Castle Rock 2-7-06

(Avalanche south of Naomi Peak occurred 2-5-06)

This large natural avalanche occurred late Sunday (2-5-06), after a week of incremental heavy snowfall and strong westerly winds. 

The slope at 9400' in elevation generally faces east.

The ~500' wide avalanche was 3-4' deep.  It stepped down into old snow, running on a buried weak layer made up of small sugary grains called facets.

Natural cornice-fall in the center of the crown probably triggered this avalanche.

The crown showed that a few layers of snow were involved.  Most of the other natural avalanches in the area failed on the upper weak layer, but this one stepped down to the lower one. 

The debris from the Super Bowl slide completely filled a large sink-hole at the bottom of the slope and covered an area equal to a few football fields.

This is looking down the right side of the long crown....

Westerly winds built some big cornices this winter in the Bear River Range.  Castle Rock is just south of Naomi Peak.  The area is accessible with a snowmobile from highway 89 through Tony Grove.

Cornice-fall probably also triggered these natural avalanches off Magog's  east ridge.

Here's another upper elevation east facing slope, and a smaller natural avalanche on Cornice Ridge.