Structurally, St. Catherine's Hill is part of the Winchester anticline. This is an upfold in the chalk at the western end of the South Downs. In the Winchester area the core of the anticline has eroded to expose older rocks in Chilcomb, Bar End and Winchester itself, leaving a near complete ring of inward-facing chalk scarp slopes including Magdalen (Morn) Hill to the north, Chilcomb Down and Telegraph Hill to the east, Deacon Hill, Twyford Down and St. Catherine's to the south and Oliver's Battery to the west. Whilst the highest part of the main ring of hills (which reaches up to at Cheesefoot Head) is of the 'Lewes Nodular Chalk Formation', St. Catherine's is of the slightly older 'New Pit Chalk Formation'. Both date from the Turonian stage of the Upper Cretaceous. St. Catherine's Hill is separated from the higher Twyford Down by the dramatic dry valley known as Plague Pits Valley to the east and south, and truncated by the valley of the River Itchen to the west.Booth K.A., 2002, Geology of the Winchester district, British Geological Survey, (booklet to accompany BGS 1:50,000 map sheet 299)Winchester, British Geological Survey 1:50,000 Map Series, Sheet 299, NERC, 2002,
