Pyroclastic fragments measuring between 2 and 64 mm emitted during volcanic explosions.
Term used for totally or partially molten magma when this reaches the surface following an effusive or moderately explosive eruption. The term lava is also used for rocks formed when the erupted magma solidifies.
Levels of alert
Scale of alert of the national civil protection service used in case of an expected or underway emergency. The scale provides for the activation phase of risk prevention, and/or the various phases of emergency management.
The relationship between the levels of criticality assessed by a Functional Centre and the different levels of alert is established, uniquely and individually, by the Regions, and is adopted during special procedures.
The declaration and the adoption of the alert level of the civil protection system is always the responsibility of relevant local authorities (municipality, province and region) as defined in art. 108, D.lgs.112/98.
Levels of criticality
A 3-level scale, which defines, in relation to each type of risk, a scenario of events that may occur in a territory.
For the hydraulic and hydrogeological risks, levels of ordinary, moderate and high criticality are defined.
The assessment of criticality levels is the responsibility of the pheripheral functional centre, when activated, or by the central functional Centre, in accordance with the principle of subsidiarity.
Organic waste with a high water content.
The phenomenon by which ground loses its shear resistance as a consequence of the application of dynamic actions such as seismic effects in non-draining conditions. The cause lies in the increase of interstitial pressures that follows the dynamic shaking: this increase, added to the initial value of the interstitial pressure, ends up by equalling the tensions normally applied, therefore cancelling effective tensions and as a consequence also resistance. Loose sandy surface soil deposits below the ground water table level are particularly susceptible to dynamic liquefaction.
Branch of geology which deals with the study of earth's crust forms and phenomena that modify it.
Description of a geometric succession of rock strata, in which can be distinguished different intervals due to the nature of the rocks that form them, regardless of the presence of fossil associations (basis of biostratigraphy) or the age of the rocks (basis of chronostratigraphy).
The thin external layer of the planet Earth, on average about 70 km thick, which includes the earth’s crust and the uppermost mantle.
Description of the geometric series della successione geometrica delle rocce in profondità, distinte sulla base della loro natura – alluvioni, depositi lacustri, depositi vulcanici, calcari, ecc. – , a prescindere dalla presenza di associazioni fossilifere, base della biostratigrafia, o dall’età delle rocce, base della cronostratigrafia.