Preprints
Filtering by Subject: Volcanology
The different character of the recent eruptions of Galápagos shield volcanoes (Ecuador): La Cumbre vs. Sierra Negra
Published: 2018-08-14
Subjects: Earth Sciences, Physical Sciences and Mathematics, Volcanology
In the last year, two Galápagos volcanoes had shown eruptive activity. The three observed eruptions produced multiple lava flows along eruptive fissures and vents covering several square kilometers. After eight years of quiescence, La Cumbre volcano, Fernandina Island experienced two short-lived eruptions, on 4 September 2017 and 16 June 2018. The eruptions were characterized by very short [...]
Shark-fins: overturned patterns linked to shear instabilities at the flow-bed boundary. Examples from the deposits of the 2006 pyroclastic currents at Tungurahua volcano (Ecuador)
Published: 2018-08-06
Subjects: Earth Sciences, Geology, Geomorphology, Physical Sciences and Mathematics, Sedimentology, Volcanology
Enigmatic structures grouped under the term "shark-fins" are documented in laminated deposits of pyroclastic currents. They consist of an overturning of a few laminae on a decimeter scale, forming overbent "flames" or convolute laminae, which occur in successive, periodic patterns. More than 200 shark-fins were investigated and measured in cross-laminated deposits from the 2006 pyroclastic [...]
Pyroclastic dune bedforms: macroscale structures and lateral variations. Examples from the 2006 pyroclastic currents at Tungurahua (Ecuador)
Published: 2018-08-06
Subjects: Earth Sciences, Geology, Geomorphology, Physical Sciences and Mathematics, Sedimentology, Volcanology
Pyroclastic currents are catastrophic flows of gas and particles triggered by explosive volcanic eruptions. For much of their dynamics, they behave as particulate density currents and share similarities with turbidity currents. Pyroclastic currents occasionally deposit dune bedforms with peculiar lamination patterns, from what is thought to represent the dilute low concentration and [...]
The Dark Geo-Cultural Heritage of Volcanoes: Combining Cultural and Geoheritage Perspectives for Mututal Benefit
Published: 2018-06-30
Subjects: Earth Sciences, Physical Sciences and Mathematics, Volcanology
It is now widely accepted that vulnerability is in part culturally and historically contingent. Similarly, geoheritage cannot be readily disentangled from cultural values and cultural heritage given that the assignment of value to a given geosite is conducted in the present and that many if not most geosites are also sites of culture-historical significance. Vice versa, most tangible cultural [...]
Field evidence for the lateral emplacement of igneous dykes: Implications for 3D mechanical models and the plumbing beneath fissure eruptions.
Published: 2018-06-06
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure, Volcanology
Seismological and geodetic data from modern volcanic systems strongly suggest that magma is transported significant distance (tens of kilometres) in the subsurface away from central volcanic vents. Geological evidence for lateral emplacement preserved within exposed dykes includes aligned fabrics of vesicles and phenocrysts, striations on wall rocks and the anisotropy of magnetic susceptibility. [...]
Vibrational modes of hydraulic fractures: Inference of fracture geometry from resonant frequencies and attenuation
Published: 2018-05-27
Subjects: Earth Sciences, Environmental Sciences, Geophysics and Seismology, Glaciology, Physical Sciences and Mathematics, Volcanology
Oscillatory seismic signals arising from resonant vibrations of hydraulic fractures are observed in many geologic systems, including volcanoes, glaciers and ice sheets, and hydrocarbon and geothermal reservoirs. To better quantify the physical dimensions of fluid‐filled cracks and properties of the fluids within them, we study wave motion along a thin hydraulic fracture waveguide. We present a [...]
Time scales of shallow magma chamber replenishment at Campi Flegrei caldera.
Published: 2018-05-23
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Volcanology
Ascent of primitive magmas from depth into shallow, partially degassed reservoirs is commonly assumed to be a viable eruption trigger. The resulting processes of convection and mixing have played an important role both in pre- and syn-eruptive stages in many eruptions of different sizes at the unrest Campi Flegrei caldera in Southern Italy. We performed numerical simulations of magma chamber [...]
Extrusion dynamics of deep-water volcanoes
Published: 2018-05-15
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Volcanology
Submarine volcanism accounts for c. 75% of the Earths volcanic activity. Yet difficulties with imaging their exteriors and interiors mean the extrusion dynamics and erupted volumes of deep water volcanoes remain poorly understood. Here, we use high-resolution 3-D seismic reflection data to examine the external and internal geometry, and extrusion dynamics of two Late Miocene-Quaternary, [...]
The Mesozoic and Palaeozoic granitoids of north-western New Guinea
Published: 2018-05-09
Subjects: Earth Sciences, Geochemistry, Geology, Other Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure, Volcanology
A large portion of the Birds Head Peninsula of NW New Guinea is an inlier that reveals the pre-Cenozoic geological history of the northern margin of eastern Gondwana. The peninsula is dominated by a regional basement high exposing Gondwanan (Australian) Palaeozoic metasediments intruded by Palaeozoic and Mesozoic granitoids. Here, we present the first comprehensive study of these granitoids, [...]
Volcanic ash generation mechanisms: Fingerprints in phase distribution highlighted by QEMSCAN particle mineralogical analysis
Published: 2018-05-03
Subjects: Earth Sciences, Physical Sciences and Mathematics, Volcanology
Volcanic ash particle properties depend upon their genetic fragmentation processes. Here, we introduce QEMSCAN particle mineralogical analysis (PMA) to quantify the phase distribution in two ash samples collected during activity at Santiaguito, Guatemala and assess the fingerprint of fragmentation mechanisms. Volcanic ash from a Vulcanian explosion and from a pyroclastic density current resulting [...]
The shape and distribution of Maar craters using the MaarVLS database.
Published: 2018-04-11
Subjects: Earth Sciences, Physical Sciences and Mathematics, Volcanology
A maar crater is the top of a much larger subsurface diatreme structure produced by phreatomagmatic explosions and the size and shape of the crater reflects the growth history of that structure during an eruption. Recent experimental and geophysical research has shown that crater complexity can reflect subsurface complexity. Morphometry provides a means of characterizing a global population of [...]
Ambient noise image Campi Flegrei 2011-2013
Published: 2018-03-26
Subjects: Earth Sciences, Environmental Monitoring, Environmental Sciences, Physical Sciences and Mathematics, Tectonics and Structure, Volcanology
Earthquakes at Campi Flegrei have been low-magnitude and sparse for more than thirty years, denying onshore monitoring observations of their usual source for structural constraint: seismic tomography. Here, we used ambient seismic noise recorded between 2011 and 2013 to reconstruct period-dependent Rayleigh-wave velocity maps of caldera-wide structures and volcanic reservoirs. The lowest [...]
Investigation of variable aeration of monodisperse mixtures: implications for Pyroclastic Density Currents
Published: 2018-03-13
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Volcanology
The high mobility of dense pyroclastic density currents (PDCs) is commonly attributed to high gas pore pressures. However, the influence of spatial and temporal variations in pore pressure within PDCs has yet to be investigated. Theory suggests that variability in the fluidisation and aeration of a current will have a significant control on PDC flow and deposition. In this study, the effect of [...]
Mechanical models to estimate the paleostress state from igneous intrusions
Published: 2018-03-09
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure, Volcanology
Dikes and sills represent an important component of the deformation history in volcanic systems, but unlike dikes, sills are typically omitted from traditional paleostress analyses in tectonic studies. The emplacement of sheet intrusions is commonly associated with mode I fracturing in a low deviatoric stress state, where dilation is perpendicular to the fracture plane. Many natural examples of [...]
The stratigraphy and eruptive history of the Palaeogene Arran Volcanic Formation, western Scotland: a proximal record of caldera-forming eruptions
Published: 2018-02-01
Subjects: Earth Sciences, Physical Sciences and Mathematics, Volcanology
Caldera-forming volcanic eruptions are among the most dangerous, and can generate extensive pyroclastic deposits and deliver ash into global atmospheric circulation systems. As calderas collapse, the eruptions can deposit thick proximal ignimbrite sequences and thinner ignimbrites more distally. However, the proximal record of caldera collapse is often obscured by later intrusions, volcanism, [...]