Scientists and engineers from many disciplines have been studying the formation of fractures in fine-grained natural geologic materials and fill. Naturallyoccurring fractures in the fine-grained materialscan create preferential flow paths, which can allow water to infiltrate quickly, resulting in recharge to underlying aquifers but also allowing contaminants to pass through to aquifers, potentially threatening ground water drinking water sources. They can also create zones of weakness that allow piping in dams and slip zones in fill materials. Glacially related fine-grained materials are widely distributed across the northern hemisphere,including the U.S. states of Minnesota,