Monday, November 27, 2006

A Look at Lava...

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.

11 comments:

k said...

Boy. This is one of your posts that give me that wanderlust in a big way...

Anonymous said...

Good stuff, kid. Aww did well in his camera purchase. Did you have that Yavapi County publication when I was there?
I trust your days off in the high country did you good.

Hermano

Steve said...

I enjoyed taking the drive with you. Nice information to go with super pictures.

Granny J said...

Glad the geology was a hit (for some folks, at least!) Glad the camera was capable of the moment! And, Bill, that publication may or may not have been around while you were here. It didn't explain lots of questions I have, like how the hell did that lava cap at Big Bug Mesa get way up there at 7000 ft. and where did it come from???

Karen of Scottsdale said...

oh I love geology -- thanks for the great photographs and explanations.

Granny J said...

I took a leap of likelihood there in some of my observations, Karen. Don't have a degree or two in geology like my bro, hermano, there!

Granny J said...

And as for you, k, I think I have wanderlust almost all the time! Have to satisfy it in small ways most of the time nowadays.

coyoteradiotheater said...

lol, just goes to show how your mind-set can color what you see. Everytime I make that drive I think about a tired old car I had and what a very tough time it would have with that grade.

Granny J said...

And you are reminding me of that ramp for out-of-control trucks about halfway down that grade. I've yet to see a vehicle coming to a stop there -- or even entering the ramp. I think it's a 6% grade.

k said...

I think it's genetic. It explains those old time pioneers behind me, ones that came here in 1640 and 1642, that homesteaded in Missouri and Texas via covered wagon, the grandma from Scotland and the grandad from Sweden and great-gdad from some old-time Jewish *ghetto* in the Russian countryside...

It's always with me. Just kind of reined in for the duration.

Many of your posts leave the horse taking the bit in its mouth and tugging those reins free...

Granny J said...

The LH never understood that I liked to go out walking -- wherever. He'd say, "where are you going". My answer tended to be "out". A guy thing, I guess, or an engineer sort of thing. Anyhow, since he always needed a goal if we were going to do any wandering the bush, I'd pore over the topo quads, spot a likely sounding (or looking) spot & we'd head there. Saw a heck of alot of countryside that way.

 
Photo Blog Blog Top Sites Blog Directory for Prescott, AZ

Local Blogs - Blog Top Sites