Page 113 - Caldera Volcanism Analysis, Modelling and Response

88 Roberto Sulpizio and Pierfrancesco Dellino

Figure 18 Examples of lithofacies associations in PDC deposits of Pollena (a) and (e) and
Upper Pollara (b) eruptions; (c, d) sedimentological model that illustrates the observed lithofa-
cies association of picture (a) and (b); (f, g) sedimentological model that illustrates the observed
lithofacies association of picture (e).

achievement is the description of different types of PDCs within a continuum of
phenomena, in which the dominance of fluid or solid particles on motion
determines the wide range of observed deposits. Of primary importance is also the
involvement of the granular flow theory in description of the particle–particle
dominated (lower) part of PDCs. Since PDCs are density stratified, particle–particle
interaction plays a role in all types of PDCs, although with the likely exception of
extremely diluted currents. The interpretation of some deposits using granular flow
theory has opened some interesting perspectives for future research. The first is