Citation: Obrebski, M., R. M. Allen, M. Xue, and S.-H. Hung (2010), Slab-plume interaction beneath the Pacific Northwest, Geophys. Res. Lett., 37, L14305, doi:10.1029/2010GL043489.
Whose abstract and a summery I've seen on the web. I haven't read the original article, fortunately I live within walking distance of the USGS Library in Menlo Park Ca.
The article uses some mantle geophysical sensing to claim that the Yellowstone hot spot brunt through the soft subducted Juan de Fuca plate and caused the flood basalts of Washington, the Snake River, and east to where it lies beneath Yellowstone Caldera, today. The regional map shown in the science news web site shows the trend of the volcanos that begin at the Oregon/Nevada border and trend with a slight bend to the left toward the north east. The summary says that the mantle plume forced its way up about 19 MYA through a rip or weakness in the subducting plate. I wonder if the authors of the paper have considered the Mendecino Transform as the weakness. It would be a transcurent fault that connects a former southern jog of the East Pacific Rise that was partly destroyed to create the San Andreas fault system of California (Atwater, 1970). This article claims that the effect of the mantle plume slowed the rate of subduction of the plate, which would happen if the plate in the mantle is disrupted and cannot exert pulling force on the remaining plate.
I have to find out the ages of the Washington Flood Basalts to find if they are generally older than the string of calderas that mysteriously begin just south of them and just north of the Basin Range Province. It has been known for some time that the latter was a region of uplift, extension and then volcanism which is older than 19 MYA. If the ages are right, the mantle plume may have caused all of these features as it lay trapped under the crust, heating and stretching and then emerging once the pent up heat and magma is released as the flood basalts and lesser regional volcanism of the Basin Range. Once that happens, the plume emerges through the crust as the string of caldaras with a change in plate motion possible about 16 MYA, roughly.
I have also been wondering for some time if the East Pacific Rise segment that was subducted is really extinct. There is the thing called the San Andreas Anomaly in which not all the convergence of North America and Pacific Plate is accounted for my strike slip on the SAF. A mantle plume could explain the oddly wide orogenic provinces of Western North America, but so could a not quite dead spreading center that might be taking strain off the SAF and trying to open a seaway further east. Maybe someday there will be beach front property in Death Valley and Los Vagas as the Gulf of California extends into North America.
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