Search results for "Geomorphology"

Early warning thresholds for partially saturated slopes in volcanic ashes

2013

Rainfall-induced landslides in steep soil slopes of volcanic origin are a major threat to human lives and infrastructure. In the context of constructing early warning systems in regions where extensive data on landslide occurrences and associated rainfall are inexistent, physically-based tools offer the possibility to establish thresholds for measurable field quantities. In this paper, a combined finite element infinite slope model is presented to study the transient hydraulic response of volcanic ash slopes to a series of rainfall events and to estimate seasonal safety factors. Furthermore, analytical considerations of partially saturated infinite slopes are made to define capillary stress…

Tidal currents in the Malta - Sicily Channel from high-frequency radar observations

2015

Two years of sea surface current measurements acquired since August 2012 by High-Frequency SeaSonde radars over the relatively shallow shelf area dividing the Maltese Islands from Sicily (the Malta - Sicily Channel), are used to characterize the surface tidal currents in the region. Tidal currents are generally weak and concentrated in the semidiurnal and diurnal bands, barely exceeding 3cms-1 in the semidiurnal band (M2, S2), and below 6cms-1 in the diurnal band (K1, O1). In the middle part of the basin, the M2 currents oscillate along the main Channel axis; on the contrary the S2 oscillations are oriented along the energetic Atlantic Ionian Stream (AIS) flow. Diurnal tides have a more cir…

Sedimentation in a tropical, microtidal, wave-dominated coastal-plain estuary

1996

The Mono estuary is an infilled, microtidal estuary located on the wave-dominated Bight of Benin coast which is subject to very strong eastward longshore drift. The estuarine fill comprises a thick unit of lagoonal mud deposited in a ‘central basin’between upland fluvial deposits and estuary-mouth wave-tide deposits. This lagoonal fill is capped by organic-rich tidal flat mud. In addition to tidal flat mud, the superficial facies overlying the ‘central basin’fill include remnants of spits resting on transgressive/washover sand, an estuary-mouth association of beach, shoreface, flood-tidal delta and tidal inlet deposits, and a thin sheet of fluvial sediments deposited over tidal flat mud. Af…

A possible tsunami deposit around the Jurassic–Cretaceous boundary in the Boulonnais area (northern France)

2005

Abstract An unusual succession of facies locally deposited around the Jurassic–Cretaceous boundary in the Boulonnais (northern France) is attributed to a tsunami event by comparison with recent tsunami deposits. This sedimentary succession includes basal erosion with reworked lithified blocks, soft-sediment deformations, an erosional conglomerate overlain by wood fragments and clays containing continental and marine fossils in one setting and conglomerate with mixed fauna in an other setting. The tsunami probably affected the coast of the Boulonnais area of the London–Brabant Massif. The origin of the event is unknown. It was most probably triggered by an earthquake, but other origins such …

Pantelleria island (Strait of Sicily): volcanic history and geomorphological landscape

2017

Pantelleria is a volcanic island located in the Strait of Sicily, 95 km far from the Sicilian coastline and 67 km from Cape Bon (Tunisia). The volcanological history of the island begins approximately 324 ka BP and the last eruptive event was a submarine eruption that occurred on 1891 A.D. Eruptive activity was characterized by seven very intense explosive events, the latest being the Green Tuff (44 ka). They have all produced ignimbrite sheets that covered large sectors of the island. The landscape of the island mirrors the variety of the eruptive styles and their interplay with volcano-tectonics. The most evident geomorphological features are represented by: (i) the mantle-like distributi…

El Lahar Tinguiririca: su significado entre los Lahares chilenos

1982

The Tinguiririca lahar is an example of many similar landforms, which cover large surfaces 60th in andine valleys and the Chilean longitudinal depression. I t is smaller than other ones in Chile, but - at the same time - better conserved, offering good conditions for genetic, kinematic and geochronologic studies, respecting volcanic mudflows. From the genetic and kinematic point of view, the longitudinal lahar profile may be in two parts: a) An upper and middle accumulative area, with concave transverse profile; b) A low accumulative area; whose transverse profile is convexe. These two profiles could be explained by means of braking process in lateral parts, related to central parts, as a f…

2017

Abstract. The aim of this study is to present a framework that provides new ways to characterize the spatio-temporal variability of lateral exchanges for water flow and solute transport in a karst conduit network during flood events, treating both the diffusive wave equation and the advection–diffusion equation with the same mathematical approach, assuming uniform lateral flow and solute transport. A solution to the inverse problem for the advection–diffusion equations is then applied to data from two successive gauging stations to simulate flows and solute exchange dynamics after recharge. The study site is the karst conduit network of the Fourbanne aquifer in the French Jura Mountains, wh…

Des particules charbonneuses, t�moins des variations de l'�rosion chimique d'un bassin versant calcaire durant l'holoc�ne (bassin de chaillexon, doub…

1999

Matter fluxes result from chemical and mechanical weathering that vary as a function of climate, relief, lithology and human activities. The aim of this paper is to characterize chemical weathering variations in the past using coaly particles found in both the geological substratum and the Holocene lacustrine sediments of a calcareous basin (Chaillexon lake, Doubs, France). Results point out that chemical weathering was the predominant erosional process in the watershed, which may be due to the calcareous nature of the bedrock. The significant variability of this process relative to mechanical weathering during the Holocene period can be interpreted as a consequence of the development of th…

Effects of the 6th September 2002 earthquake: damage amplification in the south-eastern sector of Palermo explained by GIS technology

2009

During the 6th September 2002 earthquake the highest damage level in Palermo was observed in the SE sector.
 This is a recent urbanization area where reinforced concrete structures predominate. A detailed analysis of soil
 properties in Palermo was carried out by City-GIS to investigate a possible role of nearsurface geology on earthquake
 effects. City-GIS is a tool dedicated to natural hazard evaluation in urban areas. The availability of high
 density of well log data (stratigraphic and geotechnical) allowed a realistic modeling of surface geology and
 physical-mechanical properties that control the seismic response. In wide zones of the above mentioned sector
 of…

Evaporite karst in Italy: A review

2017

none 16 si Although outcropping rarely in Italy, evaporite (gypsum and anhydrite) karst has been described in detail since the early 20th century. Gypsum caves are now known from almost all Italian regions, but are mainly localised along the northern border of the Apennine chain (Emilia Romagna and Marche), Calabria, and Sicily, where the major outcrops occur. Recently, important caves have also been discovered in the underground gypsum mines in Piedmont. During the late 80s and 90s several multidisciplinary studies were carried out in many gypsum areas, resulting in a comprehensive overview, promoting further research in these special karst regions. More recent and detailed studies focused…