Search

The Colli Albani volcano has been active since c. 600 ka and is presently quiescent. Rock stratigraphy indicates that the activity of the volcano has undergone major changes in terms of eruption style, average eruption rate and location of active vents. The chemistry of the Colli Albani products is remarkably mafic, K-rich and silica undersaturated. Nevertheless, the volcano has experienced all types of eruption styles, from plinian explosive paroxysms, to milder strombolian and hawaiian eruptions, to effusive, including large- and small-scale phreatomagmatism. The first period of activity of the volcano is termed the ‘Vulcano Laziale’ period, and lasted from c. 600 ka to c. 355 ka. During this period, the volcanism was predominantly explosive, with an average eruption rate of 1 km3 ka21. At least seven intermediate- to large-volume ignimbrites (VEI 5–7) were erupted and emplaced over an area larger than 1600 km2, forming an extensive ignimbrite shield around the central, continuously forming c. 8 8 km2 caldera. The caldera complex and the ignimbrite shield are named the ‘Vulcano Laziale edifice’. The Vulcano Laziale edifice can in turn be subdivided into a lower ‘Pisolitic Tuffs succession’ (c. 600– 500 ka), in which ignimbrites are dominated by large-scale phreatomagmatism associated with the likely presence of an early caldera lake, and an overlying ‘Pozzolane Tuffs succession’, in which ignimbrites show a dominantly magmatic fragmentation style, probably in response to progressive exhaustion of the caldera lake. The typical succession of these mafic ignimbrites is composed of a sub-plinain to plinian basal scoria fall deposit covered by the main dark scoria and ash tabular ignimbrite sheet found as far as.30 km from the caldera rim and across ridges several hundreds metres in elevation, and is characterized by co-ignimbrite breccias at proximal locations. Major ignimbrites erupted with an average interval of c. 40 ka. After each paroxysmal ignimbrite eruption, volcanic activity was predominantly effusive to mild explosive, and was concentrated along peri-caldera fissure systems, forming continuous scoria cone and lava ridges, together with more explosive eruptions from intracaldera vents. The last major caldera-forming eruption of the Vulcano Laziale period occurred at c. 355 ka, emplacing the ignimbrites of the Villa Senni formation. Following this eruption, the complex Tuscolano-Artemisio peri- and extracaldera fissure system, predominantly composed of scoria cones and lavas, formed in response to the deflation of the caldera and peri-caldera area, together with formation of the intracaldera Faete stratovolcano. These edifices were emplaced between c. 355 and c. 180 ka, an interval termed the ‘Tuscolano–Artemisio–Faete period’. Although similar peri-caldera and intracaldera activity occurred earlier, that is, after each major caldera-forming eruption during the Vulcano Laziale period, the Tuscolano–Artemisio–Faete period was subject to a significant reduction in average eruption rate, by one order of magnitude, of 0.1 km3 ka21, which can be related to a consistent reduction in the deep recharging of the plumbing system, and suggesting why no further ignimbrite eruptions occurred after 355 ka. Peri-caldera activity began along the northern and eastern peri-caldera ring fractures (Tuscolano and Artemisio sections, respectively) and after c. 300 ka progressively migrated outwards to extracaldera positions (Pantano Borghese section) and to the western peri-caldera fractures (S. Maria delle Mole section). The activity of these latter fracture systems ended almost simultaneosly, together with that of the Faete intracaldera stratovolcano, between c. 280 and c. 250 ka. After 250 ka, activity migrated to the south (Monte Due Torri section). The most recent activity along this latter peri-caldera area interfingers (between c. 200 ka and c. 180 ka) with phreatomagmatic products, which instead became dominant in the most recent activity of the Colli Albani volcano. Beginning from c. 200 ka (Via dei Laghi period), the western section of the pericaldera area has been the site of repeated very small- to small-volume, maar-forming phreatomagmatic eruptions, which formed both monogenetic and polygenetic maars, collectively named the Via dei Laghi maar field. The most recent of these maars is the polygenetic Albano maar, which was formed after c. 70 ka by at least seven eruptions migrating along a NW–SE-trending, 3.5-km-long fracture. The last eruption of the maar occurred at ,23 ka. Subsequent phreatic activity occurred throughout the Holocene, with lahars originating from dramatic withdrawals of the deep maar lake, at least up to the Eneolithic time (6000–5000 years ago) and probably up to Roman times (fourth century BCE), when the Romans dug a tunnel drain to keep the lake at a constant low level. The Albano area is currently the site of volcanic gas emissions, ground uplift and periodic seismic swarms, which may indicate persistent activity of a magmatic body at depth.

This work presents the results from a multidisciplinary study carried out in the southern branch of the Larderello geothermal field (Travale-Montieri area) that is based on the integration of field data with information of the deeper structures as derived from interpretation of seismic reflection profiles and the P-T-t history of the metamorphic substratum as reconstructed from borehole data. Our data document that the structural and metamorphic signature of the metamorphic substratum is chiefly related to a prograde HT/LP metamorphic overprint, spanning in age from c. 2.8 to 0.7 Ma. The metamorphic climax was attained within the K-feldspar zone and equilibrated at P-T conditions of about 650°C (garnet-biotite thermometry) and 0.2 GPa (andalusite stability field). We interpret these new findings as the evidence of Pliocene-Pleistocene thermal metamorphism associated with multiple granite intrusions at shallow levels in the crust. These results (i) add strength to the interpretations emphasising the role of Neogene thermal metamorphism on the tectono-metamorphic signature of the basement rocks found at depth in the Larderello geothermal field; and (ii) provide insights on the thermal structures of the crustal section hosting the geothermal field and on the modes through which the long-lived positive thermal anomaly operated in Southern Tuscany.

This work presents the results of a multidiscipinary study carried out in the southern branch of the Larderello geothermal field (Travale – Montieri area), which was based on the integration of field data with information on the deeper structures as derived from interpretation of seismic reflection profiles and the P – T – t history of the metamorphic substratum as reconstructed from borehole data. Our data document that the structural and metamorphic signature of the metamorphic substratum is chiefly related to a prograde HT – LP metamorphic overprint, ranging in age from c. 2.8 to 0.7 Ma. The metamorphic climax was attained within the K-feldspar zone and equilibrated at P – T conditions of about 0.2 GPa and 650 8C. We interpret these new findings as evidence of Pliocene – Pleistocene thermal metamorphism associated with multiple granite intrusions at shallow levels in the crust. These results (1) add strength to the interpretations emphasizing the contribution of Neogene thermal metamorphism to the tectonometamorphic signature of the basement rocks found at depth in the Larderello geothermal field, and (2) provide insights on the thermal structures of the crustal section hosting the geothermal field and on the modes through which the long-lived positive thermal anomaly operated in southern Tuscany

An integrated structural, anisotropy of magnetic susceptibility (AMS) and paleomagnetic study was carried out on Plio-Pleistocene sedimentary basins in eastern Sicily. These basins belong to three main tectonic domains: the Tyrrhenian hinterland domain, the Catania foredeep domain, and the Hyblean foreland domain. We sampled 329 oriented samples from 25 sites in selected areas from the different tectonic domains. The AMS is typical for weakly deformed sediments, with a magnetic foliation sub-parallel to the bedding plane, and a well-defined magnetic lineation. The orientation of the magnetic lineation is strongly controlled by the main tectonic deformation recorded in the basins. Structural and AMS data define a transition fromNW–SE extension in the Tyrrhenian hinterland domain, to E–Wcompression in the Catania foredeep domain, to E–W extension in the Hyblean foreland domain, respectively. Reliable paleomagnetic results have been obtained in 12 out of 25 sampled sites. Data show that no significant rotations occurred in any of the studied basins at least since the middle Pleistocene. These results allow us to define an upper limit to the large rotations about vertical axes that have been previously found in the Calabria and Sicily regions.

Many characteristics of the natural environment where Rome has developed for the last 3000 years have played a major positive role in promoting the excellence of Rome as a political, economic and administrative power, the so-called Caput Mundi of the ancient world. Aside from anthropological and ethnological factors, the positive geological and geomorphological setting of the future site of Rome favoured the settlement of several archaic villages along the left bank of the Tiber River since the beginning of the third millennium B.P. The sites were strategically located, being characterized by proximity to the river, over isolated tufaceous cliffs dominating the alluvial plain, the abundance of spring water and the wide availability of stones and natural building material that promoted a quick technological development of building and infrastuctural services to the growing town. The main natural factors playing a strategic role in the development of the long-lived city of Rome have been: - The geomorphology of the distal volcanic plateau - Tiber river network and the related alluvial deposits - The surface geology and its natural materials - The hydrogeology and microclimatic constraints

Some deep wells (1400–3000 m) have been drilled into the volcanic system of the Sabatini Mts., north of Rome, in search of high enthalpy geothermal fluids. Baccano caldera has formed over a carbonate structural high with a Quaternary volcanic cover, on the inside of a large graben that developed from the Upper Miocene and is characterized by a strong positive thermal anomaly. A spatially irregular Neogenic neoautochthon cycle, an allochthonous flysch complex (‘Sicilidi’ s.l.) and a Meso-Cenozoic ‘basal’ carbonate sequence were recognized in the sediments crossed by these wells below the volcanic cover. The observed structural setting can be correlated to that of analogous outcropping structures (Mt. Soratte) and shows a tensional tectonic phase overlying an older, mainly compressional phase. The stratigraphic and mineralogic analyses revealed important differences in the Trias, which is mainly calcareous in the western sector of the area and anhydritic in the eastern: the two facies at present seem to be tectonically brought closer to one another. The isotopic analyses all show values comparable to those of the sedimentary carbonate host rocks, suggesting limited circulation of the hydrothermal fluids. 18 O/ 16 O analyses on specimens in the most restrictive locations next to interfaces show a relatively larger extent of isotopic exchange with aqueous fluids. Fluid circulation, which is mainly extinct, seems to belong to a closed system. Two types of circulation have been recognized: the first of these is connected to the stratigraphic discontinuities (especially at the contact between the allochthonous flysch complex and the basal carbonate sequence) and is characterized by mainly K-feldspar and Sulphide-Sulphate mineralizations; the second circulation is tied to the fracture systems and is particularly widespread in the pyroclastic cover where it appears in the form of sulphate- and carbonate-rich dykes. This system seems to have undergone a mixing with surface waters.

The characteristics of wind erosion as the dominant process involved in eroding crater ejecta deposits on Mars are studied. Present-day crater formation in mid to high latitudes involves impact into some thickness of aeolian debris, while impact in the equatorial zone is more likely to involve target materials consisting of coarse-grained aeolian lag deposits or even bedrock. Latitudinal variation dominates differences in ejecta emplacement mechanisms and probably differences in patterns of wind erosion of ejecta and surrounding intercrater materials. Escarpments develop as the deposits are eroded back toward crater rims. Erosion only takes places at escarpment edges where surface roughness may be low enough to allow particle entrainment. Preferential preservation of ejecta emplaced in thick debris may occur. An empirical model developed for wind erosion of ejecta deposits in nonmantled areas suggests that removal of ejecta materials on the average is exceedingly slow. Results suggest high differential aeolian erosion rates that are a function of both grain sizes and large-scale surface roughness.

Analytical investigations were carried out on alteration crusts of "Pietra d'Istria" used for the construction of "Palazzo Papadopoli" in Venice. The chemical and mineralogical analyses of the microstructure showed that alteration process in mainly caused by the transformation of calcium carbonate into calcium sulphate and that the greatest damages are due to the subsequent detaching of sulphatic crusts according to a weakness surface. The isotopic analyses showed that sulphur present in the crust is mainly derived from the combustion of hydrocarbons. The investigations on the climatic conditions showed the meaningful importance of the climate parameters on described alterations.

New results for the Colli Albani volcano (Roma, Italy) surveyed for the Geological Map of Italy at 1:50,000 scale (CARG Project), integrated with previous data, provide insights on caldera evolution. The Colli Albani, a quiescent volcano, became active at ∼600 ka. Eruptive compositions are consistently mafic ( 50 km 3 deposits), forming the Villa Senni Eruption Unit ignimbrites at ca. 355 ka, two edifices were built within the caldera: (1) The horseshoe-shaped Tuscolano-Artemisio (TA) composite edifice (or lithosome) consists of coalescing, peri-caldera, fissure-related scoriae cones interbedded with lava flows; the fissure system forms two segments controlled by regional fractures; (2) The steep-sided Faete stratovolcano (949 m a.s.l.) filled the caldera. The TA and Faete lithosomes partly interfinger and were emplaced at ∼350–260 ka. Their products indicate reduced eruption rates relative to the VL period and a change to effusive and mildly explosive eruptions. The most recent and still active phase of phreatomagmatic activity formed overlapping maars and tuff cones along the western and northern slopes of the volcano, collectively named Via dei Laghi composite lithosome. The Colli Albani caldera is poly-phase: (1) a piecemeal caldera is associated with large volume ignimbrites of the VL edifice; the present shape of the caldera is related to the Villa Senni eruption; 2) the TA composite edifice, erupted from peripheral-caldera fissures, is unrelated to explosive phases of caldera collapse: the TA final products cover a morphologically stable caldera wall. The peripheral fractures feeding the TA composite edifice are interpreted as volcano-tectonic structures activated during the late stage downsag of the caldera. Reduced eruption rates during the TA and the Faete stages (10 −1 km 3 /1 ka respect to >10 0 km 3 /1 ka for the VL edifice) suggest a reduced recharge of the magma chamber that may have induced prolonged deflation and downsagging of the caldera floor and the opening of outward dipping peripheral fractures. By this interpretation, the TA edifice represents the surface expression of ring dykes at depth. The absence of similar fissure-structures along the western caldera rim may relate to the deep geometry of the ring-faults dipping inward in those areas and therefore not favourably oriented for magma intrusion during a period of general subsidence. By contrast, the following and still active phreatomagmatic phase, that has emplaced the Via dei Laghi composite edifice, is located right on the western side of the caldera, and may therefore relate to resurgent conditions. Classical petrological and PERs (Pearce Elements Ratios) analyses indicate that lavas are co-genetic and show a differentiation trend up through stratigraphy driven by

[1] A century after the catastrophic event, the sources of the 1908 Messina, Southern Italy, earthquake and tsunami, which caused at least 60,000 deaths, remain uncertain. Through a simple backward ray-tracing method, we convert the tsunami travel-time data reported in a 100-years-old paper into distances and find that the sources of the earthquake and tsunami are different. Overturning a long-held assumption, reconsideration of the available tsunami, bathymetric, seismic, and seismological data indicates that the tsunami was generated by an underwater landslide.

ARTICLE I NFO The depositional and erosional history of the Lapis Tiburtinus endogenic travertine located circa 25 km to the east of Rome, Central Italy, near the Colli Albani quiescent volcano, is interpreted through three-dimensional stratigraphy and uranium-series geochronology. Analyses of large exposures located in active quarries and of cores obtained from 114 industrial wells reveal that the travertine deposit is about 20 km 2 wide and 60 m thick on average. The travertine thickness is over 85 m toward its western N-S-elongated side, where thermal springs and large sinkholes occur aligned over a seismically-active N-striking fault. The travertine age was calculated using the U/Th isochron method. Results constrain the onset and conclusion of travertine deposition at about 115 and 30 ka, respectively. The three-dimensional study of the travertine shows that this deposit is characterized by a succession of depositional benches grown in an aggradational fashion. The benches are separated by five main erosional surfaces, which are associated with paleosols, conglomerates, and karstic features. This evidence shows that the travertine evolution was mostly controlled by water table fluctuations. Chronological correlations between travertine evolution and paleoclimate indicators suggest that the travertine deposition was partly modulated by climate conditions. Other influencing factors may have been fault-related deformation and volcanic events.

Integrated petrological and structural investigations of eclogites from the eclogite zone of the Voltri Massif (Ligurian Alps) have been used to reconstruct a complete Alpine P-T deformation path from burial by subduction to subsequent exhumation. The early metamorphic evolution of the eclogites has been unravelled by correlating garnet zonation trends with the chemical variations in inclusions found in the different garnet domains. Garnet in massive eclogites displays typical growth zoning, whereas garnet in foliated eclogites shows rim-ward resorption, likely related to re-equilibration during retrogressive evolution. Garnet inclusions are distinctly different from core to rim, consisting primarily of Ca-, Na/Ca-amphibole, epidote, paragonite and talc in garnet cores and of clinopyroxene ± talc in the outer garnet domains. Quantitative thermobarometry on the inclusion assemblages in the garnet cores defines an initial greenschist-to-amphibolite facies metamorphic stage (M1 stage) at c. 450-500 °C and 5-8 kbar. Coexistence of omphacite + talc + katophorite inclusion assemblage in the outer garnet domains indicate c. 550 °C and 20 kbar, conditions which were considered as minimum P-T estimates for the M2 eclogitic stage. The early phase of retrograde reactions is polyphase and equilibrated under epidote-blueschist facies (M3 stage), characterized by the development of composite reaction textures (garnet necklaces and fluid-assisted Na-amphibole-bearing symplectites) produced at the expense of the primary M2 garnet-clinopyroxene assemblage. The blueschist retrogression is contemporaneous with the development of a penetrative deformation (D3) that resulted in a non-coaxial fabric, with dominant top-to-the-N sense of shear during rock exhumation. All of that is overprinted by a texturally teamphibolite/greenschist facies assemblages (M4 & M5 stages), which are not associated with a penetrative structural fabric. The combined P-T deformation data are consistent with an overall counter-clockwise path, from the greenschist/ amphibolite, through the eclogite, the blueschist to the greenschist facies. These new results provide insights into the dynamic evolution of the Tertiary oceanic subduction processes leading to the building up of the Alpine orogen and the mechanisms involved in the exhumation of its high-pressure roots. © 2005 Blackwell Publishing Ltd.