Saturday, February 26, 2005

Big West Spur

Giant Gap forms one of the most beautiful scenes in California. It was the subject of an etching by 19th-century landscape artist Thomas Moran. For a time in the 1860s there was a movement to rename it "Jehovah Gap," for such is the awe inspired by the place.

Except where invaded by granitic plutons, the bedrock of this part of the Sierra is metamorphic, sometimes referred to as the Western Metamorphic Belt, which in turn is divided into Western, Central, and Eastern belts. These "belts" are formed by one or more distinct formations, generally exposed as long linear masses, striking north, in slight contrast to the overall strike of the Sierra crest, to the northwest. A system of steep, largely inactive faults parallels and divides these belts.

For instance, here the Eastern Belt is made of the metasedimentary early-Paleozoic Shoo Fly Complex, plus those younger formations to its east, such as the Sailor Canyon and Tuttle Lake formations. The Eastern Belt is divided from the Central Belt by the serpentines and peridotites of the Melones Fault Zone, also called the Feather River Peridotite. In this area the Central Belt is composed largely by the late-Paleozoic Calaveras Complex. This "complex" has not been successfully divided into distinct formations, but here at least it shows an eastern metavolcanic series, and a western metasedimentary series.

The Calaveras rocks were once roughly flat-lying, but are now tipped up on edge. Even the volcanics seem to have been deposited in layers, which is clearly true of the metasediments. The shear conditions under which metamorphism occurred were such that a fabric or grain was imparted to the rock; and this fabric itself is mainly parallel to the bedding planes, of both the volcanics and the sediments.

The volcanics of the Calaveras frame Giant Gap. Despite the bedding planes and the metamorphic fabric, these rocks are quite massive and resistant to erosion. They are in faulted contact with the serpentines of the Melones Fault Zone to the east, and in the contact zone, Calaveras rocks show some evidence of crushing and fracturing. However, some of the most massive and resistant parts of these metavolcanics are immediately west of this fault, forming Giant Gap Ridge, The Pinnacles, and the Eminence, on the south wall of the canyon, and Red Ridge, Lovers Leap, and Big West Spur on the north.

Friday morning I met Catherine O'Riley for a walk on the HOUT. This High Old Upriver Trail forks away from the Canyon Creek Trail well down towards the river, and actually leads up the canyon into Giant Gap. In places it is quite hard to follow, it is really not much of a trail.

We parked along Garrett and crossed the Diggings to the east, picking up the Canyon Creek Trail in Potato Ravine and making good time on the downhill. Flowers began to appear at the bridge (Biscuit Root), and I was not too surprised to find the smaller of the two Canyon Creek Larkspurs already in bloom, right below Gorge Point, along with False Rue Anemone. Then there was Buckbrush, and Manroot, and Brewer's Rock Cress, and Brewer's Monkeyflower, this last quite a little jewel, with its rich magenta petals and golden throat-streaks. Overall we must have seen over a dozen different species in bloom. California Milkmaids were especially nice, on the steep east side of Big West Spur, where the HOUT plunges through an elfin forest of dwarf Canyon Live Oak.

The pattern of recent days was repeated: clear skies early, a few little puffballs late in the morning, and then cumulus clouds every which way, rapidly growing into thunderstorms, but not so closely packed as to exclude all sunlight.

In other words, it was spectacularly beautiful. As the clouds grew taller, breezes stirred and freshened into a steady west wind, which brought the ghosts of the Valley fog into the Sierra, in the form of a milky humid air-mass which threw a bit of chill over everything.

This mixture of billowing clouds and misty air made for an ethereal atmosphere not dissimilar from one of Moran's paintings. The views of the great cliffs and spires of Giant Gap was greatly enhanced by intricately-shaped patches of startlingly deep blue sky and brilliant white clouds, while below, at our level, the mist began to hide more distant parts of the canyon altogether.

We were out on Big West Spur, where the HOUT winds in and out of a series of rock-blades and ravines about 400 feet above the river, in extremely steep terrain, pretty much cliff upon cliff and rock upon rock. The wind began to chill us, so we moved from a rock-blade to a ravine, and that little bit of shelter was just enough. The force of the wind was broken, the force of the sun, repaired.

After resting and exploring and taking pictures of the Milkmaids and the sparkling clear river, rich in rapids and deep emerald pools, we decided to climb to the "first summit" of Big West Spur, where the ridge almost levels out, like the Diving Board, a mile or so to the west.

Near the summit we reached a rock tower with great views both up and down the canyon. Climbing higher, we visited a series of incredible viewpoints, and as we were also going north, it happened that we had a better and better view through Giant Gap into Green Valley. There was the Pyramid, there, Hayden Knoll, there, Sawtooth Ridge, and beyond Sawtooth, a line of storm clouds, with rain streaking to the ground, below.

It was a wonderful chiaroscuro scene, with bright and dark clouds, bright and dark cliffs, and we took many photographs. It is really one of the best of all vantage points on Giant Gap. To my amazement, we could see one of the two tunnels on the line of the HOUT, the West Tunnel, in Tunnel Gully, below Lovers Leap.

Eventually we had to leave, and made a slow yet steady march up and out of the great canyon, strangely moved by what we had seen. It was a truly great day in the North Fork.

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