By using new high-resolution (2 m) digital elevation model derived from the 2005 LiDAR
survey of Mt. Etna volcano (Italy), our study measured the classical morphometrical
parameters for scoria cones, i.e. W(co) (cone width), W(cr) (crater diameter), H (cone
height) as well as volume, inclination of cone slope and substrate, and a number of
other parameters for 135 scoria cones of Mt. Etna. Volume and age distribution of
cones shows that there is no direct structural control on their emplacement in terms
of Etna's rift zones. The cones are progressively smaller in size toward summit, which
can be explained by the large volcano's feeding system and progressively frequent
lava burial toward top. A careful analysis of H/W(co) ratio (determined as 0.18 for
other volcanic fields worldwide) shows that this ratio strongly depends on (1) the
calculation method of H and (2) lava burial of cone. For Etnean cones, applying an
improved method for calculating H relative to the dipping substrate results in a significantly
lowered standard H/W(co) ratio (0.137), which in turn questions the validity of the
classical value of 0.18 in the case of large central volcanoes. The reduction of the
ratio is not only due to methodology but also to the common lava burial. This can
be expressed even better if H(mean) is used instead of H(max) (H(mean)/W(co) = 0.098).
Using this measure, at Etna, well formed cones have higher ratios than structurally
deformed (e. g. double or rifted) cones. Furthermore, although the sampled scoria
cones at Etna have formed in a relatively narrow time interval (<6500 yrs BP), there
is a slight decrease in H/W(co) corresponding to erosional changes detected globally
(H/W(co) = 0.143, 0.135 and 0.115 for three age classes of Etna's scoria cones, corresponding
to average slopes of 26.6, 23.9 and 23.7 degrees). Because the morphometrical effect
of position on a dipping substrate as well as lava burial exceeds the effect of erosion,
we call attention to use caution in simply using the H/W(co) ratio of scoria cones
for detecting age, especially on large active volcanoes. (C) 2009 Elsevier B.V. All
rights reserved.
