Hazard potential of lava flows on the western slope of La Palma (Canary Islands, Spain)

摘要

Historical volcanic activity on La Palma is dominated by thin (< 5 m) low-viscosity lava flows. Future pathways of such lava flows are difficult to predict on the basis of available topographic data (e. g., topographic maps, SRTM) due to their limited resolution. The hazard potential can be assessed more accurately, however, when using slope vectors created from a high-resolution DEM. We have selected a part of the western slope of La Palma where probability of future eruptions is relatively high. Ground check provided data for areas with low slope gradient and for areas of possible damming and/or circumvention of lava flows. Potential future flow paths of lava streams were modelled starting from 15 plausible eruption centres and following the direction of maximum slope. The width of each potential flow pathway was modelled as a direct function of slope gradient but modified by pre-existing channeling or damming features. Lava flow pathways will be straight and narrow in areas with slope gradients > 45 %. Considerable broadening and development of a braided pattern can be observed in areas with slope gradients below 25 %. Due to the lack of gullies the lower cliff above the small coastal plain will be overflown in broad cascades. Severe damage to agricultural terracing and housing areas can be expected near the villages of Las Manchas and La Bombilla. One of the potential flows may annihilate Puerto Naos if powered by a high effusion rate.