How and why do glaciers deposit material?
Lodgement till is material deposited beneath the moving ice due to pressure melting and frictional drag. It largely consists of subglacial moraine. Originally it was smeared on the solid ground surface. Ablation till is englacial and supraglacial moraine which is deposited as the ice melts.Where it has not been removed by post-glacial processes it forms a blanket of unsorted material on top of the bedrock which obscures exisiting landscape features in much the same way as a layer of fresh snow. This ground moraine is very widespread over the lowlands of central and eastern England. For example, sediment cores taken in the North Shropshire Plain indicate that the till is up to 100m deep. Downcutting rivers, coastal erosion (e.g. North Norfolk coast) or human activity (e.g. for new roads) may expose this till where it can be investigated for sorting, orientation and roundness (hyperlinks).
