Well, according to Races of Stone (page 162), a Small Earth Elemental has an ECL of 5th, and consequently a reverse-engineered LA of +3 (ECL 5 - 2 HD = LA +3). A Medium Earth Elemental has an ECL of 8th (4 HD, LA +4), and a Large Earth Elemental has an ECL of 13th (8 HD, LA +5).
Granted, these...