case studies
overview of periglacial landforms in norfolk;
The most recent glacial stage in Britain,the devensian ,ended 10,00 years ago.It's glaciation was divided into 3 stages Early,Middle and late. At it's maximum the late ice sheet covered two thirds of Britain one of the areas it covered was Norfolk,this land was subjected to periglacial conditions. periglaciation refers to the conditions around the edge of the ice sheet where the climate is very cold,but the temperatures are not low enough to allow glacier ice to persist at the surface. in a periglacial environment,distinctive landforms and deposits are produced by non-glacial processes often as a result of ground freezing.the most important periglacial process is frost action,this involves repeated cycles of freezing and thawing.
pingos: there are 2 types of pingos closed and open.
closed: these pingos form by the ventual freezing and expansion of an undergroung talik in front of advancing ground ice during permafrost development.occur in lake beds or river channels.As more water freezes the pingo grows in size
open: these pingo's are formed by the development of injection ice in the freezing of groundwater rising under pressure.in the surrounding frozen ground the water is forced up as it freezes. there are fossil pingo systems in Norfolk such as those at East Walton.These are belived to be the remains of open system pingos as they were associated woth spring activity.
patterned ground: is caused by repeated freezing and thawing of the active layer in ice rich permafrost,which causes fine grained sediments to migrate downwards. when the water moves during summer thawing it creates patterns which include circles,polygons and nets.parts of west norfolk and breckland display sizeable areas of patterned ground.
The most recent glacial stage in Britain,the devensian ,ended 10,00 years ago.It's glaciation was divided into 3 stages Early,Middle and late. At it's maximum the late ice sheet covered two thirds of Britain one of the areas it covered was Norfolk,this land was subjected to periglacial conditions. periglaciation refers to the conditions around the edge of the ice sheet where the climate is very cold,but the temperatures are not low enough to allow glacier ice to persist at the surface. in a periglacial environment,distinctive landforms and deposits are produced by non-glacial processes often as a result of ground freezing.the most important periglacial process is frost action,this involves repeated cycles of freezing and thawing.
pingos: there are 2 types of pingos closed and open.
closed: these pingos form by the ventual freezing and expansion of an undergroung talik in front of advancing ground ice during permafrost development.occur in lake beds or river channels.As more water freezes the pingo grows in size
open: these pingo's are formed by the development of injection ice in the freezing of groundwater rising under pressure.in the surrounding frozen ground the water is forced up as it freezes. there are fossil pingo systems in Norfolk such as those at East Walton.These are belived to be the remains of open system pingos as they were associated woth spring activity.
patterned ground: is caused by repeated freezing and thawing of the active layer in ice rich permafrost,which causes fine grained sediments to migrate downwards. when the water moves during summer thawing it creates patterns which include circles,polygons and nets.parts of west norfolk and breckland display sizeable areas of patterned ground.