Archive for the ‘Oakland geology walks’ Category

Oakland geology in the Covidocene

30 March 2020

I’ll get around to geology in this post, but there are a few things to say first.

We’re in a new period of time when the unknown looms larger than usual and all seems pervaded with uncertainty. No one knows much, even the experts whose job it is to know. The foundations of daily life are on hold for most of us, and for some of us the foundations are gone. Few of us have been tested for the Covid virus, and a negative result only means we’ve escaped for the moment. We’re told to adopt new habits, drastic ones. They’re hard to learn and may be hard to sustain. The best way I can think of them is, every thing and every person out there is molten lava. The soundtrack is “U Can’t Touch This.”

Most of us will survive this plague, but none of us will be the same. Oakland old-timers like me have seen this sort of crisis before: in 1989, when the earthquake struck. But to most of us it’s new, still sinking in.

I’m trained in science and saturated in science, and I’m friends with uncertainty and the unknown — at least, with the ideas. The reality of this much uncertainty and unknown is daunting.

The empty streets and shuttered shops are like something from a disaster movie. Some of us seem to be living in one, others living in their own worlds. The communal stroll around Lake Merritt has become fraught as runners bull their way past, panting and sweating like zombies, as if they could outrun the six-foot rule. (We’ve got to start moving in the same direction to limit our exposure to each other.) Drivers are so thrilled by the newly open roads that they rush about in their deadly machines as if they were creatures of steel themselves, reenacting the advertisements that drew them to the car dealer. (We’ve got to phase out these noisy, noxious internal-combustion vehicles.) The disaster movie is where the beggars and homeless and impoverished have been living all along.

All right; enough of that. I’m trying to write about some ways to behave I can recommend. We were told we can still go out to exercise, and the first weekend after that directive was a disaster. For some reason, people rode their deadly machines in droves to mob the hills and beaches, cheek by jowl and swapping germs, as if they thought no one else would show up. Such people have the mistaken idea that remote preserves of selected scenery are the only things that qualify as nature. It must be those fucking car ads.

I said, enough of that: the spasms of consternation and dismay, the clamor of alarm and blame. You can get that anywhere. It even infects a contemplative introvert like me.

I recommend slowing down in every respect. When the hospitals are slammed, none of us can afford an injury. When circumstances push us out of sorts, none of us can afford to freak each other out or play games. Ease up; grant slack. Repeat as needed.

I recommend staying out of the parks and straying into the neighborhoods. People who walk their own dogs are already hip to this, right? So consider taking yourselves for a daily walk, gently leashed.

Walk, don’t run. If you sprain an ankle or blow out your knee, the doctors are too busy to help. When they say we can still go out for exercise, they don’t mean stay in personal-best shape with our accustomed Fitbit workouts. Please give that up for something more physically moderate with more room for the brain: attentive motion. Stirring your limbs and looking around, not more reps and more miles, is the basis of good health.

You don’t need a state park or a wide beach, just a spot to see the spring arrive. It always does.

And we live in an exceptionally scenic place on all scales. I’ve walked every bit of Oakland, looking intently, and each block has beguiled me with some treasure: an interesting yard, an unexpected view, a genial neighbor. There are treasures in deepest Deep East.

Treasures in Maxwell Park.

Treasures as close as your nearest parking structure (with stair-climbing as a free bonus).

If you’re still drawn to feats of strength, I have a bunch of Oakland geology walks for you to contemplate, with elevation gains, no crowds and views to fill the hungriest eye. (Just go to the home page and click the Oakland geology walks category.) These shots are from a leg of the Lake Merritt in 2100 walk that I took yesterday.

And while you’re out, meet people’s eyes, put the phone away and do the six-feet thing. That is my recommendation. Oh, and take note of the rocks and the landforms; that’s where geology begins.

This pandemic is a disaster unlike the earthquake, which was instantaneous with a long aftermath, or the drought, which was agonizingly slow and over after a rainy winter. But when it comes to our fabric of mutual well-being, disasters have a lot in common. Dr. Lucy Jones is California’s go-to public authority on earthquakes. Her book on natural disasters, The Big Ones, is a string of insightful pearls with this one at the center: “We must remember that the most dangerous threat in a disaster is a threat to our humanity.”

A circumambulation of Temescal Canyon (sort of)

2 March 2020

Temescal Canyon isn’t a name anyone uses. It’s kind of a ghost canyon, even though you’ve all driven through it many times — on Route 24 going to and coming out of the Caldecott Tunnel.

Underneath all the spaghetti and labels on that Google map is what remains of a fine little valley with steep sides and permanent streams that was once the principal water source of Lake Temescal, Oakland’s first surface reservoir. Here’s how the 1897 USGS topo map showed it.

Notice the stream northeast of the lake. The solid blue line signifies a perennial, year-round stream, and by the rules of hydrography it claims the name Temescal Creek given to its lower reaches, and hence comes the name Temescal Canyon. The other stream feeding the lake from the southeast is marked with a dot-dash line, indicating an intermittent stream; the map labels it Kohler Creek after the name of a landowner in Thornhill Canyon, but today that’s the creek called Temescal.

This annotated version shows two things: the arrows mark the Hayward fault and the dots outline the rim of the canyon.

Because the east side of the fault is rising, thanks to a bit of compression across the fault, the stream is forced to dig down harder than your average creek as the hills around it rise, and the long-term result is a watershed that’s wide at the top and narrow at the base — a wineglass canyon. As you know from my previous posts about Claremont Canyon and Shepherd Canyon, I have a thing about hiking around the rims of our wineglass canyons. This post is about that.

I call this a ghost canyon because waves of human intervention have modified it pretty seriously since that 1897 map. The original Kennedy Tunnel was punched through the hill in 1903, with the original Tunnel Road leading up to it. The 1915 topo map shows that when they built the road, the mapmakers added new detail to the contour lines on that side of the canyon. (Also, Oakland annexed all the land uphill from Berkeley.)

In addition to Tunnel Road, the Oakland Antioch & Eastern Railway was pushed through, skirting the lake on its way to the Shepherd Canyon tunnel. It ran over the Temescal Creek arm of the lake on a trestle.

Next came more infrastructure: PG&E constructed a big power line along with the Claremont “K” substation on Landvale Road in 1922, a classic industrial Deco structure, and in the process filled in the Temescal Creek arm of the lake. And then the Broadway Extension leading to the first Caldecott Tunnel bores carved up the sides of the canyon mouth even more in the 1930s. The work consumed huge quantities of rock, which was quarried from the north side of the canyon. Meanwhile residential development began on the north canyon wall. All of this is visible in the 1947 topo map.

Between then and now there was more residential development in Hiller Highlands, the big Parkwoods apartment complex in the canyon, a major expansion of Route 24 (with more quarrying to support the work), and finally the other little valley in the canyon was filled in to make the North Oakland Regional Sports Center. All of that was before the third and fourth Caldecott bores were added in this century. All that mayhem and erasure is what makes me think of it as a ghost canyon.

This patchwork of development has not created a ready set of roads to follow for a circumambulation, but I think I’ve cobbled together a trek route. And while I’ve walked all of it at one time or another over the years, I haven’t done it in one go. In fact I’m not eager to do so because it’s strenuous and a bit fraught and I need to build up strength first.

You can zoom in and explore this route at gmap-pedometer.com; this image (click to see it big) uses the OpenCycle viewing option. It starts at the Firestorm Memorial Garden at the foot of Hiller Drive, and right away goes seriously off-piste with a steep climb up the far side of the great Tunnel Road cut.

There are three fairly level stairsteps in the cut to choose from; this is the view back from the second. All three have cool views, and you avoid the heavy traffic on Tunnel Road.

The route veers off Hiller Road into a seekrit pathway that overlooks major features of the lower canyon. The power station and freeway lanes squat on the grave of the creek, with the Hayward fault slashing through the lake toward the notch in the horizon.

The spur across the narrow mouth of the canyon, carved flat for the powerline poles, is the endpoint of this trek.

And the ballfields of the sports complex smother this former stream valley. The woods to the left are an impenetrable eucalyptus thicket.

The next three miles-plus call for cautious walking: cars don’t expect hikers and the roads are narrow. But you’re high in the clean air well above the worst of the road roar. A little past the 3-mile mark, where the power line crosses the road, is an excellent place to stop discreetly and look down the ridge that forms the south wall of the canyon. That road in front of the ridge is Broadway Terrace, perhaps Oakland’s most dangerous road for pedestrians.

The long detour between miles 3 and 4-1/2 is unavoidable (trust me on this), but you can skip the last bit of Grizzly Peak Boulevard by turning right onto a footpath that’s part of the Sibley Preserve.

A little ways down Broadway Terrace is where it might feel a bit hinky. At Pine Needle Drive, you climb over the fence and locate a teeny footpath, almost a deer trail, along the power line that plunges about 200 feet to a fire road, which then climbs all the way back up to the ridgeline past a big landslide. Believe me, that is less fearsome than walking on upper Broadway Terrace.

The last leg, from the ridge down to the powerline tower pad, I can’t really vouch for as I last walked it 11 years ago. Assuming it’s not too overgrown, you should be good, and if not, then go back on the fire road down to the sports center. The pad is at the end of Pali Court, and the view back to the starting point looks like this.

Getting to and from these two endpoints is an exercise left for the reader, and I do mean exercise.

Sibley South

25 November 2019

The wonderful Sibley Regional Volcanic Preserve has a southern extension, still being developed, that opened to the public recently. It’s at the head of San Leandro Creek upstream from the village of Canyon on the west side of Gudde Ridge, a part of the hills that’s always intrigued me. The land is in the foreground of this photo of Mount Diablo I took from Huckleberry Botanical Preserve in April 2009.

The property was homesteaded in the 1860s by Patrick and Catherine McCosker and remained in the family for the rest of that century and all of the next. It was a cattle ranch for most of that time, with a small kitchen orchard. The Oakland, Antioch & Eastern railroad exited the old Redwood Peak Tunnel eastbound near the ranch entrance and stopped there at a station named Eastport, still a locality on the map.

About the time when plans were floated to punch a new state highway up Shepherd Canyon and through the hills to the Lamorinda area, the McCoskers started a rock quarry in hopes of profit during the highway construction. (Transport distance is a very important factor in the crushed-stone business.) It operated from 1958 to 1971, then continued as a rock crushing plant serving various construction projects in the area.

After that business petered out and the land languished for a while, the McCosker descendants sold a 250-acre chunk known as the Texas parcel to the developers of Orinda’s Wilder Ranch community, and as part of a deal the land was donated to the East Bay Regional Parks District. The “McCosker Sub-Area” opened to the public in December 2016.

The parcel occupies most of the valley north of Eastport, as seen here on the 1959 topo map. I’ll show the bedrock map of the same area later.

It’s precious property for native plants and a good wildlife corridor, tucked between the Huckleberry preserve and steep, remote grazing land in the Sibley preserve. The District classifies it as a Natural Unit, managed for its “unique or fragile habitat values with public access primarily limited to trails.” Its permanent stream, a major tributary of upper San Leandro Creek given the name Alder Creek, will have some 1300 feet of decaying culvert removed and be restored to good riparian habitat suitable for native rainbow trout.

To protect this wild country, access for dogs and horses will be tightly controlled. (At present, dogs are not allowed at all.) Plans include a small campground suitable for backpackers on the major Bay trails.

On a misty weekday afternoon, it feels very far from the rest of the Bay area.

On sunny days, though, the views are good. I went back yesterday to capture some.

The rocks here are mainly from three map units: the Claremont Shale (the gold strip along the valley floor), the Orinda Formation (Tor, conglomerate) and Moraga Formation (Tmb, lava flows, and Tms, associated sediments).

The Claremont peeks out of the woods near the entrance with its characteristic, steeply dipping stripes.

The Orinda pokes out of the hillside with its characteristic beds of coarse gravel and cobbles — but only in roadcuts.

Elsewhere, out on the bare hillsides, the ground is nearly pure clay soil with only rare pebbles exposed, tokens of a very different terrain dating from some 10 million years ago.

The Moraga Formation lava is harder stuff, and there are a few actual outcrops in the high hills.

Near the entrance is a flat platform with a large shed, evidently built from quarry waste. It will become a parking lot and recreation area named Fiddleneck Field. For now it’s a parking lot for boulders from other parts of Sibley. Check them out. They represent the Orinda and Moraga formations, plus a few white limestone chunks from the Moraga sediment unit or the slightly younger Siesta Formation.

Some of the lava features the distinctive amygdales, former voids filled with hydrothermal minerals, found at Sibley.

Another thing to notice here and there is small landslides, like this slump at the edge of the Fiddleneck Field platform. Others occur along the ranch roads, which were built long ago by ranchers without the advice of geotechnical consultants.

As far as I can tell, the quarrying took place in scattered pits of no great size. That area is screened by oak/bay forest and cordoned off with barbed-wire fence, so it’s hard to tell. I look forward to seeing this land opened up as the District does more work.

In the meantime, there are splendid views to be had.

Give it a visit some time.

Details of the plans for this area are in the Sibley Land Use Plan, available if you search for it from the East Bay Regional Parks District website.

Oakland geology ramble 8: Piedmont Ridge

19 August 2019

I don’t always care about rocks; geology is about more than rocks. I don’t even always care about geology; sometimes I just want a vigorous, geographically arbitrary hike. Ramble 8 is one of those — a traverse of the ridge crest above Piedmont, our highest ground west of the Hayward fault. It goes from the Rockridge BART station to the 33 line bus stop at the Leimert Bridge, on the lip of Dimond Canyon, about five miles end to end. Nevertheless, it has geology and rocks along the way. Here’s the route. There’s a map with more detail at the end of the post, where I also have some announcements.

The BART station features the “Rockridge” destination signage, mounted above a selection of Sierran boulders. This time, some ten years after it was installed, I noticed that the lettering design is quirky, contrasting “rock” and “ridge.”

You could climb Keith Avenue and barge up upper Broadway to attain the heights at Contra Costa Road, but it’s more interesting to circle behind the College Preparatory School grounds on Brookside Avenue. The school nestles in a steep little stream valley — unlike many similar places, this is not a former quarry but, apparently, a former turn-of-the-last-century park that had a short existence.

Once you get up to Contra Costa Road via Eustice and Buena Vista avenues, the walking is pretty and level. While you’re here in this remote part of town, check out the blueschist outcrop at 6063, vacant since the 1991 fire. The entire ridge on this hike is in Franciscan melange, a mudstone matrix containing odd lumps of other rock types. You won’t see much of it.

At the very end of the street is Erba Path, a steep set of stairs down to the saddle in the ridge where Broadway Terrace peaks on its way past the south entrance to Lake Temescal and points east. Cross that busy road and head right back up again on Sheridan Road, visible here at upper left.

Turn right off Sheridan at Agnes Street, unless you want to explore the little-trod path that joins Sheridan’s two halves. (Everyone should at least once.) Take high-flying Cochrane Avenue, where views east of Thornhill Canyon and Glen Highland’s settled slopes beckon.

Then jog right again up the saddle of Florence Avenue (where I sent you in the last post) to Proctor Avenue. This is pretty steep, but short. By this point you’re well above 700 feet. You’ll go higher later, but first you clamber a hundred feet down to the next saddle where Moraga Avenue crosses the ridge. Take the well-marked pedestrian crossing, but beware — this is the most dangerous road crossing of the hike.

Proceed on Estates Drive, which climbs nearly to the 800 foot contour. Up here are two curious reservoirs that date from Oakland’s water wars, when private water companies struggled to supply the fast-growing region from local sources while they vied with each other in deadly capitalist strife. (A ruinous series of bankruptcies and mergers ended in the 1920s with the formation of EBMUD.)

The Dingee and Estates reservoirs were constructed, fast and furiously, at the highest point of the Piedmont hills to provide good water pressure. EBMUD is upgrading these old concrete bathtubs to proper steel tanks, built to withstand big earthquakes on the Hayward fault just a few hundred yards east.

From here you head down again to La Salle Avenue, which takes advantage of yet another saddle in the ridge. If you’re ready to quit at this point, go left on La Salle, left again on Bruns Court and cross that high pedestrian bridge over the Warren Freeway to Montclair Park (because you can!) and catch the 33 bus at La Salle and Moraga. Otherwise, cross La Salle and stay on Estates, which is a little to the right.

Estates climbs again, not so far this time. Because this walk hits the highest spots, take Dawes Street up the hill and over, where you simply must visit the south end of Pershing Drive and admire Oakland’s best outcrop of Franciscan chert.

From here on it’s all downhill. Dawes rejoins Estates Drive here, and as you start down Estates you can see across Dimond Canyon.

Geologically and geomorphically speaking, the other side is also part of Piedmont Ridge, but the large water gap of Dimond Canyon is impassable without a long detour. So, down you go to the bus stop at the Leimert Bridge.

Along the way are two more highlights. First, at the Piedmont line the road passes the head of the former Diamond Cañon Quarry, which today houses the Zion Lutheran Church. Recent foundation work here has exposed fresh rock; maybe you’ll see some too.

And second, enjoy this wonderful volcanic breccia used for the landscaping at 170 Estates Drive. There are whole walls of it.

The house itself is something to see, too.

And as promised, here’s the detailed route map (1126 X 1126 pixels), followed by some announcements.

The excellent, out-of-print book Stories in Stone: Travels Through Urban Geology by David B. Williams is being reissued in paperback by the University of Washington Press. If I didn’t have the hardcover already I’d buy this classic. More information on David’s website.

My own book manuscript is making the rounds of a publisher, and while I await a yea or nay I’m trying to get my arms around a whole lot of scientific literature pertaining to Oakland’s rocks. It’s a ridge walk of the intellect, but I want to make Chapter 5 as good as humanly possible. I hope to buttonhole some of the real experts next month at the Geological Society of America’s annual meeting in Phoenix.

But first I’ll be giving a talk to the Friends of Sausal Creek, on 18 September at the Dimond Library, titled “Sausal Creek: The Last Million Years or So.” You read it here first (unless you follow me on Twitter, @aboutgeology), and I’ll repeat the announcement in the Q&A thread soon.