Jacqueline Annen, Layout designer

Gliding avalanches occur on smooth ground such as grassy slopes.

the factors that cause the initially very slow gliding movement to suddenly turn into a rapid slide – i.e. into an avalanche.

Researchers at the WSL Institute for Snow and Avalanche Research SLF are trying to get to the bottom of this problem. They, together with soil experts from ETH Zurich, are therefore systematically investigating – for the first time – the heat and water transport between snow and soil in field studies, laboratory experiments and computer simulations. Their findings suggest that a so-called ‘capillary barrier’ forms at the interface between the two materials, which are both porous. This barrier prevents water from passing from the finepored snow into the soil, which has coarser pores. The water then accumulates at the interface, where it acts like a lubricating film that enables the snow cover to glide over the soil.

Michael Lombardo, a doctoral student at SLF, is investigating these processes in experiments in the lab. His measurements involve filling a cylinder with a layer of sand or natural soil, and then adding snow and installing temperature and humidity sensors at various points. During each experiment, Michael slowly heats the snow until meltwater seeps out and watches to see whether this accumulates at the interface with the soil.

A large-scale research facility yields new insights Michael is conducting some of his experiments at the SINQ neutron source, a large-scale research facility at the Paul Scherrer Institute PSI.