Hiking on the San Andreas Fault

Scrambled eggs and rocks
Scrambled eggs and rocks

You can’t have eggs without salt. I’m too far from my predatory roots to enjoy the quick snap and slurp of a stolen shell. I need to scramble my eggs on a propane-fueled cook stove, scramble them just like the heat- and pressure-scrambled rocks around us. Back in La Mesa, we moved the salt and pepper from the picnic basket to our emergency earthquake supplies, prioritizing, intuiting that the need for spices was imminent. We haven’t had a major earthquake in way too long: the earth is grinding, hitched, holding, so we packed the important stuff into The Big One boxes, and now found ourselves camping on the largest earthquake fault zone in North America without salt and pepper in our picnic basket. Charlie pointed out the irony after I complained about the tasteless eggs. Do we need a 7.5 earthquake to enjoy a decent scramble?

Six-million-year sandstone cliffs
Eight-million-year sandstone cliffs

We joined the Stanford club on this weekend’s outing, led by Monte Marshall, geologist and geophysicist emeritus from SDSU. Monte grew up in San Diego, got his PhD at Stanford, a good decade or two before Charlie passed through. We crouched and chatted under an 8-million-year towering sandstone cliff, in Box Canyon, near Painted Canyon in the Mecca Hills where we began our hikes into the past. Last major earthquake at this spot was some 300 years ago. Not good. When’s St. Andy going to pop? Hopefully not tonight. I don’t like that car-sized boulder resting next to our tent. It crumbled off the upthrust mountain flanking our sleeping canyon, during who knows what event when.

Trusty Jeep still gets us there
Trusty Jeep still gets us there

I was in the Loma Prieta earthquake, during the World Series in 1989. Headed for my car and bang! had to hold onto a tree in our jiggling topsy-turvy business park. My friend, Karen, almost got slammed by a heavy filing cabinet as she narrowly escaped out her office door. My apartment in San Franscisco was a mere three miles from where people and their cars accordioned into a collapsed Bay Bridge, dying, thirsty, forced to spend the worst nights of their lives until rescue or death. Thinking about them made it hard for me to sleep in my comfortable bed. I wanted to call out to them across the City and its rippling Bay waters, Hold On! Please hold on.

Sedimentary beds torqued 90 degrees skywards
Sedimentary beds torqued 90 degrees skywards

The 6-million-old San Andreas fault snakes through these Mecca Hills, skirts the Salton Sea, and heads on down into Mexico and up past San Franscisco. This naughtly little mountain builder, this is the edge where two tectonic plates, the North American and Pacific, grind elbows and topple cities in their sibling rivalry for movement. And who knows? Maybe the tectonic plates are fueled by magnetic currents in the mantle and any destruction to civilizations inhabiting their relatively thin crusts above is really not their fault.

Bear with me through the puns. The really cool rocks, literally cooled now, are 1.8 billion years old, which we pondered and touched as we hiked up the canyon, blackish greenish gneiss and schist with white feldspar veins lapping through, sitting as the basement under fluffy tan sandstone cliffs, which we dismissed as modern and irrelevant, a mere 8 million years.

Girls blow off lecture to explore
Girls blow off lecture to explore
Nice view of the fault

The basement rock, these darker, precambrian sedimentary layers, formed when our continent lived in another time zone and perhaps on a latitude that now hosts diving seals and Antarctic research stations–who knows what part of Pangaea these layers first settled upon–then were chucked up violently, thrust out of earth’s cemetery for us to gawk at, caress, even sit on (since they’re pretty cool), thanks to the San Andreas fault, strike-slip zones, or subduction zones where one part of the crust dives under another and causes massive mountain building.

Orogeny leads to Cataclysmic Mountain Slides.

Who's knocking?

We set up camp as far away from the crumbing sandstone cliffs as possible. We slept next to a huge boulder–when did that topple down? I didn’t want to be in the way of any future headaches.

Maeve and her friend Maddison scaled the scarps, traversed the fins of mudstone ridges that got squeezed up during the last earthquake here. I read the rocks like a history book with scrambled up pages. Pages of a once-sedimentary sea bed, or river bed compacted with its contemporary rocks and gravel, with thousands of seas and river layers atop and compressed into one-inch layers down toward the mantle, then torqued 90 degrees and thrust thousands of feet above, back into the sky, where they had once settled and sank, now rippled, bent, twisted. Powerful force, this restless earth.

bending squishing squeezing
bending squishing squeezing

Three hundred years is too long for grinding plates to not relieve pressure. The Pacific plate is trying to zipper North, secede from the North Atlantic plate. It would have been nice to straddle that fault line, on our hike, but earth has filled the crevice with soil, in these ensuing 300 years, the last time there was a rupture this part of the fault. We settled for signs of pressure, squeeze, and polish when Monte struck his geologic hammer into the mudstone hillside and retrieved rocks that revealed their sudden pressured exodus from deeper within the crust. I took one, to put on my desk.

We're so little

I thought everybody knew about tectonic plate movement and that it existed forever. Not so, theoretically. When Monte was a student in the early 70s, the chair of his department scoffed at such novel theories. When Monte went to a conference in Russia in the mid 70s, scientists tethered to communist-closed information and policy still laughed at him. But when he went to a conference in Siberia in the early 90s, the old-guard, still alive and kicking, didn’t believe in the new- now old-fangled tectonic-plate theories. Well, at least we don’t have to do blood sacrifices when mother earth rears her ferocious head.

Heading into the slot at night

The best part of the weekend was when, Saturday night, after an appetizer-happy hour, we set out with flash lights into a darkened slot canyon, a freak feature of geology that is nonetheless beautiful. Monte thought it would be much more fun to climb through it in the dark, with a slit of stars overhead.

A woman hiked ahead, reassuring her claustrophobic, perhaps acrophobic—Stanford-grad daughter, that she would be ok. This older woman, but not so old, wearing a man’s wedding ring on her index finger, boldly climbed, squeezed and scrambled through places only magma should climb; and then came daughters, younger children, and other people with dogs.

A perch for Maeve and Maddison

I found it mildly hilarious that Monte never said that anything was too difficult for anyone or anyone’s animals, regardless of lawyers in the Stanford alum club. That he was fearless of lawsuit and litigation, just like old Europe. He did say that if he ever thought of such liabilities, he would never host such outings. But he did ask himself, lying awake the night before the weekend, ‘should I take these people into this potentially dangerous fault zone—who knows when it’s going to rupture again…and yet it never does when I take my classes up there.’

And he did say to us that children should stay with their parents at night in the slot canyon at all times. Which the index ring-fingered widow already knew.

I marveled, earlier in the day, how Monte himself scrambled up a scarp that I was tempted to scoot back down on my butt. When I watched him closely, his hands shook with the shaking that comes with an imminent older age that will rage, rage against the coming night, rage rage for a midnight hike. After a most pleasant happy hour with intelligent conversationalists. (Tho I must say to the ex-fusion research guy who was extolling the cheapness of nuclear power, dude, even with breeder facilities you’ll still have to dump waste in Yucca Mountain, and what’s the long-term price of that?)
In the slot canyon, everyone heaved and helped, with boosts, hand holds, miners’ lamps, flashlights. At one point, a rock arrow pointed off the sand trail to the left, but many had already stepped over the minor rock lintel next to it and kept moving forward. One man asked if anyone read ar(row)bic and I exulted about hiking among clever punsters, knowing all would be well. Someone spotted a tarantula and we were all curious, except my daughter Maeve, who tends to be incuriously arachnaphobic. The arrow-followers ended up on an endless hike, whereas we lintel-hoppers came out through the slot canyon into a star-studded mesa-topped sky. We climbed out onto a landing, of sorts, with a rock cairn pointing our way. Maeve and Megan, unfortunately, saw this as proof that the Blair Witch comes out even to mesas coughed up by the San Andreas.

Dry waterfall
Megan ponders near dry waterfall

5 Replies to “Hiking on the San Andreas Fault”

  1. San Diego, Calif. – An earthquake with the magnitude of 4.1 has struck just north of the Palomar Observatory in northern San Diego County. The earthquake, moderate in size and strength, didn’t do any

  2. Monte Marshall says he plans to write a book. Otherwise, I liked the book “Geology of Anza-Borrego” by Paul Remeika and Lowell Lindsay for more info about this part of the desert.

  3. Nice post. There’s a similar topic thats related to this in Yahoo answers or Google groups, I think. I’ll find the link and post it back here.

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