Archive for the ‘the Fan’ Category

Lobe 8 of the Fan: Evergreen Cemetery hill

15 June 2015

Cemeteries occupy some of Oakland’s nicest hillsides. Evergreen Cemetery, unlike the others, has a whole hill to itself. The hill consists entirely of sand, silt and gravel laid down in a large alluvial fan (the Fan) back some time in the Pleistocene. Later, stream erosion cut the Fan into pieces, which I have numbered west to east from 1 to 8. This one’s the smallest and, all things considered, the sweetest.

lobe8-evergreencem

This is the view from 64th Avenue, the hill’s gently sloping side. The NL bus runs past here, too.

Below is the terrain view in google Maps, where I’ve marked it along with lobes 6 and 7.

lobe8-topo

This is the view from across MacArthur Boulevard at 68th Avenue/Church Street. The hill is pretty secluded, with trees screening it on most sides. When you’re there, your eyes are lifted to distant views, which is fitting. The homes on the far side of 68th probably excavated into the edge of the hill when they were built.

lobe8-from-church

When the weather’s right, you can get a good view of it from Outlook hill, for instance from Delmont Avenue:

lobe8-millsmont

or from the overlook at the end of Simson Street. These days the cemetery is doing its part in the drought. Most homeowners are, too.

lobe3-from-simson

The geologic map (as seen in this earlier post) shows a little more Fan alluvium to the north and east of the hill, but it’s topographically subdued.

The Mills College lobe

19 April 2015

The big alluvial fan of old Pleistocene gravel making up Oakland’s most unusual topographic feature—the Fan—is cut by stream erosion into eight lobes, which I’ve numbered from west to east. Lobe 7 is entirely inside the grounds of Mills College, as shown here on the geologic map.

lobe7-geomap

Seminary Creek passes the west side and Lion Creek the east. These streams are responsible for carving the hill away from the rest of the Fan. Of all the bits of the Fan, only this hill and Pill Hill stand isolated from adjoining bedrock. I’m unaccountably fond of both.

Here’s an impression of its topography from Google Maps. The numbers mark the locations of the photos that follow.

lobe7-topo

The hill is densely wooded, for the most part, which limits views of it and views from it. I’ve done what I can, but it’s hard to take in by eye.

I have walked the hills and streets on all sides of this feature, and so far I haven’t found any spot where it stands out in a photo. You have to go there and walk it to get a sense of it. This walk goes clockwise around it. We start where Kapiolani Road is bumped off its straight line by the hill and a footpath takes you up its flank.

lobe7-rise

As I said, most of the hill is wooded, but along the west flank there are spots with a view. The next two photos look from the top of the hill over Seminary Creek’s valley (the creek is culverted here) toward the populated slopes of Maxwell Park hill, lobe 6.

lobe7-to-maxwell1

millshill-over-SemCk

Near the north end of the hill is a footpath down the hill’s western slope to a little-used parking lot along MacArthur Boulevard.

mills-SemCkvalley

From there you can see a fair bit of the hillside.

mills-lobe

You can continue through the woods along Seminary Creek, then take the path past the little graveyard where the Millses, Cyrus and Susan, are buried.

the-millses

A peek inside the Fan on Piedmont Avenue

19 February 2015

Construction is going on at the lot formerly occupied by a well-behaved motorcycle club, at 4225 Piedmont Avenue by the Kona Club. What caught my eye is that it offered a clean cut into the stuff that constitutes lobe 2 of the Fan.

I’ve referred to the Fan often over the years, but I haven’t formally introduced it. Here it is on the Oakland geologic map.

the-Fan

It’s a former alluvial fan that was last active during the Pleistocene, which has been dissected by several younger streams. There’s nothing else quite like it in the East Bay, and I think of it as the Fan with a capital F. I divide it into eight separate lobes. Lobe 2 has two separate parts, Pill Hill and Montgomery/Thermal hill. Anyway, I keep an eye on it because it’s rarely exposed. Only excavations and a few stream banks display it.

Here’s what it looks like from a distance.

piedmont4225-1

There’s indistinct bedding that slopes down to the left. The material is gravely clayey sand that’s quite firm and well behaved. Here’s a closeup of a gravely layer; the stones are large pebble size (about 50-60 millimeters) and represent the Franciscan rocks just uphill in the Piedmont block.

piedmont4225-2

Farther over, the wall of the excavation has been carved with a backhoe, and the clayey matrix is so strong that most of the stones have been cut in two, even the tough black argillite.

piedmont4225-3

This is alluvium—sediment carried and laid down by streams. The rock clasts are rounded, showing that they’ve been carried in a stream for some distance, although most of the rocks are sandstone that doesn’t endure long. The hardest chert pebbles are still pretty rugged.

Down on the ground was this very typical Franciscan chert boulder, shattered by the builders after enduring for more than a hundred million years.

piedmont4225-4

The lot will become a nice set of dwellings. The builders are blogging about the job, complete with cool drone shots.