Archive for the ‘oakland geology views’ Category

Lower Piedmont Park walk (#28)

10 August 2012

Walk number 28 in Charles Fleming’s Secret Stairs East Bay winds around the fine homes and hills of Piedmont along the valleys of Wildwood and Bushy Dell creeks. Here’s the route, shown on the Google Maps topo base.

walk 28 topo

The first and last part of the loop is in the watershed of Wildwood Creek while the rest is in the Bushy Dell Creek watershed. (They run down Lakeshore and Grand Avenues respectively, separated by Warfield ridge, and combine down at Lake Merritt where their names are sunk in bronze by the pergola.) Geologically, the walk covers the uppermost part of the big Pleistocene alluvial fan and the edge of the Franciscan bedrock block that underlies most of Piedmont.

geologic map

We start at the Lakeshore-Winsor split in the stream valley and make our way toward the divide. On Portsmouth Road the high ground of the bedrock zone stands out ahead.

At the far end is a steep climb to Wildwood Avenue, where we can look back across the stream valley to the ridge topped by Calmar Avenue, on the Oakland side of the city line.

Turning the other way, we look over the valley of Bushy Dell Creek. Once a large formal garden, this part of the valley was filled and leveled for its current use as a sports complex. It appears never to have been a quarry, unlike Dracena Park to the north or Davie Tennis Stadium to the south.

We turn upstream along the creek, where the land is relatively untouched. Just above this spot is the site of what was reputed as a sulfur spring.

The geologic setting doesn’t really give much support for the presence of a proper sulfur spring like the one in Walnut Creek, but after all this time the question is moot. Certainly I didn’t notice any odor. The grotto was very pleasant anyway, and there’s real bedrock all around. It’s mapped as Franciscan sandstone of the Novato Quarry terrane.

The route goes farther up and takes a loop past a pair of boulders.

Take a close look at these: they’re genuine Oakland-style blueschist, globs of old ocean crust that have been carried tens of kilometers down into the earth along a subduction zone, then spat back out, possibly more than once. (The details are at the bleeding edge of California geology.) The one boulder displays good color and mineralogy:

The other has some nice slickensides to show us.

Coming back downstream and past the baseball diamond, we pass the entrance to the football field. The view looks down the valley toward the lake and downtown.

Near here we can see more exposures of the sandstone bedrock, but soon afterward the route returns to the alluvial fan. The two substrates make subtly different topography, but that can be hard to see given the heavily landscaped landscape.

Palm Drive offers a picturesque farewell view of the Bushy Dell Creek valley.

Again we cross the divide between the two watersheds at Wildwood Avenue. The near valley is accentuated by glimpses of the higher hills.

I never get tired of this stuff.

Here’s the route in more detail.

route map

Bella Vista hill

22 July 2012

Bella Vista hill is part of the big Pleistocene alluvial fan that sprawls across the middle of Oakland, as shown by the “Qpaf” code on the geologic map.

pleistocene fan

The “Qmt” code is the marine terrace I’ve discussed before. The fan is dissected by modern streams into several lobes, which take their position in today’s cityscape as distinct topographic hills as seen in Google Maps topography:

topography

Bella Vista hill lies in the polygon defined by Park Boulevard, East 34th Street, MacArthur Boulevard, 14th Avenue, East 18th Street and 8th Avenue. All of those street run in valleys or saddles, except that East 18th is on a break in slope. The numbers refer to the following photos, taken from across or in the valley of 14th Avenue Creek.

The hill is low on its bayward side, as shown here from E. 22nd Street.

It has a corrugated surface, such that 9th, 10th and 12th Avenues run on high ground and 8th, 11th and 13th run up declivities. Higher up on the hill, the ground is steeper and the allee of palms marking the former Francis Smith estate is the defining feature of the hill.

The top of the hill has two eminences. The more dramatic one is on the south where Highland Hospital frowns down upon the stream valley.

hospital

Hospitals, like schools, were traditionally sited to take advantage of fresh air. Highland Hospital took its very name from this practice. Here’s a view of the whole hospital complex on the southern boss of the hill.

highland hospital

The northern knob is higher, exceeding 200 feet elevation. At its high end, 10th Avenue becomes Bella Vista Avenue and curves across this peak. Old palm trees from the Smith estate mark it from a distance.

Borax Smith knew what he was doing when he picked this hilltop for his home base. The hills on the fan to the south are a bit higher, but the views to every other direction were unimpaired from that spot. If you want to walk the crest of this hill, go up 10th or 12th Avenue and jog across to 13th and take it all the way up to the I-580 overcrossing.

San Antonio hill, north side

23 June 2012

Bella Vista hill is my name for the lobe of the big Pleistocene alluvial fan (see the geologic map) lying between Haddon Hill and San Antonio hill. This view is from the south edge of Bella Vista hill, at 13th Avenue and E. 23rd Street, looking at the steep northern side of San Antonio hill.

san antonio hill

The valley separating the hills houses a stream called the 14th Avenue Creek on the watershed map. A long tongue of marshland once extended up 14th Avenue that is now a flat park between 14th and 15th avenues. Across that valley, San Antonio hill rises to about 225 feet at San Antonio Park, just a few blocks from the water’s edge. It is the most prominent part of the fan, as seen from BART.

The north edge of the hill is much steeper than the slope we’re standing on, the south edge of Bella Vista hill. So that’s three hills in succession that have this asymmetrical profile: Haddon, Bella Vista and San Antonio. That pattern does not continue, though.

Now that I’ve walked all over Bella Vista hill, I should present it next.

The hills of Mountain View

5 May 2012

A few years ago in this space I called Mountain View Cemetery “a manicured showcase of the lower Oakland hills.” While you’re visiting the dead, it is pleasant to lift your eyes to the hills and consider the living world.

cemetery hills

The cemetery’s ground reflects its variety of bedrock geology, as shown on the geologic map.

mountain view geologic map

The entrance area is young stream fill with a fringe of higher, older Pleistocene alluvium (Qpaf), then going outward and upward we have the Franciscan sandstone (Kfn) and then Franciscan melange (dark blue) with large enclaves of greenstone, or altered basalt (fg), and chert (fc) making up the highest hilltops. Their elevation corresponds with their resistance to erosion.

The result of this progression of materials is a concave hillslope, or a tilted natural amphitheater. And not only does that present clear sightlines to a range of landforms at a variety of distances, but the mountains of the Berkeley Hills also function as borrowed scenery beyond. All that is hard to gather into one photo, but we are all welcome to try.

“Mountain View” really should be spelled with two spaces between the words. The place is not just a view of mountains—although it is, to the east and across the bay to more mountains—it’s a mountain of views. Mountains and views. And Oakland has other examples all along its uplands.

Haddon Hill from Ivy Hill

29 April 2012

Ivy Hill is a small but distinct lobe of the big Pleistocene alluvial fan of central Oakland, a wedge between Park Boulevard and 8th Avenue bounded on the west by East 18th Street. This view is from nearly at its high point, at East 21st Street and 7th Avenue, looking at and over Haddon Hill.


haddon hill

Click the photo for a 1150-pixel version. The tall trees beyond the telephone pole are in Smith Park, on Park Boulevard, at the foot of Haddon Hill. Beyond the hill are a whole bunch of buildings on the other side of Lake Merritt. Left of the light pole are the Elihu Harris building and City Hall; to their right is the heart of downtown with Mount Tam behind and the blue glass face of One Lakeside in front. Right of the telephone pole is the Kaiser Center buildings and St. Paul’s Tower behind the street trees. The dark tower on the right is the ugly place by the lake. Clustered at the right are the Bellevue-Staten Building, on the lake, and two buildings all the way over on Pill Hill.

Haddon Hill

22 April 2012

Lately I’ve been walking on the part of Oakland underlain by the large Pleistocene alluvial fan (see the city geologic map). As I go, I mentally map it into separate entities, and one of them is Haddon Hill, bounded by the lake, 580 and Park Boulevard. In the past I only saw the hill from the lake, as in this shot from New Year’s Day 2007.

haddon hill

The west face of the hill, seen here, is quite steep. The opposite side of the hill slopes more gently down to the valley of Park Boulevard, and then the opposite side of Park is also quite steep. That doesn’t seem to be a general pattern, but it is curious. The photo below is taken from across Park, at 7th Avenue and Ivy Drive, and looks up Spruce Street to the highest point on the hill, where the St. Vartan Armenian Church sits.

haddon hill

The elevation there is about 180 feet. That doesn’t sound like much, but the ground around it is low and it can feel like a trek on foot. The hilltop area has views much grander than you would think, but they’re hard to photograph.

haddon hill view

The topo map shows that the hill extends across 580 a little bit, where Alma Place is. The real edge of the hill, then, would be Indian Gulch (Trestle Glen).

Lift up your eyes

26 March 2012

One thing I love about the hills is that they grace every part of Oakland, even the plainest, most utilitarian parts of town, like Peralta Street. You don’t have to be riding BART or high on a freeway or in a park to enjoy the hills, just out and about.

peralta street

And those parts of town, in turn, don’t hold back. They get in your face and don’t pretend to be someplace else.

do something positive

Those parts of town help keep me honest. I recommend them.


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