Recent Literature
All papers on this page are available via Web of Science database
Below is a list of the four most recent articles and their abstracts published on the Galeras Volcanic Complex. All titles (in white) are linked to the Web of Science page, where the .pdf is downloadable.
Title: Gas storage, transport and pressure changes in an evolving permeable volcanic edifice
Author(s): Collinson, A. S. D.; Neuberg, J. W.
Source: JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH Volume: 243 Pages: 1-13 DOI: 10.1016/j.jvolgeores.2012.06.027 Published: OCT 15 2012
Abstract: The total volume of gas in a magma, dissolved and subsequently exsolved, greatly influences the degree of explosiveness of a volcanic system. There is a marked contrast between the behaviour of a volcano in an "open" system compared to one which is "closed". It is therefore essential to understand the entire degassing process: gas transport, storage and loss. A particular focus of this study is the effect different permeabilities and pressure gradients within a volcanic edifice have on the degree and pattern of the gas velocity. Gas loss is modelled numerically in two dimensions using a finite element approach, which allows the specification of boundary conditions with respect to pressure and different permeability domains within the volcanic edifice. By combining the time-dependent continuity equation and Darcy's law, a partial differential equation is derived and solved for the pressure. The associated pressure gradient is then used within Darcy's law to determine the corresponding gas velocity distribution. This method is used not only for stationary systems in equilibrium, but also as a time-dependent progression. It permits the modelling of different situations to study how various volcanic characteristics affect the gas loss. The model is used to investigate the change in pressure and gas in response to time-dependent scenarios. These are a dome collapse or sudden increase in permeability by magma rupture at the conduit margin, the formation of cracks within the lava dome and sealing by crystallisation.
Our results show that a combination of high and low permeability regions is required for effective gas storage. High permeability allows the gas to enter the system, but impermeable areas act to confine the gas, thereby increasing its pressure and consequently, increasing the amount of gas which may be dissolved in the melt. Furthermore, our results show that permeability is an essential factor influencing the response time to system changes, which could be linked in future to deformation and other geophysical observations. Our model is highly versatile and sheds new light on the understanding of gas storage and transport in a permeable volcanic edifice. (c) 2012 Elsevier B.V. All rights reserved.
Title: Digital elevation model uncertainty and hazard analysis using a geophysical flow model
Author(s): Stefanescu, E. R.; Bursik, M.; Cordoba, G.; et al.
Source: PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES Volume: 468 Issue: 2142 Pages: 1543-1563 DOI: 10.1098/rspa.2011.0711 Published: JUN 8 2012Times Cited: 0 (from Web of Science)
Abstract: This paper describes a new methodology to quantify the variation in the output of a computational fluid dynamics model for block and ash flows, when the digital elevation model (DEM) of the terrain and other inputs are given as a range of possible values with a prescribed uncertainty. Integrating these variations in the possible flows as a function of input uncertainties provides well-defined hazard probabilities at specific locations, i.e. a hazard map. Earlier work provided a methodology for assessing hazards based on variations in flow initiation and friction parameters. This paper extends this approach to include the effect of terrain error and uncertainty. The results are based on potential flows at Mammoth Mountain, CA, andGaleras Volcano, Colombia. The analysis establishes the soundness of the approach and the effect of including the uncertainty in DEMs in the construction of probabilistic hazard maps.
Title: Co-eruptive subsidence at Galeras identified during an InSAR survey of Colombian volcanoes (2006-2009)
Author(s): Parks, M. M.; Biggs, J.; Mather, T. A.; et al.
Source: JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH Volume: 202 Issue: 3-4 Pages: 228-240 DOI:10.1016/j.jvolgeores.2011.02.007 Published: MAY 30 2011Times Cited: 1 (from Web of Science)
Abstract: Establishing a time series of deformation is one of the keys to understanding and predicting the magmatic behaviour of active volcanoes. Satellite techniques represent an increasingly useful tool for measuring volcanic deformation over timescales spanning days to decades. Colombia contains numerous young or active volcanoes, many of which are inaccessible. We use L-band (23.6 cm wavelength) radar data acquired between 2006 and 2009, to survey 15 active volcanoes along the Colombian segment of the Northern Volcanic Zone. Analysis of 100 interferograms showed that the majority of volcanoes were not deforming. However, independent interferograms display an average subsidence of 3 cm on the northeast flank ofGaleras, coinciding with the January 2008 eruption. We combine InSAR, field measurements and source modelling to determine the origin, size and location of the source of subsidence at Galeras. Our results suggest that this signal was caused by deflation of the magma chamber associated with the January 2008 event. Modelling provides insight into the depth to source (similar to 2 km) and a volume change (-6.5 x 10(5) m(3)) which is consistent with that derived from modelling contemporaneous tilts and the volume of material erupted. Previous studies based on various datasets support the existence of a resident/recurring chamber at this location, over a decadal timescale. Our InSAR results corroborate the hypothesis of shallow magma storage beneath Galeras and provide the first piece of evidence that can be linked to a particular eruption. (C) 2011 Elsevier B.V. All rights reserved.
Title: S-wave attenuation characteristics in the Galeras volcanic complex (south western Colombia)
Author(s): Ugalde, Arantza; Carcole, Eduard; Vargas, Carlos A.
Source: PHYSICS OF THE EARTH AND PLANETARY INTERIORS Volume: 181 Issue: 3-4 Pages: 73-81 DOI: 10.1016/j.pepi.2010.04.009 Published: AUG 2010Times Cited: 0 (from Web of Science)
Abstract: Vertical-component, short period seismograms from 435 well located volcano-tectonic earthquakes are used to estimate S-wave attenuation in the Galeras volcanic complex (south western Colombia) using coda waves. The coda magnitudes (M(c)) of the events are less than 2. Event depths are less than 10 km and hypocentral distances up to 16 km. Intrinsic absorption (Q(i)(-1)) and scattering attenuation (Q(s)(-1)) are estimated by means of a fitting procedure between the observed and synthetic coda envelopes in four frequency bands (1-2, 2-4,4-8, and 8-12 Hz). The observations are compared with the theoretical predictions by an accurate approximate analytical solution of the radiative transfer equation which is based on the assumptions of multiple isotropic scattering, impulsive isotropic point source, and a medium with homogeneous scattering and absorption properties. Results show that scattering is strong and it constitutes the predominant attenuation effect in this region. In the frequency range analyzed in this study the values of the mean free path for scattering of S waves range between 2.7 <= l <= 8.1 km, which are clearly higher than those obtained in other volcanic regions of the world, but about two orders of magnitude smaller than average estimates for the Earth's crust. The characteristic length scale of intrinsic absorption gives values of 2.5 <= l(a) <= 77 km, which are on the same order as the usual values for the Earth's crust. (C) 2010 Elsevier B.V. All rights reserved.
Below is a list of the four most recent articles and their abstracts published on the Galeras Volcanic Complex. All titles (in white) are linked to the Web of Science page, where the .pdf is downloadable.
Title: Gas storage, transport and pressure changes in an evolving permeable volcanic edifice
Author(s): Collinson, A. S. D.; Neuberg, J. W.
Source: JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH Volume: 243 Pages: 1-13 DOI: 10.1016/j.jvolgeores.2012.06.027 Published: OCT 15 2012
Abstract: The total volume of gas in a magma, dissolved and subsequently exsolved, greatly influences the degree of explosiveness of a volcanic system. There is a marked contrast between the behaviour of a volcano in an "open" system compared to one which is "closed". It is therefore essential to understand the entire degassing process: gas transport, storage and loss. A particular focus of this study is the effect different permeabilities and pressure gradients within a volcanic edifice have on the degree and pattern of the gas velocity. Gas loss is modelled numerically in two dimensions using a finite element approach, which allows the specification of boundary conditions with respect to pressure and different permeability domains within the volcanic edifice. By combining the time-dependent continuity equation and Darcy's law, a partial differential equation is derived and solved for the pressure. The associated pressure gradient is then used within Darcy's law to determine the corresponding gas velocity distribution. This method is used not only for stationary systems in equilibrium, but also as a time-dependent progression. It permits the modelling of different situations to study how various volcanic characteristics affect the gas loss. The model is used to investigate the change in pressure and gas in response to time-dependent scenarios. These are a dome collapse or sudden increase in permeability by magma rupture at the conduit margin, the formation of cracks within the lava dome and sealing by crystallisation.
Our results show that a combination of high and low permeability regions is required for effective gas storage. High permeability allows the gas to enter the system, but impermeable areas act to confine the gas, thereby increasing its pressure and consequently, increasing the amount of gas which may be dissolved in the melt. Furthermore, our results show that permeability is an essential factor influencing the response time to system changes, which could be linked in future to deformation and other geophysical observations. Our model is highly versatile and sheds new light on the understanding of gas storage and transport in a permeable volcanic edifice. (c) 2012 Elsevier B.V. All rights reserved.
Title: Digital elevation model uncertainty and hazard analysis using a geophysical flow model
Author(s): Stefanescu, E. R.; Bursik, M.; Cordoba, G.; et al.
Source: PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES Volume: 468 Issue: 2142 Pages: 1543-1563 DOI: 10.1098/rspa.2011.0711 Published: JUN 8 2012Times Cited: 0 (from Web of Science)
Abstract: This paper describes a new methodology to quantify the variation in the output of a computational fluid dynamics model for block and ash flows, when the digital elevation model (DEM) of the terrain and other inputs are given as a range of possible values with a prescribed uncertainty. Integrating these variations in the possible flows as a function of input uncertainties provides well-defined hazard probabilities at specific locations, i.e. a hazard map. Earlier work provided a methodology for assessing hazards based on variations in flow initiation and friction parameters. This paper extends this approach to include the effect of terrain error and uncertainty. The results are based on potential flows at Mammoth Mountain, CA, andGaleras Volcano, Colombia. The analysis establishes the soundness of the approach and the effect of including the uncertainty in DEMs in the construction of probabilistic hazard maps.
Title: Co-eruptive subsidence at Galeras identified during an InSAR survey of Colombian volcanoes (2006-2009)
Author(s): Parks, M. M.; Biggs, J.; Mather, T. A.; et al.
Source: JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH Volume: 202 Issue: 3-4 Pages: 228-240 DOI:10.1016/j.jvolgeores.2011.02.007 Published: MAY 30 2011Times Cited: 1 (from Web of Science)
Abstract: Establishing a time series of deformation is one of the keys to understanding and predicting the magmatic behaviour of active volcanoes. Satellite techniques represent an increasingly useful tool for measuring volcanic deformation over timescales spanning days to decades. Colombia contains numerous young or active volcanoes, many of which are inaccessible. We use L-band (23.6 cm wavelength) radar data acquired between 2006 and 2009, to survey 15 active volcanoes along the Colombian segment of the Northern Volcanic Zone. Analysis of 100 interferograms showed that the majority of volcanoes were not deforming. However, independent interferograms display an average subsidence of 3 cm on the northeast flank ofGaleras, coinciding with the January 2008 eruption. We combine InSAR, field measurements and source modelling to determine the origin, size and location of the source of subsidence at Galeras. Our results suggest that this signal was caused by deflation of the magma chamber associated with the January 2008 event. Modelling provides insight into the depth to source (similar to 2 km) and a volume change (-6.5 x 10(5) m(3)) which is consistent with that derived from modelling contemporaneous tilts and the volume of material erupted. Previous studies based on various datasets support the existence of a resident/recurring chamber at this location, over a decadal timescale. Our InSAR results corroborate the hypothesis of shallow magma storage beneath Galeras and provide the first piece of evidence that can be linked to a particular eruption. (C) 2011 Elsevier B.V. All rights reserved.
Title: S-wave attenuation characteristics in the Galeras volcanic complex (south western Colombia)
Author(s): Ugalde, Arantza; Carcole, Eduard; Vargas, Carlos A.
Source: PHYSICS OF THE EARTH AND PLANETARY INTERIORS Volume: 181 Issue: 3-4 Pages: 73-81 DOI: 10.1016/j.pepi.2010.04.009 Published: AUG 2010Times Cited: 0 (from Web of Science)
Abstract: Vertical-component, short period seismograms from 435 well located volcano-tectonic earthquakes are used to estimate S-wave attenuation in the Galeras volcanic complex (south western Colombia) using coda waves. The coda magnitudes (M(c)) of the events are less than 2. Event depths are less than 10 km and hypocentral distances up to 16 km. Intrinsic absorption (Q(i)(-1)) and scattering attenuation (Q(s)(-1)) are estimated by means of a fitting procedure between the observed and synthetic coda envelopes in four frequency bands (1-2, 2-4,4-8, and 8-12 Hz). The observations are compared with the theoretical predictions by an accurate approximate analytical solution of the radiative transfer equation which is based on the assumptions of multiple isotropic scattering, impulsive isotropic point source, and a medium with homogeneous scattering and absorption properties. Results show that scattering is strong and it constitutes the predominant attenuation effect in this region. In the frequency range analyzed in this study the values of the mean free path for scattering of S waves range between 2.7 <= l <= 8.1 km, which are clearly higher than those obtained in other volcanic regions of the world, but about two orders of magnitude smaller than average estimates for the Earth's crust. The characteristic length scale of intrinsic absorption gives values of 2.5 <= l(a) <= 77 km, which are on the same order as the usual values for the Earth's crust. (C) 2010 Elsevier B.V. All rights reserved.