Cooling rates and thermal-geomechanical properties of the lava flows of Tajogaite eruption (La Palma, Canary Islands) for land use planning and infrastructures reconstruction.

Lava flows emitted by the Tajogaite eruption (La Palma, Canary Islands) have covered an approximate area of 12 million m2, with thicknesses of up to 80 m. Type Aa flows represent more than 90% of the surface, the rest being Pahoe-hoe type. The urgent need to rebuild the affected roads has been the highest priority, along with territorial planning with urban proposes, infrastructures and agricultural development, being the lava temperature one of the most critical restrictive condition.Geological, geotechnical and thermal investigations have been carried on including 4 boreholes up to 10 m deep in which a detailed geotechnical characterization and systematic measurement of temperatures at different depths. Temperatures measurements on the lava surface were also recorded using drones and in situ thermocouples. Detailed maps of lava flow thicknesses and geological cartographies, including fractures and volcanic cavities have been made. An empirical model of lava cooling rates has been developed based on geological, geotechnical data and temperature measurements.Additionally a new cooling rate model has been developed as a function of depth, based on exponential equations in accordance with Newton's cooling law that relate temperature to time and whose main parameter is the cooling coefficient. This model has been applied to different lava depths. The results obtained indicate an acceptable agreement between the numerical models and the recorded data of temperatures. These results have been applied to the reconstruction of infrastructures and urban planning, allowing to identify favorable areas for infrastructures reconstruction and land use planning.