Wright Peak, Mt. Konocti

I was always interested in this mountain as a volcano. Years ago I was quite interested in the idea that the Sutter Buttes were in fact the southernmost Cascade - either way they're anomalous in their own right, but part of my argument was that they were close to, or not far south from, the Mendocino Triple Junction where the North American Plate, the Pacific Plate, and the Juan de Fuca (or at its southern extent, Gorda) Plate, the latter of which is a subducting rather than transverse plate associated with Cascade volcanism. These are the remnants of the Farallon Plate which once subducted under North America all the way to the Rockies.



Plates are physical objects, less abstract than you might think; the JDF for example can be measured as bending 60-80 degrees downward as it melts into the mantle about 200 miles inland (DiPietro, 2018.) The map above comes from a 1997 USGS report, "Tectonic Controls on Magmatism and Geothermal Resources in the Geysters-Clear Lake Region, California: Integration of New Geological, Earthquake Tomography, Seismicity, Gravity, and Magnetotelluric Data", and you can see the Triple Junction is actually about a hundred miles north of Konocti, and the Buttes are about 15 miles north of Konocti, over in the Central Valley. Some Tahoe-worthy views there, consistent with the elevation difference of 3,000' from lake to summit.







Of course, there are several volcanoes around here (St. Helena, Hood, Geyser Peak) and a) it's never that simple, plus b) what does it mean to talk about something being a "Cascade" or not? Case in point, there are flat fields of lava from just the last few thousand years around southern Oregon directly between Cascades - no one would argue that these flows resulted from the same process that created e.g. the Sisters, but is it a "Cascade"? This region has to do with more recent volcanism (~2 million years ago) resulting from a gap created by the San Andreas meeting the Triple Junction. The prominent dark colored rock you see in one of the photos below is actually sedimentary rock uplifted during the volcano's formation, not basalt.

Other notes: the oldest site of human habitation is at adjacent Borax Lake, one of several smallers lakes now separated by volcanic deposits. Clovis points dating from 12,000 years ago have been found there, with their age initially doubted but later confirmed by other means. Unless you have DNA, it is always both highly speculative and politically charged to try to determine if the people then make up a large part of the ancestry of the people who lived there at the time of contact with Europeans - case in point, Pomo people speak a language in the Hokan family and can be found as far south as San Diego County, and probably preceded Ohlone speakers (in the Penutian language family; at nearby Olompali, there was a turnover in the archaeological record about 4,000 years ago possibly corresponding to the arrival of proto-Miwoks who occupied it when they were trading with Russians and Mexicans.) The fire tower is from 1889, which surprised me (I would've placed it in the WPA era), and was being actively used by a lookout the day I was up there - and he was quite busy. It's been a bad fire seeason, and you can see the smoke layer in some of the pictures of the Glass Fire to the south, still not fully contained. The mountain was a healing place for the Pomo and boy did I need that yesterday. If you're interested in this stuff, there's a California State Parks report here, and another USGS report on the geological history of the Clear Lakes region.