LA “MEMORIA” GEOLOGICO-GEOMORFOLOGICA IN ALCUNE CITTÀ DELL’UMBRIA E DINTORNI ATTRAVERSO I MATERIALI DELL’ANTICO EDIFICATO URBANO

Abstract

L. Gregori, Geologic-geomorphologic “memory” in some of Umbria's cities and surroundings by means of ancient urban
building materials. (IT ISSN 0394-3356, 2007).
The complex geological history of Umbria has led to an extreme lithological and geomorphological variability. Calcareous lithotypes are present, deriving from Apenninic structures, bordering the region towards East, while siliciclastic lithotypes crop out in the West part of the region and igneous rock in the South-East part. The whole region is crossed from North to South by one of the greatest intramountain depressions in Umbria, i.e. the Tiberino lake, which has allowed the sedimentation of imposing fluvial and lake deposits. The historical “memory” of the past geologic landscapes can be deducted also by means of the most ancient urban buildings. The city walls, the monuments and also the simple houses of common people bear witness of the landscapes where the early inhabitants of the region used to carve out building materials.
Typical examples are the town of Città della Pieve, located on top of the Nestore paleoriver which supplied raw materials for walls and
buildings, and the Etruscan town of Orvieto, where the tufaceous stone has been carved out from the mesa to build the underground
town and the tombs outside the city walls.
Also the Etruscan tombs of the Volumi Hypogeum, located at the fore/bottom-set of the Tevere river paleodelta, are carved into deltaic deposits and behind the tombs of the Etruscan noble families conglomerated banks crop out, alternated by sands and/or muds.
The beautiful town of Civita, “the dying town” near Bagnoregio is carved out directly from the tufaceous and basaltic stone onto which
it lays and the ancient town of Carsulae, near Terni, has used for its urban developments calcareous and travertines materials coming
from Martani mountains. Finally, the world famous city of Assisi has its buildings and churches built from the typical pink stone extracted from the quarry of the Subasio mountain.
These are some of the examples representing litho-archaeologic situations in the urban fabric of Umbria's cities.The geologic history
and the subsequent surfaces aspect of the region have definitely influenced not only the location of urban sites but also their building
typology which, almost always, has made use of the native raw materials provided by the geologic and geomorphologic history of the
region, assigning to them a great value both scientifically and culturally.