-Three possible structural arrangements have been postulated that control rift instability and the 1949 fault system: a ductile deformation zone (A), a network of discrete fault segments (B), or one large basal fault (C) (Elsworth and Day, 1999).

Figure 1: Different structural features that accommodate the subsidence and instability along the western flank (Day et al., 1999).

-Numerical modeling experiments show that instabilities may be produced in the rift system by magmastatic pressure increases due to dike intrusion and the corresponding mechanical and thermal pressure changes along the decollement zone (Elsworth and Day, 1999).

-Dikes of greater than 1 m thickness and 1 km length have the potential to trigger large mass movement (Elsworth and Day, 1999).

Figure 2: Examples of dike intrusion into the La Palma edifice (Elsworth and Day, 1999).