Instant, 1RR (3) Volcanic Fallout can't be countered.
Volcanic Fallout deals 2 damage to each creature and each player. "How can we outrun the sky?" —Hadran, sunseeder of Naya
Illus. Zoltan Boros & Gabor Szikszai
2/1/2009: Volcanic Fallout can be targeted by spells that try to counter it (such as Countersquall). Those spells will still resolve, but the part of their effect that would counter Volcanic Fallout won't do anything. Any other effects those spells have will work as normal.