How does a karate player break a slab of ice with a single blow?

Because a karate player strikes the pile of tiles or slab of ice with his hand very fast. So, large momentum of his hand is reduced to zero in a short interval of time which exerts a very large force on the pile of tiles to break them.
The momentum of the hand is fully transferred to the ice slab.This creates a large amount of force.Thus he is able to break the slab.