Definition of Terms
Compression (compressive force): A force that tends to compress a member, or in this case the snowpack.
Tension (tensile force): A force that tends to elongate a member, or in this case the snowpack.
Shear Force (V): A force which tends to shear a member.
http://gallery.photo.net/photo/3008100-lg.jpg
Saltation Layer: In the case of a loose snow avalanche, it is the turbulant boundry layer in between the dense flow and the powder cloud.
Isothermal Snow: When all of the different layers that make up the snowpack are at the same temperature, this usually occurs during spring time conditions with repeated melt freeze cycles.
http://www.fsavalanche.org/Encyclopedia.aspx