 Areas that are too dry for glaciation to occur but that display characteristics of oversteepened slopes, solifluction slumps and cirques indicate the presence of a periglacial zone.Chief actions in these zones include solifluction and frost-shattering processes, the effects of which can be seen in the south of the Bristol Channel.Former periglacial lakes are known to have existed as early as the Cryogenian period, though many were also formed in the Pleistocene period.