induration. 1. the process of hardening or being hardened.
1 They're weak against the Ice and Water types in reference of erosion, which cause this elements to the ground. 2  They're immune against the Electric type because in real life, the ground is a natural sink of electrons.  The Bug type resists them because many bugs like worms live inside the ground and many of them eat it.
PokÃ©mon Database. Ground is one of the strongest types offensively: it is super-effective against five other types (as is Fighting) and Earthquake is one of the strongest moves in the game with power and accuracy both 100. Unfortunately, many Ground type PokÃ©mon are dual Rock types, lumbering them with 4x Grass and Water disadvantages.