Geology of the Upper Arkansas Valley, by Tom Karnuta

Review by Ed Quillen

Geology – August 1995 – Colorado Central Magazine

Road and Riverside Geology of the Upper Arkansas Valley
by Tom Karnuta
Published in 1995 by Geotechnics
No ISBN

When you’re surrounded by rocks, it only makes sense to know something about what they’re made of and how they got there, and Tom Karnuta here shares his ample knowledge of local geography, covering the Arkansas River from Leadville to Ca├▒on City.

In general, the book is organized by segment — Leadville to Buena Vista, Buena Vista to Salida, etc. — providing a mile-by-mile description for both motorists and river-runners.

For those on the water, he cautions readers that “it is not the intent of this book to guide one through the rapids, but to point out interesting geologic features along the river.” Even so, he notes access points to the river, and provides detailed maps for both floaters and drivers.

There’s plenty to intrigue even a mildly interested person like me. A glacier in the Clear Creek valley was so big that it pushed the river east, forcing it to cut through bedrock. The Pine Creek glacier dammed the river, and when the water breached the ice, the resulting catastrophic flood left huge boulders as far downstream as Parkdale.

Some local place names are misleading. The Chalk Cliffs on Mount Princeton are not even close to mineral chalk; they’re actually the white quartz that remained after other minerals were leached out by hot water. The Crater above Salida isn’t a crater at all, but the scar of a landslide.

What I found most interesting was his general geologic history of the region. From what I gather, the Sawatch and Mosquito ranges were one range — the Sawatch Anticline — when things started rising 70 million years ago. This mass drained eastward; these “paleovalleys” survive today as Trout Creek Pass, Ute Trail, and U.S. 50 near Howard. Later uplift produced two mountain ranges, with the Rio Grande Rift left down between the Sawatch and Mosquito ranges.

Karnuta isn’t shy about using technical terms — graben, syncline, alluvium, tuff — but they usually become clear in context, and he provides a glossary, along with clear drawings.

The photos, alas, aren’t as clear and sharp as I’d like to see them, and I have to wonder how well the ring binding will stand up to the strains of travel.

This book fills a genuine need for something more detailed than Roadside Geology of Colorado, yet still accessible to the non-expert. And if your appetite for fossils, extinct volcanoes, and hanging valleys isn’t filled, he provides a full bibliography for further exploration.

I don’t know how I’ll find room in the glovebox for this, but there’s got to be a way. I don’t want to travel around here without it.

— E.Q.