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The 312ka Fasnia eruption from the Las Cañadas Caldera on Tenerife, Canary Islands, Spain, produced a complex sequence of twenty-two intercalated units, including 7 pumice fall, 7 ignimbrite and 8 ash surge and fall deposits that define two distinct eruption sequences (Lower and Upper Fasnia sequences). The fallout units themselves are internally complex, reflecting waxing and waning of the eruption column, while many of the ignimbrites reflect multiple intra-plinian partial column collapse events associated with the injection of lithic clasts into the eruption column. The Lower and Upper Fasnia eruption phases were each terminated by caldera collapse and complete column collapse events. Probable blockage of the conduit and vent system during Lower Fasnia caldera collapse event briefly terminated the eruption, resulting in a short-lived period of erosion and sedimentation prior to the onset of the Upper Fasnia phase. The transition to the Upper Fasnia eruption phase coincided with the eruption of more geochemically homogeneous pyroclasts. In total, 62km3 of tephra were erupted, including 49km3 of juvenile clasts and >12km3 of lithic clasts. The DRE volume of magma erupted was 13km3 (Lower Fasnia>5km3, Upper Fasnia>8km3), two thirds of which (~9-10km3) was deposited purely by fallout. The Fasnia Member is one of the most complex plinian sequences known. © 2017 Elsevier B.V., The research was funded by discretionary research funds of Ray Cas, NSF grant EAR-0001013 to John Wolff, and MCyT REN2001-0502/RIES and EC EVG1-CT-2002-00058 grants to Joan Marti.

The seismic crisis at a dormant volcano, occurring without volcanic manifestation, may be defined as a failed eruption, when magma has intruded to shallow depths but ultimately fails to reach the surface. This chapter presents some best-documented cases of the seismic activity that were recorded at dormant volcanic structures at large calderas, at strato-volcanoes, and in rift settings, and were not followed by an eruption. Theoretical and experimental modeling of magma propagating to the surface shows the conditions of magma arrest near the surface. The problem of monitoring of the seismic activity at dormant volcanoes is discussed.

Seismic activity has been postulated as a trigger of volcanic eruption on a range of timescales, but demonstrating the occurrence of triggered eruptions on timescales beyond a few days has proven difficult using global datasets. Here, we use the historic earthquake and eruption records of Chile and the Andean southern volcanic zone to investigate eruption rates following large earthquakes. We show a significant increase in eruption rate following earthquakes of MW > 8, notably in 1906 and 1960, with similar occurrences further back in the record. Eruption rates are enhanced above background levels for ~ 12 months following the 1906 and 1960 earthquakes, with the onset of 3-4 eruptions estimated to have been seismically influenced in each instance. Eruption locations suggest that these effects occur from the near-field to distances of ~ 500 km or more beyond the limits of the earthquake rupture zone. This suggests that both dynamic and static stresses associated with large earthquakes are important in eruption-triggering processes and have the potential to initiate volcanic eruption in arc settings over timescales of several months. © 2008 Elsevier B.V. All rights reserved.

Volcanoes are not random phenomena, but owe their existence, location, morphology, and eruptive styles to tectonic plate motions. Volcanic landforms vary widely in size and morphology from the stereotypical towering glacier-clad stratovolcano. They range from small spatter cones to massive shield volcanoes several thousand cubic kilometers in volume or broad volcanic depressions, cinder cones being the most common volcanic construct. Their eruptions likewise span many orders of magnitude in volume. Evaluation of eruption magnitudes and frequencies contrasts the vast majority of mild-to-moderate eruptions (∼80% with volcanic explosivity index, or VEI ≤2) with the more infrequent larger, higher-impact events (5% with VEI ≥4). Increased risk from population growth in proximity to volcanoes has been mitigated by enhanced monitoring and hazard-reduction efforts.

Basaltic volcanic fields consist of one or more volcanoes within a defined area that is separate from other volcanic areas and that has an internally consistent tectonic/structural setting. Most of the volcanoes are monogenetic, each having only a single eruptive episode lasting from weeks to decades before becoming extinct, and are of small volume (typically around 1 km3 or less). These volcanoes share many eruptive processes with larger, polygenetic volcanoes of basaltic composition, including Strombolian, Hawaiian, and phreatomagmatic explosive activity and effusion of lava flows. They form a range of landforms including lava fields, scoria cones, small shields, maars, tuff cones, and tuff rings depending upon the dominance of magmatic volatiles versus phreatomagmatic explosions in driving eruptions, and upon the magma volume flux and processes within the shallow crust. Basaltic volcanic fields typically contain volcano alignments that may be related to crustal structures, and clusters of high spatial vent density that are likely related to variability in the upper mantle magma sources. Hazard assessment is complicated by the many factors that affect the timing and locations of successive eruptions within a volcanic field. Recent research on magma sources and ascent for monogenetic volcanoes suggests an important role for compositional heterogeneity in the upper mantle, and that volatile fluxes during eruptions can be of similar magnitude as at larger polygenetic volcanoes.

In the last decades, the increasing availability of comprehensive geodetic datasets has allowed for more detailed constraints on subsurface magma storage and conduits at several active volcanoes worldwide. Here, by using a large dataset of geodetic measurements collected between early January 2001 and August 2001, we identified at least six different deformation stages that allow us to quantify the surface deformation patterns before, during and after the 2001 Mt. Etna volcanic eruption. Our results are largely in agreement with previous works (e.g. the presence of a deep inflating source and a shallow dike located beneath the north-western and upper southern flanks of the volcano, respectively). However, we provide (1) finer resolution of the temporal activity of these magmatic sources, leading to (2) new evidence related to the evolution of the magmatic system and the mechanical response of the western flank, in particular during the pre-eruptive phase. Results and analysis show a clear change in the ground deformation pattern of the volcano in response to the 20–24 April 2001 seismic swarm that occurred beneath the western flank, evolving from a volcano-wide inflation to a slight deflation of the summit area. We suggest that the source responsible for the volcano-wide inflation, beginning in the fall of 2000, experienced a drastic reduction in the inflation rate in response to this seismic swarm. Moreover, we provide evidence for the presence of a new inflating source located beneath the upper southern flank at a depth of ~ 7.0 km bsl that triggered both the occurrence of the 20–24 April 2001 seismic swarm and led to the rapid ascent of magma upward to the surface after 12 July (the Lower Vents system was fed by fresh magma rising from this source). The presence of this inflating source is inferred by (1) seismological and volcanological observations coming from the 2001 eruption and (2) seismological constraints coming from a previous similar episode that occurred at Etna during the 1993–1998 period. Furthermore, both shallow deflations observed after the 20–24 April 2001 seismic swarm and during the first day of the eruption also could be due to the deflation of two adjacent portions of the same shallow (~ 2 km bsl) reservoir. Such reservoirs would feed the activity that occurred at the South-East Crater after January 2001 and the activity of the Upper Vents system during the July–August eruption, in agreement with petrochemical observations. Through an updated revision of the available data, we shed some light on the relevance of pre-eruptive activity patterns, an important element for an effective volcano monitoring., The CGPS group is kindly acknowledged for providing raw data. Pablo J. González thanks the support of a Banting Postdoctoral Fellowship by the Canadian Government.

Bezymianny Volcano is one of the most active volcanoes in the world. In 1955, for the first time in history, Bezymianny started to erupt and after six months produced a catastrophic eruption with a total volume of eruptive products of more than 3 km3. Following explosive eruption, a lava dome began to grow in the resulting caldera. Lava dome growth continued intermittently for the next 57 years and continues today. During this extended period of lava dome growth, 44 Vulcanian-type strong explosive eruptions occurred between 1965 and 2012. This paper presents a summary of activity at Bezymianny Volcano from 1956 to 2010 with a focus on descriptive details for each event.

Dikes of rift zones in the Miocene basaltic shield of Tenerife have been studied along several profiles in order to record overall variations in lateral and vertical magma flow direction and sense. Dikes were sampled for Anisotropy of Magnetic Susceptibility (AMS) and other flow indicators and dike propagation indicators were also recorded at each sampling site. Bulk susceptibilities suggest a predominance of ferromagnetic minerals in the AMS fabrics and most of the sampled dikes show normal fabrics. Magnetic fabrics have been classified according to clustering and imbrication shown by the maximum susceptibility axis on each dike margin, a procedure that provides rapid information on the direction and sense of magma flow. The flow of magma tends to be upward and steep beneath the volcanic centers of the basaltic shield massifs. Along the axes of rift zones and in those rift zones located across the flanks of the volcanic edifices (roughly normal to the main rifts), magma is mainly emplaced laterally and downward. The flow of magma is mostly towards the external parts of the volcanic centers of the basaltic shield massifs and indicates that magma propagated toward regions of lower topography. This interpretation agrees with magma being emplaced above the level of neutral buoyancy and with buoyancy as the driving pressure gradient. The observed flow patterns can be explained in terms of density gradients within the volcanic edifices, in which magma flow trajectories are toward less dense regions., This research has been funded by the Ministerio de Ciencia y Tecnología (MCYT) project BTE2003-08026.