Question

If a spreading boundary occurred on land instead of the ocean floor what woud be the long term result

Answer 1

The long term result would be that the region where it has occurred will split and the two parts will move away from each other, the growing gap between them will be filled with water which in time will become sea, there will be significant climate changes, the one part that'll be moving into more isolated position will make life forms on it to evolve in a specific way and they will become very unique in time.