User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-3146930-20130720154210/@comment-4902593-20130721061548

Dark, you should remember that when the Big Three divided the world, each one took a certain part of the earth: Hades took the underground, Poseidon took the surface and Zeus took the mountains and all terrestrial life-forms. Also, the Sky, Oceans and Underworld are already so huge that earth powers aren't so strong. So yeah that's why Hazel cannot control the surface compared to underground.