A Wilderness Walk Can Be a Journey Through Time

What if you could wrestle back the hands of time?

-- Songwriter Steve Earle

*

The road snakes deeply into Silverado Canyon, past remote clusters of homes and live oaks until it dead-ends at a parking lot seemingly at the foot of Santiago Peak. It’s a wall of a mountain, and high on its slopes weathered sandstone pokes through dried chaparral and grasses, like knife scars on a face.

Time travel, of course, is a science-fiction invention. But through quirks of geology and geography, driving this road is like riding a time machine. The higher we go in the Santa Ana Mountains, the farther back in time we travel. And the scars of sandstone represent our antiquity.

John Cooper, professor emeritus of geology at Cal State Fullerton, is a compact man with a dense knowledge of the land Orange County residents traverse every day. That sandstone, he says, is part of what geologists call the Bedford Canyon Formation, the oldest rock in Orange County, which can be seen throughout the Santa Ana Mountains.

The Bedford Canyon Formation was first identified during a 1948 excursion by geologist E.S. Larsen into the heart of the Santa Anas -- Bedford Canyon lies on the eastern slope of the Santa Anas, near Lake Matthews.

These are not the oldest rocks in Southern California. The San Gabriel Mountains, north of Los Angeles, are part of the original continental crust dating back 2 billion years. The Bedford Canyon Formation is, geologically speaking, generations younger, only about 180 million years old, and laid down as sediments on an ancient seabed.

Those sediments had to settle on something, but Cooper says no one really knows what formed the ocean bottom then. The geologic record is lost, or remains so deeply buried as to be undiscovered.

So the Bedford Formation, as far as we’re concerned, marks the beginning of time, visible to us now because of the slow-motion heaving and churning of the earth beneath our feet and the equally powerful forces of erosion.

Cooper calls the process “unroofing.”

“As you raise the mountains up, erosion becomes aggressive,” he says. The stratifications of earth are exposed like the end of a deck of cards, which Cooper can read as a historical ledger.

Thanks to Hollywood, most people have a sense of the Jurassic Period, the time when dinosaurs roamed ancient continents. This Bedford Canyon Formation was created about the same time, but so deep beneath the ocean that there were few living things to die and fossilize.

So while paleontologists have found treasure troves in Wyoming and other reaches of the eastern Rockies and Great Plains -- in ancient times a verdant lowland of intercutting, or braided, rivers -- few fossils from that era have been found here.

But the rock layers tell the story of how this land came to be.

Time, when you start at the end of Silverado Canyon Road, moves westward. We start the engine and begin retracing our route out of the mountains, cruising through eons of time at 20 mph as Cooper explains how ancient seabeds can become modern mountain ranges.

In a word, pressure. Tectonic plates form the Earth’s outer surface like the cover of a rag baseball. Heat within the Earth’s core leads to shifts in those plates, like fragmented river ice. This is not terra firma; the very ground moves, and not just during earthquakes. In a slow waltz of subduction and obduction, these plates slide under, over and alongside each other. It’s conceivable, Cooper says, that the land that was once beneath the Bedford Canyon Formation is now somewhere in Mexico.

It was such a shift that created the Los Angeles Basin. About 20 million years ago, the Santa Monica Mountains were aligned with the Santa Anas and the San Gabriels.

But the Earth’s shifting crust twisted the Santa Monicas westward, as though they were pivoting on the northern end, which created the gap that became the basin: at the time a deep sea trough that slowly filled with sediment as the land rose raised and the seas receded.

Cooper points to telltale formations as we drive. The Bedford Canyon Formation is sheathed by the Santiago Peak Volcanics, hard and speckled igneous rocks formed by ancient lava flows from long-gone volcanoes. Then comes the Trabuco layer, swaths of gravelly red deposits laid down on dry land about 90 million years ago. The color is a clue. Red indicates that oxidized iron -- geologic rust -- is present, which means the layer was exposed to air while being formed, likely the detritus of braided rivers as they flooded their banks.

The cycle repeats through the westward drive. The alluvial deposits of the Trabuco Formation cede to the conglomerates and sandstone of the Baker Member, then to the dark organic-looking rock of the Holz Shale Member. The shale indicates abundant life at the time, and here one can find the shells of ancient clams and snails. Road crews building the eastern tollway found some shells two feet across near Bee Canyon, in the foothills north of Irvine.

Cooper sees in the changing rock strata the ebbing and surging of ancient seas, the effects of the heaving crust and such vast climatic changes as the formation and thawing of ice shields and glaciers. Back and forth it went.

The Silverado Formation was laid down in coastal swamps, followed by the Santiago Formation when the land was a little drier, then the Sespe Formation, a thick blend of conglomerate and sandstone -- and the tell-tale red.

“Either the land was uplifted, causing the sea to withdraw,” Cooper says, “or about this time the Antarctic ice sled was forming big time, and when that happened, you had a lot of withdrawal of water from the ocean.”

Cooper peers out the truck window as the canyon walls slide by. He’s looking for a specific place among the bends. He spots it and moments later we’re scrambling upward.

Cooper stops at a 10-foot square of exposed, thin layers of rock that swirl like Van Gogh brush strokes, a fold of ribbons bent into shape by the intense and slow-cooking pressures of the shifting Earth. He pokes at the layers, pointing out ones of fine sand laid down at the bottom of an ancient seabed, and the coarser layers created after the seas receded and streams coursed through the area. There are several layers of each, and together they evidence a series of ancient ebbs and flows that moved so slowly nothing living at the time would have noticed them.

As Cooper talks about what once was, he fingers the outcropping again and a few grains of the softer layer fall away, the victims of unnatural erosion.

No one, of course, knows what the future will bring. But there’s a wondering sense as we look into the past that maybe the present we’re standing in will be the future, and that on some unfathomable day eons away, another John Cooper will be poking at the ribbons yet to be formed, crumbling the remnants of what we are.