1,721,227 research outputs found
A new type of volcano flank failure: The resurgent caldera sector collapse, Ischia, Italy
No full textThis study is the first description of recurrent and rapid lateral failure of the resurgent portion of a caldera complex. The sliding planes and the characteristics of debris avalanche deposits resemble those of cone sector collapses, but the main triggering mechanism proposed at Ischia caldera (Italy) is related to intermittent resurgence. During the last 33 ka, the increase in resurgence rate produced major collapses southward due to three main mechanisms that contributed to an increase in shear stress: i) magma-driven uplift, which produced increase in static loading, ii) faulting and associated deformation, which induced tilting and steepening of the original layering, and iii) earthquake shaking due to coseismic faulting. The largest episodes of flank failure occurred in the interval 8.6-5.7 ka BP. These were followed by magma eruption and a decrease in the resurgence rate. Recognition of this phenomenon is particularly important in recent/active calderas located near the coast, as it can trigger tsunamis
Dike propagation driven by volcano collapse: a general model tested at Stromboli, Italy
No full textAnalogue experiments investigate how flank collapse affects dike propagation within volcanoes. Water (magma analogue) is injected within a gelatin cone (volcano analogue) with a lateral collapse. The injections form dikes that, away from the collapse, become radial. The dikes propagating nearby the collapse focus towards the collapse sides, becoming subparallel to them, because of the stress reorientation due to the unbuttressing. Only dikes formed along the collapse axis (passing through the mean points of the collapse, map view) propagate radially within the collapse. This general model is applied at Stromboli. The Stromboli dikes cluster along and parallel to the collapse sides, similar to the experiments. Nevertheless, the current location of the conduit, along the collapse axis, leads to dike propagation within the collapse infill, rather than at its sides. This may have occurred during the 2002-03 eruption, when diking in the collapse triggered a landslide and tsunami within the collapse
Structure of a sheet-laccolith system revealing the interplay between tectonic and magma stresses at Stardalur Volcano, Iceland
No full textThis paper provides detailed structural data on the faults and intrusions of the eroded Stardalur volcano, in the Esja peninsula at the SW margin of the Icelandic rift, and new lithostratigraphic data on the host rocks. A swarm of centrally-dipping sheets, emplaced with a fan-shaped geometry in section view, depicts an ellipse in plan view with an about E-W major axis. Sheet intensity reaches 80% in one 100-m transect near the central portion of the swarm, where sheets strike E-W with sub-vertical dip. A 200-m-thick, multiply-intrusive body forms a laccolith in the middle of the centrally-dipping sheet swarm, at a higher altitude. Individual intrusive units within this laccolith are sub-vertical and strike E-W in the center, acquiring a sill-like geometry outwards, and were emplaced in a stress field locally dominated by a N-S-directed least principal stress (Ï3). Within the inclined sheet swarm, the stress tensor rotated in response to an excess magma pressure, probably linked to an underlying magma chamber, which interacted with the tectonic stresses. Crosscutting relationships between the various intrusions and with the host rock indicate that the activity in the central zone of the Stardalur volcano ended with the emplacement of the laccolith. Later eruptions, if they occurred at all, were fed by centrally-dipping sheets. In the final stage, NNE-striking regional vertical dykes and normal faults cut the previous structures in response to dominant regional plate tectonic stresses with a WNW-ESE directed Ï3 and a NNE-SSW directed intermediate principal stress (Ï2). © 2006 Elsevier B.V. All rights reserved
Do transcurrent faults guide volcano growth? The case of NW Bicol Volcanic Arc, Luzon, Philippines.
No full textHigh operating temperature HgCdTe coupled cavity plasmonic infrared photodetectors
Full text linkIncreasing the operating temperature while enhancing detectivity is paramount for the advancement of HgCdTe infrared detectors. In this context, the integration of plasmonic nanostructures emerges as one of the most intriguing avenues, promising breakthroughs in infrared sensing capabilities. Multiphysics TCAD simulations of pin nanostructured focal plane photodetector arrays unveil the potential benefits of submicron absorber thicknesses, that promise detectivities more than twice as large as those provided by conventional 5 um-thick absorbers, besides enabling operating temperatures up to 260 K. Such performance increase is discussed through the combination of numerical simulations and quantum mechanical treatment based on the occupation number formalism, describing the interaction between plasmonic and optical cavity modes responsible for the spectral broadening of the optical response, allowing for good coverage of the entire mid-infrared band ([3,5] um)
- …
