For example, the wet avalanches of spring are the product of destructive metamorphosis due to deep thawing and will occur regardless of the original nature of the snow. Again, the action of wind on snow picked up from the surface is a large factor in producing delayed-action slab avalanches. A decade of observation in the U. S. has identified 10 factors which contribute to the avalanche hazard. First, there is the depth of old snow on the slope. The fourth factor is the type of the new snow, especially its free moisture content.
Free moisture acts as a cement and improves cohesion, within limits.
But good cohesion may be dangerous as well as helpful, for it may enable the wind to pile up greater masses of snow for release in an avalanche. The fifth factor, not quite the same thing as the preceding, is the total water content of the snow, i.e., the ratio of water to snow. We have recorded one storm in which the ratio was 28 percent. Other factors being favorable, the outcome was an avalanche cycle of extraordinary violence. The solid blue line indicates the accumulated snow depth over the 42 hours recorded.