H. Pinkerton | Lancaster University (original) (raw)

Papers by H. Pinkerton

IAVCEI Proceedings in Volcanology, 1995

ABSTRACT

Routledge eBooks, Jul 13, 2022

Journal of Volcanology and Geothermal Research, 2010

Basaltic 'a'ā lava flows often demonstrate compound morphology, consisting of many juxtaposed and... more Basaltic 'a'ā lava flows often demonstrate compound morphology, consisting of many juxtaposed and superposed flow units. Following observations made during the 2001 eruption of Mt. Etna, Sicily, we examine the processes that can result from the superposition of flow units, when the underlying units are sufficiently young to have immature crusts and deformable cores. During this eruption, we observed that the emplacement of new surface flow units may reactivate older, underlying units by squeezing the still-hot flow core away from the site of loading. Here, we illustrate three different styles of reactivation that depend on the time elapsed between the emplacement of the two flow units, hence the rheological contrast between them. For relatively long time intervals (2 to 15 days), and consequently significant rheological contrasts, superposition can pressurise the underlying flow unit, leading to crustal rupture and the subsequent extrusion of a small volume of high yield strength lava. Following shorter intervals (1 to 2 days), the increased pressure caused by superposition can result in renewed, slow advance of the underlying immature flow unit front. On timescales of < 1 day, where there is little rheological contrast between the two units, the thin intervening crust can be disrupted during superposition, allowing mixing of the flow cores, large-scale reactivation of both units, and widespread channel drainage. This mechanism may explain the presence of drained channels in flows that are known to have been cooling-limited, contrary to the usual interpretation of drainage as an indicator of volume-limited behaviour. Because the remobilisation of previously stagnant lava can occur swiftly and unexpectedly, it may pose a significant hazard during the emplacement of compound flows. Constant monitoring of flow development to identify areas where superposition is occurring is therefore recommended, as this may allow potentially hazardous rapid drainage events to be forecast. Reactivation processes should also be borne in mind when reconstructing the emplacement of old lava flow fields, as failure to recognise their effects may result in the misinterpretation of features such as drained channels.

IAVCEI Proceedings in Volcanology, 1995

ABSTRACT

Long-lived eruptions from basaltic volcanoes involving episodic or steady activity indicate that ... more Long-lived eruptions from basaltic volcanoes involving episodic or steady activity indicate that a delicate balance has been struck between the rate of magma cooling in the dike system feeding the vent and the rate of magma supply to the dike system from a reservoir. We describe some key factors, involving the relationships between magma temperature, magma rheology, and dike geometry that control the nature of such eruptions.

The cinder cone that developed on Piano del Lago (the "Laghetto" cone) during the July-... more The cinder cone that developed on Piano del Lago (the "Laghetto" cone) during the July-August 2001 Etna eruption was monitored closely during daily helicopter sur- veys. The early stages of the emplacement of this vent were marked by the opening of a field of fractures just north of La Montagnola cone between 13 and 16 July. The frac- ture width increased on 17 July and they propagated around the eastern and western sides of La Montagnola cone. On 20 July, two pit craters formed at 2550 m a.s.l., and subsequently coalesced. Ballistically emplaced blocks formed a rampart on the west- ern side of the pits, while fine ash was transported by wind to the east. Phreatomag- matic activity from the pits was very intense during the following days, and three major vents aligned N-S were observed on 22 July. The activity of the Laghetto cone became increasingly magmatic on 24 July, when the ash plume was composed mostly of black juvenile ash. On 25 July, the northern vent was charact...

Journal of Volcanology and Geothermal Research, 2002

Systematic hand-held radiometer measurements of lava surface temperatures in active flows and tub... more Systematic hand-held radiometer measurements of lava surface temperatures in active flows and tubes on Kilauea volcano, Hawai'i reveal complexities that cannot be resolved in remotely sensed data from aircraft or satellites. Using portable infrared Minolta/Land Cyclops radiometers, we measured surface temperatures of flows at various distances from their sources and investigated cooling rates and the development of crust. Our measurements suggest that the upper surface of these lava flows can be split into a minimum of four thermal components; core (>1050 ˚C), visco-elastic skin (750 to 900 ˚C), rigid solid crust (<750 ˚C), and flow margins (<175 ˚C). For the 'a'a flows investigated, a cool rigid crust characteristically developed in the central part of channels within 30 m of the source vent and incandescent lava was exposed in the marginal shear zones of channels. This affects the heat loss and morphology of lava in active channels. Our investigations of temperature distributions on pahoehoe flow fields reveal temperature anomalies of up to 150 ˚C above active tubes and tumuli.

Journal of Volcanology and Geothermal Research, 1992

Non-vesicular basaltic melts behave as Newtonian fluids at temperatures above their liquidus and ... more Non-vesicular basaltic melts behave as Newtonian fluids at temperatures above their liquidus and their viscosities can be calculated using a method developed by Shaw (1972) and Bottinga and Weill (1972). Because many igneous processes involve the flow of silicates at sub-liquidus temperatures, numerous attempts have been made to calculate the interactive effects of the crystal phase. However, current methods are appropriate only for relatively low crystal concentrations, and they assume Newtonian behaviour; we argue that this assumption is invalid when bubble or crystal concentrations exceed 30%. At higher concentrations, factors other than concentration become increasingly important; these include particle shape and size distribution. A method which takes these factors into account is tested on a range of suspensions, including magmas at sub-liquidus temperatures, and rheological properties calculated using this method agree closely with the measured values. We also demonstrate that an equation which was introduced to explain large differences in measured apparent viscosities during the cooling and crystallisation of Mount St. Helens dacite (Murase et al., 1985), and which is currently used to calculate the theological properties of crystallising lavas, generates viscosities which may be in error by several orders of magnitude. This difference is argued to be caused by a combination of factors, including the ten orders of magnitude range in the strain rates utilised during the Mount St. Helens measurements causing orders of magnitude difference in the resulting apparent viscosities. Rheological data on crystallising silicic melts are reinterpreted taking into account the non-Newtonian rheology of the magmas and changes in activation energy of flow during crystallisation.

Journal of Geophysical Research: Solid Earth, 2006

Volcano observatories and researchers are recognizing the potential usefulness of thermal imaging... more Volcano observatories and researchers are recognizing the potential usefulness of thermal imaging cameras both before and during volcanic eruptions. Obvious applications include measurements of the surface temperatures of active lava domes and lava flows to determine the location of the most active parts of these potentially hazardous features. If appropriate precautions are taken, the new generation of thermal imaging cameras can be used to extract quantitative as well as qualitative information on volcanic activity. For example, they can be used to measure the temperature of lava on eruption and to reveal how the crust cools during flow emplacement. This is important for the validation of lava flow models. To ensure that meaningful temperatures are collected, thermal imaging data must be corrected for instrumental errors, emissivity of the surface being imaged, atmospheric attenuation, viewing angle and surface roughness. Controlled laboratory experiments have been undertaken to determine the emissivity of smooth and rough samples and the effects of viewing angle and to quantify the errors. Measured emissivities range from 0.973 ± 0.002 for smooth samples of basalt and 0.984 ± 0.004 for rough samples. Errors in emissivity-corrected temperatures are within ±15°C for lava at 1100°C. Variations from individual sensor receptors, which provide individual pixel temperature data, were found to be 0.6% and instrumental errors of the cameras used were 0.1%. Apparent temperatures were found to vary by less than the instrumental error for viewing angles up to 30 degrees from normal to lava, and thereafter increased by 1°Cperdegree.ByincreasingtheapparentviewingdistanceofasmallventonMountEtnafrom1.5to30m,themaximumtemperatureisshowntodecreaseby53°Cduetointegratedaveragingofradianceoverincreasedpixelareas.Ataviewingdistanceof250mthemaximumtemperaturedecreasedby1°C per degree. By increasing the apparent viewing distance of a small vent on Mount Etna from 1.5 to 30 m, the maximum temperature is shown to decrease by 53°C due to integrated averaging of radiance over increased pixel areas. At a viewing distance of 250 m the maximum temperature decreased by 1°Cperdegree.ByincreasingtheapparentviewingdistanceofasmallventonMountEtnafrom1.5to30m,themaximumtemperatureisshowntodecreaseby53°Cduetointegratedaveragingofradianceoverincreasedpixelareas.Ataviewingdistanceof250mthemaximumtemperaturedecreasedby200°C with a further 75°C decrease due to atmospheric attenuation for a relative humidity of 50%. However, errors in relative humidity measurements can lead to atmospheric attenuation correction inaccuracies up to 200°C at viewing distances of 1 km. We show how temperatures measured using thermal imaging cameras can be corrected to give improved estimates of temperature distributions on the surface of active lava flows.

International Journal of Remote Sensing, 2008

and-conditions-of-access.pdf This article may be used for research, teaching and private study pu... more and-conditions-of-access.pdf This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, redistribution , reselling , loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.

Geophysical Journal International, 2009

A rigorous analysis of the timing and location of flank eruptions of Mount Etna on Sicily is impo... more A rigorous analysis of the timing and location of flank eruptions of Mount Etna on Sicily is important for the creation of hazard maps of the densely populated area surrounding the volcano. In this paper, we analyse the temporal, volumetric and spatial data on eruptive activity on Etna. Our analyses are based on the two most recent and robust historical data catalogues of flank eruption activity on Etna, with one from 1669 to 2008 and the other from 1610 to 2008. We use standard statistical methodology and modelling techniques, though a number of features are new to the analysis of eruption data. Our temporal analysis reveals that flank eruptions on Mount Etna between 1610 and 2008 follow an inhomogeneous Poisson process, with intensity of eruptions increasing nearly linearly since the mid-1900s. Our temporal analysis reveals no evidence of cyclicity over this period. An analysis of volumetric lava flow rates shows a marked increase in activity since 1971. This increase, which coincides with the formation of the Southeast Crater (SEC), appears to be related to increased activity on and around the SEC. This has significant implications for hazard analysis on Etna.

Geochemistry, Geophysics, Geosystems, 2007

Understanding the processes involved with the advance of lava flows is critical for improving haz... more Understanding the processes involved with the advance of lava flows is critical for improving hazard assessments at many volcanoes. Here, we describe the application of computer vision and oblique photogrammetric techniques to visible and thermal images of active 'a' a flows in order to investigate distal flow processes at Mount Etna, Sicily. Photogrammetric surveys were carried out to produce repeated topographic data sets for calculation of volumetric lava flux at the flow-fronts. Velocity profiles from a distal channel were obtained by rectification of a thermal image sequence and are used to investigate the rheological properties of the lava. Significant variations of the magma flux were observed, and pulses of increased flux arrived within the flow-front region on timescales of several hours. The pulses are believed to be the distal result of more frequent flux changes observed in the vent region. Hence they reflect the importance of flow processes which are believed to cause the coalescence of flux pulses along the channel system as well as short-period variations in effusion rate. In considering advance processes for the individual flow-fronts, it must be assumed that they were fed by a highly unsteady flux, which was volumetrically at least an order of magnitude lower than that observed near the vent. Components: 10,081 words, 8 figures, 2 tables.

Coastal Engineering, 2009

This paper presents a simple nonlinear data-based modelling approach for predicting the beach pro... more This paper presents a simple nonlinear data-based modelling approach for predicting the beach profile volume at Duck, North Carolina, USA. The state-dependent parameter form of the general transfer function (SDP TF) model is used to describe nonlinearity influencing these morphological data in two case examples. Case 1 investigates the nonlinearity associated with the dependency of wave forcing on the preceding beach volume. Case 2 investigates the ability to model the variables within the well known diffusion equation for beach volume using this data-based approach. The results of this study show that the SDP TF approach can be used successfully to develop statistically robust models for describing nonlinearity in beach morphological systems. Furthermore, these models are shown to predict the beach volumes over both short (1 month ahead) and long (2 years ahead) time periods, and thus show great potential for practical applications in coastal zone management and engineering.

Bulletin of Volcanology, 2011

During long-lived basaltic eruptions, overflows from lava channels and breaching of channel levée... more During long-lived basaltic eruptions, overflows from lava channels and breaching of channel levées are important processes in the development of extensive 'a'ā lava flow-fields. Short-lived breaches result in inundation of areas adjacent to the main channel. However, if a breach remains open, lava supply to the original flow front is significantly reduced, and flow-field widening is favoured over lengthening. The development of channel breaches and overflows can therefore exert strong control over the overall flow-field development, but the processes that determine their location and frequency are currently poorly understood. During the final month of the 2008–2009 eruption of Mt. Etna, Sicily, a remote time-lapse camera was deployed to monitor events in a proximal region of a small ephemeral lava flow. For over a period of ~10 h, the flow underwent changes in surface elevation and velocity, repeated overflows of varying vigour and the construction of a channel roof (a required prelude to lava tube formation). Quantitative interpretation of the image sequence was facilitated by a D model of the scene constructed using structure-from-motion computer vision techniques. As surface activity waned during the roofing process, overflow sites retreated up the flow towards the vent, and eventually, a new flow was initiated. Our observations and measurements indicate that flow surface stagnation and flow inflation propagated up-flow at an effective rate of ~6 m h−1, and that these processes, rather than effusion rate variations, were ultimately responsible for the most vigorous overflow events. We discuss evidence for similar controls during levée breaching and channel switching events on much larger flows on Etna, such as during the 2001 eruption.

Bulletin of Volcanology, 2006

Page 1. Bull Volcanol (2006) 69: 105–108 DOI 10.1007/s00445-006-0062-9 SHORT SCIENTIFIC COMMUNICA... more Page 1. Bull Volcanol (2006) 69: 105–108 DOI 10.1007/s00445-006-0062-9 SHORT SCIENTIFIC COMMUNICATION Mike R. James . Stuart Robson . Harry Pinkerton . Matthew Ball Oblique photogrammetry with visible and thermal images of active lava flows ...

The general processes associated with the formation and activity of ephemeral boccas in lava flow... more The general processes associated with the formation and activity of ephemeral boccas in lava flow fields are well documented (e.g. Pinkerton & Sparks 1976; Polacci & Papale 1997). The importance of studying such behaviour is illustrated by observations of the emplacement of a basaltic andesite flow at Parícutin during the 1940s. Following a pause in advance of one month, this 8 km long flow was reactivated by the resumption of supply from the vent, which forced the rapid drainage of stagnant material in the flow front region. The material extruded during drainage was in a highly plastic state (Krauskopf 1948), and its displacement allowed hot fluid lava from the vent to be transported in a tube to the original flow front, from where it covered an area of 350,000 m2 in one night (Luhr & Simkin 1993). Determining when a flow has stopped advancing, and cannot be drained in such a manner, is therefore highly important in hazard assessment and flow modelling, and our ability to do this may be improved through the examination of relatively small-scale secondary extrusions and boccas. The 2001 flank eruption of Mt. Etna, Sicily, resulted in the emplacement of a 7 km long compound 'a'ā flow field over a period of 23 days. During emplacement, many ephemeral boccas were observed in the flow field, which were active for between two and at least nine days. The longer-lived examples initially fed well-established flows that channelled fresh material from the main vent. With time, as activity waned, the nature of the extruded material changed. The latest stages of development of all boccas involved the very slow extrusion of material that was either draining from higher parts of the flow or being forced out of the flow interior as changing local flow conditions pressurised parts of the flow that had been stagnant for some time. Here we describe this late-stage activity of the ephemeral boccas, which resulted in the formation of 'squeeze-ups' of lava with a markedly different texture to that of the surrounding 'a'ā flow surface. The appearance of the squeeze-up material in this flow is similar to that of the plastic lava forcibly drained from the front of the Parícutin flow. The squeeze-up features demonstrate marked morphological variation, which was found to reflect the rheology of the material being extruded, the volume of material being extruded, the extrusion rate and the geometry of the source bocca. We describe the final morphology of squeeze-ups from the 2001 flow field, which ranges from relatively fluid flows to extrusions of high-strength material that accumulated above the source bocca, forming features more akin to tumuli. Although tumulus-like in overall shape and dimensions, the morphology and inferred growth mechanisms for these structures leads to them being dubbed 'exogenous tumuli', to distinguish them from the more familiar tumuli resulting from inflation processes, which are described elsewhere (e.g. Macdonald 1972; Walker 1991; Duncan et al. 2004). The morphological data are then used together with observations of lava surface textures and squeeze-up locations to build up a picture of flow structure and flow dynamics at the time of squeeze-up formation. The structure of the crust underlying the clinker cover can be elucidated by examining the locations in which squeeze-ups occur, as extrusions exploit zones of crustal weakness. It is found that the flow crust plays an increasingly important role in determining the locus of squeeze-ups as the flow evolves. Squeeze-ups that clearly had a high strength upon extrusion formed as a result of high overpressures in the flow interior. The extrusion of such material may represent the latter stages of activity of a long-lived bocca, or the new development of a bocca in a part of the flow that had been stagnant for some time. Examination of squeeze-up textures may help determine whether the material was transported to the extrusion site in an open or closed system, or if it was stored for a significant length of time before extrusion. Information may also be gleaned concerning the maximum crystallinity at which lava can flow, which is an important parameter in flow modelling. Evidence for a mechanism by which sufficient overpressure can be generated to extrude such material is presented.

IAVCEI Proceedings in Volcanology, 1995

ABSTRACT

Routledge eBooks, Jul 13, 2022

Journal of Volcanology and Geothermal Research, 2010

Basaltic 'a'ā lava flows often demonstrate compound morphology, consisting of many juxtaposed and... more Basaltic 'a'ā lava flows often demonstrate compound morphology, consisting of many juxtaposed and superposed flow units. Following observations made during the 2001 eruption of Mt. Etna, Sicily, we examine the processes that can result from the superposition of flow units, when the underlying units are sufficiently young to have immature crusts and deformable cores. During this eruption, we observed that the emplacement of new surface flow units may reactivate older, underlying units by squeezing the still-hot flow core away from the site of loading. Here, we illustrate three different styles of reactivation that depend on the time elapsed between the emplacement of the two flow units, hence the rheological contrast between them. For relatively long time intervals (2 to 15 days), and consequently significant rheological contrasts, superposition can pressurise the underlying flow unit, leading to crustal rupture and the subsequent extrusion of a small volume of high yield strength lava. Following shorter intervals (1 to 2 days), the increased pressure caused by superposition can result in renewed, slow advance of the underlying immature flow unit front. On timescales of < 1 day, where there is little rheological contrast between the two units, the thin intervening crust can be disrupted during superposition, allowing mixing of the flow cores, large-scale reactivation of both units, and widespread channel drainage. This mechanism may explain the presence of drained channels in flows that are known to have been cooling-limited, contrary to the usual interpretation of drainage as an indicator of volume-limited behaviour. Because the remobilisation of previously stagnant lava can occur swiftly and unexpectedly, it may pose a significant hazard during the emplacement of compound flows. Constant monitoring of flow development to identify areas where superposition is occurring is therefore recommended, as this may allow potentially hazardous rapid drainage events to be forecast. Reactivation processes should also be borne in mind when reconstructing the emplacement of old lava flow fields, as failure to recognise their effects may result in the misinterpretation of features such as drained channels.

IAVCEI Proceedings in Volcanology, 1995

ABSTRACT

Long-lived eruptions from basaltic volcanoes involving episodic or steady activity indicate that ... more Long-lived eruptions from basaltic volcanoes involving episodic or steady activity indicate that a delicate balance has been struck between the rate of magma cooling in the dike system feeding the vent and the rate of magma supply to the dike system from a reservoir. We describe some key factors, involving the relationships between magma temperature, magma rheology, and dike geometry that control the nature of such eruptions.

The cinder cone that developed on Piano del Lago (the "Laghetto" cone) during the July-... more The cinder cone that developed on Piano del Lago (the "Laghetto" cone) during the July-August 2001 Etna eruption was monitored closely during daily helicopter sur- veys. The early stages of the emplacement of this vent were marked by the opening of a field of fractures just north of La Montagnola cone between 13 and 16 July. The frac- ture width increased on 17 July and they propagated around the eastern and western sides of La Montagnola cone. On 20 July, two pit craters formed at 2550 m a.s.l., and subsequently coalesced. Ballistically emplaced blocks formed a rampart on the west- ern side of the pits, while fine ash was transported by wind to the east. Phreatomag- matic activity from the pits was very intense during the following days, and three major vents aligned N-S were observed on 22 July. The activity of the Laghetto cone became increasingly magmatic on 24 July, when the ash plume was composed mostly of black juvenile ash. On 25 July, the northern vent was charact...

Journal of Volcanology and Geothermal Research, 2002

Systematic hand-held radiometer measurements of lava surface temperatures in active flows and tub... more Systematic hand-held radiometer measurements of lava surface temperatures in active flows and tubes on Kilauea volcano, Hawai'i reveal complexities that cannot be resolved in remotely sensed data from aircraft or satellites. Using portable infrared Minolta/Land Cyclops radiometers, we measured surface temperatures of flows at various distances from their sources and investigated cooling rates and the development of crust. Our measurements suggest that the upper surface of these lava flows can be split into a minimum of four thermal components; core (>1050 ˚C), visco-elastic skin (750 to 900 ˚C), rigid solid crust (<750 ˚C), and flow margins (<175 ˚C). For the 'a'a flows investigated, a cool rigid crust characteristically developed in the central part of channels within 30 m of the source vent and incandescent lava was exposed in the marginal shear zones of channels. This affects the heat loss and morphology of lava in active channels. Our investigations of temperature distributions on pahoehoe flow fields reveal temperature anomalies of up to 150 ˚C above active tubes and tumuli.

Journal of Volcanology and Geothermal Research, 1992

Non-vesicular basaltic melts behave as Newtonian fluids at temperatures above their liquidus and ... more Non-vesicular basaltic melts behave as Newtonian fluids at temperatures above their liquidus and their viscosities can be calculated using a method developed by Shaw (1972) and Bottinga and Weill (1972). Because many igneous processes involve the flow of silicates at sub-liquidus temperatures, numerous attempts have been made to calculate the interactive effects of the crystal phase. However, current methods are appropriate only for relatively low crystal concentrations, and they assume Newtonian behaviour; we argue that this assumption is invalid when bubble or crystal concentrations exceed 30%. At higher concentrations, factors other than concentration become increasingly important; these include particle shape and size distribution. A method which takes these factors into account is tested on a range of suspensions, including magmas at sub-liquidus temperatures, and rheological properties calculated using this method agree closely with the measured values. We also demonstrate that an equation which was introduced to explain large differences in measured apparent viscosities during the cooling and crystallisation of Mount St. Helens dacite (Murase et al., 1985), and which is currently used to calculate the theological properties of crystallising lavas, generates viscosities which may be in error by several orders of magnitude. This difference is argued to be caused by a combination of factors, including the ten orders of magnitude range in the strain rates utilised during the Mount St. Helens measurements causing orders of magnitude difference in the resulting apparent viscosities. Rheological data on crystallising silicic melts are reinterpreted taking into account the non-Newtonian rheology of the magmas and changes in activation energy of flow during crystallisation.

Journal of Geophysical Research: Solid Earth, 2006

Volcano observatories and researchers are recognizing the potential usefulness of thermal imaging... more Volcano observatories and researchers are recognizing the potential usefulness of thermal imaging cameras both before and during volcanic eruptions. Obvious applications include measurements of the surface temperatures of active lava domes and lava flows to determine the location of the most active parts of these potentially hazardous features. If appropriate precautions are taken, the new generation of thermal imaging cameras can be used to extract quantitative as well as qualitative information on volcanic activity. For example, they can be used to measure the temperature of lava on eruption and to reveal how the crust cools during flow emplacement. This is important for the validation of lava flow models. To ensure that meaningful temperatures are collected, thermal imaging data must be corrected for instrumental errors, emissivity of the surface being imaged, atmospheric attenuation, viewing angle and surface roughness. Controlled laboratory experiments have been undertaken to determine the emissivity of smooth and rough samples and the effects of viewing angle and to quantify the errors. Measured emissivities range from 0.973 ± 0.002 for smooth samples of basalt and 0.984 ± 0.004 for rough samples. Errors in emissivity-corrected temperatures are within ±15°C for lava at 1100°C. Variations from individual sensor receptors, which provide individual pixel temperature data, were found to be 0.6% and instrumental errors of the cameras used were 0.1%. Apparent temperatures were found to vary by less than the instrumental error for viewing angles up to 30 degrees from normal to lava, and thereafter increased by 1°Cperdegree.ByincreasingtheapparentviewingdistanceofasmallventonMountEtnafrom1.5to30m,themaximumtemperatureisshowntodecreaseby53°Cduetointegratedaveragingofradianceoverincreasedpixelareas.Ataviewingdistanceof250mthemaximumtemperaturedecreasedby1°C per degree. By increasing the apparent viewing distance of a small vent on Mount Etna from 1.5 to 30 m, the maximum temperature is shown to decrease by 53°C due to integrated averaging of radiance over increased pixel areas. At a viewing distance of 250 m the maximum temperature decreased by 1°Cperdegree.ByincreasingtheapparentviewingdistanceofasmallventonMountEtnafrom1.5to30m,themaximumtemperatureisshowntodecreaseby53°Cduetointegratedaveragingofradianceoverincreasedpixelareas.Ataviewingdistanceof250mthemaximumtemperaturedecreasedby200°C with a further 75°C decrease due to atmospheric attenuation for a relative humidity of 50%. However, errors in relative humidity measurements can lead to atmospheric attenuation correction inaccuracies up to 200°C at viewing distances of 1 km. We show how temperatures measured using thermal imaging cameras can be corrected to give improved estimates of temperature distributions on the surface of active lava flows.

International Journal of Remote Sensing, 2008

and-conditions-of-access.pdf This article may be used for research, teaching and private study pu... more and-conditions-of-access.pdf This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, redistribution , reselling , loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.

Geophysical Journal International, 2009

A rigorous analysis of the timing and location of flank eruptions of Mount Etna on Sicily is impo... more A rigorous analysis of the timing and location of flank eruptions of Mount Etna on Sicily is important for the creation of hazard maps of the densely populated area surrounding the volcano. In this paper, we analyse the temporal, volumetric and spatial data on eruptive activity on Etna. Our analyses are based on the two most recent and robust historical data catalogues of flank eruption activity on Etna, with one from 1669 to 2008 and the other from 1610 to 2008. We use standard statistical methodology and modelling techniques, though a number of features are new to the analysis of eruption data. Our temporal analysis reveals that flank eruptions on Mount Etna between 1610 and 2008 follow an inhomogeneous Poisson process, with intensity of eruptions increasing nearly linearly since the mid-1900s. Our temporal analysis reveals no evidence of cyclicity over this period. An analysis of volumetric lava flow rates shows a marked increase in activity since 1971. This increase, which coincides with the formation of the Southeast Crater (SEC), appears to be related to increased activity on and around the SEC. This has significant implications for hazard analysis on Etna.

Geochemistry, Geophysics, Geosystems, 2007

Understanding the processes involved with the advance of lava flows is critical for improving haz... more Understanding the processes involved with the advance of lava flows is critical for improving hazard assessments at many volcanoes. Here, we describe the application of computer vision and oblique photogrammetric techniques to visible and thermal images of active 'a' a flows in order to investigate distal flow processes at Mount Etna, Sicily. Photogrammetric surveys were carried out to produce repeated topographic data sets for calculation of volumetric lava flux at the flow-fronts. Velocity profiles from a distal channel were obtained by rectification of a thermal image sequence and are used to investigate the rheological properties of the lava. Significant variations of the magma flux were observed, and pulses of increased flux arrived within the flow-front region on timescales of several hours. The pulses are believed to be the distal result of more frequent flux changes observed in the vent region. Hence they reflect the importance of flow processes which are believed to cause the coalescence of flux pulses along the channel system as well as short-period variations in effusion rate. In considering advance processes for the individual flow-fronts, it must be assumed that they were fed by a highly unsteady flux, which was volumetrically at least an order of magnitude lower than that observed near the vent. Components: 10,081 words, 8 figures, 2 tables.

Coastal Engineering, 2009

This paper presents a simple nonlinear data-based modelling approach for predicting the beach pro... more This paper presents a simple nonlinear data-based modelling approach for predicting the beach profile volume at Duck, North Carolina, USA. The state-dependent parameter form of the general transfer function (SDP TF) model is used to describe nonlinearity influencing these morphological data in two case examples. Case 1 investigates the nonlinearity associated with the dependency of wave forcing on the preceding beach volume. Case 2 investigates the ability to model the variables within the well known diffusion equation for beach volume using this data-based approach. The results of this study show that the SDP TF approach can be used successfully to develop statistically robust models for describing nonlinearity in beach morphological systems. Furthermore, these models are shown to predict the beach volumes over both short (1 month ahead) and long (2 years ahead) time periods, and thus show great potential for practical applications in coastal zone management and engineering.

Bulletin of Volcanology, 2011

During long-lived basaltic eruptions, overflows from lava channels and breaching of channel levée... more During long-lived basaltic eruptions, overflows from lava channels and breaching of channel levées are important processes in the development of extensive 'a'ā lava flow-fields. Short-lived breaches result in inundation of areas adjacent to the main channel. However, if a breach remains open, lava supply to the original flow front is significantly reduced, and flow-field widening is favoured over lengthening. The development of channel breaches and overflows can therefore exert strong control over the overall flow-field development, but the processes that determine their location and frequency are currently poorly understood. During the final month of the 2008–2009 eruption of Mt. Etna, Sicily, a remote time-lapse camera was deployed to monitor events in a proximal region of a small ephemeral lava flow. For over a period of ~10 h, the flow underwent changes in surface elevation and velocity, repeated overflows of varying vigour and the construction of a channel roof (a required prelude to lava tube formation). Quantitative interpretation of the image sequence was facilitated by a D model of the scene constructed using structure-from-motion computer vision techniques. As surface activity waned during the roofing process, overflow sites retreated up the flow towards the vent, and eventually, a new flow was initiated. Our observations and measurements indicate that flow surface stagnation and flow inflation propagated up-flow at an effective rate of ~6 m h−1, and that these processes, rather than effusion rate variations, were ultimately responsible for the most vigorous overflow events. We discuss evidence for similar controls during levée breaching and channel switching events on much larger flows on Etna, such as during the 2001 eruption.

Bulletin of Volcanology, 2006

Page 1. Bull Volcanol (2006) 69: 105–108 DOI 10.1007/s00445-006-0062-9 SHORT SCIENTIFIC COMMUNICA... more Page 1. Bull Volcanol (2006) 69: 105–108 DOI 10.1007/s00445-006-0062-9 SHORT SCIENTIFIC COMMUNICATION Mike R. James . Stuart Robson . Harry Pinkerton . Matthew Ball Oblique photogrammetry with visible and thermal images of active lava flows ...

The general processes associated with the formation and activity of ephemeral boccas in lava flow... more The general processes associated with the formation and activity of ephemeral boccas in lava flow fields are well documented (e.g. Pinkerton & Sparks 1976; Polacci & Papale 1997). The importance of studying such behaviour is illustrated by observations of the emplacement of a basaltic andesite flow at Parícutin during the 1940s. Following a pause in advance of one month, this 8 km long flow was reactivated by the resumption of supply from the vent, which forced the rapid drainage of stagnant material in the flow front region. The material extruded during drainage was in a highly plastic state (Krauskopf 1948), and its displacement allowed hot fluid lava from the vent to be transported in a tube to the original flow front, from where it covered an area of 350,000 m2 in one night (Luhr & Simkin 1993). Determining when a flow has stopped advancing, and cannot be drained in such a manner, is therefore highly important in hazard assessment and flow modelling, and our ability to do this may be improved through the examination of relatively small-scale secondary extrusions and boccas. The 2001 flank eruption of Mt. Etna, Sicily, resulted in the emplacement of a 7 km long compound 'a'ā flow field over a period of 23 days. During emplacement, many ephemeral boccas were observed in the flow field, which were active for between two and at least nine days. The longer-lived examples initially fed well-established flows that channelled fresh material from the main vent. With time, as activity waned, the nature of the extruded material changed. The latest stages of development of all boccas involved the very slow extrusion of material that was either draining from higher parts of the flow or being forced out of the flow interior as changing local flow conditions pressurised parts of the flow that had been stagnant for some time. Here we describe this late-stage activity of the ephemeral boccas, which resulted in the formation of 'squeeze-ups' of lava with a markedly different texture to that of the surrounding 'a'ā flow surface. The appearance of the squeeze-up material in this flow is similar to that of the plastic lava forcibly drained from the front of the Parícutin flow. The squeeze-up features demonstrate marked morphological variation, which was found to reflect the rheology of the material being extruded, the volume of material being extruded, the extrusion rate and the geometry of the source bocca. We describe the final morphology of squeeze-ups from the 2001 flow field, which ranges from relatively fluid flows to extrusions of high-strength material that accumulated above the source bocca, forming features more akin to tumuli. Although tumulus-like in overall shape and dimensions, the morphology and inferred growth mechanisms for these structures leads to them being dubbed 'exogenous tumuli', to distinguish them from the more familiar tumuli resulting from inflation processes, which are described elsewhere (e.g. Macdonald 1972; Walker 1991; Duncan et al. 2004). The morphological data are then used together with observations of lava surface textures and squeeze-up locations to build up a picture of flow structure and flow dynamics at the time of squeeze-up formation. The structure of the crust underlying the clinker cover can be elucidated by examining the locations in which squeeze-ups occur, as extrusions exploit zones of crustal weakness. It is found that the flow crust plays an increasingly important role in determining the locus of squeeze-ups as the flow evolves. Squeeze-ups that clearly had a high strength upon extrusion formed as a result of high overpressures in the flow interior. The extrusion of such material may represent the latter stages of activity of a long-lived bocca, or the new development of a bocca in a part of the flow that had been stagnant for some time. Examination of squeeze-up textures may help determine whether the material was transported to the extrusion site in an open or closed system, or if it was stored for a significant length of time before extrusion. Information may also be gleaned concerning the maximum crystallinity at which lava can flow, which is an important parameter in flow modelling. Evidence for a mechanism by which sufficient overpressure can be generated to extrude such material is presented.