Wayne Anderson's book Iowa's Geological Past is the culmination of a life-long study of the geology of Iowa. Published in 1998 by the University of Iowa press, the 424-page volume represents the latest research and thinking on the topic and is a more thorough discussion than its predecessor, Geology of Iowa, published in 1983 by the Iowa State University Press and also written by Anderson. More than three years in the making, Iowa's Geological Past has been designated a Choice Outstanding Academic Book for 1999. One reviewer stated that the book reveals Anderson's "great understanding of and love for the topic." It presents not only new discoveries but also new interpretations of features of Iowa's geology. Because of a combination of new exposures to examine, and more thorough analyses of subsurface data, many interpretations of the state's geology have changed, and these new interpretations make this second book quite different from the earlier volume. For example, geologists have been able to work out in greater detail the environments of deposition associated with inland seas that transgressed onto the continent. As a result, some rock formations have been reclassified or renamed, and their environments of deposition have been reinterpreted. Overall, there is a better understanding of how sedimentary rocks in Iowa were formed. The glacial history of Iowa has also been significantly reinterpreted. Much more is known about the environment of an ice sheet that approximately 14,000 years ago extended over central Iowa as far south as Des Moines and then receded to the Minnesota border about 12,000 years ago. Geologists now understand that this was a stagnant body melting down and depositing a large quantity of sand and gravel. More is known about the older glaciers too. It was once believed that there were four major advances of ice, but the consensus now is that there were at least 10 advances. In general, geologists have a better understanding of how glaciers worked. The environmental aspects of Iowa's geology, an area barely touched on in the earlier book, receive a great deal more attention in the new volume. The contamination of groundwater by agricultural chemicals and the nature of the state's aquifers are discussed at length. Another feature of the geological record in Iowa that is given expanded treatment is the Manson impact crater in the northwestern part of the state. Geologists have now concluded that the pattern of deformation of sand grains and other features at the site prove that the crater was formed from the impact of an extraterrestrial object. Earlier, there was some question whether the crater resulted from impact or from subsurface volcanic processes. cont.

Having written the definitive history of Iowa's geology, Anderson is moving the subject of his attention westward to south-central Colorado, specifically to a high-elevation valley bordered on the east by the Wet Mountains and on the west by the Sangre de Cristo Mountains. So far, Anderson's study of the area has produced a monograph titled "Geology of the Custer County Area, South-Central Colorado," which he hopes will grow into a book that will be useful to the general public. After studying Iowa's sedimentary rocks and their exquisitely preserved marine fossils for four decades, Anderson has found the geologic record of south-central Colorado to be quite a contrast. The area he is focusing on is made up predominantly of igneous and metamorphic rocks and relatively unfossiliferous sedimentary rocks that are primarily the product of stream deposition. He plans to continue his study of the Wet Mountain valley and the adjacent mountains, where he has a summer home, after his retirement in June 2000. A list of Anderson's publications related to the work discussed above follows. Anderson, W.I. (1998). Iowa's geological past: Three billion years of change. Iowa City: University of Iowa Press. Anderson, W.I. (1989). Iowa geology: The early years. Journal of the Iowa Academy of Science, 96, 81-91. Anderson, W.I. (1983). The geology of Iowa: Over two billion years of change. Ames: Iowa State University Press. Anderson, W.I. (1982). Recorded in rocks. In Iowa's natural heritage (pp. 8-41). Des Moines: Iowa Natural Heritage Foundation and Iowa Academy of Science. Anderson, W. I., & Furnish, W.M. (1987). The Lime Creek formation of north-central Iowa. In Geological Society of America, Centennial Field Guide, Vol. 3, pp. 89-92. Anderson, W.I., & Furnish, W.M. (1983). Iowa's self-trained paleontologists. Proceedings of the Iowa Academy of Science, Vol. 90, pp. 1-12.   wayne.anderson@uni.edu