135 000 inhabitants of which could be threatened by future eruptions of this poorly known and unsurveyed volcano.

Near real-time monitoring of the April–May 2010 Eyjafjallajökull ash cloud: an example of a web-based, satellite data-driven, reporting system

During the 2010 eruption of Eyjafjallajokull volcano (Iceland) we set up a system designed to ingest satellite data and output volcanic ash cloud products. The system (HVOS = HotVolc Observing System) ingested on-reception data provided every 15 minutes by the SEVIRI sensor flown aboard the Meteosat Second Generation (MSG) satellite. Data were automatically processed and posted on the web to provide plume location maps, as well as to extract plume metrics (cloud top height and mass flux), in near-real time. Given the closing speeds for aircraft approaching such hazardous ash clouds, reporting delays for such products have to be minimised.

Modern Multispectral Sensors Help Track Explosive Eruptions

Due to its massive air traffic impact, the 2010 eruption of Eyjafjallajokull was felt by millions of people and cost airlines more than U.S.

HOTVOLC: a web-based monitoring system for volcanic hot spots

1.7 billion. The event has, thus, become widely cited in renewed efforts to improve real-time tracking of volcanic plumes, as witnessed by special sections published last year in Journal of Geophysical Research, (117, issues D20 and B9).

L'origine de la roche mise en œuvre pour la construction du temple de Mercure, au sommet du Puy de Dôme, élucidée, et les implications archéologiques

Abstract Infrared (IR) satellite-based sensors allow the detection and quantification of volcanic hot spots. Sensors flown on geostationary satellites are particularly helpful in the early warning and continuous tracking of effusive activity. Development of operational monitoring and dissemination systems is essential to achieve the real-time ingestion and processing of IR data for a timely response during volcanic crises. HOTVOLC is a web-based satellite-data-driven monitoring system developed at the Observatoire de Physique du Globe de Clermont-Ferrand (Clermont-Ferrand), designed to achieve near-real-time monitoring of volcanic activity using on-site ingestion of geostationary satellite data (e.g. MSG-SEVIRI, MTSAT, GOES-Imager). Here we present the characteristics of the HOTVOLC system for the monitoring of effusive activity. The system comprises two acquisition stations and secure databases (i.e. mirrored archives). The detection of volcanic hot spots uses a contextual algorithm that is based on a modified form of the Normalized Thermal Index (NTI*) and VAST. Raster images and numerical data are available to open-access on a Web-GIS interface. Tests are carried out and presented here, particularly for the 12–13 January 2011 eruption of Mount Etna, to show the capability of the system to provide quantitative information such as lava volume and time-averaged discharge rate. Examples of operational application reveal the ability of the HOTVOLC system to provide timely thermal information about volcanic hot spot activity.

Erratum to: Lava discharge during Etna’s January 2011 fire fountain tracked using MSG-SEVIRI

Le Puy de Dome (Chaine des Puys, Massif-Central francais) est un volcan de forme approximativement tronconique, d’une altitude maximale de 1465 m (figs. 1-2). Il domine son environnement immediat, le plateau des domes, de 400 m env. et la plaine de Clermont Ferrand — siege de la capitale arverne Augustonemetum — de 1100 m en moyenne.1 C’est un sommet isole, visible jusqu’a 80 kilometres. En contrebas sud du culmen, vers 1450 m, les ruines du “sanctuaire de Mercure” s’organisent en terrasses pour occuper une superficie reconnue de l’ordre de 3500 m2. Decouvert et fouille a la fin du XIXe s.,2 cet edifice a fait, au debut des annees 2000, l’objet de nouvelles etudes qui ont permis d’en revoir et preciser la restitution.3 Les ruines visibles aujourd’hui sont celles d’un tres grand monument de la premiere moitie du IIe s. (fig. 3), qui a succede, d’apres les remplois reconnus, a un monument plus petit construit dans la seconde moitie du Ier s. et dont la localisation exacte reste a preciser.4

Geology, Geomorphology and Slope Instability of the Maar Lake Pavin (Auvergne, French Massif Central)

In the paper by Gouhier, M., Harris, A., Calvari, S., Labazuy, P., Guehenneux, Y., Donnadieu, F., Valade, S, entitled “Lava discharge during Etna’s January 2011 fire fountain tracked using MSG-SEVIRI” (Bull Volcanol (2012) 74:787–793, DOI 10.1007/s00445-011-0572-y), we present data from a Doppler radar (VOLDORAD 2B). This ground-based Lband radar has been monitoring the eruptive activity of the summit craters of Mt. Etna in real-time since July 2009 from a site about 3.5 km SSE of the craters. Examples of applications of this type of radar are reviewed by Donnadieu (2012) and shown on the VOLDORAD website (http://wwwobs. univbpclermont.fr/SO/televolc/voldorad/). Although designed and owned by the Observatoire de Physique du Globe in Clermont-Ferrand (OPGC), France, VOLDORAD 2B is operated jointly with the INGV-Catania (Italy) in the framework of a technical and scientific collaboration agreement between the INGV of Catania, the French CNRS and the OPGC-Universite Blaise Pascal in ClermontFerrand. The system also utilizes a dedicated micropatch antenna designed at the University of Calabria (Boccia et al. 2010) and owned by INGV. The objective of the joint acquisition of the radar data by INGV-Catania and the OPGC is twofold: (1) to mitigate volcanic risks at Etna by better assessing the hazards arising from ash plumes and (2) to allow detailed study of volcanic activity and its environmental impact. In the paper by Gouhier et al. (2012), we failed to highlight this important collaboration between the INGV Catania and the OPGC; a cooperation essential for the past, current and future generation of such valuable data sets. Specifically we wish to acknowledge the roles of Mauro Coltelli, Michele Prestifilippo and Simona Scollo for their important input into this project, and pivotal role in setting up, and maintaining, this collaborative deployment.

Geophysical Experimental Survey on Flood Protection Dikes - The Case Study of the Loire River Basin

Maars are craters created by violent phreatomagmatic eruptions. The crater shape involves roughly circular rims whose asymmetric slopes may be unstable long after the initial eruption. Lakes that occupy many maars are natural receptacles that enclose geologic archives such as slope deposits. Here we describe the geologic and geomorphic characteristics of the maar and Lake Pavin in Auvergne with emphasis on recent and current slope instability. This is due to its geometry (the 800 × 92 m lake occupies a wide depression cut deep in pre-existing lava flows and Montchal cone), loose surficial formations on steep subaerial slopes and fractured lava scarps, and loose and gas-rich sediment on sub-lacustrine steep slopes.

Geochemical insights into the internal dynamics of debris avalanches. A case study: The Socompa avalanche, Chile

An electromagnetic induction (EMI) survey has been performed along the Loire River protection dikes (France), with a 60 km long, high speed and high resolution, field acquisition campaign. The main aim of this dikes diagnostic mission was to locate and identify potential local weakness or damaged zones inside the engineering structures. We used an EMI device (EM31) and a GPS receiver on board an experimental fiberglass cart support, designed for high yield acquisition surveys. This study allowed to provide the electrical subsurface image (conductivity) of the whole structure and allowed, in addition, for precise detection of the small-scale anomalies. The outputs consist of electrical images of both the inner dike structure and the subsurface geological environment. This fast first-phase study is efficient for detecting decametric local anomalies while giving information about the dike inner structure. Once EMI anomalous zones have been detected, further detailed investigations have been performed on selected areas, including electrical resistivity tomography (ERT) profiles and geotechnical drills. Thus, the objective of our experimental study was to scale down and optimize this second phase of the prospecting campaign, which will considerably reduce the cost and the time spent on the whole survey.