Earth is one of the basic elemental attributes found in Castlevania. However, Earth as a damage type itself only appears in Castlevania: Circle of the Moon, with later games attributing Earth spells and attacks with Strike.
Pure Earth spells
In Castlevania: Circle of the Moon, Nathan Graves can perform a couple of earth spells when combining with cards with the Golem Card. Combining Diana with the former will cause a wave of rubble to move forward when Nathan attacks with his whip, but he must grounded to perform. Combining the Apollo and Golem cards will allow Nathan summon several spears from the earth that rise up to damage enemies.
Earth weapons and weapon enhancements
Combining Mercury with Golem, the vampire killer's length is extended to reach half a screen's length, but it has a slow start up when attacking. Using Mars + Golem will let Nathan wield a hammer that will damage any ground-based enemy when it strikes the ground, though it is slow at the start of the attack.
Nathan can summon a golem when using the Uranus Golem card combination. The Golem will rise up from the bottom of the screen and cause a number of boulders to rise up and damage enemies. Oddly enough when combing it with the Saturn Card, he summons a hawk familiar that attacks enemies at high speeds, which is odd considering that earth is considered slow.
Combining Venus with Golem will increase Nathan's defense based on how much of the map has been discovered. The Jupiter Golem combo increases his invincibility frames by four seconds after he receives damage. Combining Neptune with Golem will let Nathan convert any earth damage he takes into health. Pluto Golem combo will cause an illusion of Nathan to project forth that copies everything he does.
Enemy Earth attacks
In Circle of the Moon, Both Earth Demons and Earth Armor will cause a wave of rubble to project forward. Both the Were-Horses and Minotaur can slam their weapons on the ground to cause debris to rise up. Death in his second form will cause a quake that will damage Nathan if he's on the ground.
In Lament of Innocence, Mad Divers and Evil Stabbers will burrow underground to circle Leon and reemerge for the strike. The Golem will occasionally cause a quake when it punches the ground, and in Crazy Mode it will cause debris to fall from the ceiling whenever it takes a step.
In Curse of Darkness, Assassin Zombies utilize the same technique that Mad Divers and Evil Stabbers used in Lament of Innocence. Dullahan can perform a leaping attack that unleashes shockwaves that would cripple Hector.
In Portrait of Ruin, Dragon Zombies cause debris come up whenever they slam their tails down. Elgiza uses the desert sand against Jonathan and Charlotte. Both Sand Worm and Poison Worm burrow under the sand and jut out for a surprise attack.
In Order of Ecclesia, Gravedorcus constantly travels underground to gain the upper hand on Shanoa. Goliath performs a ground punch that causes the floor to come up like spikes around the area he punched, and he uppercuts with so much force that it cause debris to fall.