Wow, I just watched the video. That certainly escalated quickly! Its amazing that they are crossing while it is in the beginnings of such a dangerous situation.
I never would have thought a rock slide could be so violent. Well yes I figured they could get that bad but wow that was flowing very fast!
that looks like a Lahar that you get on volcanoes, its what happens when ruapehu crater lake bursts its banks and mixes in with the volcanic ash and debris on its way down. doesnt have to be a volcanoe but I'd say its caused by a lake breaching further up the mountain or a water course changing direction
yeah and not atypical of a Lahar, it can start out innocent enough as the water just breaks the top of a lake, then all of a sudden the lake wall collapses and a wall of mud descends at high speed.
this is on Ruapehu, the lahar of 2007 covered the bridge and destroyed it.
It occurred during a three day group hike - the landslide happened between Horcones (park entrance) and Confluence (first base of the Aconcagua field).
The Spanish text mentions that this tour group had a guide spotter (the guy in the white shirt) who was listening for the loud sounds and watching uphill.
Apparently the slope instability is caused by soil saturation from snow melt. So while there is no visible water running on the surface, the rocks slip like a river.
Other than the close call, the thing that gets me is the volume and how long it goes for.
I've been looking into Aconcagua and Argentina as a next possible adventure.