If you enjoy living on the edge, and one of your greatest wishes is to see a volcanic event in action before your very eyes, you don't have to travel as far as Hawaii, Indonesia or even Washington State.
Because we've got our very own volcano right here in California — just over 300 miles north of Downtown Los Angeles, but a world away geologically speaking.
In fact, it's not just one volcano — but an entire volcanic field that's ripe for exploring, east of the Sierra Nevada.
It started forming as far back as 250 million years ago — and, much to the excitement of geologists, it hasn't really stopped. And you can witness some of that volcanic activity bubbling up to the earth's surface even today.
Here are nine of the best volcanic attractions along a 200-mile stretch of Highway 395 — the main artery through the Eastern Sierra region of California — for a rocky (and watery) road trip through the layers of time.
1. Mammoth Mountain
Technically known as the Mammoth Mountain Volcanic Field, the "Mammoth" we know today as a premier skiing and hiking destination is actually part of a lava-dome complex in the Long Valley Caldera — a bowl-shaped land depression (or "sink") formed by a catastrophic volcanic eruption 760,000 years ago. It was so catastrophic, in fact, that experts refer to it as a "supervolcano" eruption or simply a "supereruption." Evidence shows that it blew ash as far as Nebraska.
Mammoth Mountain itself is essentially an 11,000-foot volcano that was built by a more recent series of dozens of "eruptive episodes" — which occurred between 50,000 and 100,000 years ago. In fact, there's still hot magma underneath Mammoth Mountain, accounting for emissions of carbon dioxide and other volcanic gasses. That activity really ramped up as a result of a major seismic swarm beneath the mountain in 1989 — and ever since then, it's been a site of major "unrest" (in terms of both earthquakes and also ground uplift).
In fact, the USGS stated in a 2018 report that the Long Valley Caldera poses a "very high" threat — mostly because of how projectiles from a volcanic explosion could impact nearby populated and developed areas, a.k.a. the Mammoth Lakes community and the entire 395 corridor.
But don't let that keep you from visiting! In fact, you're more likely to feel the impacts of high altitude than be sacrificed to a boiling volcano at Mammoth. Just drink plenty of water at higher elevations and give your body some time to acclimatize. Be extra careful with UV protection, as sunburns are more likely (and can be more severe) in the thinner atmosphere.
Mammoth Mountain ski lift tickets are available for purchase online or onsite. If you're not skiing (or it's not the winter ski season), you can take a scenic ride to the top of Mammoth Mountain on the Panorama Gondola, located across from Main Lodge. Children ages 12 & under ride free (maximum 2) with each paying adult. For more tips on visiting Mammoth Mountain and Mammoth Lakes at any time of year, visit the Mammoth Lakes Tourism website.
2. Devils Postpile National Monument, Mammoth Lakes
Formed during a volcanic period (though not an explosion, per se) less than 100,000 years ago, the pentagonal and hexagonal columns of basalt of the Devils Postpile formation are surprisingly geometric — a result of fiery lava spewing out of a fissure vent, flowing downhill from somewhere in the vicinity of the Upper Soda Springs Campground at the north end of Pumice Flat to its current location.
Tens of thousands of years later, glaciers slowly floated down the Middle Fork of the San Joaquin River and excavated the mass of volcanic rock and the bottom of the lava flow — exposing the five- and six-sided posts that you see today, some towering as high as 60 feet. Their pattern is so uniform that the cross-section view from the top could easily pass for tile flooring, were it not for the striations and polish left behind by the glaciers.
It doesn't take much of a hike to get to the formation after disembarking from the Reds Meadow/Devils Postpile shuttle bus — but at 7,500 feet of elevation, your legs might feel lead-heavy and lungs squeezed tight. Note that the shuttle only operates during the summertime — which, at this elevation, is often mid-June through mid-September. You can check the historical opening and closing dates online — but just be aware that once it starts to snow, the roads close. And then, the only way to visit Devils Postpile is at your own risk via cross-country skiing or snowshoeing.
No permits required for day hiking. Dogs on leash allowed on trails and shuttle buses, but must be muzzled on shuttles. Scoop up your pup's poop and check online for the park's rules and current fire restrictions. Some areas of Devils Postpile National Monument's 800 acres are ADA compliant, but the 0.4-mile trail to the formation itself is not fully accessible.
3. Hot Creek Geologic Site, Inyo National Forest
Hot Creek Geologic Site is a literal hotbed of geothermal activity in the Long Valley Caldera. Managed by the U.S. Forest Service as part of Inyo National Forest, the lava started flowing about 333,000 years ago. Even more interesting — although much to the dismay of swimmers who are now forbidden from entering the water — it's been actively "geysering" since 2006 with new springs appearing annually!
These tiny, gassy explosions are coming from live volcanic vents and are responsible for wildly fluctuating temperatures — rising to the scalding-hot range of 200-400 degrees Fahrenheit. Once that boiling water reaches the surface, it's the climax of a 1,000-year journey that starts with the water being heated and pressurized far beneath the earth, where it percolates deep underground and circulates through a complex underground system and stored in a thermal aquifer.
The result is a geological wonder in a wide part of the Hot Creek Gorge that manifests in a colorful display of bright blue, green, and turquoise — and a pungent stench of sulfuric "rotten eggs." Start at the overlook by the parking area to take in the wild scenery from above, and then descend into the gorge via a paved interpretive trail. In case you forget, multiple signs warn you not to enter the water anywhere — because it's become too unpredictable where the next geyser will erupt.
Located 3.5 miles off Highway 395 on Airport/Hatchery Road, which is gravel and bumpy (though passable without 4WD). Open sunrise to sunset. Free admission and parking. Vault toilets at parking area. Dogs on leash are welcome. During snowy winter months, the site is accessible by snowmobile, snowshoe, or cross-country skiing via the Hot Creek Ski Trail.
4. Crowley Lake, Bishop
Crowley Lake — which is really a 12-mile-long manmade reservoir created in 1941 by the LADWP's Long Valley Dam — is located on the edge of the Long Valley Caldera (see #1 above). Much of its natural shore was formed by deposits of volcanic ash — but the "columns" or "pillars" that characterize the eastern shore were pretty much a scientific mystery until 2015. That's when scientists figured out that these stone formations were a result of freezing-cold snowpack melt hitting hot ash, resulting in boiling water and steam. As it turned out, the ash hardened into of a type of volcanic rock called tuff (which consists of at least 75% volcanic ash) — creating just one section of the area's larger Bishop Tuff formation (also visible at Owens River Gorge).
The trick is finding just the right time of year to see these stone pillars, as high water levels might obscure them. (In a drought year like 2021, that hasn't seemed to be an issue.) You can drive to the upper plateau of the columns and hike your way down — but that requires four-wheel drive, high clearance and nerves of steel to navigate the unpaved Forest Service roads. I found it easier and more enjoyable to approach the pillars from the water — by booking a kayak tour with Caldera Kayaks based in Mammoth Lakes. The outfitter also offers kayak rentals for self-guided tours — but it's nice to be brought to the formation by someone who can actually explain it to you.
When you spot this formation in the distance, with snow-capped Mount Whitney looming behind you, it looks something like a paleontological find — maybe the ribcage of a dinosaur or some other prehistoric megafauna, or the baleen of an ancient whale. Up close, you can see the spiraled upper pillars jutting out of the plateau — as though it's got more than just a few screws loose.
Additional boat rentals available from Crowley Lake Fish Camp at the Crowley Lake Marina at the South Landing. Must be at least 18 years old with a valid driver's license. Private boats are permitted but must be inspected at the Crowley Lake Fish Camp Front Gate. Open seasonally the last Saturday of April through October 31, with a restricted fishing season starting August 1.
5. Wild Willy's Hot Springs, North Landing
Sometimes called "Crowley Hot Springs" (probably because of its proximity to Crowley Lake), Wild Willy's is on BLM land located near the "Long Valley" of the Long Valley Caldera — more specifically, at the end of a hot stream that branches off from the Owens River.
It's a much milder experience than Hot Creek — with no geysering and no waters hot enough to scald anyone, even though the geothermal science behind the two sites are quite similar.
Start off at the free parking area and travel down a gradually stepped gravel trail that eventually becomes an elevated wooden boardwalk (which protects the surrounding sensitive meadow habitat). After walking about a quarter-mile, you'll reach two pools — one much hotter than the other (and also shaped like a heart). It's worth asking anyone who's there how hot the water is — and dipping a toe in before taking the full plunge.
Both pools are meant for sitting and not standing or swimming, and they both can be very slippery underfoot. It might help to wear water shoes or strapped-on sandals to secure your climb in and out of the pools. Otherwise, sit and enjoy the warmth and the scenery, as the site is sandwiched between the Sierra Nevada mountain range and the Glass Mountain Ridge (a.k.a. the northeast boundary of Long Valley Caldera).
Turn off Highway 395 at Benton Crossing Road by The Green Church. After about 3 miles, turn right at the cattle guard onto the unpaved (but maintained) Wild Willy's Hot Spring Road until you reach the dirt parking lot. (Google Maps may lead you too far down the road, so follow clearly posted signs.) Free admission and parking. Primitive site with no services.
6. Travertine Hot Springs, Bridgeport
The undeveloped Travertine Hot Springs site is pretty much right in the center of the town of Bridgeport — and its accessibility makes it one of the more popular hot springs in the area. It's made of "hot spring limestone," a.k.a. sedimentary deposits of calcium-carbonate exposed to carbon dioxide-rich water. Known better as travertine at these hot springs, it's been formed naturally into multiple terraces that the constant flow of water has smoothed out over time. The area was once quarried for building materials — used in landmarks like San Francisco's City Hall — but it's now managed by BLM as a critical area of environmental concern.