There is something invigorating about working out a rental car on mountainous dirt roads. "Let's see what this baby can do" invigorating. Okay, I thought about more than I did. And all I've got to show for it is a very dirty car. But driving 30 miles up and down over narrow dirt roads was quite an experience. It reminded me of my childhood when cousin Tom or cousin Jack would take us kids on drives in the farm's Jeep up in the hills around Hemet, California. Hang on and scream.
Mendocino National Forest consists of more of the Coast Range, which means jumbled Franciscan formation sedimentary rock. There was some serpentinite but not much granite. The elevation rises to 6000 feet in a couple of peaks, but mostly it is 2000 to 3000 feet. The serpentinite is an indication that I am near the east side of the fault area. According to geologists, the serpentine, a metamorphic rock, is at the base of the North American Plate in this region. As the Farallon Plate and the Pacific Plate subducted below the North American Plate, the serpentine ridge was the edge underneath which the descending plates passed. Serpentine is well-suited to be an edge material because it is both extremely hard and "slippery". I guess that means it has a relatively low coefficient of friction. The primary mineral in serpentinite is talc Its slipperiness has given it the common name of soapstone. It is the official state rock of California. The distinctive feature about serpentinite is its greenish color, which makes it very distinctive and attractive. Its surface occurrence is spotty because it is subject to exposure only where the edge of the North American Plate was thrust upward. Mostly I could see in road cuts.
Leaving the national forest, I traveled across the Great Valley, which is flat expanse of sediments laid down from erosion of the Coast Range to the West and the Sierra Nevada to the East. The primary river is the Sacramento, though with the extensive amount of diversion for irrigation, it doesn't look like much.
An unusual feature in the middle of the valley near Yuba City are the Sutter Buttes, which rise about 2000 feet above the floor of the valley. They are volcanic in origin, but geologists can't figure out how they arose. One theory is that they are a southern extension of the Cascade Range, which includes Mt. Shasta and Mt. Lassen. But there seems to be too great a space between Mt. Lassen and the Sutter Buttes where there is no appearance of volcanic activity to make a connection. Another theory is that they are part of the Coast Range volcanic activity. The divergent age and composition of the buttes from the other formations impairs the validity of either theory. For now, they stand alone, and have the dubious distinction of being the shortest mountain range in the world.
The first thing about Lassen Volcanic National Park is that it is high up. You have to pass through a lot of the adjoining national forest to get to Lassen. Yet the forest in the park is different. The southwest part of the park is a vast caldera of a prior volcano, Mount Tehama. The rock of the entire park is various kiinds of igneous, or volcanic, rock. Lassen became a national park in a most spectacular fashion. On May 22, 1915, Lassen Peak erupted, sending a cloud of ash four miles up into the atmosphere. Less than a year later, Congress made it the 13th national park. It was the last volcano to erupt in the lower 48 states until Mt. Saint Helens erupted on May 18, 1980. Lassen is classified as active and is expected to erupt again, though probably not for several hundred years. Lassen Peak began forming about 27,000 years ago. It is classified as a dome volcano, which means it develops a thick lava that rises and increases the size of the peak. Only a small amount of the lava pours from the top and down the sides. The 29-mile road through Lassen Park reaches a height of 8,512, the highest road in the Cascade Range. The park had only a few visitors when I was there, and it will close soon when the snow starts to fall.
Mileage: 340. Cumulative mileage: 1,278.
