Large Landslides Triggered by Caldera Collapse Events in Tenerife, Canary Islands by M. Hurlimann, E. Turon and J. Marti

La Palma El Hierro Gomera Gran Canaria Fuerteventura Lanzarote Tenerife The Canarian Archipelago

Pico de Tiende

Geologic setting

N

Incorporated model data l subaerial and subsurface geology and hydrogeology l subaerial and submarine geophysics l remotely sensed data l results of field work » dike trends » vent locations » distribution of pyroclastic deposits

Model Geometry (m) PmPm vv khkh seismic shock magma chamber inflation caldera collapse

Mohr-Coulomb failure criteria l Young’s modulus l Poisson’s ratio l density of lava/magma l cohesion l internal friction l pore water pressure l normal stress l maximum shear strength E = 7.5x10 3 MPa  = 0.25  l =  m = 2700 kg m -3 c = 0 kPa  =35º P w   max  max = c+(  -P w )tan 

Destabilizing volcanic forces

Destabilizing volcanic mechanisms 1) chamber tumescence 2) caldera collapse 3) seismicity

Numerical modeling

Chamber tumescence (m) PmPm vv khkh seismic shock magma chamber inflation caldera collapse P m = 5 MPa

Caldera collapse (m) PmPm vv khkh  v = 3 MPa to 30 MPa seismic shock magma chamber inflation caldera collapse

Seismicity (m) PmPm vv khkh k h = 0.4 g seismic shock magma chamber inflation caldera collapse

Results

Distribution of shear stresses

Potential yielding zone

Influence of seismic acceleration

Conclusions

l High shear stresses from tumescence may evolve into the head scarp l Large driving forces following caldera collapse cause destabilization at zones of weakness ~ 100 to 300 m l Ground accelerations greater than 0.3 g may trigger a landslide All 3 processes occurring as one single mechanism would likely cause failure!