It has been mentioned above that the only remaining free-faces on Beacon Hill lie on the north-western flank, one at the point of inflection of the slope and some 15m height and the second at a lower elevation and partially buried revealing a face of some 10m. It is highly likely that free-faces existed on all sides of Beacon Hill, but they have now all graded into the slope leaving only residual small rock outcrops and sudden changes in gradient. Of these former free-faces that present on the eastern slope and some distance downslope from the summit is the best preserved. The causes of poor preservation of the free-faces are complex, although some ideas may be revealed from close inspection of the dip of the strata on Beacon Hill and the inclination of dilatation joints. Figure 4 shows schematically the direction of dip of the strata observed at the main rock outcrops around the summit and the extent of weathering.

Figure 4: Approximate morphological map of Beacon Hill showing the general dip of strata.

On the western edge of the summit the general dip of the strata is from west to east at an inclination of c. 45º to the horizontal. Dilatation has clearly enlarged the jointing encouraging weathering characterised by fragmentation and rockfalls. On the eastern edge, however, the general dip is still from west to east but now almost vertical. The joints are not exposed in the free-face, unlike the high free-face of the western slope, but on the surface above it. Dilatation clearly has not been effective and joints have only opened up at the surface where they would have been exposed to congelifraction. The retreat of the eastern free-face would have occurred not by rockfalls, as on the western free-face, but by slow toppling or slab failure. These large slabs would have been inherently unstable following free-face retreat and would have collapsed pro- precluding tor development. Figure 5 shows this form of mass wasting in operation.

Figure 5: The nature of free-face retreat and grading on the eastern flank of Beacon Hill.

Significant toppling or slab failure would have occurred during periglacial times as congelifraction within the near vertical joints would appear to be the only agent capable of detaching the slabs. Many of the slabs, once removed from the free-face, came to rest en echelon and are now left as logans some of which measure several metres across. As the climatic optimum of the Holocene approached around 7000 years BP woodland had become established and a significant soil would have formed over the weathered slabs. Since then climate has deteriorated and the woodland has gone from the summit so as to allow active soil erosion. This erosion has in many places exhumed slabs weathered during the Pleistocene and even revealed the former free-face, although much of this still lies buried beneath soil and regolith. It is believed that this erosion of soil is still taking place as the Ordnance Survey triangulation pillar, erected in 1936, now stands with its concrete foundation almost 0.5m above the current level of the ground.

The association between jointing and tor survival has been discussed for the southern Pennines (Lewis, 1994). Here the best preserved tors are associated with gritstone which dips towards the free-face, not away from it. This arrangement has allowed large blocks to have become detached following weathering along joints perpendicular to the bedding planes and then to move downslope under solifluction and subsequently pile up en echelon. Swine's Back, a notable tor standing high above Jacob's Ladder on Kinder Scout, illustrates this argument well. Furthermore, the southern Pennines have also lost soil and vegetation from high elevations since the climatic optimum in the same way as Beacon Hill and this erosion is revealing large fields of clitter associated with a formerly retreating free-faces. Large areas of Kinder Scout are experiencing significant soil loss to reveal not only clitter, but possibly denuded tors as well.