Another easy way to remove all cracks in only one click.
-Asign a black mate material to whole landscape + displacement. All cracks are seen as white color.
-Change the camera from Perspective to TOP in order to see the whole landscape.
-Select Landscape Tool> Sculp > Noise
Brush Size 65536.0
Brush Fallout 1
Strenght 0.0001
Target Value?
Noise Mode Raise (I think Raise is better because all cracks normally appear in slopes and cliffs, not in plain zones. To raise down the walkable area or to remome some anomalous pikes and crests that come from WorldMachine select Lower Mode)
Noise Scale 1 ¿?
-Place the cursor in the center of the landscape and click (wait 10-20sec). If the landscape is too big, for example resize it from 100 to 25 , and then, turn back again to 100.