Large Landslides Triggered by Caldera Collapse

Events in Tenerife, Canary Islands

by M. Hurlimann, E. Turon and J. Marti

La Palma

El Hierro

GomeraGran Canaria

Fuerteventura

Lanzarote

Tenerife

The Canarian Archipelago

Pico de Tiende

Geologic setting

NN

Incorporated model dataIncorporated model data

subaerial and subsurface geology and hydrogeology

subaerial and submarine geophysics remotely sensed data results of field work

» dike trends» vent locations» distribution of pyroclastic deposits

Model Geometry

0 10000 20000

4000

- 4000

0

(m)

(m)

Pmvkh

seismicshock

magmachamberinflation

calderacollapse

Mohr-Coulomb failure criteria

Young’s modulus Poisson’s ratio density of lava/magma cohesion internal friction pore water pressure normal stress maximum shear strength

E = 7.5x103 MPa

= 0.25

l = m = 2700 kg m-3

c = 0 kPa

=35º

Pw

max

max= c+(-Pw)tan

Destabilizing volcanic forces

Destabilizing volcanic mechanisms

1) chamber tumescence

2) caldera collapse

3) seismicity

Numerical modeling

Chamber tumescence

0 10000 20000

4000

- 4000

0

(m)

(m)

Pmvkh

seismicshock

magmachamberinflation

calderacollapse

PPm m = 5 MPa= 5 MPa

Caldera collapse

0 10000 20000

4000

- 4000

0

(m)

(m)

Pmvkh

v v = 3 MPa to 30 MPa= 3 MPa to 30 MPa

seismicshock

magmachamberinflation

calderacollapse

Seismicity

0 10000 20000

4000

- 4000

0

(m)

(m)

Pmvkh

kkh h = 0.4 g= 0.4 g

seismicshock

magmachamberinflation

calderacollapse

Results

Distribution of shear stresses

Potential yielding zone

Influence of seismic acceleration

Conclusions

Conclusions

High shear stresses from tumescence may evolve into the head scarp

Large driving forces following caldera collapse cause destabilization at zones of weakness ~ 100 to 300 m

Ground accelerations greater than 0.3 g may trigger a landslide

All 3 processes occurring as one single mechanism would likely cause failure!