In reply to Dave Garnett:
> Well, if you think what you weigh compared to the mass of rock involved, as long as you didn't do it after a big freeze or lots of rain you'd probably be OK*.
With respect, just to re-iterate historic comments, frost and rain are not influences on this crack. The crack is dry, and it is below the frost action (which starts on Helvellyn well above 2000 feet).
The three influences on this crack are 1. The natural movement and whatever is causing it, 2. Local minor earthquakes which are relatively common along Thirlmere/High Rigg/Glenderaterra, 3. The drying and shrinkage that takes place at times like this (typically March to June).
Shrinkage and aridity has been a factor in a number of Lake District rockfalls over the years e.g. Buttermere tragedy of Cockermouth Mountain Rescue Team accident in 1969.
DC