There's nothing like a road trip to learn a little local geology. Aside from 89A over Mingus Mountain, my favorite earth science lesson is the short climb out of the Verde Valley through the Copper Canyon pass on I-17. Besides, the cuts through the mountain are very pretty, if you like that sort of thing. I do. Returning from my Flagstaff weekend gave me an opportunity to see what kind of photography is possible from the co-pilot's seat in the little green car. It turns out that the shutter is fast enough to let me take pictures from a car moving at highway speeds!
Take a look at that mesa capped by a lava flow up ahead! That's the elevation we're headed for.
The wall to the right (above) has a thick layer of grey basalt on top of well baked soil which in turn looks like it is sitting on older lava.
The obvious lava here is underneath the baked soil. But there must have been lava atop that to cook the dirt!
This mountain slice appears to include at least three different basaltic episodes, including a flow that filled a major crevice in the older hillside, as outlined by the pink.
Stripes like these are particularly stunning in the late afternoon or early morning sun. Brings out the red in the one-time soil layer.
As our car nears the top of the pass, the grey basalt capping the mesas is very evident. Reminds one of gnomes and similar creatures.
The final road cut at the very top of the pass is missing the lava cap. Either it eroded away or perhaps it never existed!
These two pictures (above and below) are a reminder that the same sorts of road cuts exist within the Prescott city limits! The traffic light is just beyond the entrance to Costco on SR69, while the picture below immediately precedes the entrance to the WalMart coming from the East. By the way, for a really good look at the rock layers, pop into the WalMart parking lot. Gives you an idea of what Glassford Hill (our local volcano) was up to 14 million years ago.
The Glassford Hill basalts continue across SR89 south of the Dells and over past Willow Creek Road. If you take a good look at those huge 1.4 billion year old granites of the Dells, you will see that they disappear under the northwestern flank of our volcano.
If all this rock and geologic talk gets to you, Wide World of Maps down in the Valley has a
geologic map of Yavapai County. If you go to their site, you might also look for a cool book --
Roadside Geology of Arizona. Or buy the book locally at The Worm or possibly Sharlot Hall Museum store. I also have in my library
A Prescott Area Geologic Field Guide for Earth Science Week 1999 which I probably bought at a meeting of the local archeological society; no mention of it by The Google, so I can't recommend a source other than the library.
I suspect that the Flagstone Capital of the World is ominously quiet in 2009. Probably next year, as well. Without yesterday's building boom, there is not much call for that yellow and pink and orange Coconino sandstone quarried northeast of Ashfork and over in the canyons by The Matterhorn. (Don't laugh -- look at your topo map while you motor east on the Drake Road and there it is, a big bluff that juts out from The Rim. I don't know why someone picked that memorable name.)
When the LH and I first moved to Arizona, a regular highway sight was the big flatbed truck loaded with slabs of flagstone, wired together in bundles for stability on the road. The trucks were heading out from Ashfork and Drake, destination those ever-expanding tracts of homes down in the Valley of Death.
The big flagstone yards are located in Ashfork; that is where I took these pictures the winter of 2007-8. BTW, if you want just one or two pieces of the stone for your yard or other use, take a ride out the Drake Road. There are plenty of drop offs by the roadside, free for picking up.
These reddish slabs are the same material as the famous Red Rocks of Sedona. The sandstone which is quarried comes from one of many differing sedimentary layers that comprise the Colorado Plateau.
Above, the standard packaging for the Phoenix market via flatbed truck. Other types of packaging below.
The pallet may be made in Canada, but the stone is certainly a native Arizonan.
Because the stone splits into neat flats, its main use is underfoot. Above, a staircase; below, stepping stones. A proper southwestern patio is almost always fashioned from flagstone. My fireplace is made entirely from flagstone.
The sandstone is also fashioned into bricks (above) or used locally for architectural details, such as the window lintel (below) at the Sparkes Activity Center (armory).
Then there is this sculpture in the gardens at Yavapai College. Quintessentially Arizona.
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