Rockfall info ZZ from |Wanderung| Newsletter

lulululu

Many thanks to Dave T. for contributing the following article. After reading of
the tragedy earlier this year where a father and daughter were killed by
rockfall, and trying to find a good camping spot on a recent backcountry trip,
your editor has a new-found appreciation for rocks and the hazards they pose.

"Rock fall is a hiking hazard in the young rugged mountains of BC. We see rocks
strewn across the highway and feel fortunate avoiding accident. Here’s what to
look for in the hills. Barren peaks attractive to climbers lack trees if rock is
actively scaling and falling. We take as evidence for rockfall a talus or scree
slope of jagged rock at the base of a cliff. If coarse talus rock contains
little soil and few plants, then rockfall events are frequent. Also look for
rockslide scars on hillsides. Although lower slopes are more stable, partly
because rocks are infilled with soil and plants, the view from here is not so
great. Sitting at the base of a cliff is most hazardous, but anywhere on a talus
slope is within the range of a falling rock. Rocks seem heavy and solid, but
consider that piled rocks and coffee beans take the same slope, from 30 up to 40
degrees. Any steeper and a slide occurs. Try it. Such steep slopes are not
particularly stable.

Water penetrating cracks in rock freezes and expands and wedges rock out.
Pebbles falling into cracks also act as wedges. After years to decades of freeze
and thaw, the rock is primed for fall. Rock falls happen more when sun melts ice
or when heavy rain washes out grit and soil surrounding boulders. If a creek
that normally runs clear is dirty with sediment, you’d best get out of there
quick."