Tag Archives: uplift

Lopez Canyon: Indeed, A Land Of Contrasts

Patient Reader, remember how we left Lopez Canyon last February. Green was the scene; we Viewed with rue the Spanish Pasture Mix; we admired the charcoal-rich oak soils; and we marveled at the merry bear-currant bushes sprouting everywhere. Like this:

Recall also the live oaks; their farmer-leaves (agrifolia) create, moisten, nurture, and preserve in place, the soil. View this oak terrace, in three moods: winter, spring, and summer.

The oaks hold in place remnants of the Pleistocene alluvium.

LOPEZ CANYON: WHY CARE, AGAIN?

This is the fall of the spring’s Superbloom. Last winter brought unprecedented rainfall. A year before that, a terrible fire purged the canyon; much was incinerated and the tree trunks were blackened, including the oak groves. (The fire followed on decades of nagging drought, which had left these hills scrabby and bare.) This remarkable sequence is giving the native plants an excellent toe-hold to recover and thrive here. The last time weather conditions were this good, decades back, Lopez was the municipal dump; roads were being cut and graded, etc. But now the dump is curbed, the Santa Monica Mountains Conservancy has charge of the land, and the biome can at last catch a breath and set seed for the future.

I’m fascinated by how the natives responded to the rain. The chaparral is as vibrant as can be. Note how the plant communities have negotiated an intricate pattern of “personal space” among and between species, capturing ridge-lines, rationing out soils, specific minerals, and water among the survivors. (Note how the diagonals mark out the watered spots.)

The saw-tooth goldenbush is a chaparral beauty growing tall and louche by the side of the road. Here she can set her fluffy achenes to drift with the traffic like California bindlestiff-men, to set themselves up further down the pike.

Drooping spikes of bushmallow send you round the bend.

One the most elegant trees I’ve ever seen — a red-osier dogwood, dangling fat clusters of white berries. It’s tough to see, but the osiers (twigs) are bright red. They were used by the Indians in basket-weaving. The tree sets red, green, and white (Viva Mexico!) against the ringing blue sky, to make an especially lovely sight in this Land Of Contrasts.

“Ethnobotanic: Native Americans smoke the inner bark of redosier dogwood in tobacco mixtures used in the sacred pipe ceremony. Dreamcatchers, originating with the Potawotami, are made with the stems of the sacred redosier dogwood. Some tribes ate the white, sour berries, while others used the branches for arrow-making, stakes, or other tools. In California, peeled twigs were used as toothbrushes for their whitening effect on teeth (Strike 1994). Bows and arrows were made from Cornus shoots. The tannic inner bark was used for tanning animal skins.”
— USDA/NRCS website for Western dogwood

Kagel Canyon

“What’s Wrong With California?”

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GEOLOGY DEPT.

“Uplift, my dear, it’s all about uplift.” *A piece of Top Hill, cut away to make Hansen Dam. This transected butte is one of the first scrunched-up hills to rise off the Valley floor as “the Foothills” of the San Gabriels.*

In the rainy season, our TV is filled with”Storm Watches” and breathless predictions of floods and mudslides. The apocalyptic neon disaster maps — drizzles in distant mountains — break only for interviews with (stoned) residents in far-flung canyons, teasing out their fears of, or previous experience with, hillside collapse. The constant videos of muddy arroyos and airlifted horses upset Janet. With her New England preference for worn-in mountains and bedrock that doesn’t change for centuries, and her consequent instinct for the sharp razor of moral absolutes, she put to me the Bostonian’s eternal question: “What’s wrong with California?” “Nothing,” I snapped, and left the room.

Of course, I wanted to defend our loosely-affiliated, peripatetic soil against Eastern prejudice, but is there a simple answer to the shifting geology here? My esprit d’escalier whispered “Uplift…tell her it’s all about uplift.”

What do I know about uplift? Bupkus. So I hit the Internets to learn the theory, and went up Little Tujunga Canyon for the field photos.

500 feet higher: not only uplifted, but upended. Compacted layers of mudflows and various intrusions of lava have been broken by faults, tilted and piled into mountains. This petrified alluvium may have been formed as the then-Valley floor, like Rabbit Hill.

My first shock came from finding the map above. More black = more tectonic complexity. Yikes! LOOK at Southern California! This is the youngest land on earth, protean, ad hoc; it’s constantly under pressure from hundreds of different “vectors” at the convergence of three, maybe four, different plates (the North American, the Pacific, and the Cocos Plate of the East Pacific Rise, on which Baja floats, and maybe the tiny Rivera Plate. The map below makes it clear how the whole American West is orogenically “recent,” less than 100 million years.

Southern California is the result of three different plates rubbing up against each other; the North American, Pacific, and Cocos. The Pacific is rotating counter-clockwise, which will roll coastal LA north, towards where San Francisco now sits, in geologic time. This rolling will keep piling up the mountains on the North American plate.

Clearly the View is no rock scientist…er, geologist. But Benjamin F. Howell, Jr., was. Click on the link for his 1949 Northridge master’s thesis on “Structural Geology of the Region Between Pacoima and Little Tujunga Canyons, San Gabriel Mountains, California.” Howell’s descriptions of the land are exactly to be recognized today; only he doesn’t know why. Science hadn’t learned about plate tectonics yet; so Howell’s well-described process of uplift, which is driving the very recent geology of Little Tujunga, remained a mystery.

https://thesis.library.caltech.edu/8208/1/Howell%2C%20Jr%2C%20BF%201949.pdf

Today is a big storm. When the TV news comes on later, I can now calmly reassure Janet:

“Uplift, my dear, it’s all about uplift. Strike-slip faults; you know. Plate tectonics? The Transverse Range? Alluvial fan deposits, and magma batholiths? They rise through eroding sandstone layers, leaving granite domes and ridges. The prevailing westerlies? Fog banks? Monterey Shale? Gneiss, quartz, and dolomite? They erode to pebbles and sand, wash down to the sea at San Pedro, get compressed to rock, and then a million years later, another lurch north of the Pacific Plate scrunches the sea-bed up and up into high mountains, where it splits into fault blocks, then erodes again to boulders that get washed down the creeks, gold bars and placer deposits. They all tumble back into the sandy sea bed, and are uplifted again, and again, ad infinitum.”