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The Geologist And The Case of The Scotts Valley Ruins

Mysterious rock formations in the Santa Cruz Mountains inspired early tales of lost treasure and gold. UCSC geologist Hilde Schwartz investigated and found evidence of natural wonders at work.

by Paige Welsh

Aug. 19, 2014—On a tip from a local historian, UC–Santa Cruz geologist Hilde Schwartz went to Scotts Valley in 2012 to investigate a mystery. Twelve squat tubular stones sit among the trees like lumpy flat-topped bundt cakes in the Santa Cruz Mountains. A visitor can flake away bits of sand and embedded sand dollars from the formations with a thumb. Scotts Valley residents call these rocks “The Ruins.” Fortune seekers exhumed The Ruins during the Gold Rush for historical curiosity and perhaps treasure buried by a lost civilization. No treasure was ever found, but rumor has shrouded the chimney-like rocks in mystery ever since.

Schwartz was skeptical; she suspected geology alone was at work. Under the gaze of the town’s locals, Schwartz and several colleagues studied the chimneys and confirmed her hypothesis. The Ruins formed because of methane leaking from the seafloor more than 5 million years ago, when California was underwater and hominids struggled to walk upright. The pipe-like channels created by leaking methane are called cold seeps. Gold Rush treasure hunters were wrong about the treasure, but Schwartz did find evidence of a darker kind of gold: oil that may lie beneath Scotts Valley.

Rumors of Lost Civilizations, Found Gold

The frenzy of the Gold Rush made people speculate that even dull rocks like The Ruins contained gold. It’s hard to imagine that the chunky formations—just up to four feet tall and two to six feet across—once inspired treasure-hunting companies. Schwartz has her ideas, though: “You can see how maybe if you were a little drunk and you happened to come upon them, you’d think, ‘Oh yeah, these look like Greek temples,’ or something like that.”

Most of us probably would agree with William H. Brewer, who conducted California’s first geologic survey from 1860 to 1864. He reported his disappointment in The Ruins in his book Up and Down California: “We found them a humbug—nothing near what we expected… These had been regarded as artificial works—‘chimneys of furnaces’—and at one time a company was actually formed to dig for treasures that might be buried there. So inflamed is the public mind here on hidden treasures!

The Ruins have survived thanks to the various owners who never developed the property and preserved them for future generations. The rocks now reside on private property owned by the Genn family, descendants of the Scott family, for whom Scotts Valley is named.

When Schwartz proposed studying The Ruins, the Genn family gave her access to the site and permission to take samples to put the mystery to rest. However, the neighbors were still wary. Schwartz started doing field work in Africa at age 22. The Ruins were her first suburban project. “There can be problems in both places. You have to be careful whose land and toes you’re treading on,” she says. Concerned neighbors inquired about their landmark. Schwartz learned to put a UCSC Geologic Research placard in her car and to wear an orange vest to bolster her legitimacy. “If you ever need to look official, buy an orange vest,” she says.

When The Earth Gets Gassy

Schwartz followed the evidence to The Ruins’ gassy origin. Particles of sand and detritus sink to the seafloor, eventually compressing into layers of sedimentary rock. Oil and gas in the seafloor can pool within permeable rock, such as sandstone. An oil reservoir is formed when that pooled oil or methane is capped by an impassable layer of stone. The rock layers sandwich pockets of methane and petroleum between them like the gooey filling between the pastry layers of a cherry turnover.

California was once on the ocean floor. Sediment accumulates more thickly at the center of the ocean basin, similar to the way sand in a bowl would be deeper at the center than the edges. The weight of the basin’s sediment can push methane and petroleum pockets into new spaces. “It’s like squeezing a sponge and having fluids come out the edge of the sponge,” says Schwartz.

California also lies over the restless San Andreas Fault, where the Pacific and North American tectonic plates scrape past each other relentlessly. The jamming and grinding also contributes to petroleum movement.

The chimneys of The Ruins line up perpendicularly to the Ben Lomond Fault, a minor fault parallel to the San Andreas. Schwartz believes the stress fractures that split away from the fault created cracks for the pocketed methane to bubble up through.

As the tectonic grind churned a pocket of methane, the resulting gas clamored for the path of least resistance and formed a vertical channel in the sea bed. Biochemical reactions in the seafloor process the methane and leave carbonate as a byproduct. Over time, these reactions solidified the walls of such channels into the solid carbonate chimneys we see in The Ruins.

Born in The Deeps of Monterey Bay

Many cold seeps are bubbling in Monterey Bay today. Usually they are distinguished by dense sea life surrounding the site and a few trails of bubbles. At no point do the solidified chimneys rise above the sea floor. In the case of The Ruins, by the time tectonic forces uplifted the seafloor into land, the sediment and the channels pocked with sand dollars had become the irregular sandstone slabs that Gold Rush fortune seekers once dug through.

Unlike the more famous hydrothermal vents, cold seeps are about the same temperature as the surrounding seawater. Microbes there consume sulfide and methane for energy in complete darkness. Entire communities of clams, mussels, crabs, tubeworms, and small eel-like fish can thrive on this sulfide-based and methane-based food chain. The sand dollars ensconced in The Ruins may once have lived in a similar community.

Schwartz saw these clues in the rocks. To verify her hypothesis, she and Carlos Bazan, then a senior thesis student at UCSC, drilled cores about one to two feet long from the chimney’s walls to the hollow center. She analyzed the carbonate in the cores for carbon isotope ratios. Schwartz needed to prove that the carbon that formed the carbonate chimneys came from methane, not from decomposing organisms. Like fingerprints at a crime scene, each carbon source leaves a signature isotope ratio in the carbonate. Carbonate that contains a low ratio of carbon-13 to carbon-12 isotopes points to a cold seep—and that's the chemical signature Schwartz saw.

Black Gold Beneath Santa Cruz County

While the origins of The Ruins quickly became clear, Schwartz came across a new mystery. “I think there’s a big petroleum system connected to the chimneys and to the methane, but right now I can’t prove it because I can't find it,” says Schwartz, noting that she has yet to spot petroleum-infused sandstone in place in Scotts Valley.

Most people don’t associate Scotts Valley or Santa Cruz with oil. But beneath the organic produce and the solar panels, geologists think oil reserves reside in the Santa Cruz basin. Oil companies won’t be drilling anytime soon, Schwartz notes. “It’s Santa Cruz County. That would be way more trouble than it’s worth,” she explains with a laugh. Oil companies are also barred by offshore drilling moratoriums.

Still, the oil appears naturally. For instance, dark-colored sandstone along Highway 1 is infused with tar. When petroleum bubbles up in sand, certain chemicals evaporate and a molasses-like tar stays behind. Some of the roads of San Francisco are actually paved with Santa Cruz’s own tar sand.

“What The Ruins say to me is that the whole petroleum system and the seepage system we see well-preserved along the coastline is actually bigger and extended across a wider area,” says Schwartz.

Schwartz presented her findings at a meeting of the American Geophysical Union in San Francisco in December 2012, and she hopes to publish them this year. Afterward, The Ruins may exit the scientific limelight. Few of the structures were left intact after the Gold Rush, and further studies may be too intrusive for the property owners.

One hope remains, thanks to the Gold Rush. “A bunch [of chimneys] were taken to San Francisco. They excavated them, put them on the backs of mules, and took them up to San Francisco to show them off. Either they got thrown away, or they’re in the Bay, or they’re stuck in someone’s basement. If I could hunt down some, that would be really fun,” says Schwartz.

Local historian Frank Perry, who originally pointed Schwartz to The Ruins, is less hopeful. Much of San Francisco’s 19th-century records and museums were destroyed in the 1906 earthquake, he says. He doubts The Ruins would have survived.

The residents of Scotts Valley may now ponder a new mystery. Somewhere in the Bay Area, far from its home, a lost ruin may be collecting dust. Whether it will be rediscovered by a geologic treasure hunter is still up to chance. Until then, Schwartz considers the formation of The Ruins a cold seep case closed.

Paige Welsh, an undergraduate at UC Santa Cruz majoring in marine biology, wrote this story in spring 2014 for BIOE 188: Introduction to Science Writing.

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What a fantastic story. I'm absolutely fascinated by the idea that the Ruins are 5 million-year-old cold seeps. Nice work, Paige.