Fractal analysis and morphological evolution of volcanic relief: some examples from Italy

In geomorphology several authors have discussed the fractal nature of coastlines and drainage networks, significantly quantified by the fractal dimension (D(f)), even if many other landscapes features show an intrinsic geometric irregularity. Starting from the preliminary results of a previous stud), (DELLA SETA et al. 2003), the aim of the present work is to test the power of the fractal analysis of contour lines and topographic surfaces in the morphological study of volcanic areas. In volcanic terrains, the relationships between fractal dimension, principal morphogenetic processes and elapsed time since the beginning of activity may be better constrained than in many other environments. Three volcanic areas of Italy, of varying size, have been compared by means of their fractal characteristics. Fractal dimensions of contour lines (interval <= 100 m) have been calculated using the box-counting and the compass-walk methods, while the fractal analysis of topographic surfaces has been performed, after creating DEMs, through the variogram method. Results obtained show that the D(f) values of contour lines vary according to their geometrical modifications induced by the type of main exogenous agent, even if this is not necessarily a one-to-one relationship. Moreover, the D(f) of contour lines provides a measure of the intensity of morphogenetic processes which, within the same volcanic area, generally changes with the relative age of the outcropping products. On the other hand, the D(f) of the topogaphic surface seems to typify regional morphostructures created by the major effort of endogenous forces.