Both prehistoric volcanic activity and glacier movement during the ice ages have shaped the northern Sierra Nevada, including the landscape of today's Plumas National Forest and the Lake Basin Recreation Area near the resort town of Graeagle in Plumas County, northern California. There, the upper Frazier Creek is an easily accessible terrain to explore geologically interesting features.
Most visitors come to see the Frazier Waterfalls. These falls are part of the five-mile-long path of water flowing from Gold Lake, carved out by a glacier, to the Middle Fork of the Feather River near Graeagle. According to an on-site interpretive panel, Frazier creek drops nearly 2,000 feet on its way. The top picture shows the water near the edge where it falls down a steep, stepped canyon wall (a 176-foot drop)—the stepped Frazier Falls. People have slipped and fallen off there, too! The above picture shows a nearby rock terrace structure with edges sharper than typically found in a naturally formed environment.
Some geologists believe that the sandstone and andesite formations seen next to the falls are the result of a massive volcanic eruption that was tilted on its side during California's volcanic past . During the ice ages glaciers passed over the rocks and loosened them by frost wedging—a process during which water enters rock cracks, freezes and then forces the sides apart. During warming periods glacier melting produced the step-like landscape. A panel tells us that the great steps were formed 170,000 to 190,000 years ago and asks us what we think the Frazier Falls will look like in another 170,000 years.
Scenarios: if warming continues, Gold Lake and Frazier Falls will be gone; if another ice age happens, frost wedging as well as step and terrace formation could resume; if nothing changes...well, that has never been the case in the past: a 170,000-year-long standstill is very unlikely. Scenario or not scenario isn't a theme; which scenario is the question and story to map out.
Getting there, getting around, staying safe
The Frazier Falls trailhead and picnic area is found next to County Road S501, which roughly parallels the Gold Lake Highway (County Road 519) between Graeagle and Gold Lake.
From Graeagle, drive southeast on Highway 89 and turn onto the Gold Lake Highway, which you want to follow for 1.6 miles until you arrive at the signed left-side turnoff for Frazier Falls. A four mile drive along this narrow, paved road gets you to the trailhead.
Driving north on the Gold Lake Highway from its junction with Highway 49 at Bassetts Station, you will first arrive at the S501 junction next to Gold Lake and its campground. Between this S501/519 junction and the Frazier Falls trailhead parking lot, Road S501 is not paved—it is a rough and dusty road, alright for some cars .
Along the Frazier Falls Trail, pay attention to the Beckwourth Ranger District's Stay On Trail sign: “Dangerous Cliffs Ahead - Potential for Serious or Fatal Injury.”
Keywords: natural history, geology, ice age, Pleistocene.
References and more to explore
Sherpa Guides: Plumas National Forest [www.sherpaguides.com/california/mountains/northern_sierra/plumas_nat_forest.html].
 LOVES FALLS, FRAZIER FALLS August 9, 2011 [www.petesthousandpeaks.com/Captions/2011cap/49reno/49reno.html].