Retired professor offers consummate geological classroom

Two students in last September’s Colorado Mountain College field trip led by retired geology professor Garry Zabel take in the majesty of the scenery at the bottom of the Grand Canyon, where the Colorado River carves through rock nearly 2 billion years old.

Retired Colorado Mountain College geology professor Garry Zabel points to the Great Unconformity near the bottom of the Grand Canyon. The geological feature was discovered and named by canyon explorer John Wesley Powell. A sandstone formation sits directly atop Precambrian granite, with more than a billion years of geological layers missing due to erosion and/or lack of deposition.

An overlook of the Colorado River and the Grand Canyon’s basement rock provides a place to contemplate the canyon’s geology and beauty.



Garry Zabel leads another Grand Staircase/Grand Canyon field trip through Colorado Mountain College from Sept. 25 to Oct. 5.

The course is offered for credit and also may be audited. Enrollment is limited to 18 students and the class fills quickly. For information, Zabel may be reached at .(JavaScript must be enabled to view this email address).

Prospective students should consider that the rim-to-rim hike is rated as moderate to strenuous. Participants should be in good shape and be comfortable backpacking.

Dipping my toes in the cool Colorado River on a hot day last September at the bottom of the Grand Canyon, I thought to myself, “It’s been a long time.”

It had been exactly a quarter of a century, actually, since I had joined fellow members of a Phoenix journalism program in visiting the canyon to hike from the South Rim to the river and back.

But time is relative when you’re in the canyon’s bottom, where vertical cliffs of rock nearly 2 billion years old — almost half the age of the earth — jut up from the river’s sides.

It took me 25 years to finally act on a longtime goal of hiking the canyon rim to rim, and all that time the Grand Canyon simply waited. What’s another couple decades for a canyon carved by a river at work for perhaps 5 million years, a mere sliver of time compared to the age of some of the formations it is eroding?

Geologically speaking, on this second visit to the canyon’s bottom, I looked at the surrounding scenery with a bit more of an educated eye.

The reason was that I was part of a Colorado Mountain College field trip highlighted by a five-day, north-to-south rim excursion to study the canyon’s rock layers and better understand their origins. The field trip was created and is led by now-retired CMC geology professor Garry Zabel.

The canyon was only part of an even more impressive outdoor geological classroom that began at Bryce Canyon National Park, with a look at that canyon’s formations, which date back only 35–40 million years.

Running from Bryce Canyon’s top to the Grand Canyon’s bottom is what’s known as the Grand Staircase, the most complete geological sequence in North America.

The field trip included a stop at Zion National Park, with its 200-million-year-old sandstone, and culminated with the hike into the Grand Canyon, plunging ever-downward through geological time at an average of 20,000 years per step.

For me, the field trip served as a long-overdue introduction to the stunning geology of the region in which we live.

It was high time I started to better understand, and thus better appreciate, our region’s unsurpassed geology, which contributes so much to its scenery.

In some states, geology buffs are left to examine mostly road cuts for tantalizing glimpses of buried rock formations.

On the Colorado Plateau starting in western Colorado, by contrast, the geology has been conveniently uplifted, with portions of it later eroded by rivers and other forces, exposing layer upon layer of formations deposited by ancient seas, dunes, swamps and other environments.

My canyon trip last fall was just the start of an expanding education that has resulted from signing up for other field trips Zabel has led to destinations including Moab, Utah,-area national parks and the Great Sand Dunes National Park in Colorado.

Ah, but let’s be honest.

Learning geology also is a great excuse for spending time exploring some of the Southwest’s most beautiful places.

And, as I had to admit in my Grand Canyon field trip report, I should have taken more notes — and fewer photos.


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