1,721,071 research outputs found
Landscapes and landforms connected with anthropogenic processes over three millennia. The Servian Walls at the Esquiline Hill (Rome, Italy)
No full textUrban centers are characterized by scarcity of outcrops. At the urban-planning level, the examination of results from previous geological surveys and studies may provide sufficient data for an accurate subsurficial geologic modeling. In addition, in historical centers a GIS-based multitemporal analysis of historical and archaeological maps, and the examination of archive documents and reports, may be effective especially for the detection of geomorphic changes. The application of such a methodology at the Esquiline Hill allowed to detect the three-millennia-long landscape-modification main phases connected with the construction of the oldest city walls. They include a unique sequence of anthropogenic aggradational and erosional phases that shaped many anthropogenic landforms, presently visible and invisible, or vanished. Among them, the anthropogenic hill Monte della Giustizia, vanished since the end of the 19th century CE when it was erased, and the military moat, excavated in the 6th century BCE and enlarged in the 4th century BCE, finally backfilled in the 4th century CE, since then invisible. These geomorphic changes lastly output a flat leveled landscape similar to the previous volcanic plateau. Results suggest that the “geomorphological convergence,” that is, the resemblance between natural landforms created by different morphogenetic processes, also exists between natural and artificial landforms. Moreover, the study evidenced relationships between landforms and the damage status of historical masonry buildings, specifically connected with their foundation over thick layers of geotechnically-weak anthropogenic deposits. This advises that the multidisciplinary approach may also provide risk managers additional geological features to be evaluated as potential sources of natural hazard
Geomorphology of the historic centre of the Urbs (Rome, Italy)
Full text linkBased on long-lasting multidisciplinary and multitemporal investigations, in 2016 the first geomorphological map of the central area of Rome was presented. It introduced innovative solutions for cartographic restitution of urban landforms. Under this work, the urban geomorphological analysis delved deeper, because the study focused on the smaller area of the Urbs, the ancient city centre that has been modified by human activities over millennia. The main goal of the new study was to verify if the 1:5000 scale survey could allow to improve the legend symbols, in order to better represent landforms from natural and anthropogenic processes in urban environment. Since the map scale was doubled compared with the previous and consequently the map area available was four times bigger, we were able to provide much more details. Moreover, results better highlighted the applicative significance of urban geomorphological maps as complementary tool for the assessment of natural hazards and risks
Geodiversity of the Umbria region (central Italy): a GIS–based quantitative index.
No full textThe measure of natural range related to geological bedrock, landforms and geomorphological processes is the
necessary starting point to geodiversity evaluation.
Geodiversity plays a strategic role in landscape management. Whereas geotourism and geosites are identified as
a driving power for the scientific and economic promotion of an area, the geodiversity knowledge is required for
a complete and accurate research. For example, high values of this abiotic parameter identify and support the
foundation of geoparks. According to this perspective, the geodiversity is the unifying factor for these areas of
interest.
While a subjective and qualitative approach may be adequate for geosites definition, identification and cultural
promotion, the geodiversity concept needs a different evaluation method. A quantitative procedure allows
achieving an objective and repeatable process exportable in different geographic units. Geographical Information
Systems and spatial analysis techniques are the base to quantitative evaluation involving topographic, geological
and geomorphological data. Therefore, the assessment of a numerical index derived from the overlay of spatial
parameters can be conveniently computed in GIS environment.
In this study, a geodiversity index is proposed where geological, geomorphological and landcover factors deriving
mainly from maps and field survey; topographic ones are employed from DEM and remote sensed data. Each
abiotic parameter is modelled in a grid format; focal functions do provide neighbourhood analysis and computing
variety statistics. A particular extent is dedicated to topographic information and terrain roughness, that are
strictly related to efficiency of geomorphological processes and generally corresponding to the abiotic components
variability.
The study area is located in central Italy and is characterized by a well known natural heritage. Thirty-seven
geosites are detected in the Umbria region, where seven regional and one natural parks are present. All the
area shows a strong correlation between the geological setting and the relief energy associated to topography
assessment. Three main outcrop complexes are present: a fluvial lacustrine, where the lowest slope values and
plain area are widespread; a terrigenous one, with a medium slope value; and a calcareous complex corresponding
to the mountain areas and the highest amplitude of relief. This partition matches different geomorphological
processes and landforms, ensuring a widespread distribution of geodiversity.
The final map is a digital data that localizes areas with, respectively, null or minimum, medium, and high
geodiversity values. The highest class overlaps to geosites areas, to high values of amplitude of relief and where
the geomorphological processes are more effective and various. This confirms the method accuracy.
The results obtained represent an important advancement in geodiversity research and a significant instrument for
economic development and conservation management
Geomorphology and tectonics in the Roccamonfina Volcano (Campania-Central Italy)
No full textThis paper covers part of an extensive research program on the morphological and structural conditions of different volcanic complexes of Central Italy. The aim is to single out the relationships among the present landforms, their structural arrangement and the volcanic history of these areas. The Roccamonfina volcano is examined here; it belongs to the alkali-potassic province of Central Italy and was active between 650 ka BP and up to 50 ka BP. The morphological characteristics were examined through field survey and aerial photointerpretation. Successively all the morphological elements that might provide evidence for tectonic deformations were identified; the significant alignments of such elements and volcanic forms as well have been considered to be controlled by the surface effects of deep structural setting. Moreover the statistical analysis of stream directions have shown some preferential orientations indicating tectonic control. The analysis of the parameters amplitude of relief (Ar) and drainage density (D) allowed the identification of uplifted or lowered areas with respect to the surrounding ones. Morphological data integrated with volcanological and geological ones allowed the geomorphological evolution of the study area to be reconstructed. This evolution was strongly influenced by tectonic dislocations. NW-SE and NE-SW oriented. However, the surface effects of N-S and E-W trending tectonic directions are also discernible; these dislocations have cut the volcanic products and have conditioned the emplacement of lower order streams, thus testifying the important role they played in the very recent geomorphological evolution of the Roccamonfina area
Il Monte della Giustizia all'Esquilino (Roma)
No full textIl Monte della Giustizia rappresenta un interes- sante esempio di rilievo antropico, risultato di ripetuti e talora concorrenti episodi di scavo e deposito antropico in area ur- bana, succedutisi in oltre due millenni di storia. La sua presenza è stata tuttavia cancellata dalla demolizione pianificata per esi- genze urbanistiche e posta in atto nel giro di pochi decenni. Le testimonianze della sua esistenza provengono dalla cartografia storica e da fonti iconografiche, mentre minori sono le relazioni o gli articoli di valenza geologica, tenuto conto che la sua com- pleta demolizione è avvenuta ben prima che la geologia urbana e la conservazione dei siti di rilevanza storico-culturale assu- messero rilevanza. Tuttavia, alcuni contributi anche di tipo ar- cheologico sono risultati utili per gli scopi geologici. L’analisi multitemporale ed interdisciplinare dei suddetti dati ha per- messo di ricostruire le fasi salienti della sua costruzione e de- molizione, le dimensioni e caratteristiche del rilievo che nel suo complesso sembra corrispondere all’antico toponimo del Monte Superagio, poi denominato Monte della Giustizia
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Denudation processes in the drainage basins of Fiume Sinello and morphological dynamics of the river delta (Abruzzo - Central Italy).
No full textGeomorphological classification of the landscape in urban areas. Hints from some study cases in Italy
No full textUrban geomorphology is a recent topic and its theory and practice require continuous updates. However, few studies have focused on issues specifically connected with the cartographic representation of geomorphological processes and landforms in urban environments, with the aim of reconstructing and clarifying the original physical landscape. Recent studies conducted in Italian cities have tried to propose new strategies for detecting and mapping human induced modifications to the topography, and anthropogenic landform classification has been recently deepened in the revised Italian national guidelines for geomorphological mapping, proposed by AIGeo and ISPRA. In this work, natural landforms modified by man and new artificial landforms are explored and compared in three Italian cities: Genoa, Rome and Perugia. In these urban areas, human activities have remodeled the topographic surface and become the most important landscape moulder. Many reliefs have been erased, whereas thick layers of anthropogenic deposits covered most of the natural landforms, with the result, for example, of hiding or greatly modifying the natural drainage network. Geomorphological studies in urban environments allow the reconstruction of the physical landscape before human modifications and the implementation of innovative methodological tools, and an effective legend to represent the urban landforms and their evolution over time
Entità dei processi di denudazione e variazioni morfologiche recenti nell’area di Radicofani (Toscana meridionale, Italia).
No full textThe present work is part of a wider research project conducted over the past two decades by the Dipartimento di Scienze della Terra of the University of Rome “La Sapienza”, with aim of studing the recent geomorphological evolution and morphodynamic aspects of some areas in central and southern Apennines. The goal of the present research is (1) to analyse in detail what are the main erosion processes acting on hillslopes, and (2) to estimate their relative rates. This paper presents the results of geomorphological investigation related to the Radicofani area characterized by intense morphogenetic processes and morphological change recorded in the past 50 years. The examined area, situated in the Tuscan Preapennine, near Siena, extends for about 100 km2 around the town of Radicofani close to the watershed of Orcia and Paglia rivers. The Pliocene marine claystones outcropping in this area have been uplifted during the Quaternary to several hundreds of meters up sea-level, and they are now suffering particularly intense erosion, lending to considerable badland formation. The tectonic history for this area is representative of the general history of orogenesis in the northern Apennines. Cretaceous to early Oligocene deposition occurred in a compressive foreland as the Tuscan and Ligurian Thrust sheets verged eastward in a large, subaqueous accretionary wedge. Emergence of the wedge in the Miocene was accompanied by extensional faults and formation of local graben. These graben filled with marine and terrestrial deposits. More recently, in the Quaternary, there has be regional arching of the Apennines, perhaps locally influenced by volcanism, to raise Pliocene marine deposits far above sea level. These deposits upl now outcrop at 750 meters above sea-level and show, in some cases, a clear stratification with strike about N-S and dip direction about E-ENE, a few degrees steep; in the western part of the area, the stratification is nearly horizontal or it has a western dip direction. Jointing follows a few preferential directions that seem to condition the main valley downcutting and the intense denudational processes. The analysis of landforms, surface deposits and morphogenetic processes of the study area was carried out through a detailed field survey, and compiled on a Geomorphological Map at a scale of 1:10.000 ( enclosed). The survey was systematically carried out for sixteen years (1988-2004). It allowed to gather detailed information about active morphological dynamics and evidence that the area is characterised by intense short-term morphological changes. In order to cast these data in a long-term context, an aerial-photograph interpretation analysis was made using the aerial photos of the GAI flight of 1954 and the EIRA flight of 1976; thus geomorphological characteristic of the study area was reconstructed for those years. The comparison of these situations with the one illustrating the present landscape, quantifies the morphological evolution of the area in the last 50 years . The geomorphological study has been completed by morphodinamic analysis: direct and indirect measurements have been carried out in order to have quantitative information on the erosion rate in the examined area. For direct measurements of the erosion simple metallic instruments have been used, placed in two chosen sample-areas with a badland sharp morphology. These areas represent a natural laboratory, where short-term evolution and seasonal change of landforms generated by fluvial and hillslope processes could be accurately studied, and where erosion rate could be directly measured. The metallic instruments (stakes and disks) have been placed in significant zones , but poorly accessible in order to avoid tampering. They have been used as datum points for accurate and continuous measuring, to collect a large series of data. Direct measurements have been integrated with indirect measurements carried out on the basis of the aerophotographic analysis. For a sample-area, digital elevation models (DEM), obtained using a digital video plotter (DVP, Leica) and the aerial phothographs of EIRA flight (1976) and Tuscany Region flight (1994), have been constructed. The comparison between 1976 and 1994 DEM allows to obtain a “difference map”, showing the variation of topographic surface in nineteen years and then to calculate the mean erosion rate in the chosen area. Results of geomorphological analysis evidence that important denudation processes are active in most of the studied area. Erosive processes due to channelized flow (which are responsible for the several deep valley downcutting), to sheetwash (responsible for the frequent badland and “biancana” morphologies), and to gravity (cause of continuous and frequent mass movements, both superficial and deep, active also on gentle slopes) seem to be the particularly intense. The 1988-2004 field survey has proved that processes and landforms in the sample area are involved in continuous and rapid short-term changes. The comparison of the 1954 and 1976 landscapes with the 2004 one, evidence many macroscopic morphological differences. The “biancana” areas have been reduced, by the bulldozer working over the last 50 years (especially during the 60s and in the 70s). These areas now occupy only 30% of their previous 1954 surface. “Calanchi” badlands have been less affected by human activity, because of their greater steepness, while have been mainly modified by natural causes. “Calanchi” badlands intensely shaped by runoff waters in 1954, with a characteristic network of deep incisions, steep slopes and sharp ridge-lines, seem to have today a less sharp morphology , due to an increasing impact of gravitative movements on the morphosculptural evolution. Data obtained from direct field measurements of denudational processes evidence that the mean values of erosion rate due to sheetwash range from 1,5-2 cm/year on “biancana” badland areas to 2-3 cm/year on “calanchi” badland slopes. For these slopes analyses show that the value of erosion rate increase up to 6 – 7 cm/year as a consequence of very intense mass movements . Indirect measurements confirm direct ones, shoving mean erosion rate values of about 5,5 cm/year in the above mentioned nineteen years term. KEY WORDS: Erosion, Badlands, Morphodynamics, Tuscany, Italy
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