01-08-2025
The California mountain road hiding a 'portal in time' to Jurassic era
A remote stretch of Northern California highway is hiding something truly extraordinary - not just a scenic drive, but a rare window into Earth's deep past.
Highway 199, which branches off from Highway 101 near Crescent City and winds inland along the crystal-clear Smith River, cuts through one of the only places on Earth where you can drive through exposed mantle rock - the layer that normally lies 22 miles beneath our feet.
This surreal stretch, known as the Josephine Ophiolite, is a 350-square-mile patch of upper mantle and oceanic crust that was somehow forced to the surface millions of years ago.
It now sprawls across the Klamath Mountains, creating an eerie, jagged landscape that scientists say looks more like the ocean floor than California backcountry.
Geology professor Brandon Brown of Cal Poly Humboldt has spent years studying the area - and bringing students to see it firsthand.
'You're sort of basically driving from the mantle to the ocean floor of the Jurassic as you drive from Hiouchi to the Oregon border,' he told SF Gate.
For his students, the experience is mind-blowing. 'It's just so many light bulbs' going off, Brown said. Instead of just reading about tectonic plates in a textbook, students are 'now standing in the mantle,' or standing on what was the ocean floor from 200 million years ago.
Scientists flock to the area for the same reason. Researchers come from 'literally around the world' to study the Josephine, said Brown - not just for its age, but for how visibly it confirms plate tectonics in action.
Before the theory gained widespread acceptance in the mid-20th century, scientists struggled to explain how continents moved, why mountains formed, or how fossils ended up on distant shores.
The Josephine Ophiolite, with oceanic rock clearly thrust onto land, became a smoking gun.
And it's not just what's underground that's remarkable - it's how it transforms everything you see.
'We see so many landslides and rock falls,' Brown said. That's because the exposed rock - mainly greenish serpentine and dense ultramafic material - is fragile and unstable. It doesn't behave like typical mountain rock.
The same material also affects the water. '[The] river is so clear and clean because these rocks don't pulverize into tiny pieces of clay,' Brown explained. And the surrounding peaks? '[The] mountains are so jagged and sharp.'
He calls it a rare opportunity 'to appreciate what the ocean lithosphere is made of.'
The landscape changes in more subtle - but no less striking - ways as well. Because the mantle rock is high in magnesium and low in calcium, the soil is nutrient-poor and difficult for plants to grow in.
'When I'm taking students out there to look at this, we're almost for certain going to run into a botany class,' Brown said, '…because the types of plants that grow on them is very unique due to their obscure and strange magnesium and calcium ratios.'
In some areas, you can see the transition happen right underfoot.
'You pass from redwood to giant redwood trees, and you cross the fault... Now you're looking at 100-year-old trees that are like the diameter of my arm,' he said.
'They're just sort of struggling, persisting along, using whatever nutrients they can find.'
The site even holds economic interest. The rocks are rich in metals like nickel and chromium, which are key components in stainless steel and battery production.
But for Brown, it's less about industry and more about awe - a place where the forces that shaped our planet are not just hidden below the surface, but written into the very land beneath your tires.
