1,721,061 research outputs found
Passage of debris flows and turbidity currents through a topographic constriction: seafloor erosion and deflection of flow pathways
No full textPassage of debris flows and turbidity currents through a topographic constriction: seafloor erosion and deflections of flow pathways
No full textDebris avalanche deposits on the flanks of the Canary islands: contrasts between El Hierro and Tenerife
No full text
Uplift at lithospheric swells--II: is the Cape Verde mid-plate swell supported by a lithosphere of varying mechanical strength?
Full text linkThe Cape Verde mid-plate swell is the largest amplitude oceanic mid-plate swell on Earth at ?1800 km in diameter, with a crest ?2.2 km high, and long-wavelength positive geoid, gravity and heat flow anomalies of 8 m, 30 mGal and 10–15 mW m?2, respectively. These characteristics and its location on the slow moving-to-stationary African Plate, which concentrates the volcanism and associated geophysical anomalies within a relatively small areal extent, makes it an ideal location to test various proposed mechanisms for swell support.Wide-angle seismic refraction data have been acquired along a ?474 km profile extending north–south from the swell crest. In this paper, the 2-D velocity–depth crustal model derived from forward modelling of phase traveltime picks is tested using two independent inversion approaches. The final crustal velocity–depth model derived from the combined modelling, shows no evidence for widespread thickened crust or for lower crustal velocities exceeding 7.3 km s?1 that are indicative of undercrustal magmatic material.Using the final velocity–depth model to constrain the crust for 3-D ‘whole plate’ lithospheric flexure modelling of island loading alone, we show that the lithosphere of the Cape Verde region appears stronger than expected for its age. Regional-scale modelling suggests that the majority of the swell height is supported by dynamic upwelling within the asthenosphere coupled with, but to a lesser degree, the effect of a region of low density in the deeper lithosphere, originating most likely from conductive reheating of the overlying plate due to its slow-to-stationary motion. When this regional upward-acting buoyancy force is considered in the context of the shorter wavelength flexure associated with island loading, modelling suggests that the apparent high plate strength is a consequence of, in effect, a regional unbending of a lithosphere that has a long-term strength typical for its age
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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Offshore continuation of volcanic rift zones, El Hierro, Canary Islands
No full textEl Hierro is the youngest and most southwesterly of the seven Canary islands. The established view, based on subaerial geology, is that El Hierro is a classic example of an oceanic island with 120° –– spaced volcanic rift arms (VRZs) forming a "mercedes star". However, new offshore data do not support this simple interpretation. Instead of the discrete ridges of VRZs, we observe (to the NW and NE) broad areas of irregular morphology, which suggest that rifting activity might not be confined to narrow zones. Furthermore, our data suggest that the anomalously long and steep-flanked Southern Ridge could be part of an older, eroded volcanic edifice that predates much of the other submarine flanks of El Hierro. The Southern Ridge has a distinctive gullied morphology, which strongly contrasts with adjacent flanks. There is also a ~400-m-deep saddle in its longitudinal profile 15 km from the coastline, which we interpret as evidence that the Southern Ridge did not form by continuous dyke intrusion from the El Hierro volcanic centre. South of the saddle, mean flank slopes are 10° steeper (~30°) with a sharp slope break at 3700 m between the ridge and smoothly sedimented seafloor. These steeper slopes and lack of landslide scars to the south of the saddle indicate that the Southern Ridge is a stable edifice, relative to the rest of El Hierro. Surrounding sediments to the southeast appear to onlap the Southern Ridge. A large landslide deposit, El Julan (estimated age >200 ka), occurs to the west of the ridge. This landslide appears to have been constrained from spreading southeastwards by the Southern Ridge, resulting in an elevation difference of 300 m for the seafloor on either side of the ridge
- …
