Istituto di Fisica dell'Atmosfera (I.F.A.- C.N.R.), Roma, Italy

The correlation between geomagnetic field reversals and volcanism is investigated, according to the speculated consequence on volcanoes of the transient electric currents in the geodynamo, through Joule's heating, before and after every reversal event. We evaluate the temporal variation during the last ~ 70 Ma both of the magma emplacement rate Q(t) from the Hawaii hot spot, and of the speed v(t) of the Pacific plate, by means of the observed volumes of islands and seamounts along the Hawaii/Emperor Seamounts chain, and their respective radiometric datings. Results confirm expectations. A justification of the volcanic crises that lead to the generation of the large igneous provinces during the last ~ 250 Ma also emerged. We describe in detail the complex pattern of the timings of the different effects. Joule's power is generally responsible for ~ 75-80% of magmatism, and friction power only for ~ 20-25%; but, on some occasions almost ~ 100% is fuelled by friction alone. The visco-elastic coupling between lithosphere and asthenosphere results ~ 96% viscous, and ~ 4% elastic.

No average status can be defined for the sources of the external magnetic field over the polar caps, no index can provide with any such model, the observation of no single quantity or parameter can give the ultimate solution. Rather, every case history has to be considered independently. It is possible, however, to approach the problem from an interdisciplinary viewpoint, and to attempt to make an instant modelling of the electric currents that flow in the ionosphere and magnetosphere above the area of aeromagnetic prospecting. A few relevant previous such examples are discussed (such as Akasofu's inference on magnetospheric substorms derived by means of polar auroras, or the presently unfashionable Svalgaard vortex by means of the observed geomagnetic field and dealing with the pattern of the electric field within the magnetosphere, or the Sun-aligned auroral arcs inside the oval that are monitored by satellite, or, perhaps, the luminosity curve of polar auroras). It appears likely that some substantial achievement will be attained altogether with the progress in the understanding of the general pattern of a few typical recurrent configurations over the polar caps, in terms of a multidisciplinary input from different observations, either by ground-based observatories, or by space platforms.

The separation of the field produced by different internal sources can be accomplished by means of the so-called spatial spectrum of the geomagnetic field of internal origin. It is shown how such a rationale, when suitably interpreted, allows to recognize the field that is originated by electric currents that flow either on the Inner-Core Boundary (ICB), or on the Core-Mantle Boundary (CMB), or on the Asthenosphere-Lithosphere Boundary (ALB). It appears crucial, however, to rely on satellite measurements alone, because ground-based and ship- and air-borne records are severely perturbed by the crustal field. Therefore, it is shown, on the basis of a critical reconsideration of a few key-papers in the literature, that the best approach is to avoid mixing together all kinds of measurements. Satellite data are best suited for recognizing the dynamo field, while ground-based, ship- and air-borne records, which are measured much closer to crustal sources, are best suited, after subtraction of the satellite-derived dynamo field, for inferring the geomagnetic anomalies that are to be associated with crustal sources alone.

A model is investigated, by which the encounters of the solar system with dense interstellar clouds ought to trigger either geomagnetic field reversals or excursions, that produce extra electric currents within the Earth dynamo, that cause extra Joule's heating, that supplies volcanoes and endogenous processes. Volcanoes increase the Earth degassing into the atmosphere, hence the concentration of the minor atmospheric constituents, including the greenhouse gases, hence they affect climate temperature, glacier melting, sea level and global change. This investigation implies both theoretical studies and observational data handling on different time scales, including present day phenomena, instrumental data series, historical records, proxy data, and geological and palaeontological evidences. The state of the art is briefly outlined, mentioning some already completed achievements, investigations in progress, and future perspectives.

The science of environment is per se multi- and inter-disciplinary. It is not possible to separate the role of the physical, chemical, biological, and anthropic factors, respectively. Research must therefore rely on suitable natural laboratories, where all different effects can be simultaneously monitored and investigated. Stromboli is a volcanic island slightly North of Sicily, within a tectonic setting characterised by a Benioff zone, curved like a Greek theatre, opened towards the Tyrrhenian Sea, with deep earthquakes. Moreover, it is a unique volcano in the world in that since at least ~ 3000 years ago, it has exploded very regularly, about every 15^20 min. Hence, it is possible to monitor statistically phenomena occurring prior, during, and after every explosion. The Istituto Nazionale di Geofisica e Vulcanologia (INGV) has recently established a permanent Laboratory and an extensive interdisciplinary programme is being planned. A few main classes of items are to be considered including: (1) matter exchange (solid, liquid, gas, chemistry); (2) thermal and/or radiative coupling; (3) electromagnetic coupling; (4) deformation; (5) biospheric implications; and (6) anthropic relations since either the times of the Neolithic Revolution. Such an entire multidisciplinary perspective is discussed, being much beyond a mere volcanological concern. We present here the great heuristic potential of such a unique facility, much like a natural laboratory devoted to the investigation of the environment and climate.

A frequent approach when attempting to manage a natural catastrophe is in terms of a numerical model, by which we try to forecast its occurrence in space and time. But, sometimes this is difficult or even unrealistic. On more pragmatic grounds we can appeal to a formal analysis of the historical time series of every catastrophe of concern. Only approximately, however, can such series be likened to a point-like process, because the "detector-mankind" experienced substantial changes versus time. Nevertheless, such algorithms can be approximately applied by means of a few suitable assumptions. In the ultimate analysis, four basic viewpoints can be considered: i) either by assuming that phenomena are periodic; ii) or by assuming that an event occurs only whenever some energy threshold is attained (calorimetric criterion); iii) or by assuming that it occurs only whenever the system experiences some abrupt change in its boundary conditions; or iv), whenever no such algorithm is viable due to scanty observational information, just by applying fractal analysis, in terms of the box counting method, or some other more or less related and/or equivalent algorithms. The mutual relations, advantages, and drawbacks of any such approach are briefly discussed, with a few applications. They already lead to an apparently successful long-range forecast of a large flood in Northern Italy which occurred in 1994, and to the prevision of the next explosive eruption of Vesuvius. But the success of every application is closely determined by the quality of the historical database, or by the physical information that is fed into the analysis, rather than by mathematics that per se have only to be concerned with avoiding some arbitrary input being added, based only on the human need for simplicity. The present paper gives a synthesis of several algorithms that were previously independently applied on a simple intuitive basis to different case studies, although with no comparisons or discussion of their similarities and/or differences.

Acoustic Emissions (AE) are effective for monitoring ground deformation and temporal variation of its porosity. AE are complementary to seismic information, related to the same area, though AE and earthquakes focus on observational evidence concerned with substantially different space- and time-scales. AE information is pertinent (i) either for geodynamically stable areas, where it probes the diurnal thermal and/or tidal deformation, (ii) or for seismic areas where it provides some as yet unexploited precursors, (iii) or for volcanic areas, where it appears capable of recognising precursors originated by some hot fluid that penetrates by diffusion into rock pores, from those associated with eventual plutonic magma intrusions, (iv) and also for monitoring periods of time during which a volcano is «inflated» by underground hot fluids compared to others during which it «deflates». Upon direct comparison between 6 data sets concerned with different physical settings, it seems to be possible (fig. 3 and table II] to distinguish a few significantly different behaviours associated either (i) with a mere compression (such as it occurs for Stromboli, Vesuvius, and a sample compressed in the laboratory), or (ii) with a slip strain, such as it typically occurs in association with faulting or with diurnal thermal rock deformation.