Search results for "Explosive material"
showing 9 items of 49 documents
Protection concepts from optical radiation used in places of danger from explosion of gases, vapour or cloud of particles
2005
Use of optical systems in hazardous locations can result in ignition of surrounding explosive atmosphere. The conducted research work allowed to propose three protection concepts. The primary protection concept - inherently safe optical radiation - consists in use of optical radiation with power, energy or irradiance incapable of causing ignition of surrounding explosive atmosphere. However, the arbitrary determination of values of these parameters is considered as excessively rigorous. The work presents the proposed protection concepts in relation to zone classification. The author describes his own method to determine safe values based on probability mathematics that can be used not only …
Exploring the explosive-effusive transition using permanent ultraviolet cameras
2017
Understanding the mechanisms that cause effusive eruptions is the key to mitigating their associated hazard. Here, we combine results from permanent ultra-violet (UV) cameras, and from other geophysical observations (seismic very long period, thermal, and infrasonic activity), to characterize volcanic SO2 flux regime in the period prior, during, and after Stromboli's August-November 2014 effusive eruption. We show that, in the two months prior to effusion onset, the SO2 flux levels are two times average level. We explain this anomalously high SO2 regime as primarily determined by venting of rapidly rising, pressurized SO2-rich gas pockets, produced by strombolian explosions being more frequ…
H2O-content and temperature limit the explosive potential of rhyolite magma during Plinian eruptions
2019
Abstract Recent rhyolite eruptions on Earth have demonstrated their capacity to produce a multitude of hazards, including ash formation lasting months and impacting the large reaches of the southern hemisphere. Nevertheless, the underlying mechanisms driving these eruptions are not yet fully understood. Magmatic volatiles, especially H2O, dictate whether volcanic eruptions proceed explosively or effusively. Experimental evidence for the role played by H2O in driving explosive fragmentation is rare, in particular in the eruption of rhyolitic magma. Here we show that when hydrous rhyolitic obsidians from Chaiten Volcano (Chile) are experimentally heated above their glass transition temperatur…
Ultraviolet camera measurements of passive and explosive (Strombolian) sulphur dioxide emissions at Yasur volcano, Vanuatu
2020
Here, we present the first ultraviolet (UV) camera measurements of sulphur dioxide (SO2) flux from Yasur volcano, Vanuatu, for the period 6–9 July 2018. These data yield the first direct gas-measurement-derived calculations of explosion gas masses at Yasur. Yasur typically exhibits persistent passive gas release interspersed with frequent Strombolian explosions. We used compact forms of the “PiCam” Raspberry Pi UV camera system [1,2] powered through solar panels to collect images. Our daily median SO2 fluxes ranged from 4 to 5.1 kg s−1, with a measurement uncertainty of −12.2% to +14.7%, including errors from the gas cell calibration drift, uncertainties in plume direction and distance, and…
Explosive eruptions with little warning: Experimental petrology and volcano monitoring observations from the 2014 eruption of Kelud, Indonesia
2019
Explosive eruptions that occur with little or no precursory unrest (less than a month) pose the greatest hazards from volcanoes to nearby populations. Here we focus on the preeruptive conditions for these explosive events, their triggers and how these eruptions evolve. We concentrate on Kelud volcano, where we have conducted a set of petrological experiments to understand preeruptive storage conditions for several recent eruptions. For the 2014 explosive eruption, we combine this with an analysis of interferometric synthetic aperture radar measured deformation. Our data suggest that both explosive and effusive eruptions at Kelud are sourced from a magma storage system at 2-4 km. However, ex…
Massive submarine gas output during the volcanic unrest off Panarea Island (Aeolian arc, Italy): Inferences for explosive conditions
2005
The possibility of understanding natural processes leading to explosive events in volcanic systems provides advantages for a better management of possible volcanic crises. On account of the possibility of the occurrence of other phenomena, such as tsunamis, the explosions driven by submarine volcanic systems are of particular interest, although little investigated. The recent sudden increase in the degassing activity of the submarine geothermal system of Panarea Island (Aeolian arc), has allowed us to better understand the way in which the quiet degassing activity of a submarine hydrothermal system may develop if new magma or magmatic gases feed it. We focused our investigations on the crat…
Frequency Based Detection and Monitoring of Small Scale Explosive Activity by Comparing Satellite and Ground Based Infrared Observations at Stromboli…
2014
Abstract Thermal activity is a common precursor to explosive volcanic activity. The ability to use these thermal precursors to monitor the volcano and obtain early warning about upcoming activity is beneficial for both human safety and infrastructure security. By using a very reliably active volcano, Stromboli Volcano in Italy, a method has been developed and tested to look at changes in the frequency of small scale explosive activity and how this activity changes prior to larger, ash producing explosive events. Thermal camera footage was used to designate parameters for typical explosions at Stromboli (size of spatter field, cooling rate, frequency of explosions) and this information was a…
Spectroscopic capture of 1 Hz volcanic SO2fluxes and integration with volcano geophysical data
2009
[1] Here we present a novel spectroscopic approach to capturing, with unprecedented time resolution and accuracy, volcanic SO2 fluxes. This is based on two USB2000 spectrometers, coupled to cylindrical lens telescopes, each collecting light which has transited horizontal sections of the rising plume. We report on field data from Stromboli volcano, in which the entire emission rate from the volcano was measured, as well as flux signatures associated with individual crater explosions. The latter were integrated with seismic and thermal data, demonstrating correlations in both cases, and representing the first such geophysical-geochemical data corroboration on this timescale. Such a holistic e…
Detecting explosive substances by the IR spectrography
2014
Fast and safe detection methods of explosive substances are needed both before and after actualized explosions. This article presents an experiment of the detection of three selected explosives by the ATR FTIR spectrometer and by three different IR hyperspectral imaging devices. The IR spectrometers give accurate analyzing results, whereas hyperspectral imagers can detect and analyze desired samples without touching the unidentified target at all. In the controlled explosion experiment TNT, dynamite and PENO were at first analyzed as pure substances with the ATR FTIR spectrometer and with VNIR, SWIR and MWIR cameras. After three controlled explosions also the residues of TNT, dynamite and P…