Steamboat Springs — Steamboat author Tom DeLancey’s new book will rearrange readers’ perception of the Yampa Valley, particularly if they think they know it well.

DeLancey, who taught geology at Colorado Mountain College for 20 years, is releasing “A Geologic Field Guide to Steamboat Springs and Vicinity” on Sunday with a book-signing event at Off the Beaten Path Bookstore.

This is not a geology textbook, though it contains a good deal of science. Rather, it is a guide for people who would enjoy outings that take them to an interesting mineral deposit, a fossil site or a notable geologic formation, perhaps one they have driven past dozens of times without fully appreciating it.

The guide represents the author’s effort to share some of the field trips he has taken his students to throughout the years.

“It’s been 20 years of making these trips with students. They have always commented that the field trips were the highlight of their experience,” DeLancey said.

Who knew that you could pull off U.S. Highway 40 west of Maybell in Moffat County and search for fire agates of gemstone quality in an otherwise bland-looking road cut? Were you aware that some of the stones on Rocky Peak at the head of Strawberry Park are among the oldest rocks on earth? They are about 2.7 billion years old. DeLancey explains it all with his clear writing and hand-drawn maps and illustrations.

The book ties together the well-known volcanic sites across Routt County from Hahn’s Peak to the Rabbit Ears formation and Finger Rock near Yampa. All three of the those familiar landmarks are distinctly different from one another.

Finger Rock, near Yampa is the remains of a 12 million-year-old volcanic neck, DeLancey said. It’s within sight of the Flat Tops, which are capped with a basalt lava flow.

The Rabbit Ears on the mountain pass of the same name comprise sedimentary deposits of igneous material left by an old volcanic vent that is so eroded it’s difficult to discern on the landscape. And Hahn’s Peak, in North Routt, is a very old volcano dating back 60 million years to the end of the age of the dinosaurs.

DeLancey’s field guide also offers most readers a deeper understanding of the hot springs in the Steamboat area than they previously might have had.

DeLancey’s new book also dispels an apparent myth about the famed Steamboat Springs, long described as being a small, chugging geyser until it was disrupted when the railroad arrived in Steamboat in the early 20th century.

“It probably was not a geyser,” DeLancey said. “It doesn’t show any signs of geysers we know of.”

Instead, the author surmises, the sound of the bubbling spring probably was amplified by a small cave adjacent to the spring that acted as an amphitheater.

To reach Tom Ross, call 970-871-4205 or email tross@SteamboatToday.com