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

Rocks of the Crusher Quarry

11 April 2015

This former quarry in Laundry Farm encompassed the ground now occupied by Belfast and Bermuda Avenues, just south of Horseshoe Canyon and Leona Heights Park. One source, the Laundry Farm map, shows something called the Hotel Mine in this area but I have found nothing about that mine, only information about the Crusher Quarry. It was operated by the E. B. & A. L. Stone Company around the turn of the last century.

Here’s where we start, at this fire road just north of Bermuda Avenue off Mountain Boulevard.

crusher1

The square object is the upturned west end of a long, arcing concrete ramp. It slopes down to ground level and levels off beneath some oak trees.

crusher2

Then it turns up again, as if aiming at the old quarry face.

crusher3

Here’s the broken upper end.

crusher4

This was once the working middle part of a cable tramway, a set of steel cables that carried huge buckets back and forth between the rock face and the crusher. The ramp therefore describes a roughly catenary curve corresponding to the natural sag in the cables.

Onward to the high working face of the quarry.

crusher5

This is highly fractured “Leona rhyolite” that needed little processing because it was already naturally half-crushed. The name of the quarry may be typical 19th-century American irony.

crusher6

The stone has acquired a typical blushing orange hue because it releases a lot of iron, which oxidizes and hydrates forming thin crusts on exposed surfaces. I think that the notable deposits of red and yellow ocher in this area, which were widely known among Bay Area native tribes, arose from many thousands of years of uplift, fracture and weathering of this rock.

crusher7

Higher on the hillside above the quarry, you can find lots of natural outcrops. They show signs of working in places. I think the stone has a nice presence.

crusher8

You’ll see sheltered spots with the glimmer of various shades of ocher; also evidence of wildlife.

crusher9

On the way back out, take time to see what’s blooming in the raw land the quarry left behind. These are called red maids.

crusher10

And the fine gravel even supports an underground ecosystem that produced this emerging mushroom.

crusher11

The locals enjoy and watch this place, so there isn’t any tagging or bottle-smashing to speak of. Climbing is dangerous; stick to Berkeley’s rock parks for that. Visit discreetly and leave the place cleaner than it was when you came.


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