line sub-parallel to that of the Severn gorge. Another, the Oakengates Channel, approximates the line of the A442 immediately northeast of the town centre whilst a third, the Shifnal Channel, runs beneath the course of the Wesley Brook south from Shifnal. Kettle holes During deglaciation, ice masses often wasted away in situ to leave kettle holes, some of which remain today as part of the county's population of meres; there is a notable assemblage in the Ellesmere area. One kettle hole unearthed during gravel extraction at Condover in 1986 yielded numerous bones of a woolly mammoth. Periglacial features Freeze-thaw cycles operated on the exposed quartzites of Stiperstones leading to the development of rock tors and of patterned ground i.e. stone stripes and polygons. Dolerite screes on Titterstone Clee also date from such processes at that time. Landslips There are numerous landslips recorded within the Ironbridge gorge and further downstream around Apley Forge and along parts of the Borley Brook, near Highley. Landslips have also occurred within Clun Forest. Alluvium River silt, sands and gravels (termed alluvium) occupy the floodplains of the major Shropshire rivers with especially widespread floodplains around the confluence of the Vyrnwy with the Severn on the county's western margins and downstream of Shrewsbury. Multiple terraces are developed within the valley of the Severn and that of the Worfe which joins it north of Bridgnorth. Published work The Geological Survey Memoirs provide the most comprehensive details of the local geology but unfortunately not all the county is covered and all are now dated - most were published nearly a century ago. The last traditional memoir was that for Sheet 166 (Church Stretton) published in 1968; the Telford Memoir incorporates the studies undertaken for the new town development, on which it concentrates (published 1995) and the most recent (2001) is for Sheet 165 (Welshpool), which includes a little of the extreme west of the county. Otherwise the most comprehensive description is contained within Peter Toghill's book. Details of local and regional studies are published by the Shropshire Geological Society. See also Geology of Great Britain Wenlock Edge Long Mynd#Geology Longmyndian Supergroup Uriconian References External links Shropshire Geology Natural England Geology of Shropshire