 To the west and north is the valley of the Turkey Brook, which meets the Cuffley Brook here before flowing east to the Lea; the valley has cut through the gravels to the underlying London Clay.To the south and east are the lower and later gravels and 'brickearths' of the Lea Valley.The former course of the New River runs up the north side of the Turkey Brook valley north and west of the hill, before crossing the valley to run south-east between Forty Hill and Clay Hill, the limit of the higher glacial hills to the west.