1,721,018 research outputs found
I fenomeni franosi: aspetti geomorfologici, metodi di studio e distribuzione in Italia
No full textVengono discusse le complesse problematiche legate agli aspetti geomorfologici, ai metodi di studio e alla distribuzione in Italia dei fenomeni franosi
Part 3: The Sila Massif high-standing plateau and the terrace orders in the ionian coastal belt.
No full textSi tratta di una guida ad una escursione del terzo convegno RETREA
Some considerations about seismic geomorphology and paleoseismology.
No full textSeismic geomorphology studies landforms which developed in connection with earthquakes. Among them, two different end members may be distinguished: 1) seismo-tectonic landforms, including surface faults and fractures, land uplift and subsidence at different scales, surface bulges, elongate ridges, and any other permanent ground deformations directly related to tectonic stress, and 2) seismo-gravitational landforms, such as landslides, deep-seated gravitational slope deformations, sinkholes, and fissures due to sediment compaction or liquefaction and sand blows, connected with both seismic shaking and gravitational stress. A clear-cut distinction between the two categories of landforms is not always easy to make (and in many instances not really useful), while there are, in many cases, ground effects that might be (and should be) considered as simultaneous combinations of seismo-tectonic and seismo-gravitational processes. This applies especially to surface fracturing and faulting which could be the combined result of tectonic stress, stress produced by seismic shaking, and gravitational stress. The objective of this paper is to review selected case histories mainly from Italy and the Mediterranean region, in order to show the importance of a comprehensive study of earthquake-generated landforms for understanding the seismicity level of the area under investigation. We argue that in earthquake prone areas, seismic landforms often constitute typical patterns (seismic landscapes) whose recognition, mapping and paleoseismological analysis may help in the evaluation of seismic hazard
Morphometry as a tool to investigate the tectonic influence on landscape evolution: the example of northern Calabria (southern Italy).
No full textIn active tectonic landscapes, topography is shaped by the interactions of tectonic activity that uplift and deform rocks and geomorphic processes that erode and unroof rocks. So in active orogens, the production of topography, that reports an uplift rate equal or higher than erosion rate, is an expression of plate convergence and of its interaction with erosional and depositional processes(Hovius, 2000; Willett and others, 2001). The study of uplift is a way to add important information to the comprehension of the mechanisms that build up mountain chains. In the Italian Apennines, the topographic growth of the range was slow during the phase of major crustal shortening (Miocene-Pliocene), but accelerated significantly in the Quaternary, when it was already dominated by extension Such disparate rates of rock uplift above sea level should influence the development of peculiar landforms. We have investigated the geomorphic expression of active tectonics in northern Calabria (southern Italy). Here the Apennines are a narrow, rugged peninsula, comprises pre-Alpine plutonic and metamorphic rocks, continental and oceanic metamorphic rocks overlying tectonically Mesozoic carbonates and flysch .Low-standing extensional basins surrounding the relief (Catena Costiera and Sila Massif) are filled by several upper Tortonian–Holocene depositional sequences made up of poorly consolidated marine and fluvial conglomerate, sand, and clay.We examined the tectonic geomorphology of a transect across northern Calabria, focusing on the general morphometry, drainage patterns, and river longitudinal profiles. Using several methods of map and DEM-based topographic analyses, the strong tectonic influence on the geomorphology and landscape evolution has been characterized.The collected data are consistent with a landscape dominated by extensional tectonics, following regional relative base level fall (rock and surface uplift). The overall drainage pattern for the study area argues for streams that must adjust to local extensional structures (evidenced by several knickpoints on stream long profiles, high SL index values) and to a recent strong uplift (convex general shape of stream long profiles, high residual relief). In particular, they compete with each other to integrate into the Sila Massif interior, where a high-standing plateau is characterized by gentle upland surface. A similar rolling landscape is located also on top of Catena Costiera, although its dimension is much less. Six cross sections provide a common frame of reference for comparing data extracted from the topographic analysis. Moreover two swath profiles, including maximum, minimun, mean and residual elevations underline again the influence of local extension and regional uplift on the present topographic setting.The comparison of the morphometry data with the field observation of a gentle upland surface of low local relief and of five terrace orders on the Ionian coast (0.6 mm/yr rates of coastline emergence in the last 330.000 years; Gliozzi, 1988; Molin et al., 2002), confirms the broad uplift of the area. These results speak to a paleo-landscape less rugged than the modern relief indicating a previous slow uplift that allowed the emergence of at least part of the study area before Quaternary. At the end of lower Pleistocene, a strong acceleration of the uplift rate generated the present relief isolating the relics of the old landscape on the Catena Costiera top and on the Sila Massif pla
Object-Oriented Mapping as a Tool for the Assessment of Landslide Hazard in Higly Urbanized Areas
No full textThe assessment and mitigation of landslide risk affecting hillslopes in highly urbanized and infrastructured environments are often problematic due to the inadequacy of the traditional approach based on landslide inventories and the absence of a shared language between the different scientific-technical operators (geologists, engineers, architects, environmentalists, economists, jurists) and recurrent understanding problems with policymakers, stakeholders, and property owners. Therefore, innovative technologies and working procedures are required to address these problems. In this context, the European INSPIRE Directive and the Italian national Catalog of Territorial Data with the related Geo-Topographic DB provide positive responses in terms of data standardization and transdisciplinary interoperability. On the other hand, the application of the object- oriented geomorphological mapping of landslides and, even more, the recently proposed Landslide Object-Oriented Model (LOOM) make it possible to develop a more thorough approach to assess the spatial and temporal relationships between landslides and affected slopes. Following the above perspective, the InterUniversity Research Center for Prevision and Prevention of Great Risks (C.U.G.RI.) produced the LOOM-based “eventory” of landslides over a sector of the Tyrrhenian coastal belt, northwest of Salerno city, in the framework of a multi-disciplinary investigation project launched by the Campania Regional Administration to assess the landslide risk. The quantitative assessment of the geomorphological expert-judgment procedures has been carried out exploiting morphometric indexes: the Topographic Position Index (TPI) for automatic slope features recognition, and the Slope-Area plots for surficial process domains. Furthermore, the application of the INSPIRE, and related Italian National Geo- Topographic DB standards allowed transdisciplinary interaction between scientists, technicians, and managers. Such proposal can support the risk management procedure, adding in the Value Judgement and Risk Tolerance Criteria simplicity and effective interoperability in trans-disciplinary frameworks
The topographic analysis as a tool to reconstruct the recent evolution of Elba Island: a preliminary study
No full textElba, the main island of the Arcipelago Toscano (Tuscany, Italy), is a fragment of the Apennines. It is structurally characterized by the overthrusting of several tectonic units, made of sedimentary rocks (Carboniferous to Eocene) and oceanic crust (Cretaceus), partially affected by metamorphism. Since Miocene, the island, together with the Tuscany area, has been affected by the magmatic activity accompanying the Tyrrhenian basin extension. In particular normal faults controlled the emplacements of igneous intrusions (the Elba plutons of Mt. Capanne and Porto Azzurro) in late Miocene. In this framework, we carried out the topographic analysis of the island, focusing on two main topics: stream long profiles and topographic features. Although stream long profiles generally show a concave-up shape, most of them are relatively straight and some are convex. Moreover, they also show several knickpoints and knickzones, that appear not related to bedrock lithology changes, suggesting that they are still adjusting their course in response to recent uplift. By analysing the topography of Elba, we found out several low sloping (>15°) surfaces, mostly placed on interfluves, at elevations ranging between 15 m and 700 m a.s.l. Marine deposits lay on the low slope surfaces up to an elevation of 120 m. According to correlation to the nearby coastal belt of Tuscany, where similar deposits have been referred to the Middle-Upper Pleistocene, it seems possible to assign the same ages to the Elba deposits. The sequence of the upper surfaces suggests the occurrence of a previous uplifting. On the basis of the collected data, we could conclude that the Elba island has been uplifted at least since the Middle Pleistocene, testifying its involvement in the general Quaternary arching of the Apennines (maximum rate ~1 mm), even if at a much less rate (~0.2-0.1 mm/yr)
Inquadramento Geologico Regionale, in "Guida all’escursione", Convegno "Rilevamento Geomorfologico di Terreno e da Remote Sensing, Trattamento dei Dati tramite GIS per la Gestione del Terrritorio e la Mitigazione dei Rischi Geo-Ambientali"
No full textBreve sintesi geologica dell'area interessata dall'escursione sul terreno organizzata dal convegno
River channel dynamics in the contact area between the Romanian Plain and the Curvature Subcarpathians
No full textHolocene climate phases from buried soils in Tigray (northern Ethiopia): comparison with lake level fluctuations in the Main Ethiopian Rift
No full textStratigraphic analysis of alluvial/colluvial sequences and 14C dating have been used as proxies for Holocene climate changes in the highlands of Tigray (northern Ethiopia). The studied records show alternations of buried soils and peaty' clayey sediments, pointing to wet, stabilization phases, and organic-free colluvium layers resulting from the abrupt occurrence of dry-climate episodes. The 14C dates, mostly unpublished, cluster in the 11,090-9915, 9465-9135, 8450-7330, 6720-3635, 2710-2345, and 1265-790 cal yr B.P. time spans. Evidence of subsequent pedogenesis is lacking in the area, apart from a buried humified horizon dated at 300 +- 60 14C yr B.P. (460-295 cal yr B.P.).Both the timing and the pattern of Tigray paleoclimatic events fit the corresponding framework, based on lake level changes, previously mplemented for the Main Rift Valley. These findings give further support for arguing that the forcing mechanisms of the wet/dry fluctuations during the Holocene were effective over a large scale
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