Then again, such a ploy might result in several hundred years of acid rain, denuding the continent of all vegetation.
Okay, I’ll bite. Where would the acid come from? Since there would be no direct contact between the water and the magma, just water and very hot rock, once a limited amount of sulfur has been leached out of them, the steam should be pretty clear.
The idea of the water is that it should remove a lot of heat from one side of the magma, which in turn would lower the upwell pressure.