Mon, Dec 01, 2008
 Tour road, mile 3.5. Loma Verde trailhead. Cross-sectional view of the western Rincon Mountains, illustrating the position of the upper and lower plate rocks in relation to the Catalina detachment fault. The Saguaro National Park Loop Drive is visible on the left slope.
Photos courtesy of Arizona Geological Survey
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Down to earth Geology guides are great maps for day-trippers
Arizona Daily Star
Tucson, Arizona | Published: 04.11.2006
A leisurely drive through Saguaro National Park is a feast for the eyes and a favorite of out-of-town guests.
And thanks to a book recently published by the Arizona Geological Survey, it's also a trip through the eons-in-progress processes that formed the mountains and canyons that make Arizona's landscape unique.
"A Guide to the Geology of Saguaro National Park" begins with a basic overview: tectonic plate movement, magma, the formation of faults. Then it moves into what amounts to a self-guided tour of the geology of the park, broken down into the Rincon (east) and Tucson (west) mountain areas.
The Geological Survey has been publishing books targeted to the general public since 1991. Former state geologist Larry Fellows brainstormed the original idea and shepherded most of the project.
Some of the books — such as the ones on Sabino Canyon and the Catalina Highway or the volume on the White Mountains — are of the self-guided-tour nature. Others, like "A Home Buyer's Guide to Geologic Hazards in Arizona," focus on the practical aspects of geology's effects.
"We're filling in the information gaps for Tucsonans and out-of-towners," says state geologist M. Lee Allison. "We're answering that question of 'How did it all get here?' This area has so much geological diversity, it's phenomenal. You had volcanoes and plates colliding and magma and chunks of mountains falling. Even glaciers."
John V. Bezy, drawing on the work of others, has written several volumes in the series. Each time, he says, he has tried to create a book that "will take you by the hand."
The Saguaro National Park volume, the latest in the 17-book series, highlights 20 features, marked off by easy-to-follow mileage directions, and the authors designed every stop with safety in mind.
To find the first one, the Pinal Schist, which is in Saguaro National Park East, drive half a mile from the entrance of the driving trail, then walk 35 yards. Those following the book can either spot the features from the road or walk to them fairly easily.
"There's no sense in taking people's time telling them about something they can't get to," Bezy says.
Each entry also has a picture showing what to look for and is often highlighted to enhance understanding.
To get to the second stop, the guide says, drive to mile 0.6 and look toward the southeast to find a pediment.
As with the other entries, a picture clearly shows the pediment, which can be difficult for novices to spot. Under the picture, several paragraphs describe what the pediment looks like — think a layer of sand and pebbles; how it forms — erosion; and why it's important geologically — pediments can signal water.
The copy can read like a textbook, but overall it's accessible to the layperson and packed with elementary earth-science tutoring. It's complicated enough to challenge most adults but simple enough that children can understand it with help. A family could make the trip in a short afternoon.
While the information is structured to be understandable, it's also designed with scientific accuracy in mind.
At least three geologists — one academic, one in government service and one in the private sector — vet the books before publication. Bezy and the other authors comb through more than three decades of scientific study and log in days of field research for each volume.
"We cover almost every square inch of the area," Bezy says. Crews take rock samples, do age-testing and odometer readings and sketch maps.
Allison, admitting his vocational bias, says geology is vitally relevant to both Arizona's past and its future.
"Arizona lives and dies on the geology of this region," he says. "Tourism is huge here. Ground water is a big issue. Minerals and mining really formed our history."
And our parks, with their beautiful mountain hikes, relate directly to plate movements and volcanic explosions that happened millions of years ago.
The scenery of this state is "a billion years of history at your fingertips," Allison says.
And now there's a handy guide that will fit in your glove compartment.
● Contact reporter Erin White at ewhite@azstarnet.com or 807-8429.
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