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Best‐fit results from application of a thermo‐rheological model for channelized lava flow to high spatial resolution morphological data
Author(s) -
Harris Andrew,
Favalli Massimiliano,
Mazzarini Francesco,
Pareschi Maria Teresa
Publication year - 2007
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2006gl028126
Subject(s) - channelized , geology , lava , channel (broadcasting) , rheology , flow (mathematics) , volumetric flow rate , open channel flow , mechanics , geomorphology , volcano , materials science , physics , telecommunications , composite material , seismology , computer science
The FLOWGO thermo‐rheological model links heat loss, core cooling, crystallization, rheology and flow dynamics for lava flowing in a channel. We fit this model to laser altimeter (LIDAR) derived channel width data, as well as effusion rate and flow velocity measurements, to produce a best‐fit prediction of thermal and rheological conditions for lava flowing in a ∼1.6 km long channel active on Mt. Etna (Italy) on 16th September 2004. Using, as a starting condition for the model, the mean channel width over the first 100 m (6 m) and a depth of 1 m we obtain an initial velocity and instantaneous effusion rate of 0.3–0.6 m/s and ∼3 m 3 /s, respectively. This compares with field‐ and LIDAR‐derived values of 0.4 m/s and 1–4 m 3 /s. The best fit between model‐output and LIDAR‐measured channel widths comes from a hybrid run in which the proximal section of the channel is characterised by poorly insulated flow and the medial‐distal section by well‐insulated flow. This best‐fit model implies that flow conditions evolve down‐channel, where hot crusts on a free flowing channel maximise heat losses across the proximal section, whereas thick, stable, mature crusts of ′a′a clinker reduce heat losses across the medial‐distal section. This results in core cooling per unit distance that decreases from ∼0.02–0.015°C m −1 across the proximal section, to ∼0.005°C m −1 across the medial‐distal section. This produces an increase in core viscosity from ∼3800 Pa s at the vent to ∼8000 Pa s across the distal section.