>Autism the thread
Okay, so I've done a lot of thinking about this and I've organized Ground-type moves into several categories based on their properties. There are a few that don't particularly fit anywhere, so I'm welcome to suggestions.

Tectonic: These moves tend to be high base power and physical in nature. Some cause spread damage and are also weakened by Grassy Terrain. They typically reference geologic processes within the earth's crust.
Moves: Bulldoze, Earthquake, Fissure, Magnitude, Precipice Blades, Tectonic Rage
Osseous: These moves reference bone and are mostly exclusive to the Cubone family. They are generally lower base power and most hit multiple times.
Moves: Bone Club, Bone Rush, Bonemerang
Alluvial: Moves that utilize mud. In general they are low base power special moves with shaky accuracy. Many carry secondary effects.
Moves: Mud Bomb, Mud Shot, Mud Sport, Mud-Slap, Muddy Water*
Arenaceous: These moves utilize sand. They are generally supportive, emphasize defensive play. Chip damage over time seems to be a theme.
Moves: Sand Attack, Sand Tomb, Shore Up, Sandstorm*
Percussive: These are moderately powerful physical moves that stand out from all other Ground moves in that the user makes contact with the enemy. Their nature seems divided between burrowing attacks and slamming the opponent with earthen materials that compose their body.
Animistic: These moves draw upon the mystical or spiritual energies of the Earth.
Moves: Earth Power, Land's Wrath
Uncategorized: These moves have no clear placement.
Moves: Thousand Arrows, Thousand Waves, Spikes, Rototiller
Moves marked with asterisks (*) are not Ground-type moves but I believe them to be closely related.