Rock Slide In Colombia

A large rock avalanche
occurred at 03:27:30 PDT, August 2 10, in the Mount Meager Volcanic Complex southwest British Columbia.
The landslide initiated as a rock slide in Pleistocene rhyodacitic volcanic rock with the collapse of the secondary peak of Mount Meager. The detached rock mass impacted the volcano’s weathered and saturated flanks, creating a visible seismic signature on nearby seismographs. Undrained loading of the sloping flank caused the immediate and extremely rapid evacuation of the entire flank with a strong horizontal force, as the rock slide transformed into a debris flow.
The disintegrating mass travelled down Capricorn Creek at an average velocity of 64 metre per second, exhibiting dramatic super-elevation in bends to the intersection of Meager Creek, 7.8 km from the source. At Meager Creek the debris impacted the south side of Meager valley, causing a run-up of 270m above the valley floor and the deflection of the landslide debris both upstream (for 3.7km) and down-stream into the Lillooet River valley (for 4.9km), where it blocked the Lillooet River for a couple of hours approximately 10 km from the landslide source.
Disposition at the Capricorn Meager confluence also dammed Meager Creek for about 19 hours, creating a lake 1.5 km long.
The over-topping of the dam and the predicted outburst flood was the basis for a night time evacuation of 1500 residents in the town of Pemberton, 65 km downstream. High-resolution GeoEye satellite imagery obtained on 16 October, 2010 was used to create a post-event digital elevation model.