D&D4 Wiki
earthsoul genasi racial power

Special: When a character gains earthshock, the player chooses which ability score, Strength, Constitution or Dexterity, to use for earthshock's attack roll throughout the character's life.

Target: each enemy within this power's area of effect and touching the ground

Attack: Strength + 2, Constitution + 2, or Dexterity + 2 vs. Fortitude
The bonus to the attack roll increases from +2 to +4 at 11th level, and to +6 at 21st level.

Hit: "The target is knocked prone."[FRPG:10]

Earthshock is a racial encounter power gained by genasi who choose the Earthsoul option for the Elemental Manifestation racial trait at 1st level.