Protect and Enjoy: Volcanoes, Glaciers & Earthquakes – Forming Land Trust Lands, Part 1

The view of Carpenter Valley from the air shows the glacial U-shaped profile, as well as the recessional moraine that divides Lower Carpenter Valley (Truckee Donner Land Trust) from Upper Carpenter Valley (private property).

Note: This is the first in a series of Protect and Enjoy stories planned over the coming months looking at the science, the history and the culture that make Land Trust lands truly special.

Standing in the “Secret Garden” of Lower Carpenter Valley, if you were able to take off, flying tens of thousands of feet straight up in the air, you might notice Carpenter Valley is part of a pattern repeating along the eastern flank of the Sierra Crest.  

Oblong scallops like Emerald Bay on Lake Tahoe’s west shore, Olympic Valley, Donner Lake, Carpenter Valley and Independence Lake run downhill from the sharp-edged crest in much the same way, with much the same size and shape. Some are filled with water, while others, like Carpenter, are lush, green meadows with streams meandering through.

Their similarities aren’t a coincidence – they’re all the result of glaciation. And while Yosemite Valley’s glacial origin may be the most famous of the Sierra, the landscapes we love owe no less to the power of ice a thousand feet thick slowly working its way downhill.

“There was an ice field along the crest of the Sierra Nevada, maybe 1,000 feet thick, feeding all these glaciers that carved U-shaped valleys – as opposed to V-shaped valleys eroded by running water,” said Jake Hudson, a geologist and engineer with NV5 who has worked with the Land Trust on a variety of projects.

That glaciation happened in the last two million years, when the ice sheet would have covered much of the Sierra Crest, with only the tallest mountains peeking out above the ice like Castle Peak. Van Norden Meadow – part of the Land Trust’s Royal Gorge campaign, would have been under that ice sheet.

But we have to go back earlier – between five and fifteen million years ago – to understand what would be carved by the glaciers, Hudson said. 

While classic Sierra granite characterizes much of Donner Summit, Frog Lake Cliff, and boulders strewn around Lower Carpenter Valley and our other crest properties – volcanic rock plays an important role in the tapestry of our landscape carved by ice, Hudson said.

 “It would have looked very similar to the Modoc Plateau of the Cascades,” Hudson said. “Castle Peak is a good example where we can see very flat-lying lava flows at the top – the topography must have been very gentle when the lava erupted.”

That’s where granite comes into the picture, when the Sierra Nevada batholith – a massive body of granite, uplifted from underneath the volcanic plateau as the result of tectonics, forming the Sierra Nevada. Like layers of a cake, volcanic material sat atop the granite, setting the stage for glaciers to cut down and expose the dramatic landscape we enjoy today, he said.

Along with the characteristic U-shape of the valleys and lakes in question, glaciers left their mark in other ways. The huge masses of ice acted as conveyer belts, Hudson said, depositing rock in unique patterns and in places often miles from their origins.

 Returning to Lower Carpenter Valley, hikers can spot evidence of this in lateral moraines – deposits of rock and silt along the sides of the valley, and a recessional moraine – a deposit that divides the upper and lower portions of the valley that was left when the glacier receded, Hudson said.

Frog Lake under the cirque of Frog Lake Cliff, photo by Jim Easterbrook.

Elsewhere as with Donner Lake, Frog Lake and Independence Lake, terminal moraines at the glacier’s furthest reach created dams – turning the valleys into lakes. The dramatic 1,200-foot granite Frog Lake Cliff is a cirque formed by the glacier too.

Peaks like the recently protected Red Mountain – named for the color of its volcanic rock, were left behind when two parallel glaciers (Carpenter Valley and Euer Valley) left a ridge above the ice, Hudson said.

The volcanic rock of Red Mountain catches the morning light, photo by Robb Hirsch.

In some places, glacial erratics – granitic boulders dropped on top of the underlying volcanic rock, have been deposited in seemingly improbable locations – like near the top of Johnson Canyon on the Donner Lake Rim Trail.

“You can see it from Rainbow Bridge looking across at Johnson Canyon – there are granitic boulders way up the slope near the Drifter Hut – that’s how high the glaciers were,” Hudson said.

The most recent stretch of the Donner Lake Rim Trail, as it continues west toward Northwoods Boulevard, weaves between still more glacial erratics hundreds of feet above Donner Lake.

Things didn’t end with the recession of the glaciers, however. Turning our attention back to Royal Gorge, the spectacular hoodoos and arches along Razorback Ridge and Rowton Peak demonstrate continued erosion at work.

“The columns and arches are a feature where volcanic lahar material – flows of lava and pyroclastic material – are sculpted by wind and water, supported by large boulders,” Hudson said. 

The dramatic hoodoos and sculpting along Razorback Ridge at Royal Gorge, photo by David Bunker.

To have a look at the work of volcanoes and glaciers on Land Trust lands for yourself, visit our Explore page for maps, hike descriptions and more of Lower Carpenter Valley, Independence Lake, Royal Gorge, Johnson Canyon and Donner Summit Canyon.

Stay tuned for Part 2 of our look at geology on Land Trust lands in the coming months when we look at Waddle Ranch and Elizabethtown in the Martis Valley, and the Land Trust’s most recent project – Truckee Springs.

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.