Wednesday, September 10, 2014
The vast caldera of the
Erupts siliceous ash from time to time.
It’s far from the Cascade subduction zone
Therefore, a mantle plume’s the suspect prime.
But magma conducts electricity
Conductors in the mantle lie out west
The tomographic maps are very pretty
But show no melt where theory would suggest
A plume, with mantle source below the crust
Should yield a seismic and conductive trace.
Because we can’t detect deep melt we must
Explain resistance far below this place.
A pulsed hotspot, or plate-related stall?
Or maybe plumes do not exist at all.