Economist: SINCE 1904, when Prince Piero Conti managed to get a light bulb to flicker in an Italian lava field, geothermal power has depended on volcanic heat. The earth’s crust needs to be thin, with high temperatures just below the surface. Cold water is pumped down a deep borehole and returns superheated to spin a turbine. To power its tiny and now spluttering economy, Iceland has already made use of what scientists call volcanism. Fiery bits of the Philippines also run on geothermal …