A very powerful but delicate spell that needed to find the critical weak spots/trigger points to initiate a fast-cascade eruption of four volcanos, simultaneously.
'One becomes exhausted when using sorcery in proportion to the intricacy of the spell, not the amount of energy used ...'
-- Kiera the Thief, Orca, Steven Brust
While not completely true in Shadowrun, it has its comparisons. Yes, great energy was required, but great finesse too; it's gotta be tough to set off only four volcanoes in the Cascade chain ...