Geology of Northern Arizona

April 18 to May 4.

Geology of the Basin and Range

The Basin and Range will be the topic of my Fall class at Yavapai College in Sedona. The Basin and Range is a complex area in Arizona that has experienced tremendous amounts of extension which began about 17 million years ago. Previous to this, central and southern Arizona were elevated higher than the Colorado Plateau and rivers generally went from south to north, opposite the direction they go today! But after stretching of the earth's crust began, the Basin and Range floundered, causing this area to subside substantially and reversing the direction of drainage in Arizona. It's an exciting story you will want to know more about. If you live in the Verde Valley, join us on the following dates for the 3 hour class sessions which run from 6 to 9 PM at the Sedona Center: November 14, 16, 21, 28 and 30. Our four day field trip will be from December 3 to 6 and we will visit Organ Pipe Cactus National Monument as well as a few surprise areas along the way. Get hip on landscapes and take a geology class!

The Geology of Bryce and Zion National Parks

In the spring semester at Yavapai College, Sedona, I taught The Geology of Bryce and Zion National Parks (GLG 106). The class met on Monday and Wednesday nights, April 4, 6, 11, 13 and 20, with a four-day field trip to Zion April 15 to 18.

Learning about the geologic history of the earth in a classroom setting with a professional geologist can be a very rewarding experience, and taking field trips to see first hand what the evidence looks like is never to be forgotten. You missed it this year, but keep an eye out for another opportunity!

Earthquakes and Volcanoes of Northern Arizona

The Inner Basin of the San Francisco Peaks, looking west. Photo courtesy USGS.

My Earthquakes and Volcanoes class at Yavapai College in Sedona was a rousing success! The class consisted of 14 students and the highlight for everyone was two, two-day field trips visiting such scenic wonders as the San Francisco Peaks, Sunset Crater, Grand Falls, the House Mountain volcano near Sedona, and the Teepees near Camp Verde.

Students learned how the Inner Basin of the Peaks (photo right) may have formed. A theory proposed by Dr. Wendell Duffield states that a Mt. St. Helens type of eruption blew the top off of the mountain, creating the basin. However, no ash deposits from such a blast have been found. A more likely scenario was proposed recently by Dr. Richard Holm who found evidence that the top of the mountain collapsed in a cold debris avalanche. Students looked at the evidence for both theories and came up with their own conclusions. Most agreed that a cold debris avalanche is the most likely way that the San Francisco Mountain lost it's top between 440,000 and 220,000 years ago! People who live in Flagstaff see the Peaks every day but most likely do not give a thought for how the mountain attained its shape. Students in these classes routinely look at such landscapes and try to figure out how and when they formed! It's truly amazing to see how people come alive when they become aware of how our earth shapes itself.

Grand Falls on the Little Colorado River is higher than Niagara and although it is seasonal, our field trip arrived just hours after it started running from the recent snowmelt. The falls are about 200 feet high and were formed about 150,000 years ago when a lava flow from the south filled an old canyon, causing the river to be diverted around the newly-formed barrier and over it's former rim. At House Mountain, I led a group to the place where these volcanic rocks were erupted onto the ancestral Mogollon Rim. I had not visited this outcrop since my field work days in the late 1980's!

Everyone in the class now feels like they know about the volcanism and faulting that has created much of the Northern Arizona landscape.