Great Plains Geology

Review: Great Plains Geology, R. F. Diffendal, Jr., 2017.Great Plains Geology

The Great Plains of America only seem a boring and flat expanse if you haven’t lived in them, as I did in my earlier life, or only travel in certain parts of them.

University of Nebraska geologist Diffendal is out to convince you otherwise.

What the Great Plains are, where they are, is a matter of some dispute. Diffendal includes a map with 50 different versions of the Great Plains. They range from the Sierra Nevadas in the west to past the Mississippi River Valley, from north of the Arctic Circle to Mexico. Diffendal’s definition extends from Alberta and Saskatchewan in the north down to a nick out of Mexico, the Rocky Mountains in the west but excludes the eastern parts of the Dakotas, Nebraska, Kansas and includes little more than the panhandle of Oklahoma, and parts of Texas. (My wife thinks Diffendal excluded Iowa just out of typical Nebraskan hostility to her native Iowa.)

Diffendal’s boundaries largely follow John Wesley Powell’s boundaries of the area and seems to be based on two requirements: land covered by the Cretaceous Western Interior Seaway and not glaciated in the Pleistocene.

Diffendal starts with a concise summary of the geologic history of the area. Diagrams, maps, and a glossary make this accessible to a newbie to geology. There is diagram laying out the eras of geologic history including known periods of glaciation and impact events from comets and meteorites. (The Precambrian/Proterozoic Eon has certainly been delineated a lot more since I was introduced to historical geology 30 years ago.)

Then Diffendal takes on his road trip of 57 sites that includes every Canadian province and U.S. state in the Great Plains except Oklahoma. (I was rather disappointed he drew his Great Plains boundary west of the Oklahoma’s Arbuckle Mountains.) Diffendal has photos of each site and notes its geological, paleontological, historical, and archaeological interest.

As you would expect from his center of operations, Diffendal finds a surprising amount to see in Nebraska. As a South Dakotan partisan, I think he should have included Spearfish Canyon and the Needles. An example of the book’s humor at Mount Rushmore: “ . . . four U.S. presidents may distract your eyes and thoughts from the important thing here, the geology.”

One benefit of this broad treatment of a large area is that, unlike the more detailed and focused “road trip” geology books I have covering certain states, Diffendal helps you see the broad geologic context of things.

Diffendal throws some appendixes in on the different zones of the Great Plains, the scientific history behind certain geologic concepts, and a worthy guide to traveling the area. (Don’t ignore his warnings about suddenly variable weather and deserted roads.)

I got this book as a review copy from NetGalley, but I liked it well enough that I’m going to buy a hard copy to take along with all the other geology books I take on road trips.


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