Photos

A few photos, mostly from field work

To do the Propagation Saw Test (PST) test, drag the blunt edge of a snow saw up along a pre-identified weak layer. If the fracture jumps ahead of the saw to the end of the column before half the colum has been undercut, then fractures are likely to spread far enough to release slab avalanches where snowpack conditions are similar.	$Deep tap test to assess the fracture character of a weak snowpack layer$ Deep Tap Test: If tapping on the shovel causes a sudden planar fracture ("pop") or a sudden collapse ("drop"), this is an indication that fractures may spread far enough to release a slab avalanche where snowpack conditions are similar.
This is an early photo of measuring the stress below a skier. In a new study, we are measuring the dynamic stress in the snowpack under skiers, snowboarders, hikers, snowmobiles, and snowshoers.	$A fracture in a weak layer that has initiated under a skier but not propagated.$ This photo shows a fracture that has initiated in a weak layer under under a skier but has not propagated. A slab avalanche requires fracture initiation PLUS fracture propagation.
	The yellow tarp is keeping snow off a high-speed camera and a laptop computer.

	$A buried surface hoar layer (unfractured)$ A layer of surface hoar crystals, about 20 mm thick. The relative lack of bonding makes layers of buried surface hoar persistent, i.e. snow to gain strength and disappear as a weak layer.
A tiny dry slab avalanche on a bump - triggered by a skier several metres away. Observations such as these indicate that skiers may trigger slab avalanches on the same weak layer where snowpack conditions are similar and the slope is sufficiently steep.	$Crown fracture in Cariboo Mountains$ Crown fracture of a large dry slab avalanche in the Cariboo Mountains.
A shear frame test to measure the shear strength of aweak snowpack layer.	$Deep tap test to assess the fracture character of a weak snowpack layer$
$A dry snow slab overlying a weak layer of unfractured buried surface hoar near a whumpf site$ This photo taken near a slab avalanche shows a thick layer of buried surface hoar (frost) under a slab. The adjacent slab avalanche released on the weak layer of buried surface hoar.	$A close up of the unfractured buried surface hoar layer near the whumpf site$ This is a close up of the weak layer of buried surface hoar (frost) in the photo to left.
There are many closures on many mountain roads in western Canada every year. Although safety is the top priority, it is desireable to keep closures short since closures to transportation routes are costly. The true cost should include the cost of missed just-in-time deliveries.

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