Thursday, September 29, 2011


State Route 128 at Lake Berryessa

IT’S TOUGH TO RIDE A NICE MOTORCYCLE and not be stopped from time to time for conversations with a total stranger. Outside of the other day over near Clear Lake when an aging man in house slippers wandered across the street, engaged me about my BMW and then tried to panhandle me for “enough money to, you know, get a hot dog or something,” conversations usually start with the bike and may move on to topics or those proverbial points unknown.

Monticello Dam
THE FIRST LEG of the “North Coast – Volcanic Legacy Tour” found me crossing the Coast Range on State Route 128. This sinewy highway leads from the hot dry floor of the Sacramento Valley, through rolling hills, vineyards and redwoods until finally emerging at the coast below Fort Bragg. An hour into this ride, I find myself at the overlook for Monticello Dam which serves as a good place to stretch legs and take on a slug or two of water.

Two gentlemen approach from the west on bikes – one on a Cannondale the other, I think, on a Novara from REI.  (I find I know bikes, but I don't really know bikes.)

Berryessa's Glory Hole
Walking back from a look at Berryessa’s glory hole, I appreciate the bare-naked geology of the area and found myself reflecting upon the upward thrusts of our earth’s rather fluid crust. I recalled how I’d taught some very basic geology to fourth graders. The vicinity around what used to be the Monticello Valley illustrates how layers once well below the ocean’s surface have been lifted and bent by tectonic forces as far away as the mid-Atlantic. I was wondering about the advisability of putting a solid concrete dam across a gorge made up of clearly mobile strata.

“How far to Davis?” asked one. “And is it down hill?” chimed the other.

I responded.

“We’re thinking of taking the Pleasants Valley Road,” one said as the other looked at his watch.

Having just ridden it myself, I explained that such a detour would add quite a bit of climbing and mileage if Davis were the goal.

The first one looked at the GSA. “Trade ya,” he said with a grin. “I’ve got a Dakar at home.”

We laughed.

“Can’t do that,” I said, “but I can put one of you guys on the seat backward and you can take footage of the other one coming down the hill. That’s what bicyclists like BMWs for, isn’t it?”

More laughter.

THE GENTLEMEN, probably each eight or ten years my senior had pedaled west from Calistoga. I calculated that this had involved more than a little up and down and was glad my bike was outfitted with a motor.

October 2010 - file
One of them pointed to Monticello Dam’s moorings across the canyon. “Some pretty dramatic tilt."

“Yeah,” I said, remembering about my days as a classroom teacher and preparing (like a fool) to show off a bit. “Seems strange to build a dam and hold up all that water where the crust moves around so much. I sure as hell wouldn’t want to live down stream.”

His riding partner shook his head. “Oh, no, no, no.” He pointed down the valley, then turned and pointed across the pool of water. “These rocks, why, they haven’t moved in the past six million years. Maybe eleven and a half million.”

“Mid-Atlantic ridge…” I began.

“…Nope. Now out eighty miles west there in the San Andreas rift zone, there’s where you’ll have some movement. Wouldn’t be smart to do a reservoir like this there. And yeah, I guess it does start back in the Atlantic, but the critical movement is on the coast.”

I decided to shut up and listen. (This is rare.)

Layers - tilted layers
He continued, “You go down the road a bit and you get an excellent view of the different layers that used to be on the floor of the ocean back about the early or maybe the mid-Pleistocene Epoch. You’ll see some thin layers of shale that had lay on the floor and compressed. In between, there’ll be these thicker layers of more granular material that had flowed down from the Sierra and settled to the bottom.” He pointed across the highway from the dam. “There’s a pretty good example right there.”

I thought I knew most of this stuff, but in no way did I know it like this biker.

“Those rock slides you see every once in a while along here? Exfoliation.”

“The onion skin effect?” I asked.

“Similar to the granite in the Sierra. Except not technically onion skin because the rock isn’t…”

Courtesy US Geologic Survey Bulletin
I didn’t catch the word he used. But it turns out he is a retired Ph.D. and taught this stuff to university students for a career. As he went on, I thought about the additional units I could use on my college transcript. I wondered if he’d sign off on ‘em for me.

AT LENGTH, his partner tapped his watch and asked if I could recommend a lunch spot, stopping the geologist mid-sentence.

A view toward the San Andreas Rift Zone
Hopefully they stopped at the Putah Creek Café in Winters. I know I had something to chew on as I mounted the Beemer and headed west toward the rift zone.

© 2011
Church of the Open Road Press

No comments:

Post a Comment