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An invitation from Thomas Lee Caldera to Dr. Hector P. Garcia.
No full textAn invitation from Thomas Lee Caldera to Dr. Hector P. Garcia for his graduation from Miller High School
Surface deformation of Long Valley caldera and Mono Basin, California investigated with the SBAS-InSAR approach
No full textWe investigate the surface deformation of the eastern California area that includes Long Valley caldera and Mono Basin. We apply the SAR
Interferometry (InSAR) algorithm referred to as Small BAseline Subset (SBAS) approach that allows us to generate mean deformation velocity
maps and displacement time series for the investigated area. The results presented in this work represent an advancement of previous InSAR
studies of the area that are mostly focused on the deformation affecting the caldera. In particular, the proposed analysis is based on 21 SAR data
acquired by the ERS-1/2 sensors during the 1992–2000 time interval, and demonstrates the capability of the SBAS procedure to identify and
analyze displacement patterns at different spatial scales for the overall area spanning approximately 5000 km2. Two previously unreported
localized deformation effects have been detected at Paoha Island, located within the Mono Lake, and in the McGee Creek area within the Sierra
Nevada mountains, a zone to the south of the Long Valley caldera. In addition a spatially extended uplift effect, which strongly affects the caldera,
has been identified and analyzed in detail. The InSAR results clearly show that the displacement phenomena affecting the Long Valley caldera
have a maximum in correspondence of the resurgent dome and are characterized by the sequence of three different effects: a 1992–1997 uplift
background, a 1997–1998 unrest phenomenon and a 1998–2000 subsidence phase. Moreover, the analysis of the retrieved displacement time
series allows us to map the extent of the zone with a temporal deformation behavior highly correlated with the detected three-phases deformation
pattern: background uplift-unrest-subsidence. We show that the mapped area clearly extends outside the northern part of the caldera slopes;
accordingly, we suggest that future inversion models take this new evidence into account. The final discussion is dedicated to a comparison
between the retrieved InSAR measurements and a set of GPS and leveling data, confirming the validity of the results achieved through the SBASInSAR
analysis.Published277–2891.3. TTC - Sorveglianza geodetica delle aree vulcaniche attive3.2. Tettonica attiva4.3. TTC - Scenari di pericolosità vulcanicaJCR Journalreserve
Seismic and Gravity Structure of the Campi Flegrei Caldera, Italy
No full textWe present a comprehensive review of seismic and gravity observations and tomographic models produced over the past four decades in order to understand the structure of the crust beneath the Campi Flegrei caldera. We describe the main lithological and structural discontinuities defined through these observations, illustrate their geophysical responses, and discuss the constraints they give to the understanding of magmatic and volcanic processes. Micro-seismic crises related to caldera unrest, and ambient seismic noise measurements provide comprehensive seismic data to local earthquake and ambient noise tomography. In combination with reflection data from onshore and offshore active seismic experiments, velocity tomography reconstructs the elastic properties of the caldera between surface and ~4 km depth. Active experiments also define the depth of lithological interfaces and deep (~7.5 km) partially molten bodies. Seismic attenuation tomography provides information complementary to velocity tomography, defining lateral lithological changes and the geometry of onshore and offshore fluid and magma bodies down to 4 km depth. Once compared with seismic analyses, gravity data highlight lateral changes in the offshore caldera structures. During the deformation and seismo-geochemical unrest (1982–1984), they permitted to reconstruct a minor (<1 km lateral extent) melt volume related to the point of maximum uplift measured at the caldera. Seismic coda-wave amplitude inversions depict the caldera rim limits in analogy to velocity tomography and map the lateral extension of ~4-km-deep deformation source. Once combined with the results from velocity tomography and gravity inversions, they reconstruct the feeding systems that connect deep deformation source and shallow vents across the eastern caldera, capped by a seismic horizon around a depth of 2 km
Ground deformation of Long Valley caldera and Mono Basin, eastern California, mapped by satellite radar interferometry
No full textWe have illustrated the key results of the Differential SAR Interferometry
(DInSAR) analysis focused on the ground deformation of Long Valley caldera
and Mono Basin, eastern California. In particular, we have applied the DInSAR
algorithm referred to as Small BAseline Subset (SBAS) approach and processed
21 SAR images, spanning the time interval from 1992 to 2000, acquired from
descending arbits by the ERS-1 and ERS-2 sensors of the European Space
Agency (ESA). The deformation affecting the resurgent dome of Long Valley
caldera has been highlighted as well as the previously unreported subsidence of
the Pahoa island, located in Mono Lake.Published439–4411.3. TTC - Sorveglianza geodetica delle aree vulcaniche attive3.2. Tettonica attiva4.3. TTC - Scenari di pericolosità vulcanicaJCR Journalreserve
Unrest at Campi Flegrei Caldera (Southern Italy) during the last decade
No full textCampi Flegrei caldera is located just west of the city of
Naples, within the central-southern sector of a large graben called
Campania Plain. It is an active volcanic area marked by a quasicircular
caldera depression, probably formed by a huge
ignimbritic eruption occurred about 39000 years ago. This
caldera was generated by collapses produced by strong explosive
eruptions. The only eruption in historical times occurred in 1538building a spatter cone called Mt. Nuovo. Campi Flegrei area
periodically experiences significant deformation episodes, with
uplift phenomena reaching more than 3.5 m in 15 years (from
1970 to 1984), which caused during 1983-84 the temporary
evacuation of about 40000 people from Pozzuoli town.
The structural complexity of the Campi Flegrei area, together
with the evidence of a strong interaction between magmatic
chamber and shallow geothermal system, calls for a detailed
characterization of the substructure and of the magma-water
interaction processes.
The Campi Flegrei caldera is characterized by high volcanic
risk due to the explosivity of the eruptions and to the intense
urbanization of the surrounding area, and has been the site of
significant unrest for the past 2000 years (DE NATALE et alii,
2006). The caldera floor was raised to about 1.7 meters between
1968 and 1972; then a subsidence phase of about 0.2 m occurred
between 1972 and 1975 followed by a stable period until 1981.
Between 1982 and 1985 new uplift occurred and the caldera rose
about 1.8 m, without eruptive phenomena...Presidenza della Repubblica;Ministero dell'Ambiente e della Tutela del Territorio e del Mare;Regione Toscana;Regione Emilia Romagna;Dipartimento di Protezione Civile;ISPRA;Università di Pisa;Università di Siena;Comune di Pisa;Provincia di PisaPublishedPisa1.3. TTC - Sorveglianza geodetica delle aree vulcaniche attive4.3. TTC - Scenari di pericolosità vulcanicaope
Sedimentary and volcano-tectonic processes in the British Paleocene Igneous Province: a review
No full textResearch on the British Paleocene Igneous Province (BPIP) has historically focused on the emplacement, chemistry and chronology of its elaborate central intrusive complexes and lava fields. However, the BPIP has also been dramatically shaped by numerous erosion, sedimentation and volcano-tectonic events, the significance of which becomes ever clearer as localities in the BPIP are re-investigated and our understanding of volcano-sedimentary processes advances. The resultant deposits provide important palaeo-environmental, palaeo-geographical and stratigraphical information, and highlight the wide range of processes and events that occur in ancient volcanic settings such as the BPIP. In this paper we review the sedimentary and volcano-tectonic processes that can be distinguished in the BPIP, and conceptualize them within a generalized framework model. We identify, and describe, the sedimentary responses to four broadly chronological stages in the history of the BPIP volcanoes: (1) the development of the lava fields, (2) early intrusion-induced uplift, (3) caldera collapse and (4) post-volcano denudation and exhumation of central complexes. We highlight and illustrate the range of sedimentary processes that were active in the BPIP. These operated on and helped shape a dynamic landscape of uplands and lowlands, of alluvial fans, braided rivers, lakes and swamps, and of volcanoes torn apart by catastrophic mass wasting events and/or caldera collapse
Caldera structure, amount of collapse, and erupted volumes: The case of Bolsena caldera, Italy
No full textCalderas are common on volcanoes, but their structure is seldom visible. The 19-kmwide Bolsena caldera, Italy, formed between 0.6 and 0.2 Ma. The largely preserved structural rim and subsurface data make Bolsena ideal to investigate caldera structure in relation to the subsidence and erupted volume. In this paper, we use remote sensing, fi eld analysis, and available subsurface data. At the surface, the caldera passes from a down-sag (south rim) to a narrow and densely faulted area (north rim), with outer normal and inner reverse faults. The caldera structure on the widely faulted east rim appears to be scale dependent, with a staircase-like fault zone (larger scale), horst-and-graben-like structures (intermediate scale), and domino-like structures (smaller scale). Subsurface data indicate asymmetric collapse, with a northward increase in subsidence, ranging from diffuse (to the south) to focused (to the north) deformation at the surface. The collapse rate, constant between ca. 490 and 175 ka, was more than magma output between ca. 330 and 130 ka, highlighting signifi cant (~200 m) and prolonged (~200 ka) posteruptive subsidence. As the nearby Latera caldera (west rim of Bolsena) was mostly active between ca. 265 and 160 ka, much of the subsidence at Bolsena may be related to this activity, suggesting a common magmatic reservoir. The subsidence-related structural variations along the caldera rim and the signifi cant posteruptive subsidence found at Bolsena have not been found in other calderas. © 2012 Geological Society of America
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Three-dimensional p-velocity structure of the summit caldera of Newberry Volcano, Oregon
No full textA three-dimensional high-resolution seismic study of the summit caldera of Newberry Volcano, Oregon, was conducted by the US Geological Survey using an adaptation of the method applied by Mercessian et al. (1984). Preliminary interpretation of the traveltime residuals reveals a ring of high P-velocity material coinciding with the inner ring fault system of the caldera in the upper 2 km. A zone of lower P velocities extends deeper than 2 km in the center of the caldera. 9 refs., 5 figs
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