Up The Road: Geology Nerd’s Tour Of Grover Hot Springs State Park

Jan 29, 2020

Grover Hot Springs State Park, where you can also hike, snowshoe, and ski cross-country.
Credit Ken Lund

Need a spa vacation but can barely make the rent?

I say: Head for Grover Hot Springs mid-week to grab one of those 20 first-come winter campsites near the park entrance (in summer, this is the picnic area). Then just settle in.

Just west of Markleeville, some 40 miles south of Tahoe, is Grover Hot Springs State Park, the perfect hot-soak antidote for weary skiers and snowshoe hikers. 

Tucked into a mountain meadow near the northeastern edge of the Mokelumne Wilderness, the spring-fed pools at Grover Hot Springs aren't particularly pretty. Think: public swimming pools with changing rooms and nice hot showers. Yes, swimsuits are required here.

But, “pretty” is hardly the point. If you’re a hardy soul seeking a therapeutic soak followed by a quick roll in the snow, this is the place for you.

Pools are closed for annual cleaning for two weeks in September, but otherwise open all year—if you can get here. (In winter, be prepared; bring chains and a snow shovel.) In summer, Grover Hot Springs can get crowded—and when pools all full up, you need to wait for others to leave before you can come in. All the more reason to go now, right?

Some California state parks exist to protect and preserve cultural history. Others emphasize natural history. And some do a pretty good job of both, including Grover Hot Springs.

Though Tahoe was, and is, the geographical and spiritual center of life for the Washoe people, these hot springs were always valued too, for physical and spiritual healing. Then as now, native people cultivated and gathered useful plants in the meadow and forests here.

As for natural history, a special state report, The Geological Gems of the California State Parks, explains the geology of Grover Hot Springs, created by tectonic-plate faultlines—not unique on the eastern slope of the Sierra Nevada, but definitely different than areas where hot springs are caused by volcanic activity.

Before this area was commercially developed, “there were a dozen springs and seeps in two marshy areas about 100 yards apart, at the edge of the meadow on the southern side of Hot Springs Creek.” In the early 1900s, both the meadow’s hot and cold springs were “improved,” for mixing, to achieve temperatures comfortable for bathing.

In winter, when you steep in these spring-fed pools you get to gaze up at stunning snow-covered peaks. Faulting gets credit for the spectacular views, too, a notable feature of the Sierra Nevada’s eastern face.

It’s all because of colliding tectonic plates, in this case the American continental plate and the heavier Pacific plate. Faults, or fractures in the earth’s crust that cause differential movement, are often associated with plate boundaries, as are earthquakes. Pressure and friction along this subduction zone melt the sinking heavier rock, turning it into magma that crystalizes and solidifies into igneous rock, such as granite.

When groundwater seeps into the earth along fault lines, magma heats it. Because hot water is less dense than cool water, it rises through the fractures and faults, collecting dissolved minerals on its way, finally bubbling up as a hot spring. Cold surface water flows down, replacing the escaping hot water, continuing the cycle.

There you have it. The geology nerd tour of Grover Hot Springs.