China Wall: A Tale of Two Rocks

Drive up Foresthill Divide to China Wall Staging Area
 and you pass over an ancient river channel that still contains gold.

China Wall sits atop a ridge between the North and Middle Forks
of the American River in Placer County, California

Perhaps this story starts in late November 2009, with the snowshoes I bought at Costco. Yes, it was an impulse buy. I saw them and had to have them. They were only $69.99!

I first tried them out in the snows at Donner Pass. Then I learned of a place called China Wall on Foresthill Divide. It's mainly a staging area for snowmobilers, but it's also popular with cross country skiers and snowshoers.

My first trip to China Wall, the day after Christmas, was purely exploratory. I took a solitary walk eastward along the ridge of Humbug Canyon. For about 1/8 mile I followed a black bear track, which appeared to be one day old.

Black bear track

Journey to Cape Horn Tunnel, January 2, 2010:

I returned to China Wall on January 2nd. Although the parking lot had several vehicles and people, my journey to Cape Horn Tunnel was solitary. I walked westward along the ridge. Off in the distance - 6.17 miles, bearing 121 degrees - was the start of Euchre Bar Trail, my favorite trail about which I will write later. Halfway downhill, I saw a bear track in the snow.

Euchre Bar Trail in the distance

The entrance to Cape Horn Tunnel is a water-filled hole by the dirt road. The tunnel was built to reach the gold bearing gravels in an ancient river channel.

I poked around a bit, and from the hillside near the tunnel entrance I picked out two rocks. One was metasedimentary sandstone and the other was quartz from a perpendicular vein. Hmmmm. How did the sandstone, which began as mere sand at or below sea level, get turned to rock and ultimately reach this elevation of 4,340 feet? Why is there a perpendicular quartz vein amidst the sandstone? And what about that ancient gold bearing river channel in front of me? Well, let's find out!

Entrance to Cape Horn Tunnel

How Was the Sandstone Rock Created?

This story starts about 450 million years ago, in the Paleozoic Era, specifically the Ordovician and Silurian Periods. There was a continent named Laurentia that looked nothing like modern North America. Off its western coast was a chain of islands forming what is called the Antler Arc. Sand collected either along the western shore of Laurentia or at the base of one of the islands. Erosion piled sediments atop the sand. Over time the sand was pushed further and further downward. Heat and pressure changed the sand to sandstone.

Plate tectonics moved the sandstone from deep below sea level to that hillside (although, not yet to the 4,340 ft level). Subduction began in the Mississippian Period. The heavier oceanic plate met the lighter continental plate and slid underneath it. The sandstone and the other sediments atop the oceanic plate were scraped off and crammed against the continental plate.

These rocks are part of a formation called the Shoo Fly Complex. (Shoo Fly was a small town north of Quincy, California.)

How did the quartz vein intrude the sandstone? And why is it perpendicular to the ground?

In the Mesozoic Era, when dinosaurs roamed these parts, the ancestral Sierra dominated the landscape. Its mountains towered possibly as high as the Andes, and the ocean lapped at its base. Subduction created this ancient range. The descending rocks, heated to the melting point, created a range of volcanoes, the ancestral Sierra Nevada, against which rested the Shoo Fly Complex.

The rocks descending into the trench contained water. The superheated water - containing silica and bits of gold - rose through perpendicular fissures in the upheaved rocks of the Shoo Fly Complex. Silica cooled to become the perpendicular quartz vein amidst the sandstone. Men would later search for the gold.

And there's an ancient gold bearing river channel?

When the subduction process ended, the ancestral Sierra could rise no higher, and gravity and wind and water slowly brought the mountains down. Over the march of geologic time, by pebble and grain, the range was deposited into the ocean. Today the level Central Valley holds the remains of these mountains.

In this process, rivers ran westward to the sea. The waters flowed over those gold-bearing quartz veins. The rivers flowed over the ages, turning this way and that, wearing away hillsides, moving and pushing boulders and rocks, and depositing gravel and sand. And little by little came more and more gold.

Here comes our own Cenozoic Era, and in the Tertiary Period, specifically the Miocene and Pliocene Epochs, volcanic activity commenced again. The pyroclastic flows coming from the east took the easiest paths downhill - they followed the riverbeds. When they cooled, they left a hard cap over the gold bearing gravels.

And there were many pyroclastic flows. At Gray Eagle Shaft near Foresthill, the miners went down 364 feet to bedrock, and encountered four separate layers of andestic tuff.

Erosion continued, but it was the softer Ordovician-Silurian hills that were melting away. What were riverbeds became ridges.

And how did that little sandstone rock reach an elevation of 4,340 feet above sea level?

We finally reach the creation of the modern Sierra Nevada. The Basin and Range Province sits on a hot spot that is causing it to spread apart. A few million years ago, in the Pliocene, the westward expansion of the Basin and Range tilted a large block. That tilting, which continues to this day, created the Sierra Nevada mountain range.

That's what lifted the sandstone rock. That's also why the drive on the ridge over the ancient riverbeds from Foresthill to China Wall is on a slight uphill grade.

If there's still gold in those ancient riverbeds, why not just go after it?

The early miners didn't know about plate tectonics, but they figured out the ancient riverbeds quickly enough, and soon they were digging tunnels underneath the volcanic flows to reach the gold bearing gravels.

A lot of gold was taken from these gravels. And gold is still there waiting to be discovered. It just costs a lot of money to look for it. And then there are the environmental regulations to contend with. Since the returns usually don't exceed the cost, today there are only a handful of active mining operations in the area. The rising price for gold, however, is generating more interest in exploration throughout the old Mother Lode.

Just remember, as you drive up the divide to China Wall, that gold remains below in those ancient gravels.

A Hike to Tinker Knob

The Pacific Crest Trail connects Donner Pass with Tinker Knob. I've hiked portions of the trail twice, and the entire trail twice, and I like it so much that I plan on many more hikes.

Heraclitus said that you can't step twice into the same river. That also means that you can never hike the same trail twice. Both the trail and you have changed, and there's always something new to see.

The new thing I saw on my July 19, 2009 hike was a black bear.

First, some numbers. The starting point at Donner Pass is 7,053 feet above sea level. The ending point at Tinker Knob is 8,949 feet. The distance between the two points is 7.47 miles. The elevation gain is 1,896 feet, with many ups and downs between the two points.

I pulled into an empty parking lot. I was the first hiker on the trail that morning. I took off at 6:30 AM. The low rays of the sun were on the granodorite cliffs of Donner Pass. I had a 906 foot climb to the crest. The mosquitoes were a bother. Soon I was in the forest (Upper Montane Belt, specifically). Mount Judah blocked the sunlight. I was lost in my thoughts as I continued along.

Sunrise at Donner Pass.

I encountered the black bear at 7:15 AM. I walked by it without noticing it. The bear was about twenty yards from me. It kept still until I passed, and then it took off. I heard the sudden crashing sound and turned around. I saw the back end of the bear as it ran uphill. Its thick coat was a cinnamon color. I fumbled for my camera, but within seconds the bear was gone.

Where the black bear was.

Was I ever in danger of attack by that black bear on that lonely Sierra trail? I did some checking on the ever-trustworthy Internet and found that of the twelve recorded black bear attacks in California since 1980, not one occured in Placer County. I was in Placer County when I encountered the bear. As such, I was in absolutely no danger of a black bear attack.

I reached sunshine at Roller Pass, and soon I was at the crest. Here you can look miles south down the crest of the Sierra. The trail to Tinker Knob would now be fairly level.

I saw a bear paw print in the dirt of the trail. I don't know if it was from the bear I encountered.

Black bear paw print.

A large patch of snow covered the trail east of Mount Lincoln. This section is away from the sun and the snow is the last patch to melt. I walked around it and continued on. I now hiked along ancient volcanic ash flows and clusters of beautiful wildflowers.

The trail along the crest divides the flow of water. Water from rain falling on the west side goes down the Sierra and into the Pacific Ocean. Water from rain falling on the east side travels down the Truckee River and into the Great Basin, to collect in Pyramid Lake until it evaporates.

Snow blocking the trail.

A view down the crest.

Summer wildflowers.

Tinker Knob comes into view after rounding Anderson Peak.

Tinker Knob in sight.

I met a man from Los Angeles who said he was spending the summer hiking the Pacific Crest Trail from the Mexico border to the Canada border.

I took one final and steady climb up the crest, and reached the base of Tinker Knob. Getting to the top of this volcanic vent requires attention, for the path is narrow and steep, and the talus is very loose.

Final approach to Tinker Knob.

I reached the summit and had a good look around. To the southeast was Lake Tahoe, to the north was the crest of the Sierra, and far to the west was the deep canyon of Royal Gorge.

Military ammo can containing trail register.

View to Lake Tahoe.

View north along the crest.

View to Royal Gorge.

I took my lunch (a military Meal Ready to Eat) and some water. I didn't get too relaxed, because I didn't want my leg muscles to cramp.

Now followed a pleasant 7.47-mile walk to my truck. And waiting for me at home, two cold bottles of Sierra Nevada Pale Ale.

The Confluence

Prior to James Marshall's discovery of gold at nearby Sutter's Mill (on the South Fork) in 1848, only a handful of people of European origin, trappers mostly, had been to what is now called the Confluence, where the North Fork and the Middle Fork of the American River meet.

Looking upstream, the North Fork on the left and the Middle Fork on the right.

Looking downstream.

Whenever I go to the Confluence, I never fail to think of how the first argonauts literally picked up gold nuggets from the riverbanks; how with tin cups they scooped up gold from the shallow gravels; and how with knives they pried gold from the quartz veins in the exposed slate. The world will never see that again.

And then I say a silent "Thank You" to our eleventh president, James K. Polk, for provoking the war with Mexico that brought California and its wonderful American River into the United States.

View from Stagecoach Trail.

The Confluence was crawling with people during the early days of the Gold Rush. They pitched their tents on any reasonably level ground available. It was a frenetic and violent time, as told by such place names as Murderer's Bar and Robber's Roost. The miners meted out their own justice, for government authority did not extend this far. Once the easy gravels had been worked, the miners joined together to build large wooden flumes to divert the river and reach the gold at bedrock. When that gold was collected, the era of placer mining was over, and the miners left the Confluence.

Gold still flows downstream and collects at the Confluence, and it draws the recreational goldpanners.