Megadeslizamientos en las Islas Canarias

[ES] Los deslizamientos gravitatorios implicando volúmenes relativamente reducidos (millones de m3) son muy frecuentes, no así los que afectan a decenas, centenares e incluso miles de km3. Estos deslizamientos gigantes o megadeslizamientos son especialmente importantes y frecuentes en las islas oceánicas, particularmente en sus primeras etapas de desarrollo en escudo. Fueron descubiertos en las Islas Hawaii, donde alcanzan volúmenes ?prodigiosos? de miles de km3, pero es en las Canarias donde, a pesar de su menor volumen, son particularmente espectaculares y donde han sido mejor estudiados, tanto en sus etapas pre- y post-colapso en tierra, como las características y extensión de sus depósitos de avalancha en los fondos marinos. Los megadeslizamientos no sólo son procesos muy importantes en el desarrollo de las islas oceánicas y en sus riesgos naturales, sino que influyen en su variabilidad petrológica y aportan importantes recursos paisajísticos en forma de espectaculares valles y calderas

La erupción submarina de 2011-12 en El Hierro (Islas Canarias): cronología de eventos y gestión de la crisis

VIII Congreso geológico de España, Oviedo, 17-19 julio 2012

Geoquímica de cenizas volcánicas a lo largo de dos transectas en Sudamérica: implicaciones ambientales

VIII Congreso geológico de España, Oviedo, 17-19 julio 2012

Los depósitos de ceniza volcánica del Pleistoceno Superior-Holoceno de la región de Tafí del Valle-Cafayate, noroeste de Argentina

VIII Congreso geológico de España, Oviedo, 17-19 julio 2012

IMBER mini-Symposium with Spanish oceanographers

Celebrado en la Sala de Grado de la Facultad de Ciencias del Mar (ULPGC) el 18 de junio de 2013

Effects of ocean acidification on the brown alga "Padina pavonica": decalcification due to acute and chronic events

[EN] Since the industrial revolution, anthropogenic CO2 emissions have caused ocean acidification, which particularly affects calcified organisms. Given the fan-like calcified fronds of the brown alga Padina pavonica, we evaluated the acute (shortterm) effects of a sudden pH drop due to a submarine volcanic eruption (October 2011–early March 2012) affecting offshore waters around El Hierro Island (Canary Islands, Spain). We further studied the chronic (long-term) effects of the continuous decrease in pH in the last decades around the Canarian waters. In both the observational and retrospective studies (using herbarium collections of P. pavonica thalli from the overall Canarian Archipelago), the percent of surface calcium carbonate coverage of P. pavonica thalli were contrasted with oceanographic data collected either in situ (volcanic eruption event) or from the ESTOC marine observatory data series (herbarium study). Results showed that this calcified alga is sensitive to acute and chronic environmental pH changes. In both cases, pH changes predicted surface thallus calcification, including a progressive decalcification over the last three decades. This result concurs with previous studies where calcareous organisms decalcify under more acidic conditions. Hence, Padina pavonica can be implemented as a bio-indicator of ocean acidification (at short and long time scales) for monitoring purposes over wide geographic ranges, as this macroalga is affected and thrives (unlike strict calcifiers) under more acidic conditions

Mass-transport deposits on Mediterranean continental margins

Extensive mass transport deposits and multiple slide scars testify widespread and recurrent submarine sediment failures occurring during the late Quaternary on the SW-Adriatic and SE-Sicilian margins. These mass movements and their consequences contributed to shape the continental slopes and fill the basins with characteristic signatures. Geomorphological, seismo-stratigraphic, sedimentological and biostratigraphic data provide clues to: 1) define distinct failure mechanisms investigating on factors that determine dissimilar organization of coeval displaced masses, 2) reconstruct successive phases of failure stressing on the same location where slide scars crosscut and mass-transport deposits overlap, 3) analyze regional setting and indicate the most suitable place where to calculate mass wasting frequency. Discussions on the role of fluid flow, currents activity and tectonic deformation determine a wider view on the construction of the studied continental margins.

Simulación URANS 2D del flujo alrededor de un cilindro para 104 ≤ Re ≤ 106 con tratamiento de paredes

Máster Universitario en Sistemas Inteligentes y Aplicaciones Numéricas en Ingeniería (SIANI)

Studio di fenomeni d'instabilità gravitativa sui fondali marini, con particolare riferimento all'isola di Stromboli

In the last decade the interest for submarine instability grew up, driven by the increasing exploitation of natural resources (primary hydrocarbons), the emplacement of bottom-lying structures (cables and pipelines) and by the development of coastal areas, whose infrastructures increasingly protrude to the sea. The great interest for this topic promoted a number of international projects such as: STEAM (Sediment Transport on European Atlantic Margins, 93-96), ENAM II (European North Atlantic Margin, 96-99), GITEC (Genesis and Impact of Tsunamis on the European Coast 92-95), STRATAFORM (STRATA FORmation on Margins, 95-01), Seabed Slope Process in Deep Water Continental Margin (Northwest Gulf of Mexico, 96-04), COSTA (Continental slope Stability, 00-05), EUROMARGINS (Slope Stability on Europe’s Passive Continental Margin), SPACOMA (04-07), EUROSTRATAFORM (European Margin Strata Formation), NGI's internal project SIP-8 (Offshore Geohazards), IGCP-511: Submarine Mass Movements and Their Consequences (05-09) and projects indirectly related to instability processes, such as TRANSFER (Tsunami Risk ANd Strategies For the European region, 06-09) or NEAREST (integrated observations from NEAR shore sourcES of Tsunamis: towards an early warning system, 06-09). In Italy, apart from a national project realized within the activities of the National Group of Volcanology during the framework 2000-2003 “Conoscenza delle parti sommerse dei vulcani italiani e valutazione del potenziale rischio vulcanico”, the study of submarine mass-movement has been underestimated until the occurrence of the landslide-tsunami events that affected Stromboli on December 30, 2002. This event made the Italian Institutions and the scientific community more aware of the hazard related to submarine landslides, mainly in light of the growing anthropization of coastal sectors, that increases the vulnerability of these areas to the consequences of such processes. In this regard, two important national projects have been recently funded in order to study coastal instabilities (PRIN 24, 06-08) and to map the main submarine hazard features on continental shelves and upper slopes around the most part of Italian coast (MaGIC Project). The study realized in this Thesis is addressed to the understanding of these processes, with particular reference to Stromboli submerged flanks. These latter represent a natural laboratory in this regard, as several kind of instability phenomena are present on the submerged flanks, affecting about 90% of the entire submerged areal and often (strongly) influencing the morphological evolution of subaerial slopes, as witnessed by the event occurred on 30 December 2002. Furthermore, each phenomenon is characterized by different pre-failure, failure and post-failure mechanisms, ranging from rock-falls, to turbidity currents up to catastrophic sector collapses. The Thesis is divided into three introductive chapters, regarding a brief review of submarine instability phenomena and related hazard (cap. 1), a “bird’s-eye” view on methodologies and available dataset (cap. 2) and a short introduction on the evolution and the morpho-structural setting of the Stromboli edifice (cap. 3). This latter seems to play a major role in the development of largescale sector collapses at Stromboli, as they occurred perpendicular to the orientation of the main volcanic rift axis (oriented in NE-SW direction). The characterization of these events and their relationships with successive erosive-depositional processes represents the main focus of cap.4 (Offshore evidence of large-scale lateral collapses on the eastern flank of Stromboli, Italy, due to structurally-controlled, bilateral flank instability) and cap. 5 (Lateral collapses and active sedimentary processes on the North-western flank of Stromboli Volcano), represented by articles accepted for publication on international papers (Marine Geology). Moreover, these studies highlight the hazard related to these catastrophic events; several calamities (with more than 40000 casualties only in the last two century) have been, in fact, the direct or indirect result of landslides affecting volcanic flanks, as observed at Oshima-Oshima (1741) and Unzen Volcano (1792) in Japan (Satake&Kato, 2001; Brantley&Scott, 1993), Krakatau (1883) in Indonesia (Self&Rampino, 1981), Ritter Island (1888), Sissano in Papua New Guinea (Ward& Day, 2003; Johnson, 1987; Tappin et al., 2001) and Mt St. Augustine (1883) in Alaska (Beget& Kienle, 1992). Flank landslide are also recognized as the most important and efficient mass-wasting process on volcanoes, contributing to the development of the edifices by widening their base and to the growth of a volcaniclastic apron at the foot of a volcano; a number of small and medium-scale erosive processes are also responsible for the carving of Stromboli submarine flanks and the transport of debris towards the deeper areas. The characterization of features associated to these processes is the main focus of cap. 6; it is also important to highlight that some small-scale events are able to create damage to coastal areas, as also witnessed by recent events of Gioia Tauro 1978, Nizza, 1979 and Stromboli 2002. The hazard potential related to these phenomena is, in fact, very high, as they commonly occur at higher frequency with respect to large-scale collapses, therefore being more significant in terms of human timescales. In the last chapter (cap. 7), a brief review and discussion of instability processes identified on Stromboli submerged flanks is presented; they are also compared with respect to analogous processes recognized in other submerged areas in order to shed lights on the main factors involved in their development. Finally, some applications of multibeam data to assess the hazard related to these phenomena are also discussed.

Analysis of eruptive and seismic sequences to improve the short-and long-term eruption forecasting

Forecasting the time, location, nature, and scale of volcanic eruptions is one of the most urgent aspects of modern applied volcanology. The reliability of probabilistic forecasting procedures is strongly related to the reliability of the input information provided, implying objective criteria for interpreting the historical and monitoring data. For this reason both, detailed analysis of past data and more basic research into the processes of volcanism, are fundamental tasks of a continuous information-gain process; in this way the precursor events of eruptions can be better interpreted in terms of their physical meanings with correlated uncertainties. This should lead to better predictions of the nature of eruptive events. In this work we have studied different problems associated with the long- and short-term eruption forecasting assessment. First, we discuss different approaches for the analysis of the eruptive history of a volcano, most of them generally applied for long-term eruption forecasting purposes; furthermore, we present a model based on the characteristics of a Brownian passage-time process to describe recurrent eruptive activity, and apply it for long-term, time-dependent, eruption forecasting (Chapter 1). Conversely, in an effort to define further monitoring parameters as input data for short-term eruption forecasting in probabilistic models (as for example, the Bayesian Event Tree for eruption forecasting -BET_EF-), we analyze some characteristics of typical seismic activity recorded in active volcanoes; in particular, we use some methodologies that may be applied to analyze long-period (LP) events (Chapter 2) and volcano-tectonic (VT) seismic swarms (Chapter 3); our analysis in general are oriented toward the tracking of phenomena that can provide information about magmatic processes. Finally, we discuss some possible ways to integrate the results presented in Chapters 1 (for long-term EF), 2 and 3 (for short-term EF) in the BET_EF model (Chapter 4).

Geological and Structural evolution of the Eurasia Africa plate boundary in the Gulf of Cadiz Central Eastern Atlantic Sea.

Iberia Africa plate boundary, cross, roughly W-E, connecting the eastern Atlantic Ocean from Azores triple junction to the Continental margin of Morocco. Relative movement between the two plate change along the boundary, from transtensive near the Azores archipelago, through trascurrent movement in the middle at the Gloria Fracture Zone, to transpressive in the Gulf of Cadiz area. This study presents the results of geophysical and geological analysis on the plate boundary area offshore Gibraltar. The main topic is to clarify the geodynamic evolution of this area from Oligocene to Quaternary. Recent studies have shown that the new plate boundary is represented by a 600 km long set of aligned, dextral trascurrent faults (the SWIM lineaments) connecting the Gloria fault to the Riff orogene. The western termination of these lineaments crosscuts the Gibraltar accretionary prism and seems to reach the Moroccan continental shelf. In the past two years newly acquired bathymetric data collected in the Moroccan offshore permit to enlighten the present position of the eastern portion of the plate boundary, previously thought to be a diffuse plate boundary. The plate boundary evolution, from the onset of compression in the Oligocene to the Late Pliocene activation of trascurrent structures, is not yet well constrained. The review of available seismics lines, gravity and bathymetric data, together with the analysis of new acquired bathymetric and high resolution seismic data offshore Morocco, allows to understand how the deformation acted at lithospheric scale under the compressive regime. Lithospheric folding in the area is suggested, and a new conceptual model is proposed for the propagation of the deformation acting in the brittle crust during this process. Our results show that lithospheric folding, both in oceanic and thinned continental crust, produced large wavelength synclines bounded by short wavelength, top thrust, anticlines. Two of these anticlines are located in the Gulf of Cadiz, and are represented by the Gorringe Ridge and Coral Patch seamounts. Lithospheric folding probably interacted with the Monchique – Madeira hotspot during the 72 Ma to Recent, NNE – SSW transit. Plume related volcanism is for the first time described on top of the Coral Patch seamount, where nine volcanoes are found by means of bathymetric data. 40Ar-39Ar age of 31.4±1.98 Ma are measured from one rock sample of one of these volcanoes. Analysis on biogenic samples show how the Coral Patch act as a starved offshore seamount since the Chattian. We proposed that compression stress formed lithospheric scale structures playing as a reserved lane for the upwelling of mantle material during the hotspot transit. The interaction between lithospheric folding and the hotspot emplacement can be also responsible for the irregularly spacing, and anomalous alignments, of individual islands and seamounts belonging to the Monchique - Madeira hotspot.

Geochronology, geochemistry and isotopic compositions of the volcanic rocks from oceanic (Hawaii) and continental (Eifel) intra-plate environments

The Eifel volcanism is part of the Central European Volcanic Province (CEVP) and is located in the Rhenish Massif, close to the Rhine and Leine Grabens. The Quaternary Eifel volcanism appears to be related to a mantle plume activity. However, the causes of the Tertiary Hocheifel volcanism remain debated. We present geochronological, geochemical and isotope data to assess the geotectonic settings of the Tertiary Eifel volcanism. Based on 40Ar/39Ar dating, we were able to identify two periods in the Hocheifel activity: from 43.6 to 39.0 Ma and from 37.5 to 35.0 Ma. We also show that the pre-rifting volcanism in the northernmost Upper Rhine Graben (59 to 47 Ma) closely precede the Hocheifel volcanic activity. In addition, the volcanism propagates from south to north within the older phase of the Hocheifel activity. At the time of Hocheifel volcanism, the tectonic activity in the Hocheifel was controlled by stress field conditions identical to those of the Upper Rhine Graben. Therefore, magma generation in the Hocheifel appears to be caused by decompression due to Middle to Late Eocene extension. Our geochemical data indicate that the Hocheifel magmas were produced by partial melting of a garnet peridotite at 75-90 km depth. We also show that crustal contamination is minor although the magmas erupted through a relatively thick continental lithosphere. Sr, Nd and Pb isotopic compositions suggest that the source of the Hocheifel magmas is a mixing between depleted FOZO or HIMU-like material and enriched EM2-like material. The Tertiary Hocheifel and the Quaternary Eifel lavas appear to have a common enriched end-member. However, the other sources are likely to be distinct. In addition, the Hocheifel lavas share a depleted component with the other Tertiary CEVP lavas. Although the Tertiary Hocheifel and the Quaternary Eifel lavas appear to originate from different sources, the potential involvement of a FOZO-like component would indicate the contribution of deep mantle material. Thus, on the basis of the geochemical and isotope data, we cannot rule out the involvement of plume-type material in the Hocheifel magmas. The Ko’olau Scientific Drilling Project (KSDP) has been initiated in order to evaluate the long-term evolution of Ko’olau volcano and obtain information about the Hawaiian mantle plume. High precision Pb triple spike data, as well as Sr and Nd isotope data on KSDP lavas and Honolulu Volcanics (HVS) reveal compositional source variations during Ko’olau growth. Pb isotopic compositions indicate that, at least, three Pb end-members are present in Ko’olau lavas. Changes in the contributions of each component are recorded in the Pb, Sr and Nd isotopes stratigraphy. The radiogenic component is present, at variable proportion, in all three stages of Ko’olau growth. It shows affinities with the least radiogenic “Kea-lo8” lavas present in Mauna Kea. The first unradiogenic component was present in the main-shield stage of Ko’olau growth but its contribution decreased with time. It has EM1 type characteristics and corresponds to the “Ko’olau” component of Hawaiian mantle plume. The second unradiogenic end-member, so far only sampled by Honololu lavas, has isotopic characteristics similar to those of a depleted mantle. However, they are different from those of the recent Pacific lithosphere (EPR MORB) indicating that the HVS are not derived from MORB-related source. We suggest, instead, that the HVS result from melting of a plume material. Thus the evolution of a single Hawaiian volcano records the geochemical and isotopic changes within the Hawaiian plume.

Rezente Bodenbewegungspotenziale in Schleswig-Holstein (Deutschland)

Die Entwicklung des Nordwestdeutschen Beckens und seiner rezenten Topographie ist geprägt von einer Vielzahl endogener und exogener Prozesse: Tektonik, Vulkanismus, Diapirismus, Eisvorstöße, elsterzeitlichen Rinnen und die Ablagerung von quartären Sedimenten. Mit Hilfe der Quantifizierung von Bodenbewegungspotenzialen wurde für Schleswig-Holstein der Einfluß von Tiefenstrukturen (insbesondere Salzstrukturen und tektonische Störungen) auf die Entwicklung der rezenten Topographie in Schleswig-Holstein untersucht. Dabei wurden folgende Parameter berücksichtigt: (1) Salzstrukturen; (2) Tektonischen Störungen; (3) Oberflächennahe Störungen, die mit einer hohen Wahrscheinlichkeit an der Erdoberfläche ausstreichen; (4) Elsterzeitliche Rinnen (tiefer 100 m); (5) Historische Erdbeben; (6) In Satellitenbildszenen kartierte Lineamente (7) Korrelationskoeffizienten, die zwischen 7 stratigraphischen Horizonten des „Geotektonischen Atlas von NW-Deutschland“ berechnet wurden. Die Ergebnisse zeigen, dass in Schleswig-Holstein großflächig rezente Bodenbewegungs-potenziale auftreten, die auf tektonische Störungen und Salzstrukturen zurückzuführen sind und sich hauptsächlich auf den Bereich des Glückstadt Grabens beschränken. In den 5 Gebieten Sterup, Tellingstedt Nord, Oldensworth Nord, Schwarzenbek und Plön treten die höchsten Bodenbewegungspotenziale auf. Sie dokumentieren rezente Prozesse in diesen Gebieten. In den Gebieten Sterup, Schwarzenbek und Plön sind aktive, an der Erdoberfläche ausstreichende Störungen lokalisiert, deren Auftreten auch durch kartierte Luft- und Satellitenbildlineare belegt wird. Im Gebiet Plön werden die ermittelten Bodenbewegungspotenziale durch eine, sich rezent vergrößernde Senke bei Kleinneudorf bestätigt. Unterhalb der Senke führen, begünstigt durch tektonische Störungen, Lösungsprozesse in tertiären Sedimenten zu Hohlraumbildungen, die das rezente Absacken der Senke verursachen. Für Bereiche höchsten Bodenbewegungspotenzials kann ein Einfluß von Tiefenstrukturen auf die Entwicklung der rezenten Topographie nachgewiesen werden. So beeinflussen oberflächennahe Störungen in dem Gebiet Plön die Entwicklung des Plöner Sees. Im Gebiet Schwarzenbek verursacht ein N-S orientiertes Störungsband ein Abknicken des Elbverlaufs. Weiterhin kann ein Einfluß der Entwicklung der rezenten Topographie durch eine Interaktion zwischen Eisauflast und Salzmobilität in den Gebieten Sterup und Oldensworth nachgewiesen werden. Demnach ist die Ablagerung quartärer Sedimente und somit der Grenzverlauf der Flußgebietseinheiten Eider und Schlei-Trave zwischen den Salzstrukturen Sterup und Meezen beeinflusst durch eine aktive Reaktion beider Salzstrukturen auf Eisauflast. Im Bereich Oldensworth zeigen geologische Schnitte von der Basis Oberkreide bis zur rezenten Topographie, dass die Salzmauern Oldensworth und Hennstedt die Ablagerung quartärer Sedimente aktiv beeinflussten. Weiterhin orientiert sich der Elbverlauf von Hamburg bis zur Mündung an den Randbereichen von Salzstrukturen, die bis in den oberflächennahen Bereich aufgestiegen sind.