Archive for November, 2013

The Kitchener scarp

30 November 2013

The recent walk by the Oakland Urban Paths group took us past a catastrophe I hadn’t seen before: the landslide of 15 January 1970. It removed nearly all the homes on the east side of Kitchener Court, just south of the LDS Temple, and dumped the ground into the valley of upper Peralta Creek. The land is still empty and uninhabitable. Here’s a look south over the scarp from Kitchener.


The slide wiped out the middle of London Road between a tiny stub at the top of Maple Street and the forlorn end trailing off of Maiden Lane. The Hayward fault is mapped right through the foot of the slide. The site of my photo is across the pink strip opposite the “J” on this portion of the Oakland geologic map.


I frankly can’t vouch for any of the bedrock divisions shown here, but the dashed line of the fault is close enough to reality. For orientation, here’s the equivalent area in Google Maps. Rettig canyon, where Peralta Creek cuts through the bedrock ridge of Leona keratophyre (pink) and mixed Franciscan rocks (KJf), is in the patch of green at lower center.


39th Avenue fault gauge revisited

27 November 2013

2-1/2 years ago, I presented a photo of a cut mark in the curb of 39th Avenue where the Hayward fault is mapped. This month I happened to visit the spot during an Oakland Urban Pathways walk, and I took the opportunity to take a new photo.


It has moved slightly, just a few millimeters, in the intervening time.

The U.S. Geological Survey monitors the fault closely through Oakland. They don’t measure this mark, or if they do it’s not definitive. The definitive survey is along a longer line across the fault, because the fault movement isn’t limited to a perfectly thin geometric plane. Their measurements show that this part of Oakland is creeping approximately 4 millimeters per year. Heck, here’s a good source, from a 2000 paper by the USGS guys that was published in Geophysical Research Letters:


The authors note that Oakland has a relatively slow rate of creep, and they interpret that as a sign that the fault here is more extensively locked than it is elsewhere. The area and degree of locking bears directly on the energy the fault is capable of releasing. Mind you, we have over a decade of new data and new thinking since that paper was published, but the data is sound.

Huckleberry saddle

18 November 2013

The entrance to Huckleberry Botanic Regional Preserve is at a low point in the spine of the Oakland Hills, where the steep eastern arm of Thornhill canyon has cut headward toward the equally steep canyon of San Leandro Creek. Both canyons are steep because the rock between them is the tough Claremont chert. The saddle between the two canyons provides good views to the west and east, and a little path (labeled Huckleberry Path on the map) leads north from the Huckleberry entrance, a private entrance to the preserve for the residents of Elverton Drive. That’s where I got these pictures, first looking southwest toward downtown:


and due west, over the opposite wall of Thornhill canyon, toward the Golden Gate.


Turn around, and it’s just a few steps to find these views of the Las Trampas Ridge area—


—and Mount Diablo, which never ceases to surprise me when I see it from Oakland. I think of Diablo as a whole different domain, reachable only by a drive through the tunnel and not visible west of Lafayette. But here it is, looking downright neighborly.


Only a few Oaklanders get to see the view east; we’re a westward-leaning city.


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