Archive for the ‘Oakland geology walks’ Category

A walk in Oakland’s original platform

29 April 2024

I was asked to lead a walk in the old part of Oakland for a group of engineering geologists that ends at a brewpub. The 3.8-mile route I chose feels too good to keep private. It’s as much about interesting parts of town as about interesting bits of geology.

Here’s how it relates to the geologic map.

Start down by Heinold’s near the wolf, in Jack London Square.

Admire the fountain, check the nearby bathroom, then head along the shore, past the pavement, to the point where Lake Merritt Channel reaches the Estuary. Admire the hills running from here to Mission Peak, down the waterway in Fremont. This is the shape of the East Bay: a row of high hills, a level plain, a wide bay.

The channel, once upon a time, separated the villages of Oakland and San Antonio (later named Brooklyn). Boats were the usual way between the towns — Oakland the squatter village of farm estates wrangling with Don Vicente Peralta over ownership of his ranch land, San Antonio the older shipping depot for Don Antonio Peralta’s ranch and the farms of his peaceable neighbors.

Turn hillward and take Oak Street, then Fallon Street to the Oakland Museum of California. The whole walk so far, the last mile and a half, skirts the edge of the natural platform that made Oakland such an attractive site for developers. The sunken museum entrance on 10th Street is right on the line between this platform, made of windblown sand dunes that accumulated during the latest ice age, and old wetlands that have been filled in since 1850. The dunefield slopes up to the left and the filled land still lies low.


View down 10th Street past the museum on the left

Enter the museum and walk through to the public garden, a good place to sit or use the museum’s bathrooms. Along the way, say hi to J. B. Blunk’s redwood sculpture “The Planet.”

In the garden, notice how the museum works with the natural slope.

Exit the far side and cross the busy 12th Street causeway to Lake Merritt. Here’s where to study the hills and perceive the level landforms around the lake that formed at different times in the latest ice age. (I’ve made an annotated panorama of just this view.) After that, walk up onto the dune platform, by crossing the lawn next to the Camron-Stanford House, and go left a block to 13th Street. From there to City Hall is about a mile passing by some major buildings old and new.

At City Hall, inspect the moat around the building, which is part of its base-isolation retrofit after the 1989 earthquake. This landmark piece of seismic engineering is in all the textbooks. (A similar system was recorded in action during the recent Taiwan earthquake; the video is on Xitter.)

The last mile winds through picturesque parts of old Oakland. One notable building is the Wilcox Block on Broadway at 9th Street, our oldest commercial structure. It survived the great earthquake of 1868, the year it was built, without significant damage, as well as 1906 and 1989.

The route ends in the middle of a tempting set of brewpubs that have made the old Warehouse District a beer fan’s destination. Which to choose is an exercise left for the reader.

Temescal Creek, the lower reach

22 January 2024

Temescal Creek, North Oakland’s largest stream, looms large in local history going back to Ohlone times. The Ohlones had a permanent camp a short distance east of Telegraph Avenue, where the creek’s perennial flow supported a health center. The people would gather in their sweat lodge for lengthy steam baths, then cool off in the stream. Early visitors described the place with the word temescal, a native name for similar facilities in Mexico, and the name stuck to the neighborhood as well as the creek.

Temescal Creek drains a hefty share of the Oakland Hills, including Claremont Canyon, Vicente Canyon, Temescal Canyon and Thornhill Canyon. The county flood control district has this handy map outlining Temescal Creek’s watershed, the land whose runoff provides its water.

In this post I’ll focus on the Bay end of the creek, where the stream is covered up and honored mainly as an idea. I define this stretch as starting just west of the Rockridge BART plaza at Forest Street, the point where it’s joined by its last tributary, Claremont Creek. This part.


Original stream course superimposed on the modern map. Numbers mark features in this post.

In the old days, this part of Temescal Creek flowed down a gentle slope across a wide, grassy alluvial plain―the East Bay flats―between low natural levees. Parts of the creek bed were willow thickets where the Ohlones’ agricultural fires did not penetrate. A large shellmound marked its mouth along the Bay. It’s thought that during Ohlone times, the streams in the East Bay coastal plain didn’t cut into the ground as deeply as today. The changes in land use set in motion by the Spanish and their successors led to fluvial incision and the formation of arroyos. Today the creek runs a good 20 feet below the surroundings.

When the Americans first took over this territory, they used the stream to establish property lines but otherwise left it alone, except to build bridges over it on the main roads. Then in 1871 “Captain” Edward Wiard opened the Oakland Trotting Park on his land near Shellmound Park, as seen in this 1876 map, and chose to cover the creek. That was the first culverting of the stream. By that time, its headwaters had been harnessed by Anthony Chabot’s dam for the Contra Costa Water Company, Oakland’s first municipal water provider. Farms, factories, canneries and other industries located near the creek in the next decades. They found its natural floods inconvenient.


Detail of the King map, from the Rumsey collection

Today the entire lower segment of Temescal Creek is encased in a concrete channel, bound by human needs. Most of it is covered up entirely. This part of the creek has some major constructions: freeways, the eight-track-wide railyard of Emeryville, Emery High School, the Children’s Hospital complex at MLK Boulevard, the Logan development at Temescal, the Rockridge BART station. These projects had the money to underground the creek and can’t be undone. The county flood control district entombed the rest for completeness’ sake, and between that agency and the home owners, the creek in their back yards will never be exhumed.

That leaves the creek to be memorialized by symbolic acknowledgments. I’ve visited them all to write this post. I’ll start in Rockridge and end at the Bay.

1. The Rockridge-Temescal Greenbelt, also known as Frog Park, has turned a 2000-foot stretch of culverted creekbed between Hardy Park and Redondo Playground into a rich neighborhood asset. In Hardy Park, at the upstream end, is a large grate over the culvert where you can stand and listen to the water.

The rest of the greenbelt consists of a secluded path with understated exhibits and a faux streambed that can be filled with running water when the pumps are activated. This is the part behind the DMV building, site of the Lusk Cannery in the 1880s.

2. On Telegraph Avenue at 51st Street is this utility box with a stream-centered mural.

3. Just the other side of the PG&E substation, on Shattuck Avenue is this installation that deserves more visitors than it gets. The site was once a trolley yard.

The Children’s Hospital complex, a little farther west across the freeway, originated in a grant of land from the heirs of Solomon Alden, whose lavish farm estate straddled the creek and supplied Lusk’s cannery.

All of these places were part of the village of Temescal around the turn of the last century. Oakland annexed it in 1897, and you could say the town has been hidden as well as the stream. A 2012 Oakland North article has more detail on the Temescal segment of the creek.

From the hospital the stream culvert runs between the back yards of homes. The butt end of Genoa Street offers a glimpse. Large trees also mark the stream’s course, as they do elsewhere in Oakland. From here west, the stream flows across nearly level ground.

4. Adeline Street is in Emeryville here, barely west of the city line. The creek is recalled at 5200 Adeline in the Bakery Lofts development, a former factory that once straddled the creek. The creek can be heard through the pipe, which opens into the culvert.

5. The Oakland-Emeryville border turns west here and wanders with the creek for a couple of blocks. This segment is occupied by attractive little Temescal Creek Park, a joint project of the two cities. Here too are steel grates, near the east and west ends, where you can hear the stream below rustling.

6. One of Emeryville’s community gardens occupies a parcel on top of the culvert at the east end of 48th Street.

7. A short distance west on San Pablo Boulevard, facing Emery High School, is this little treatment honoring the creek.

8. Beyond more culvert about a half-mile west, the stream emerges at Horton Street in Emeryville’s exciting new Horton Landing Park, a pedestrian landmark featuring a dramatic bridge over the railroad tracks and connections to the Emeryville Greenway. Though final landscaping is still in progress, I think it’s already worth a trip from anywhere in the Bay area.

Crossing the bridge over the wide railyard, between its walls of new buildings, feels a little like going through rocky hills over a river gorge. The footpath itself curves, a nod to the buried stream beneath.

The exposed creek bed in this stretch is naked now. There may be plans to revegetate it, perhaps with native willows again.

The educational memorialization park west of the bridge is a meandering avenue of chiseled granite and etched glass exhibits about the Ohlone people: how they used to live and what they’ve gone through. It’s a starting point; the tribes are still here and need from the rest of us more than these exhibits.

The city’s park ends at Shellmound Street, at the old shoreline. The Emeryville Shellmound was the greatest topographic feature in the area, and the site is central in the little city’s history. As with the creek, the shellmound is honored more in its absence than it was during its presence.

9. The stream continues under the freeway to its current mouth on the Bay, free at last.

The coast here is part of the Emeryville Crescent State Marine Reserve, now just a park in embryo form. The mouth of the creek is not easily accessible yet; the birds and advancing pickleweed seem to like it that way despite the trash and traffic.

This is not exactly where the historical stream ran, but it will have to do for the next few centuries. Perhaps later generations will find opportunities to spring Temescal Creek from its prison. On the geological time scale, creeks like this roam about the landscape as they slowly build up the coastal alluvial plain.

Merriewood spur

20 March 2023

Since my previous post, I’ve gone ahead and hiked the faceted spur next to the Montclair spur. It holds the Glen Highlands and Merriewood neighborhoods, so I’ve named it the Merriewood spur because Merriewood Drive is the nicest part of the walking route.

The 1897 topo map shows the spur in its clean, original state between the narrow mouths of two wineglass valleys, Temescal and Thornhill Canyons. The Hayward fault runs diagonally through Lake Temescal.

As I detailed in my circumambulation of Temescal Canyon, this part of town has undergone a serious amount of human modification since then. But it has appreciably affected the ridge route on the spur only at its northwestern tip, as seen in the digital elevation model.

Looking at this image, I note that the spur is larger and more deeply eroded than the Montclair spur. It’s conceivable, though not at all certain, that the main incision includes a large landslide. Other than that the image reveals no great secrets.

The route around the spur is about four and a half miles. This is one version that starts and ends at the north parking lot of Lake Temescal Regional Park. The hike along the north limb of the spur follows PG&E’s major power line, and the portion on the south limb follows city streets.


Zoom in on it at gmap-pedometer.com

It’s a climb of about 800 feet. A shorter version could start from Montclair Village and reach the north end of the spur via Pali Court. Or you could try the version I took, going up to Broadway from the Rockridge BART station and ending in Montclair (thus qualifying as a ramble).

The rest of this post will focus on the rocks to be seen along the north limb, because unlike the Montclair spur, the Merriewood spur includes a variety of rock units, as shown on the geologic map. I can’t vouch for the accuracy of the map along the south limb, where precious little bedrock is visible in a casual walk.


Jsv, Leona Volcanics; KJfm, Franciscan melange with chert and greenstone blocks; KJk, Knoxville Formation; Kr, Redwood Canyon Formation; Ku, undivided Great Valley Sequence; Tcc, Claremont chert; Tes, Eocene mudstone; Tsm, Sobrante Formation; Tush, unnamed Miocene mudstone.

Here’s a view of the west end of the ridge from halfway up, just to the left of “Tush” on the geologic map. I was last here in November of 2008.

It shows Lake Temescal and the shutter ridge behind it, the PG&E station in front of it and the power line pad carved into the west end of the spur.

I climbed up from Broadway to the power line because the footing is pretty good at this time of year. The clean-cut slope exposes dark, crumbling shale of the Knoxville Formation. I’m excited to see this perishable stuff.

The western tip of the power line pad exposes the familiar rugged, red-stained rocks of the Leona Volcanics.

The contact between these units is important, but rarely exposed. I want to return and look for it.

Farther up the slope, the rocks change to this sandstone. The boundary between the black shale and the blond sandstone is the enigmatic, long-inactive Chabot fault, and the two rocks differ in age by about 60 million years.

The “Ku” unit lumps together a bunch of rocks that correspond to a whole set of Cretaceous rocks, the Great Valley Sequence, that farther south is divided into several different formations. It might be possible to map those units into this part of the hills, but the last person to try, Jim Case in the early 1960s, gave up.

Turning around, I spotted the same set of stones that puzzled me in 2008.

This time my accrued years of experience, plus the acid bottle I didn’t have with me the last time, told me right off that these are limestone, not native to the area (unless I and all my predecessors are badly mistaken). They look like river rocks that have been etched by exposure to our slightly acidic rainfall over the years.

Presumably PG&E brought in a truckload once upon a time for some reason. I also visited the old, deteriorating Horse Hill dirt jump and saw that it had a fresh tire track.

A little farther uphill, the roadbed displays some bedding features — offshore channel deposits, tilted nearly perpendicular.

This view looks up toward the top of the climb right at the edge of the “Ku” belt, where the soft Sobrante Formation mudstone underlies a long-lived landslide I’ve featured here before (in 2008 and 2018).

The continuing collapse of the hillside has opened a new front. Landslides don’t give up easily. The continued existence of this walking route is not guaranteed.

That’s the north limb of the Merriewood spur. Having walked it, I can now vouch for the whole circumambulation of Temescal Canyon, and maybe some day I’ll actually hike it all in one go.

This view is from the south limb, near the bottom. Thornhill Road, visible at lower left, marks the valley of Temescal (formerly Kohler) Creek.

We’re looking across the narrow mouth of Thornhill Canyon, then across the narrow valley marking the Hayward fault, then across the narrow water gap of Dimond Canyon, then across the wide San Francisco Bay basin to the Santa Cruz Mountains.