CAN IMPROVED UNDERSTANDING OF FROST CRACKING HELP ANTICIPATING FOCAL ZONES FOR ROCKFALL FROM DEGRADING PERMAFROST?

Rock damage due to freezing controls many phenomena on planetary surfaces. Here, we aim to investigate, how rock fall from degrading permafrost areas is preconditioned by the growth of ice-filled fractures and, whether this can be used to constrain likely locations for future rock fall better. This hypothesis of preconditioning is supported by analogies of ice-enriched transient layers in permafrost soils, by observed cryo-fracturing in soft rock and by the presence of suitable temperature gradients not only in bedrock active layers, but also insight steep alpine ridges. In order to explore the sensitivity of this phenomenon to e.g., temperature regime, moisture supply and rock type, however, corresponding simulations tools need to developed and tested against realistic conditions. To explore this scaling of theoretical insight and lab evidence to real conditions, we develop and use an outdoor sensing system to monitor acoustic emission, temperature and moisture in a steep rock face. This is done at two adjacent sites, one dry and one moist, at 3500m a.s.l. in the Swiss Alps. Our results confirm the feasibility of monitoring acoustic emissions in outdoor conditions and yield rich data and a large catalogue of acoustic events. Based on first analyses, the importance of freezing on rock damage can be demonstrated and further characterized.