English: Partially formed Shakehole, Bronkham Hill This shows clearly the method of formation of these shakeholes, shrinkholes or Dolines as they are called. The dark space is the hole where the chalk has been dissolved by water over thousands of years. This particular hole could be seen to extend many metres down. Overlying the hole can be seen the gravelly layers of the Bagshot Beds. Initially this gravelly/sandy layer bridges the hole but then it collapses into the hole leaving a depression. In this case the front half nearest the camera has already collapsed while the rear half remains as a bridge over half of the hole. As the Bagshot beds are very loosely constituted, the rear half will soon collapse into the hole as well leaving the conical depression on the surface. The open hole is approximately 2m X 0.8m