Late Quaternary environmental catastrophes and landscape evolution in Northern ItalyFrancesca Ferrario, Fabio Brunamonte, Alessandro M. Michetti, Leonello Serva The recent landscape evolution of an area is governed by extreme natural events, which are able to change the geography and stratigraphy of entire regions. The understanding of geohazards is therefore based on knowledge of the natural environment of the area and its territorial setting. The Po Plain is the foredeep of both the Alps and the Apennines mountain belts, and is commonly regarded as a relatively “stable” area characterized by moderate seismicity and by the low relief landscape typical of a large alluvial basin. Being one of the most industrialized and vulnerable areas in Europe, we selected 4 key areas to illustrate how the rigorous geological analysis allows to identify, assess, and mitigate extreme geological hazards, which might be a serious factor of environmental risk for the local industrial plants and large metropolitan areas: - A quarry located along the Monte Netto growing anticline, near Brescia, is the first site in the Po Plain that shows evidence of repeated paleoseismic surface faulting: 3 strong (M6 to 6.5) paleoseismic events, representative of maximum credible event, have been recorded during the last ca. 40 ky BP; this emphasizes the coseismic surface rupture hazard in a region that was reportedly only characterized by “blind” faults; - The Piedmont region, despite a very low historical seismicity, displays geomorphic and structural features similar to those seen near Brescia; major evidence of active tectonics is the growth of the isolated Trino relief, and the recent diversion of the regional river network (Po, Tanaro, Bormida); conservatively, the likelihood of strong earthquakes equivalent to the ones identified at Monte Netto cannot be ignored; - The Como urban area lies on very recent palustrine sediments, an environment showing remarkable Holocene subsidence, and high potential for liquefaction and coastal flooding; new observations suggest the occurrence of Holocene paleoseismic events, with megalandslides on the bottom of Lake Como, possible secondary effects (tsunamis), and surface ruptures along a major thrust fault; - Through a detailed site analysis for a non-hazardous waste landfill in the municipality of Cairo Montenotte, in the Bormida drainage basin, we detected 2 major morphogenetic crises occurred at ca. 40 and 18 kyr BP in relation to glacial and post-glacial processes; with inception of Holocene mild climatic conditions the site becomes relatively stable, allowing to evaluate the compatibility between the plant and the local environment. |
