[ENVIRON] Quantifying lava flow dynamics with a very-long-range terrestrial laser scanner

Lead Research Organisation: Lancaster University
Department Name: Lancaster Environment Centre


One of the main controls on the maximum length of lava flows is the lava effusion rate. With reasonable effusion rate estimates, models can now forecast the flow lengths for short lived eruptions relatively accurately. However, for longer eruptions, maximum flow lengths are additionally controlled by complex processes such as the formation of breakouts from channels, flow inflation and the development of lava tubes, which remain significant challenges to model. Observations of active flows have revealed that effusion rate variations over relatively short timescales (of order hourly) could strongly influence maximum flow lengths by either reinforcing channel levees (and thus promoting the potential for lava tube formation) or by forming breakouts and driving channel switching. Hence, in order to improve flow models, it is critical to understand the effect of short-term variations in flux on lava channels: do surges in lava effusion generally aid or hinder the formation of lava tubes and hence extend or reduce flow lengths compared to current model estimates? One of the best ways to address these issues is to acquire repeated topographic measurements and temperature data of active flows in order to constrain the dynamics involved during short term effusion rate changes. Very-long-range terrestrial laser scanners (TLSs) are now capable of imaging volcanic terrain over distances up to ~3.5 km, and can deliver topographic data at the accuracy required. However, on volcanoes, the usually rough and inhospitable terrain can make instrument site selection for optimum data coverage time consuming and difficult. Furthermore, a trade off between measurement range and acquisition rate means that at these distances, point cloud data can only be acquired at relatively low rates. Consequently, detailed surveys over extended areas can be slow and this currently prevents data being taken sufficiently frequently for flow dynamics to be determined. This project will use a very-long-range TLS to investigate active lava flow processes on Mount Etna, Sicily. By optimising data acquisition procedures through the development of a survey planning software tool, survey times will be reduced sufficiently for flow dynamics to be captured. The survey planning tool will enable optimal instrument sites to be identified and automated data acquisition procedures calculated. The topographic data will be combined with ground-based thermal imagery in order to quantify the critical processes involved with channel switching, flow inflation and breakout formation that control final flow lengths in long-term lava eruptions. The development of TLS survey planning will enable sub-hourly data set collection over day-long periods of active lava flows on Etna, where suitable lava flow eruptions have occurred annually. The data would capture the topographic changes in the vent and channel regions that characterise changes in effusion rate. The advance rate and thickness of flow fronts will be determined, and evidence for flow inflation (which may precede tube formation) and levee instability (a precursor for levee collapse and breakout formation) correlated with channel flux. For breakout events, the prevailing channel, flow-front and lava flux conditions, will be ascertained and used to identify conditions of instability. Consequently, the requirements for breakouts to fully develop into channel switching events can be considered.


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