Wednesday, September 29, 2021

Fossil Falls

The massive potholes of Fossil Falls
0.6 miles round trip, 50 feet elevation gain
Difficulty: Easy
Access: Decent gravel road to trailhead, no fee required

Fossil Falls is an oft-overlooked geological oddity in California's Owens Valley, a landscape of a water-scoured basalt slot canyon where the Sierra Nevada meets the Mojave Desert. The name may initially seem a bit misleading, as there are neither fossils nor a waterfall here. Instead, Fossil Falls is a canyon created by an ancient waterfall on the Owens River during previous Ice Ages. The hike to reach the rim of Fossil Falls is very short, but Fossil Falls itself provides a plethora of options for exploration and rock scrambling. Visitors who feel comfortable with rock scrambling can descend into the canyon of Fossil Falls for an intimate look at the potholes and petroglyphs that mark the columnar basalt walls of this ancient waterfall.

I visited Fossil Falls during a November road trip to Death Valley and the Eastern Sierra. The site is far from major metropolitan areas, the closest being Los Angeles, 3 hours to the south. If you're not local, it doesn't make too much sense to travel all this way just for Fossil Falls, but if you're passing by US 395 to points north in the Eastern Sierra or if you're in Ridgecrest, Fossil Falls makes a nice short detour. I reached Fossil Falls from Ridgecrest, following CA Highway 178 west and then US 395 north from town. I took US 395 north for 25 miles and then turned right onto Cinder Road shortly after passing Little Lake. I followed Cinder Road- a rocky gravel road- a mile east and then turned right at a junction for the Fossil Falls BLM site; I then followed this gravel road for a mile past the Fossil Falls campground to a small parking area for the Fossil Falls site. There was a pit toilet and enough room for about 15 cars.

From the southeast corner of the parking lot, a quarter mile trail led across a rocky and flat desert landscape to reach Fossil Falls. The Mojave Desert was quite open here, which meant that I had great views of the surrounding mountains around Owens Valley: the Sierra Nevada rose to the west, the colorful cinder cone Red Hill was just north, and the Coso Range lay to the east. Arriving at Fossil Falls, two paths branched out to visit the rim along either side of the canyon; it's worth checking out both sides.

The head of the canyon looks like a collection of basalt hoodoos from the top. The basalt that forms the canyon and that lies under the surface of the valley here is a result of eruptions from the Coso Volcanic Field, of which both Red Hill and the Coso Range are a part. This is a very geologically active spot: volcanic eruptions built the Coso Range and remnant geothermal energy still feed numerous hot springs in the area. Unfortunately, most of these geothermal features and most of the Coso Range itself are within the boundaries of the China Lake Naval Air Weapons Center, meaning that they're off-limits to the public. However, the geothermal energy here does power a series of geothermal power plants on the military property that together constitute the third largest geothermal energy project in California after projects at the Geysers near Santa Rosa and at the Salton Sea.

At Fossil Falls, cooling lava flows hardened and shrank into basalt, forming vertical columns with geometrical shapes. This basalt covered the floor of Owens Valley here. In previous Ice Ages, the Basin and Range and the Mojave Desert were able to support large lakes due to the increased snowfall in the region. Both Owens Lake and China Lake were true lakes at that time; Owens Lake eventually expanded to the point that it overspilled its current endorheic basin, sending an ancient Owens River flowing south through the gap between the Sierra Nevada and the Cosos. At the current site of Fossil Falls, the ancient Owens River plunged over a basalt ledge on its path to China Lake. The river gradually eroded out a narrow slot canyon into the basalt: the top of Fossil Falls is the point where the river plunged down into its canyon. As the climate warmed around 10,000 years ago, the lakes dried up and the Owens River stopped flowing; today, we're left with the scars that the river left on this landscape.

One of the most interesting features left by the flowing water are the deep, round potholes scoured out by the Owens River. Formed when rushing water agitated small rocks stuck in imperfections in the rock, some of the potholes were spherical holes in the rock just a foot or two wide while others were cylindrical, over 5 feet wide, and cut over 20 feet into the basalt. 

Fossil Falls and the Sierra Nevada
Red Hill and the eroded basalt of Fossil Falls
The canyon itself was very narrow with steep walls due to the columnar nature of the basalt: basalt is very hard and resistant to erosion but rushing water was able to remove entire columns to leave vertical walls. Visitors from the Pacific Northwest may see echoes of the Grand Coulee's Dry Falls here, as both were formed by similar processes; Dry Falls, however, was a far larger waterfall in its heyday.

Fossil Falls
Many visitors will find it sufficient to see Fossil Falls from above, which makes for a short and easy hike. However, those who wish to do so can descend into the canyon for some additional exploration. Entering the canyon requires rock scrambling and makes this hike substantially more difficult; understand during your descent that you'll have to ascend anything you drop down and also that the smooth basalt surfaces are quite slippery. I chose to enter the upper portion of the canyon but turned around at a major dry fall. Use your judgement to avoid putting yourself in a dangerous situation.

The exquisitely eroded walls of Fossil Falls
Being inside the canyon gave me a greater appreciation of the canyon's sculpted walls. Fossil Falls felt like an odd cross between the slot canyons of Utah and the coulees of Washington State's Columbia Plateau. Here were dark, gleaming basalt walls that reminded me of the coulees; but here were also beautifully sculpted curves in the rock that wouldn't have been out of place at Antelope Canyon.

Descending into the canyon
Inside the slot canyon at Fossil Falls
I spotted one petroglyph on the eastern walls of the canyon: the rock carving had the form of an antelope or perhaps a bighorn sheep. The Coso People lived in the area around Fossil Falls and the Coso Range for perhaps around 10,000 years; the Northern Paiute who lived in Owens Valley when European Americans began settling the area in the late 19th century may have been related to the Coso People. While much is unknown about the Cosos, they left an indelible mark on this landscape in the form of hundreds of thousands of petroglyphs. The densest collection of Coso petroglyphs are in the Coso Range itself at Little Petroglyph Canyon, where the basalt walls of canyon are decorated with countless figures of humans and sheep. Little Petroglyph Canyon is one of the most archaeologically significant sites in the United States and is one of the largest known collections of petroglyphs in the country. However, access is limited because it lies on the China Lake naval base; visitors who wish to see it can sign up for guided weekend tours from Ridgecrest's Maturango Museum after passing a background check. 

Petroglpyh on the walls of Fossil Falls
While it's easy to blow by Fossil Falls on your way up or down US-395, this is a worthy stop where the Sierra Nevada meets the Mojave if you have a half hour or hour to spare.

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