5) What happens to weak layers in the long run?

5) What happens to weak layers in the long run? How can they stabilize?

*Of course in this region melting or rainfall and the percolation of meltwater to the weak layer will result in considerable strengthening upon re-freezing. Appreciable meltwater establishes channels or columns that when penetrating weak layers act as rebar upon re-freezing. In each subsequent meltwater producing event the same channels or meltwater columns tend to be utilized again.

*It is also common in our climate for heavy snowfall and the strengthening compression and rounding of overlying layers to make it so that the weak layers become too deeply buried and hence no longer reactive. In some cases the weak layers may remain but don't become an issue again until spring (or other warming and melting events) when weakening of the weak layer once again may result in avalanching. These weak layers may also react to heavy loading.

*For faceted layers, compression and strength gain from a rounding influence (under a temperature and pressure region where rounding is the dominant form of metamorphism) can cause a weak layer of facets or depth hoar to gain sufficient strength so as to no longer be a concern.

*For an ice layer absent meltwater percolation the weak layer probably would still remain but may no longer be reactive beneath a thick layer (s) of rounded snow grains.

*For surface hoar that lies between adjacent layers of soft snow the surface hoar, while still standing, will embed as would a blade into the adjacent soft snow layers allowing sufficient contact between the now adjacent layers for decent bonding to take place.

*For surface hoar that has collapsed between surrounding layers of soft snow strength gain is somewhat more problematic as the adjacent layers to the surface hoar cannot make contact and can form only tenuous bonds to the hoar, probably mainly bonding in recesses between the larger hoar grains.

*For surface hoar overlying a hard surface with softer snow layers above the situation is even more of a problem as the surface hoar can only bond poorly to the underlying hard surface.

*For faceted snow or depth hoar grains lying on top of a hard layer the same thing is true as in the last surface hoar situation.

In both of the lattrer two cases the snowpack will have a long term problem regarding bond strength to the hard layer.     

Thanks so much Gary--that is really great information!