Thermal Hill and the Broadway lobe

This is my own neighborhood so I don’t always think of documenting it: the western edge of the Pleistocene-age alluvial fan, labeled Qpaf (for “Quaternary Pleistocene alluvial fan”) on the geologic map below.

broadwaylobe-geomap

The Broadway lobe consists of two separate hills of this old sediment: Pill Hill on the south and Thermal Hill (as labeled on the 1912 map) on the north. (In a post five years ago I called it Montgomery ridge, after the street running up its crest.) Broadway Creek runs west of Thermal Hill and crosses the gap in the lobe to join Glen Echo Creek. The only spot it isn’t culverted is in the backyards of Brook Street, down near its mouth. It runs right under Tech High and Mosswood Park. Its valley is in the foreground of this photo, looking up 42nd Street past Opal, Manila and Emerald streets toward Broadway. Click the photo for a big version.

42dSt-big

The tall trees and associated homes are on the ridge. Behind them is the top of Mountain View Cemetery’s property and its continuation south, and the high hills where Skyline meets Pinehurst. Thermal Hill is modest in comparison, but walk over it, or keep an eye on it as you ride along Broadway, and you’ll know it’s there.

Farther south, 40th Street runs straight over the ridge. You really notice because the rest of 40 Street, all the way to Emeryville, is flat as can be.

40St-hill

Once upon a time the streetcar line punched right through it (the 40th Street cut), and today the original 40th Street, the lefthand one in this view, is named 40th Street Way while the former cut, filled in again, is named 40th Street.

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6 Responses to “Thermal Hill and the Broadway lobe”

  1. Pete Veilleux Says:

    Any idea why it’s called Thermal Hill? I used to live on Thermal St over near 90th ave and i’ve wondered how it got that name too.

  2. Andrew Says:

    The hill gets good morning sun and is sheltered from bay breezes on the inland side. I’ve been on Thermal Street and it was plenty warm, but no more so than the rest of Toler Heights.

  3. Jeff Says:

    I teach math at Park Day School (located just about where you were standing in the 42nd street photo). This year we did a project I call “Gobs of Goo” in which we built a 3D topographic model of the Oakland area. If I do it again next year I’m going to subtitle it “Lobes of Qpaf”!

  4. Arleen Feng Says:

    Thermal Hill may just have been a name dreamed up by developers when when the area was first subdivided for residential parcels in the area on the eastern portion of the ridge. The streets from Montgomery to Piedmont show on an earlier 1877 city map suggesting that was laid out at one time.

    If you go to the County Assessor’s online parcel viewer at http://www.acgov.org/assessor/maps.htm you can view the assessor’s parcel maps for each block which have notes referring to one or more original tract maps on which they were based.

    I believe the “Book-page” listings after the tract names refer to the older city surveyor’s block system, used before the county took over the documentation of surveys. Further research might be to look up the old city block maps in the Oakland History room; Some time back I found the one for Highland Terrace (Gilbert and Terrace Sts. on the western part of the ridge where I live) that was filed in 1904. There might have been some re-dividing or re-surveying of portions of the Thermal Hill tract as smaller groups of lots were sold off to builders, perhaps because they wanted different size lots and/or to rework surveys that might not have been very well done in the first place.

    One good thing about Qpaf–it’s a bit more consolidated than the more recent Holocene Qhaf, hopefully will produce somewhat less amplification of earthquake shaking.

  5. Arleen Feng Says:

    The Broadway branch of the creek does have another short daylighted section between MacArthur and 38th St, recently restored or at least revegetated as part of a “Serenity Garden” behind Kaiser’s new Broadway Medical Office Building.

  6. Andrew Says:

    Thanks for both your comments, Arleen. I don’t mind using an old developer’s promotional name; the important thing for me is to have a name at all for the smaller features of our landscapes, just as we have names for the tiniest of neighborhoods. “Thermal Hill” is as good a name as any, and it’s plausible.

    As for the little segment of Broadway Branch you mention, it’s not in the Serenity Garden but just upstream, behind one or two homes on Manila.

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