The book divides into a geology section, a geography section, and a travelogue section. The geography section points out that it is fairly difficult to define the “Great Plaines” physiographic province; some authors have the plains extending as far north as Great Slave Lake and as far east as central Illinois; however the general consensus is north to central Alberta, east to about the 100th meridian, south to the Rio Grande, and west to the Rockies. The geology section is handicapped because it still isn’t 100% settled why the Great Plains are there; it’s pretty clear why they are flat (they’re on the craton) but not at all clear why they are above sea level; the author goes with “uplift” that has something to do with subduction of the Juan de Fuca plate. An illustration of low angle subduction would help.

The travelogue section is the bulk of the book and gives along list, by province and state from north to south, of various places you can actually see geology on the Great Plains, as opposed to endless ranchland and center pivot irrigators. I’ve been to a lot of the places mentioned and they are all pretty interesting, but I feel they would give something of a mistaken impression to a visitor from outside the area – that there are more geologic features than there actually are. There are isolated outcrop of more resistant rock, usually given an evocative name – Castle Rock, Chimney Rock, Courthouse Rock – and the Black Hills, and now and then a volcano, but in most of the plains you could start a bowling ball rolling at the base of the Rockies and not have it stop until it got to the Mississippi. Concentrating on the outcrops also misses some of the evocative nature of having that endless sky; I remember reading an article about early settlers in Nebraska. They were from Norway and were used to hills and valleys; when they got to the plains some of them went off the walls before they got used to it. The flip side is the author of the article then interviewed their descendants who had grown up with the expanse; one farmer allowed, sheepishly, that he didn’t like to visit the creek on his property because “…there was a tree there and he felt closed in…”. The traditional place for anchorite solitude is the mountains; if you really want solitude try western Nebraska; it grows on you. ( )

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.

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.

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. ( )