Nonconformity is a term used in geology to describe a type of unconformity where younger sedimentary rocks are deposited on top of older, eroded rocks, which can include either sedimentary or igneous formations. This geological feature indicates a significant gap in the geological time record, as it reflects a period of erosion or non-deposition. Nonconformities can provide valuable insights into the geological history of an area, revealing changes in environmental conditions over time.