Abstract The AVHotRR routine has been in operation since 2006 to process satellite data for monitoring active volcanoes in the Mediterranean area. Although originally developed to work with advanced very high-resolution radiometer (AVHRR) data, AVHotRR has been developed over the years to adapt to other sensors. In this work we present an improved version of the algorithm for hot-spot detection and effusion rate estimate. The underlying principles upon which the algorithm is based are discussed, focusing on the enhancements. The currently implemented version makes it possible to integrate results from different datasets in order to better constrain the detection of volcanic hot spots. In particular, the high temporal resolution of the SEVIRI instrument aboard MSG is key to reducing false positives in AVHRR and moderate resolution imaging spectroradiometer MODIS images. We propose here a new detection method based on the wavelet transform of SEVIRI data. Results from the application of AVHotRR to a dataset of AVHRR and SEVIRI images from Mt Etna, Italy, are presented and discussed with reference to the advantages and limitations of the algorithm.

Abstract VolcFlow is a finite-difference Eulerian code based on the depth-averaged approach and developed for the simulation of isothermal geophysical flows. Its capability for reproducing lava flows is tested here for the first time. The field example chosen is the 2010 lava flow of Tungurahua volcano (Ecuador), the emplacement of which is tracked by projecting thermal images onto a georeferenced digital topography. Results show that, at least for this case study, the isothermal approach of VolcFlow is able to simulate the velocity of the lava through time, as well as the extent of the solidified lava. However, the good fit between the modelled and the natural flow may be explained by the short emplacement time ( c. 20 h) of a thick lava ( c. 5 m), which could limit the influence of cooling on the flow dynamics, thus favouring the use of an isothermal rheology.

Abstract Etna volcano is characterized by frequent effusive eruptions from the summit craters or from flank fissures, and these have often threatened villages, infrastructures and tourist facilities. Considerable experience of lava-flow mitigation has been gained by scientists working on this volcano, and in this paper we principally discuss the problems arising from lava flows emplaced during the 2002–03 flank eruption, when eruptive fissures opened both on the northern and southern flanks of the volcano, feeding lava flows towards several villages, tourist facilities and forests. We highlight the importance of the monitoring system to follow the spreading of eruptive fissures and predict when they stopped propagating. We illustrate the value of thermal mapping in identifying active lava flows, in measuring effusion rates to estimate the maximum distance that flows can travel, and in obtaining reliable lava-flow simulations in real time in order to predict possible paths of the lava flow and to adopt the most appropriate solutions to limit its damage. Collaborations between scientists from different institutions and fields once again proved essential to understand and model the eruptive processes, to mitigate hazards and to obtain the best results.

Abstract Using the NEODAAS-Dundee AVHRR receiving station (Scotland), NEODAAS-Plymouth can provide calibrated brightness temperature data to end users or interim users in near-real time. Between 2000 and 2009 these data were used to undertake volcano hot spot detection, reporting and time-average discharge rate dissemination during effusive crises at Mount Etna and Stromboli (Italy). Data were passed via FTP, within an hour of image generation, to the hot spot detection system maintained at Hawaii Institute of Geophysics and Planetology (HIGP, University of Hawaii at Manoa, Honolulu, USA). Final product generation and quality control were completed manually at HIGP once a day, so as to provide information to onsite monitoring agencies for their incorporation into daily reporting duties to Italian Civil Protection. We here describe the processing and dissemination chain, which was designed so as to provide timely, useable, quality-controlled and relevant information for ‘one voice’ reporting by the responsible monitoring agencies.

Abstract Devonian reef systems are thought to represent the greatest phase of global reef development in the Phanerozoic. Despite this, ecological and environmental controls on the sedimentary nature of these vast systems have scarcely been investigated and remain enigmatic. The Late Devonian (Frasnian) Alexandra Reef System, exposed in the Northwest Territories of Canada, developed on a ramp that was situated on the western margin of Laurussia. The system consists of two reef complexes. The second reef complex developed basinwards of the first after sea level fell ~ 17 m. In contrast to stromatoporoid (± coral)-dominated reef facies in the first reef complex and the upper part of the second reef complex, reef facies in the lower part of the second reef complex are dominated by stromatoporoid-microbe associations. These include significant renalcid boundstone and stromatolite accumulations that are not found elsewhere in the reef system. It is concluded that the occurrence of the stromatoporoid-microbe reef facies indicates that a shift in the reef environment from oligotrophic to mesotrophic conditions took place. The mechanisms of nutrification were linked to the platform geometry, sea-level position, and oceanographic system, indicating that on carbonate ramps, systems tracts of falling sea level (forced regression) and sea-level lowstand may be particularly susceptible to nutrification. A nutrient-gradient model developed to explain different types of reef facies in the Alexandra Reef System indicates that trophic resources were an important control on the composition of Devonian reef-building communities, and that Devonian reefs and carbonate platforms were not highly susceptible to nutrient-invoked drowning.