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A geologist friend has commented on Alan's message as follows: I know of this and something about the underlying causes. The British Geological Survey have a monitoring scheme in place - somewhat curtailed by the Foot and mouth problem. The department in Durham also have plans to look at the physics of the rock failure problem. The fissures have opened in the last few years and are thought to be the consequence of two processes, either: - differential subsidence in the underlying coal measures (mining) - reactivation of faults caused by allowing the water table in the coalfield to rebound. This is as a consequence of strategic switching off of pumping operations to save money now the deep mines are defunct. Mike ---------------- Alan Vickers wrote: > Hi - The following is a precis of an article that appeared in 'Sunderland Echo' for tuesday 12th February: > > " A number of mysterious holes and cracks have appeared at various places in the are of Tyne & Wear and Co Durham of north-east England. The area is from Cleadon in the north to Cassop in the south. > > Research by a final-year engineering geology student at University of Sunderland has identified a feature common to all - underlying geology and coal mining history. > > The possibility is that rising water in former coal mines could be leading to the collapse of the ground above them - creating the holes. Research so far has shown that they occur in areas where limestone and dolomite exist on top of the sand dunes which were laid down millions of years ago and where the sand dunes are more than 15 metres thick and and also that the holes form on lines close to known geological faults. > > The research is being carried out by Janet Atkinson who is drawing up a 'hazard map' to point out which areas are potentially at greater risk of suffering from holes. > > Alan.