Geoscience Reference
In-Depth Information
(a)
(b)
(c)
(km)
Fig. 4.6 Velocities of long gravitational waves, of a solid slide and of the front of a viscous slide
in the Malaspina strait. Velocities of the solid slide are calculated for various friction coefficients
(from 0 to 0.2) (a). Froud numbers, corresponding to these velocities (b). Depth profile in the
strait (c). Adapted from [Rabinovich et al. (2003)]
For comparison, calculations were performed for the movement of a landslide in
the form of a solid body sliding down the slope under the influence of the forces
of gravity and of friction (between the landslide and the bottom). The friction co-
efficient
k
was set within the range from 0 to 0.2. The results of calculations are
presented in Fig. 4.6.
The motion dynamics of a solid body on an inclined plane under the influence of
the force of gravity with account of friction is such that there exists a 'critical' in-
clination of the bottom,
, at which the down-pulling force is balanced by the force
of friction, and the landslide moves without acceleration,
k
= tan
ψ
ψ
. It can be con-
sidered that the 'break-off' and subsequent sliding down of the landslide body takes
place precisely, when the 'holding' forces (of friction) weaken (for instance, owing
to erosion at the edge of the sedimentary layer) so much as to allow the down-pulling
force to start to exceed the force of friction. The characteristic slope of the bottom
near Texada island is
6
◦
, which corresponds to
k
= 0
.
1. For this value, the max-
imum velocity of the solid landslide amounts to the value
U
max
= 33
.
1m/s at a
ψ
≈
