Clobbering Strike (Ex): Whenever you score a critical hit against an opponent with a spell that requires an attack roll, you may immediately attempt to trip your opponent as a swift action. You do not provoke an attack of opportunity as normal for this trip attempt. You cannot be tripped in return when using this ability.
By RAW, the only Oracle/Cleric spells this seems to affect are the Inflict/Cure spells, since they're the only touch attack spells that they normally get. If expanded to (Su) abilities, in addition to those two it only affects Touch of Acid, which doesn't seem like much of a "clobbering strike", and Mighty Pebble additionally, which would mean you had to take another revelation just to get any effect out of it.
I think it would make sense to expand this to Earth spells and abilities that involve attacking, like Magic Stone and Rock Throwing, and maybe let the Oracle pick a few Earth spells from the Elementalist wizard spells list in place of normal spells known, just to give them some options.
By RAW, the only Oracle/Cleric spells this seems to affect are the Inflict/Cure spells, since they're the only touch attack spells that they normally get.
Clobbering Strike (Ex): Whenever you score a critical hit against an opponent with a spell that requires an attack roll, you may immediately attempt to trip your opponent as a swift action. You do not provoke an attack of opportunity as normal for this trip attempt. You cannot be tripped in return when using this ability.
Admonishing ray, arrow of law, dread bolt, harm, holy ice, searing light, shard of chaos, slay living, spear of purity, spiritual ally, spiritual weapon.