There is now an automated monitoring system on the North Buttress of Castle Rock in Thirlmere to measure crack widening of the unstable block at the top of the crag. This is a continuation of the long-term observations collected by a local FRCC member since May 2012.

Recent measurements show an acceleration in the rate of crack widening, with ~0.5 cm opening between the 20-24 Sept. This may be a relatively mundane fluctuation in the movement rate and a continuation of the long-term crack opening and acceleration in autumn which has not been monitored at this resolution before. Alternatively this can be an indication of a precursor to a final failure phase. The duration of the failure phase is very hard to predict and could range from a few weeks to several years depending on the final threshold, and, if this threshold is reached in the autumn/winter period that usually shows the most movement. In some cases these rates of movement won’t lead to the block becoming detached.

At present there is a correlation between temperature and crack extension / rate of opening. The detailed ongoing monitoring will allow us to better understand the mechanics and dynamics of the rock mass. In the graph below temperature is plotted in the red line and crack widening (extension – Ext) shown in blue.

Information supplied by Professor Jeff Warburton (Durham University) and Dr Stuart Dunning (Newcastle University)