The only Earth attacks in the game, the QAKEspell and CRACKspecial attack, are both KO attacks that affect multiple foes. Characters can gain resistance to Earth with a Ribbon, the ARUBspell, or the WALLspell. Many creatures resist Earth, especially any creature depicted as able to fly or swim. Nothing in the game is weak against Earth magic.
The only Earth attacks in the game, the Quakespell and Earthquakespecial attacks, are both instant KO attacks that affect multiple foes. Characters can gain resistance to Earth with a Ribbon, the NulMgcspell, or the NulAllspell. Many creatures resist Earth, especially any creature depicted as able to fly or swim. Nothing in the game is weak against Earth magic.
The "Earth" family is an interesting one, consisting of what appears to be subterranean, plantoid, or otherwise earth-related creatures. The only weapon in the game that has a special power against them is the Gaia Blade, but the family is not common enough that it's really worth worrying about for very long.
Earth is available to the party primarily in the form of the Quakespell, which hits the party as well as its foes. This can be mitigated with Float (which grants immunity to most Earth attacks) or Gaia Gear, and while very few monsters have a weakness to Earth, it is extremely powerful against non-flying monsters.