Tensile strength and strength changes in new snow layers

ABSTRACT. The tensile strength (rupture modulus) of new snow layers was measured at a 3,200m elevation Colorado site during February and March, 1998 to determine a) if the cantilever-beam test produced consistent results within a layer at a given time and b) to measure the change in strength over a period of days. 80 tests were conducted on 16 layers by calculating tensile strength at ruptureon cantilever beams 10 to 16 cm thick which were excavated into the new snow. The strength tests a) produced reasonably consistent results, and b) indicated a substantial increase in tensile strength within the snow layers tested during a period of 2 to 4 days after a fresh snowfall. Two periods of widespread, natural soft-slab avalanches occurred in the new snow prior to tensile-strength increases. Natural avalanche activity stopped as the snow layers increased in strength by approximately a factor of two