Britain and Ireland: glacial landforms from the Last Glacial Maximum

Abstract At the Last Glacial Maximum (LGM), Britain and Ireland were covered by the British–Irish Ice Sheet (BIIS): a dynamic ice mass that comprised the southwestern extremity of the much larger European Ice Sheet Complex. However, our understanding of the extent of the BIIS has changed dramatically in recent years from a previously established view of a more restricted ice sheet, located mostly on the present-day landmass, and with significant ice-free enclaves, to an extensive marine-terminating ice sheet. Deciphering the extent and chronology of the BIIS is critical for understanding landscape evolution. It is now clear that the LGM was just one phase of an evolving ice-sheet complex, with evidence for asynchronous maximum extents across the ice-sheet sectors. Based on the lateral extents of the BIIS, the ice mass must have been sufficiently thick to completely submerge the highest terrain in the interior of the ice sheet. The widespread presence of trimlines and strongly weathered mountain summits is now mostly interpreted as evidence of nonerosive cold-based ice, rather than as LGM ice thickness markers in the landscape. Deciphering landscape history using geomorphology alone (in the absence of geochronology) is therefore complicated and can be problematic. Our understanding on the evolution of the ice sheet through time has been dramatically improved in recent years by comprehensive geochronological programmes involving BRITICE-CHRONO and other teams.