Loess is a deposit of windblown silt. The term is derived from German and means "loose," though it is commonly pronounced in the United States as "lus."
Loess is prominent in the hills of Southern Indiana and was created as a result of the Wisconsin Glaciation that occurred during the Ice Ages. Glacial melting carried large silt deposits into the river systems of the area that separated out quickly during low winter water levels. The heavy silt deposits did not allow vegetation to grow, which allowed the silt to be easily swept away by wind. The silt was then deposited in large quantities against the eastern bluffs of the state.