earth-shaking

from The Collaborative International Dictionary of English v.0.48

earth-shaking \earth-shaking\ adj.
   sufficiently significant to affect the whole world; as,
   earth-shaking proposals; an earth-shaking event.

   Syn: world-shaking, world-shattering(predicate), world
        shattering(predicate).
        [WordNet 1.5]

from Moby Thesaurus II by Grady Ward, 1.0

47 Moby Thesaurus words for "earthshaking":
      big, big-league, big-name, big-time, bigwig, bigwigged, booming,
      consequential, considerable, deafening, double-barreled,
      ear-piercing, ear-rending, ear-splitting, forte, fortissimo, full,
      grand, great, heavyweight, high-powered, important, loud,
      loud-sounding, loudish, major, material, momentous, name, pealing,
      piercing, plangent, resounding, ringing, self-important,
      significant, sonorous, stentoraphonic, stentorian, stentorious,
      substantial, superior, thunderous, tonitruant, tonitruous,
      window-rattling, world-shaking