21. Geodetic mapping were modernized through a wide range of constituents by GPS in alternative surveying techniques from the mid-1990s, to share new benchmarks of a height modernization for future mapping, carting and navigation, that that made the old markers true relics of a land-based precision of the past.
22. In the Bay Area, of course, the e ground is hardly stable beneath our feet, if the sense of that instability had seemed to have only grown. In San Francisco and the Bay Area, the geodesic markers are, we increasingly realize, shifting in elevation on the ground underneath our feet. Despite the huge effort that went into the placement of those bench marks in the previous century, the bench marks have a half-life that the folks who placed them in concrete monuments did not foresee: plate tectonics of the California coast spaceborne geodesy allows have created a disturbing picture of shifting elevations across the region, as sediment contracts in drought; subsidence of low-lying region coastal lands reveals vertical land motion (VLM) is as much as several centimeters/year, independently of land movement of fault lines of the converging Pacific and North American tectonic plates.
Aquifer depletion can create subsidence of up to tens of centimeters per year, far beyond the ‘slow subsidence’ California experiences, droughts create considerable subsidence with sediment contraction on California’s coast–here measured in VLM of up to 2.5 mm upwards, or subsidence of the same interval.
In California as a whole, the sinking of a mere two centimeters annually may seem less striking, but in a population center of such low elevation, it is alarming. The picture of California is alarming, and something of a serious counterweight or undertow to the huge pull of coastward migration in the past fifty to sixty years.
We can now integrate a remarkably large dataset of vertical uplift in the western United States, to image the vertical velocity of uplift across the western United States, here focussing on the Sierras, that are important to investigate in relation to climate change and anthropogenic activities to get bearings on a changing world–to briefly move way from the shoreline, and place its vertical movement in a broader context of geodetic change.
The markers on the ground in the Bay Area are tokens of a residue of optimistic push for collective projects of the past, affixed as a memory in bronze disks or medallions, of eight to ten cm. diameter; they remind me of the slightly smaller antiquated media the MiniDisk, even if they are not encased in crystal but set in stone or pavement. From the 1880s these benchmarks for surveying proliferated as benchmarks for a network of national mapping, including a triangle on summits of mountain peaks, remainders of a spatiality we have lost, and also a form of my focus and absorption of discarded geographic information, as if a sort of refuge from the vacuuming up of geolocation data. As much as celebrating my own visibility as a flâneur of urban space, the markers were a sort of rejoinder to the “cyber-flânerie” of online worlds, these old geodetic markers seem to retain an old use-value in their own visibility has led me to fetishize them as a traces of a counter-spatiality that needs to be redeemed.
The markers provided something of a n evocation of local pasts and past spatialities for the city walker and flâneur, as well as a timely reminder, at a difficult time, that in Berkeley, CA, that the external world only exists in the mind of the beholder, as much as their eye. Reading the ground was taking a time-dive of sorts; this was an always open library, scattered, off the shelves distributed for collective consultation on the ground and across public lands.
The seventeen markers of the Hayward fault line that run through Oakland CA make one wonder why the fault is named Hayward, but is also a bit of a hidden landmark in the urban ground, on which we could trace outdoor walks along fault lines–a nice place for a picnic in the pandemic that promised outdoor science lessons for greater familiarity with the hidden topography of seismic risk.
The sense of these networks thrown atop the landscape, but that existed within our collective consciousness, seem to have cousins in the markers, about the same size–half the diameter of a compact disk, to use a similarly antiquated medium as a metaphor–that remind folks in Berkeley of the underground network they would do well to visualize and understand by which curbside waste drains from local points to the bay, added, at a far later point, by the advocacy group Save the Bay, as a water pollution prevention program, putting stock in the signs on all storm drains with stainless steel markers, to encourage public awareness of links of natural and built environment that were less clear to many urban residents. If most Berkeley residents understood how watershed drains to the bay, the exceptions one might give oneself to pollute car oil–“out of sight, out of mind”–the greater in-migration from other cities called for a collective consciousness of pollution’s costs, encouraged by an improvised logo. If the estuary drains 64,000 sq miles, by far the greatest number of pollutants enter the bay as urban run off, after all, from streets, homes, businesses, and cars, often through the storm drain system that directly enters the Bay, without filtration. (Educational outreach of Save the Bay asks students map storm drains near their schools, to realize the local sites of such drainage sites near the school that might introduce pollutants into bay water.)
If the shift to emulate geographic benchmarks was a visible change in the East Bay’s strategy to stave off the local entrance of the amazingly high estimate of oil residents 11,000 gallons of oil Bay Area residents send to the San Fransisco Bay daily–twenty times greater than the estimated leak of from an underwater pipeline off Richmond’s Long Wharf that spread a sheen over San Pablo Bay as 600 to 750 gallons of water and diesel fuel spurted over two hours into the Bay waters and left the coast smelling like a gasoline station, and polluting its protected habitat.
Attempt to instill consciousness of oil drains at a local level in the East Bay seemed a Sisyphean struggle.
But the shift to bechmark-like curbside disks that replaced spraypaint as a public education about pollutants, inviting us to trace clearer interconnections between road drainage and coastal pollution of nearby waters: