*Introduction to the Sedimentary Geology, Genesis, and Evolution of the Pontine Plain in Relation… DOI: http://dx.doi.org/10.5772/intechopen.111683*

was surveyed for the 1:50,000 scale Geological Map of Italy (CARG Project) [18], provide insights into the caldera evolution. Colli Albani, a quiescent volcano, was active at approximately 600 ka. The eruptive products are consistently mafic (<50% SiO2); nevertheless, the morphology and dominant explosive eruptive style are like those of felsic calderas [19]. The volcano is a composite, containing multiple superposed edifices or lithosomes. The oldest edifice (Volcano Laziale (VL), ca. 600–350 ka) is a 1600 km2 plateau of low-aspect ignimbrites (VEI 5–7) with a central caldera. After the last large eruption (>50 km of deposits), forming the Villa Senni Eruption Unit ignimbrites at ca. 355 ka, two edifices were built within the caldera. The first is the horseshoe-shaped Tuscolano–Artemisio (TA) composite edifice (or lithosome), which

#### **Figure 13.**

*A composite stratigraphic column of the Colli Albani volcano (simplified after Giordano et al., 2006). The studied section (from Pozzolane Nere to Pozzolanelle) is emphasized with colors. B photograph of the studied section within the Imater quarry. Diagrams with contours are Schmidt polar nets (lower hemisphere) representing the density (red: Maximum data density) of extensional fracture poles measured in the studied volcanic units. The diagram with the cyclographic data is a Schmidt net (lower hemisphere) showing the attitude of subvertical N-striking strike-slip faults observed in the quarry exposure. Red dots along the cyclographic data are fault subhorizontal striae. C–D close-up photographs showing details from the exposure shown in B. In C, note the presence of fractures, particularly in the Tufo Lionato ignimbrite. E close-up photograph showing a N-striking fault surface with subhorizontal striae [16, 17].*

#### **Figure 14.**

*Cartoon showing the possible volcanological and magmatological evolution of the Colli Albani plumbing system. Here, the magma chamber and plumbing systems have been reconstructed with petrological, isotopic, and geochemical data and geological and geophysical interpretations of the geological and structural setting of the Alban Hills prevolcanic units. Xenoliths from the Alban Hills volcanic rocks along with information from deep wells drilled in the area allowed the reconstruction of the stratigraphy of the substratum of the volcano, whereas the thicknesses of the main geological units were derived from gravimetric and seismic data [14].*
