The first evidence of a 1100 F surface-heating spot on the Earth's surface would be fires. And, that's (BIG IF) sufficient power density could be maintained on a spot of ground to heat it to 1100F!
Since these spots are "transitory" (leaving no continuing grass/forest fires and charred terrain) -- claiming they are DEW effects is evidence of unclear (or "conspiracy-biased) thinking.
As for magma plumes being the only potential source of subsurface-origin hot spots -- you might want to review the video of Freund's paper on "Solid State Effects Heating" linked in DocRock/s #39... Very interesting theory -- and more-interesting data! (Not often you hear applause for a data plot in the middle of a paper...)
TXnMA
