Protect and Enjoy: Volcanoes, Faults and Glacial Dam Bursts – Forming Land Trust Lands Part 2
Waddle Ranch, a seemingly serene property, was shaped by lava and earthquake faults. Photo by Elizabeth Carmel
In Forming Land Trust Lands, Part 1, Geologist Jake Hudson explained the dramatic forces of ice and fire that formed Land Trust properties near the Sierra Crest, leaving jagged peaks, sharp ridges, u-shaped valleys and intricate hoodoos in places like Royal Gorge, Frog Lake and Lower Carpenter Valley.
But take a walk along the verdant Elizabethtown Meadow, through the gentle, rolling woods of Waddle Ranch, or along the Truckee River in the soon-to-be-opened-to-the-public Truckee Springs property, and a keen eye can pick out the influences of geological forces no less dramatic.
Earthquake faults lie beneath seemingly placid meadows, some of California’s most recent volcanic activity hides in plain sight, and picturesque granite boulders sitting among the sage landed miles from where they started in a torrent of rushing water that changed the entire region.
“Martis Valley has some of the youngest volcanic rocks in all of California,” Hudson said, an engineer and geologist with NV5. “Along with Mammoth Mountain and Lassen, Martis has volcanic rock dating back 1.1 million years, erupting long after the uplift that formed the Sierra.”
The rough, jagged rock on some of Waddle Ranch are the result of five distinct volcanic flows that have been mapped in the area, released by tectonic faults, rather than what one might traditionally picture in the form of a volcano, he said.
The main fault in the area – called the Polaris Fault, can also be found in Elizabethtown Meadow.
Elizabethtown Meadow follows the Polaris Fault
“Prominent fault scarps are visible in that meadow – where the crack in the earth left a sharp step between one side lifting and the other side subducting,” Hudson said. “The Polaris fault continues along the west side of Waddle Ranch on its way north.”
Not far away, the Land Trust’s latest project – Truckee Springs – owes its shape and topography to forces farther away, starting in Lake Tahoe.
The stepped terraces of Truckee Springs are the result of glacial outwash.
During past ice ages, glaciers creeping down what today are Olympic Valley and Alpine Meadows, blocked the Truckee River Canyon near Lake Tahoe, damming its waters and raising the entire lake by as much as 600 feet, Hudson said.
Some theories say those ice dams broke catastrophically, while others say dams made of rock and debris (moraines) left behind by the glaciers broke. Either way, a massive flood of water rushed down the Truckee River Canyon, carrying everything from sand to giant boulders with it.
“That’s why you can find 10-foot-tall boulders as far down as Gold Ranch, and you’ll find them all along Truckee Springs,” Hudson said.
The stepped topography of Truckee Springs is called an outwash terrace – where different glacial events (the most recent being on the order of 12,000-20,000 years ago) sent glacial wash downstream, depositing in stepped flats along the river.
“Where the Cottonwood Restaurant sits in one outwash terrace, the one below forming Truckee Springs is newer,” Hudson said.
This is part of a series of stories titled “Protect and Enjoy,” including the previous article on geology, as well as this one about long-lost species returning to Land Trust Lands.
Want to learn more about an aspect of natural science on Land Trust lands? Or are you an expert who’d love to lend some insight? Please send an email to greyson@tdlantrust.org with your idea.