Heat loss measured at a lava channel and its implications for down-channel cooling and rheology

Harris, Andrew; Bailey, John E.; Calvari, Sonia; Dehn, J.

doi:10.1130/0-8137-2396-5.125

Cited by 39 publications

(62 citation statements)

References 16 publications

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“…Fink and Zimbelman 1986;Wadge and Lopes 1991). A density of 2,740 kg/m 3 [calculated from the LFS1 lava composition of Corsaro et al (2007) using Bottinga and Weill (1970)] corrected for a vesicularity of 22% (Harris et al 2005), our 19 field measurements of flow-front thickness gave a yield strength of 2.6-3.4×10 3 Pa for lobe 3 (h o =4.1 to 5.6 m) compared with 5.6 to 12.6×10 3 Pa (h o =9 to 20 m) for all other lobes.…”

Section: Flow Frontmentioning

confidence: 99%

The distal segment of Etna’s 2001 basaltic lava flow

et al. 2009

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Etna's 2001 basaltic lava flow provided a good example of the distal flow segment between the flow front and stable channel, across which the flow evolves from channel-contained to dispersed. This zone was mapped with meter precision using LIDAR data collected during 2004 and 2005. These data, supported by field mapping, show that the flow front comprised eight lobes each 10 to 20 m high. The flow front appears to have advanced not as a single unit, but as a series of lobes moving forward one lobe at a time. Primary lobes were centered on the channel axis and marginal lobes were off-axis. The lobes advanced as breakouts of low-yield-strength lava from the flow core of the stalled flow front. Marginal lobes were abandoned and contributed to marginal levees flanking the transitional channel. For Etna's 2001 flow, the transitional channel is 140 m wide, 700 m long and fed a 240-m-long zone of dispersed flow; the change from stable to transitional channel occurred at a major reduction in slope. Above this, the stable channel is 5.2 km long, 55 to 105 m wide and bounded by 15-to 25-m-high levees, and the stable channel is located over a previous channel. In a final stage of activity, lava ponding at the break-in-slope that marks the terminus of the stable channel put pressure on the eastern levee, causing it to fail. Liberated lava then fed a final break-out to the east. Similar flow front-features occur at other volcanoes, indicating that similar processes are characteristic of dispersed flow zones.

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Section: Flow Frontmentioning

confidence: 99%

The distal segment of Etna’s 2001 basaltic lava flow

et al. 2009

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“…While heat losses from the flow surface are radiation (Q rad ) and convection (Q conv ), heat loss by conduction (Q cond ) will also occur through the flow base. Thus Q out ¼ Q rad þ Q conv þ Q cond Harris et al 1998Harris et al , 2005Keszthelyi and Self 1998;Keszthelyi et al 2000).…”

Section: Thermal Approachmentioning

confidence: 99%

“…Effusion rate also influences pressure conditions within an inflating unit and the morphology of the flow surface (Anderson et al 1998;Denlinger 1990;Fink andGriffiths 1992, 1998;Gregg and Fink 2000;Griffiths and Fink 1992;Iverson 1990;Rowland and Walker 1990). In addition, effusion rate and flow velocity affects flow heat loss and cooling, and hence crystallization rates (Crisp and Baloga 1994;Dragoni 1989;Dragoni and Tallarico 1994;Dragoni et al 1992;Harris et al 1998Harris et al , 2005Keszthelyi 1995;Keszthelyi and Self 1998;Pieri and Baloga 1986;Sakimoto and Zuber 1998). Thus, effusion rate, velocity and volume are important input parameters into lava flow models and simulations, and/or have been the outputs of others (e.g.…”

Section: Introductionmentioning

confidence: 99%

Lava effusion rate definition and measurement: a review

2007

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Measurement of effusion rate is a primary objective for studies that model lava flow and magma system dynamics, as well as for monitoring efforts during on-going eruptions. However, its exact definition remains a source of confusion, and problems occur when comparing volume flux values that are averaged over different time periods or spatial scales, or measured using different approaches. Thus our aims are to: (1) define effusion rate terminology; and (2) assess the various measurement methods and their results. We first distinguish between instantaneous effusion rate, and time-averaged discharge rate. Eruption rate is next defined as the total volume of lava emplaced since the beginning of the eruption divided by the time since the eruption began. The ultimate extension of this is mean output rate, this being the final volume of erupted lava divided by total eruption duration. Whether these values are total values, i.e. the flux feeding all flow units across the entire flow field, or local, i.e. the flux feeding a single active unit within a flow field across which many units are active, also needs to be specified. No approach is without its problems, and all can have large error (up to ∼50%). However, good agreement between diverse approaches shows that reliable estimates can be made if each approach is applied carefully and takes into account the caveats we detail here. There are three important factors to consider and state when measuring, giving or using an effusion rate. First, the time-period over which the value was averaged; second, whether the measurement applies to the entire active flow field, or a single lava flow within that field; and third, the measurement technique and its accompanying assumptions.

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“…In recent years, ground-based thermal imaging has also been increasingly applied to the study of effusive activity. Fieldbased thermal camera data, for example, have been used for detailed analyses of lava flow field morphology and evolution Harris et al 2005b;Lodato et al 2007), as well as parameterization and monitoring of lava channel dynamics (Harris et al 2005c;Bailey et al 2006;Coppola et al 2007;James et al 2007). Groundbased thermal cameras have also allowed the detection and monitoring of dike emplacement Spampinato et al 2008), calculation of the magma budget of a lava lake (Oppenheimer et al 2004), the nature and dynamics of Strombolian explosions and the morphology of cinder cones (Calvari and Pinkerton 2004).…”

Section: Introductionmentioning

confidence: 99%

A comparison of field- and satellite-derived thermal flux at Piton de la Fournaise: implications for the calculation of lava discharge rate

et al. 2009

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We present thermal measurements made by high spatial resolution ground-based (a hand-held thermal camera) and low spatial resolution space-based (MODIS) instruments for a lava flow field active during the last phase of the May-July 2003 eruption at Piton de la Fournaise (La Réunion). Multiple oblique ground-based thermal images were merged to provide full coverage of the flowfield. These were then corrected for path length attenuation and orthorectified, allowing the at-surface radiance emitted by the flow-field to be estimated. Comparison with the radiance recorded by the MODIS sensors during the eruption reveals that, for clear-sky conditions and moderate-to-low viewing angles (satellite zenith <40°), the satellite measurements represent ∼90% of the at-surface radiance, and thus represent valuable data for quantifying volcanic thermal anomalies. Nevertheless, extreme viewing geometries and the presence of clouds strongly affect the radiance reaching the sensor and affected data from 94% of the overpasses. Ground-based thermal data were used to investigate an empirical relationship between the radiant heat flux and lava discharge rate during the emplacement of pahoehoe flows. While the average radiation temperature for flow surface that were 6-24 h old ranged between 500 K and 625 K, the ratio between radiative heat flux and Time-Averaged lava Discharge Rate (TADR) ranged between 1.5×10 8 J m −3 and 3.5×10 8 J m −3 . This relationship was used to estimate TADR values from optimal MODIS data and produced results in line with those obtained from GPS surveys . Our results underscore the importance of ground-based thermal analysis for the interpretation of satellite measurements, particularly in terms of calculating discharge rate trends.

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Heat loss measured at a lava channel and its implications for down-channel cooling and rheology

Cited by 39 publications

References 16 publications

The distal segment of Etna’s 2001 basaltic lava flow

The distal segment of Etna’s 2001 basaltic lava flow

Lava effusion rate definition and measurement: a review

A comparison of field- and satellite-derived thermal flux at Piton de la Fournaise: implications for the calculation of lava discharge rate

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