Natural relief on mountainous volcanic islands has deep ravines, steep rocky slopes and high coastal cliffs. Volcanic formations have very heterogeneous rocks and soils. Besides, civil and building works sometimes include high cuts on the terrain and, as a result, many urban areas have been affected by rock falls and landslides. We show two case studies of the Canary Islands:
Rock fall hazard study and stabilization methods on Los Teques slope, Mogán, Southern Gran Canaria Island, and
Geologic-geotechnical study for a footpath project in Morro Jable coastal cliff, Pájara, Southern Fuerteventura Island. We conclude that sometimes classic methods of rock masses characterization are ineffective, while detailed geological studies are the best way to define and evaluate unstable zones on the slopes and to design the most convenient stabilization methods.