Amplification of the Destructive Effects of Rock Falls by Sliding on Volcanic Soils: Examples from the Anaga Massif (Tenerife Island, Spain)

This paper provides geomorphological and geotechnical observations on the amplification of the destructive behaviour of rock falls on rocky slopes in the Anaga massif (Tenerife Island, Spain) covered with soils rich in organic matter, within a high rainfall regime. The soil organic matter would be the determinant factor of this process, because it would reduce the soil strength as a result of overcoming the liquid limit during heavy rains. Thus the soil could develop a semi-fluid consistency, triggering a more efficient sliding of the blocks of rock along the slope and, hence, amplifying the destructive effect of the rock falls. Other potential determinant factor would be that the soil fine fraction could undergo a sudden change in its microfabric related to the dynamic load caused by the rock fall, similar to the mechanism described to explain the landslides developed in clayey soils.