Yeah, your Geomancy command does different things based on the ground your Geomancer is standing upon. Unfortunately, you have to learn each Geomancy ability before your Geomancer is truly helpful. Learn Hell Ivy, get into a battle, and stand on some grass. It should give you an idea of how Geomancy works.

To use Geomancy when standing on rocky terrain requires a different skill (Local Quake?), et cetera, et cetera, and so on. Learn all the skills and see how versatile those hippies are. <3