ALBERT

Description: Jan Kozák, Vladimir Cermák: the illustrated history of natural disasters Content Type Journal Article Pages 1-2 DOI 10.1007/s00445-011-0495-7 Authors Jan Lindsay, Institute of Earth Science & Engineering, The University of Auckland, Rm 503, Level 5, 58 Symonds St., Auckland, New Zealand Journal Bulletin of Volcanology Online ISSN 1432-0819 Print ISSN 0258-8900

Description: C. Troise, G. De Natale and C.R.J. Kilburn (eds): Mechanisms of activity and unrest at large calderas Content Type Journal Article Pages 1-1 DOI 10.1007/s00445-011-0492-x Authors Ioan Seghedi, Institute of Geodynamics, Romanian Academy, Bucharest, Romania Journal Bulletin of Volcanology Online ISSN 1432-0819 Print ISSN 0258-8900

Description:    The Nesjahraun is a basaltic lava flow erupted from a subaerial fissure, extending NE along the Þingvellir graben from the Hengill central volcano that produced pāhoehoe lava followed by ‘a‘ā. The Nesjahraun entered Iceland’s largest lake, Þingvallavatn, along its southern shore during both phases of the eruption and exemplifies lava flowing into water in a lacustrine environment in the absence of powerful wave action. This study combines airborne light detection and ranging, sidescan sonar and Chirp seismic data with field observations to investigate the behaviour of the lava as it entered the water. Pāhoehoe sheet lava was formed during the early stages of the eruption. Along the shoreline, stacks of thin (5–20 cm thick), vesicular, flows rest upon and surround low (〈5 m) piles of coarse, unconsolidated, variably oxidised spatter. Clefts within the lava run inland from the lake. These are 2–5 m wide, 〉2 m deep, ∼50 m long, spaced ∼50 m apart and have sub-horizontal striations on the walls. They likely represent channels or collapsed tubes along which lava was delivered into the water. A circular rootless cone, Eldborg, formed when water infiltrated a lava tube. Offshore from the pāhoehoe lavas, the gradient of the flow surface steepens, suggesting a change in flow regime and the development of a talus ramp. Later, the flow was focused into a channel of ‘a‘ā lava, ∼200–350 m wide. This split into individual flow lobes 20–50 m wide along the shore. ‘A‘ā clinker is exposed on the water’s edge, as well as glassy sand and gravel, which has been locally intruded by small (〈1 m), irregularly shaped, lava bodies. The cores of the flow lobes contain coherent, but hackly fractured lava. Mounds consisting predominantly of scoria lapilli and the large paired half-cone of Grámelur were formed in phreatomagmatic explosions. The ‘a‘ā flow can be identified underwater over 1 km offshore, and the sidescan data suggest that the flow lobes remained coherent flowing down a gradient of 〈10°. The Nesjahraun demonstrates that, even in the absence of ocean waves, phreatomagmatic explosions are ubiquitous and that pāhoehoe flows are much more likely to break up on entering the water than ‘a‘ā flows, which, with a higher flux and shallow underlying surface gradient, can penetrate water and remain coherent over distances of at least 1 km. Content Type Journal Article Pages 1-14 DOI 10.1007/s00445-011-0480-1 Authors John Alexander Stevenson, S.E.A.E.S., University of Manchester, Williamson Building, Oxford Road, Manchester, M13 9PL UK Neil Charles Mitchell, S.E.A.E.S., University of Manchester, Williamson Building, Oxford Road, Manchester, M13 9PL UK Fiona Mochrie, S.E.A.E.S., University of Manchester, Williamson Building, Oxford Road, Manchester, M13 9PL UK Michael Cassidy, Lancaster Environment Center, Lancaster University, Lancaster, LA1 4YQ UK Harry Pinkerton, Lancaster Environment Center, Lancaster University, Lancaster, LA1 4YQ UK Journal Bulletin of Volcanology Online ISSN 1432-0819 Print ISSN 0258-8900

Description:    Palaeomagnetic techniques for estimating the emplacement temperatures of volcanic deposits have been applied to pyroclastic and volcaniclastic deposits in kimberlite pipes in southern Africa. Lithic clasts were sampled from a variety of lithofacies from three pipes for which the internal geology is well constrained (the Cretaceous A/K1 pipe, Orapa Mine, Botswana, and the Cambrian K1 and K2 pipes, Venetia Mine, South Africa). The sampled deposits included massive and layered vent-filling breccias with varying abundances of lithic inclusions, layered crater-filling pyroclastic deposits, talus breccias and volcaniclastic breccias. Basalt lithic clasts in the layered and massive vent-filling pyroclastic deposits in the A/K1 pipe at Orapa were emplaced at 〉570°C, in the pyroclastic crater-filling deposits at 200–440°C and in crater-filling talus breccias and volcaniclastic breccias at 〈180°C. The results from the K1 and K2 pipes at Venetia suggest emplacement temperatures for the vent-filling breccias of 260°C to 〉560°C, although the interpretation of these results is hampered by the presence of Mesozoic magnetic overprints. These temperatures are comparable to the estimated emplacement temperatures of other kimberlite deposits and fall within the proposed stability field for common interstitial matrix mineral assemblages within vent-filling volcaniclastic kimberlites. The temperatures are also comparable to those obtained for pyroclastic deposits in other, silicic, volcanic systems. Because the lithic content of the studied deposits is 10–30%, the initial bulk temperature of the pyroclastic mixture of cold lithic clasts and juvenile kimberlite magma could have been 300–400°C hotter than the palaeomagnetic estimates. Together with the discovery of welded and agglutinated juvenile pyroclasts in some pyroclastic kimberlites, the palaeomagnetic results indicate that there are examples of kimberlites where phreatomagmatism did not play a major role in the generation of the pyroclastic deposits. This study indicates that palaeomagnetic methods can successfully distinguish differences in the emplacement temperatures of different kimberlite facies. Content Type Journal Article Pages 1-21 DOI 10.1007/s00445-011-0493-9 Authors Giovanni Fontana, Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN UK Conall Mac Niocaill, Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN UK Richard J. Brown, Department of Earth Sciences, Durham University, Science Labs, Durham, DH1 3LE UK R. Stephen J. Sparks, Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queen’s Road, Bristol, BS8 1RJ UK Matthew Field, DiaKim Consulting Limited, Wells Road, Wookey Hole, Wells, BA5 1DN UK Journal Bulletin of Volcanology Online ISSN 1432-0819 Print ISSN 0258-8900

Description: J.A. Dóniz Páez: Volcanes basálticos monogenéticos de Tenerife (Monogenetic basalt volcanoes of Tenerife) Content Type Journal Article Pages 1-1 DOI 10.1007/s00445-011-0490-z Authors Miguel J. Haller, Universidad Nacional de la Patagonia San Juan Bosco, Centro Nacional Patagónico–CONICET, Bv. Brown 2915, 9120 Puerto Madryn, Argentina Journal Bulletin of Volcanology Online ISSN 1432-0819 Print ISSN 0258-8900

Description:    Rift zones at the divergent plate boundary in Iceland consist of central volcanoes with swarms of fractures and fissures extending away from them. Fissure swarms can display different characteristics, in accordance with their locations within the ∼50-km-wide rift zones. To better discern the characteristics of fissure swarms, we mapped tectonic fractures and volcanic fissures within the Kverkfjöll volcanic system, which is located in the easternmost part of the Northern Volcanic Rift Zone (NVZ). To do this, we used aerial photographs and satellite images. We find that rifting structures such as tectonic fractures, Holocene volcanic fissures, and hyaloclastite ridges are unevenly distributed in the easternmost part of the NVZ. The Kverkfjöll fissure swarm extends 60 km north of the Kverkfjöll central volcano. Holocene volcanic fissures are only found within 20 km from the volcano. The Fjallgarðar area, extending north of the Kverkfjöll fissure swarm, is characterized by narrow hyaloclastite ridges indicating subglacial volcanism. We suggest that the lack of fractures and Holocene volcanic fissures there indicates decreasing activity towards the north in the easternmost part of the NVZ, due to increasing distance from the long-term spreading axis. We argue that arcuate hyaloclastite ridges at the eastern boundary of the Northern Volcanic Rift Zone are mainly formed during deglaciations, when three conditions may occur; firstly, eruption rate increases due to decompression of the mantle. Secondly, the high tensile stresses accumulated during glaciations due to lack of magma supply may be relieved as magma supply increases during deglaciations. Thirdly, faulting may occur during unloading due to differential movements between the thinner and younger Northern Volcanic Rift Zone crust and the thicker and older crust to the east of it. Content Type Journal Article Pages 1-20 DOI 10.1007/s00445-011-0496-6 Authors Ásta Rut Hjartardóttir, Institute of Earth Sciences, University of Iceland, Askja, Sturlugata 7, 101 Reykjavík, Iceland Páll Einarsson, Institute of Earth Sciences, University of Iceland, Askja, Sturlugata 7, 101 Reykjavík, Iceland Journal Bulletin of Volcanology Online ISSN 1432-0819 Print ISSN 0258-8900

Description:    Maar volcanoes represent a common volcano type which is produced by the explosive interaction of magma with external water. Here, we provide information on a number of maars in the ultrapotassic Sabatini Volcanic District (SVD, Roman Province) as young as ∼90 ka. The SVD maars are characterised in terms of crater and ejecta ring morphologies, eruptive successions and magma compositions, in light of the local substrate settings, with the aim of assessing magma–water interaction conditions, eruption energetics and genetic mechanisms. Feeder magmas spanned the whole SVD differentiation trend from trachybasalts–shoshonites to phonolites. From the ejected lithic fragments from aquifer rocks, the range of depth of magma–water explosive interaction is estimated to have been mostly at ∼400–600 m below ground level, with a single occurrence of surficial interaction in palustrine–lacustrine environment. In particular, the interaction with external water may have triggered the explosive behaviour of poorly differentiated magmas, whereas it may have acted only as a late controlling factor of the degree of fragmentation and eruption style for the most differentiated magma batches during low-flux ascent in an incipiently fragmented state. Crater sizes, ejecta volumes and ballistic data allow a reconstruction of the energy budget of SVD maar-forming eruptions. Erupted tephra volumes from either monogenetic or polygenetic maars ranged 0.004–0.07 km 3 during individual maar-forming eruptions, with corresponding total magma thermal energies of 8 × 10 15 –4 × 10 17  J. Based on energy partitioning and volume balance of erupted magmas and lithic fractions vs. crater holes, we consider the different contributions of explosive excavation of the substrate vs. subsidence in forming the SVD maar craters. Following available models based on crater sizes, highly variable fractions (5–50%) of the magma thermal energies would have been required for crater excavation. It appears that subsidence may have played a major role in some SVD maars characterised by low lithic contents, whilst substrate excavation became increasingly significant with increasing degrees of aquifer fragmentation. Content Type Journal Article Pages 1-24 DOI 10.1007/s00445-011-0506-8 Authors Gianluca Sottili, Dipartimento di Scienze della Terra, Sapienza-Università di Roma, P.le Aldo Moro 5, 00185 Rome, Italy Danilo M. Palladino, Dipartimento di Scienze della Terra, Sapienza-Università di Roma, P.le Aldo Moro 5, 00185 Rome, Italy Mario Gaeta, Dipartimento di Scienze della Terra, Sapienza-Università di Roma, P.le Aldo Moro 5, 00185 Rome, Italy Matteo Masotta, Dipartimento di Scienze della Terra, Sapienza-Università di Roma, P.le Aldo Moro 5, 00185 Rome, Italy Journal Bulletin of Volcanology Online ISSN 1432-0819 Print ISSN 0258-8900

Description:    Lastarria volcano (25°10′ S, 68°31′ W; 5,697 m above sea level), located in the Central Andes Volcanic Zone (northern Chile), is characterized by four distinct fumarolic fields with outlet temperatures ranging between 80°C and 408°C as measured between May 2006–March 2008 and April–June 2009. Fumarolic gasses contain significant concentrations of high temperature gas compounds (i.e., SO 2 , HCl, HF, H 2 , and CO), and isotopic ratios ( 3 He/ 4 He, δ 13 C–CO 2 , δ 18 O–H 2 O, and δD–H 2 O) diagnostic of magmatic gas sources. Gas equilibria systematics, in both the H 2 O-H 2 -CO 2 -CO-CH 4 and alkane–alkene C 3 system, suggest that Lastarria fumarolic gasses emanate from a superheated vapor that is later cooled and condensed at relatively shallow depths. This two-stage process inhibits the formation of a continuous aquifer (e.g., horizontal liquid layer) at relatively shallow depth. Recent developments in the magmatic gas system may have enhanced the transfer and release of heat causing shallow aquifer vaporization. The consequent pressure increase and aquifer vaporization likely triggered the inflation events beginning in 2003 at the Lastarria volcano. Content Type Journal Article Pages 1-16 DOI 10.1007/s00445-011-0489-5 Authors Felipe Aguilera, Departamento de Geología, Universidad de Atacama, Av. Copayapu 485, Copiapó, Chile F. Tassi, Department of Earth Sciences, University of Florence, Via G. La Pira 4, 50121 Florence, Italy T. Darrah, Department of Earth and Environmental Sciences, University of Rochester, 227 Hutchinson Hall, Rochester, NY 14627, USA S. Moune, Laboratoire Magmas et Volcans, Observatoire de Physique du Globe de Clermont-Ferrand, Université Blaise Pascal, 5 rue Kessler, 63038 Clermont-Ferrand Cedex, France O. Vaselli, Department of Earth Sciences, University of Florence, Via G. La Pira 4, 50121 Florence, Italy Journal Bulletin of Volcanology Online ISSN 1432-0819 Print ISSN 0258-8900

Description:    Ischia is an active volcanic island in the Gulf of Naples whose history has been dominated by a caldera-forming eruption (ca. 55 ka) and resurgence phenomena that have affected the caldera floor and generated a net uplift of about 900 m since 33 ka. The results of new geomorphological, stratigraphical and textural investigations of the products of gravitational movements triggered by volcano-tectonic events have been combined with the information arising from a reinterpretation of historical chronicles on natural phenomena such as earthquakes, ground deformation, gravitational movements and volcanic eruptions. The combined interpretation of all these data shows that gravitational movements, coeval to volcanic activity and uplift events related to the long-lasting resurgence, have affected the highly fractured marginal portions of the most uplifted Mt. Epomeo blocks. Such movements, mostly occurring since 3 ka, include debris avalanches; large debris flows (lahars); smaller mass movements (rock falls, slumps, debris and rock slides, and small debris flows); and deep-seated gravitational slope deformation. The occurrence of submarine deposits linked with subaerial deposits of the most voluminous mass movements clearly shows that the debris avalanches impacted on the sea. The obtained results corroborate the hypothesis that the behaviour of the Ischia volcano is based on an intimate interplay among magmatism, resurgence dynamics, fault generation, seismicity, slope oversteepening and instability, and eruptions. They also highlight that volcano-tectonically triggered mass movements are a potentially hazardous phenomena that have to be taken into account in any attempt to assess volcanic and related hazards at Ischia. Furthermore, the largest mass movements could also flow into the sea, generating tsunami waves that could impact on the island’s coast as well as on the neighbouring and densely inhabited coast of the Neapolitan area. Content Type Journal Article Pages 1-28 DOI 10.1007/s00445-011-0501-0 Authors Marta Della Seta, Dipartimento di Scienze della Terra, Università degli Studi di Roma “La Sapienza”, Piazzale Aldo Moro, 5, 00185 Rome, Italy Enrica Marotta, Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Napoli “Osservatorio Vesuviano”, Via Diocleziano, 328, 80124 Naples, Italy Giovanni Orsi, Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Napoli “Osservatorio Vesuviano”, Via Diocleziano, 328, 80124 Naples, Italy Sandro de Vita, Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Napoli “Osservatorio Vesuviano”, Via Diocleziano, 328, 80124 Naples, Italy Fabio Sansivero, Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Napoli “Osservatorio Vesuviano”, Via Diocleziano, 328, 80124 Naples, Italy Paola Fredi, Dipartimento di Scienze della Terra, Università degli Studi di Roma “La Sapienza”, Piazzale Aldo Moro, 5, 00185 Rome, Italy Journal Bulletin of Volcanology Online ISSN 1432-0819 Print ISSN 0258-8900

Description:    Strombolian-type volcanic activity is characterized by a series of gas bubbles bursting at the top of a magma column and leading to the ejection of lava clots and gas emission at the surface. The quantitative analysis of physical parameters (e.g., velocity, size, and mass fluxes) controlling the emission dynamics of these volcanic products is very important for the understanding of eruption source mechanisms but remains difficult to obtain in a systematic fashion. Ground-based Doppler radar is found to be a very effective tool for measuring ejecta velocities at a high acquisition rate and close to the emission source. We present here a series of measurements carried out at Mt. Etna’s Southeast crater, using an L-band volcanological Doppler radar, during the 4 July 2001 Strombolian eruptions. Doppler radar data are supplemented by the analysis of video snapshots recorded simultaneously. We provide here a set of physical parameters systematically retrieved from 247 Strombolian explosions spanning 15 min and occurring during the paroxysm of the eruption from 21:30 to 21:45 UT. The time-average values give a maximum particle velocity of V max p = 94.7 ± 24 \text m / s , a bulk lava jet velocity of V \text PW - rad = 37.6 ± 1.9 \text m / s , and an initial gas velocity at the source vent of V 0 g = 118.4 ± 36 \text m / s . The time-averaged particle diameter is found to be about D \text PW - rad = 4.2 ± 2.1 \text cm . The volume and mass gas fluxes are estimated from time-averaged source gas velocities over the sequence duration at Q v g = 3 - 11 ×10 3 \text m 3 \text/ s and Q m g = 0.5 - 2 ×10 3 \text kg / s , respectively. Content Type Journal Article Pages 1-7 DOI 10.1007/s00445-011-0500-1 Authors Mathieu Gouhier, Clermont Université, Université Blaise Pascal, OPGC, Laboratoire Magmas et Volcans, 5, rue Kessler, BP 10448, 63000 Clermont-Ferrand, France Franck Donnadieu, Clermont Université, Université Blaise Pascal, OPGC, Laboratoire Magmas et Volcans, 5, rue Kessler, BP 10448, 63000 Clermont-Ferrand, France Journal Bulletin of Volcanology Online ISSN 1432-0819 Print ISSN 0258-8900