Civil and Building Engineering.

Glaciers transport rock and other materials that are embedded in the ice or are picked up from the surfaces of rock as the glacier moves. The material carried along by a glacier is termed drift. Glacial deposits are of two general types: moraines or till and outwash. Till is deposited directly by the glacial ice and is characterized by a wide range of particle sizes. Stones and boulders can exhibit scratches or striations due to being carried along by the ice. Moraines occur when a glacier dumps a large amount of irregular material at the edge of the ice sheet that is deposited as the glacier retreats. A large amount of material may be dumped in an area if the glacier stalls in its retreat

The outwash from melt water is mainly fine-grained material that forms a plain or apron. The material is usually stratified and may exist as long, winding ridges. Many glacial deposits create a problem for the foundation engineer because of their lack of homogeneity. A particular problem for deep foundations occurs when a glacier leaves a deposit of boulders. Not only will the deposit be difficult or impossible to map, but penetrating the boulders with piles can be extraordinarily difficult.

Varved clay occurs with seasonal deposition into lakes, but such soil is most often associated with glaciation. Each layer or varve contains a wide range of grain sizes, with gradation from coarsest at the bottom of the layer to finest at the top. Walker and Irwin (1954) write that a lake was formed when the Columbia River was dammed by ice during the last Glacial Era and that seasonal deposition occurred in the lake for hundreds of years, resulting in the Nespelem Formation found chiefly in the valley of the Columbia River and along its tributaries. While perhaps not typical of varved clay found elsewhere, the varved clay along the Columbia yielded greatly varying results in field and laboratory tests, lost strength due to even minor disturbance, was
unsuitable for foundations, and was susceptible to sliding.