From Worms Knowledge Base
This one works like an Earthquake, only the terrain is also ripped apart to create a large canyon between the two land masses. The location of the Crevice can be selected, allowing accurate targetting of an enemy worm.
Vibrating land is already in for the Earthquake, so that's no problem. Ripping the land apart shouldn't present too much of a problem either, the game should 'draw' a jagged line from top to bottom at the selected location, dividing the landscape in two, and then each half should be moved horizontally away from the other. The only problem is what happens when the land is moved past the edge of the map, where the game does not allow land to exist.
This weapon seems to be a bit on the easy side. Although you may have to take care that your worms don't fall victim to the seismic movements, it seems all too easy to target anywhere on the map, and create a chasm that will undoubtedly drown any worms in the way.
This weapon resembles the Earthquake too much. Crevices can be created by many other weapons, it does not need to be a weapon in its own right.