The central Apennines, which cover the area from the Metauro to the Sangro and Volturno valleys, are younger, more calcareous and dolomitic than the Apennines further south. On the Adriatic flank, the whole zone is characterized by a hilly belt of Pliocene marine deposits. The mountains themselves can be divided into a northern Umbria - Marche section and a southern Abruzzo section.
The northern Umbria - Marche section is made up of deep sea and marly formations, starting in a northwest to southeast direction and ending by running almost north - south toward the south. The peaks of this section vary between 10001200 m and 1500-400 m and are often rounded or flat-topped. The geology is composed of various types of limestone: compact and homogeneous, cherty, marly, and thin bedded (scaglia). The same asymmetry applies to this area of the Apennines as further north. On the inner Umbrian side of the mountains there are rather longer mountain basins than in Tuscany filled with broadly similar sequences of lake and river deposits (the Tiber valleys, the valleys of Gubbio, Gualdo Tadino, and Norcia). On the Adriatic side, the shorter traverse of rivers cuts across the geological folds before entering Pliocene deposits nearer the coast.
The Gubbio valley is one example of the intermontane lake basins of the western side of the Apennines, which is of interest to republican Italy as the location of the city of Iguvium.9 The valley nestles in one of the depressions that formed in the Apennines. The key local topographical feature is a prominent limestone escarpment, in part the watershed of the peninsula, that runs the length of the northeastern edge of the valley, reaching an apex of nearly 1,000 m at its central point behind the city of Gubbio. This escarpment dominates a valley at between 300 and 500 m, filled with heavy Pleistocene terraces, later alluvial fans, and colluvial infill. A large proportion of the alluviation and colluviation was probably a consequence of human activity dated in part to the republican period, when rural settlement increased considerably. As a consequence of the central infill of the valley, drainage takes place both to the southeast and the northwest, ultimately reaching the Tiber from two tributaries. To the southwest lie the lower sandstone hills between Gubbio and the neighboring city of Perugia. The whole valley forms a self-contained territory flanking the higher Apennines and the major communication route through to the Adriatic followed by the Flaminia to the east.
The southern Abruzzo section is generally greater in height, rising from the lower mountains of 500-700 m to the upper peaks of some 1,500 m. The mountains are also distributed in three bands of heights forming an even more considerable barrier. From the Adriatic coast one reaches first the Monti della Laga (2,455 m), the Gran Sasso complex, and the Maiella massif (2,795 m). In the middle, there is a broader complex centered on the Velino massif (2,487 m). On the far side, there is lower range of mountains including the Monti Ernici, reaching only 2,000 m in height. Some important rivers arise in these mountains (e. g., the Tronto and the Aterno) and one, the Sagittario, runs through the large intermontane basins of L’Aquila and Sulmona, which are similar in character to those of Umbria and Tuscany further north and west. On the Adriatic flank of these mountains, the coast is bordered by a belt of clays, sands, and conglomerates.
World History
