One boy asked, why can't skate on the floor, said:
Because ice is slippery and very hard, and the floor is not such a firm and not slippery.
But sometimes the stone floor; he is slick and solid, and to ride on the stone floor still cannot.
When we ride on ice, the ice under pressure ice skates melts. Between the skates and the ice layer of water. Without this layer of water, to skate on the ice would be as difficult as on the floor. Water, like oil in a car, reduces friction between the skate and the ice.
In severe cold forming a water layer at a loss, and friction between the skate and the ice increases. That's why frost sliding skates on the ice deteriorates.
The movement of glaciers from the mountains is for the same reason. Under the weight of the lower layers of ice it melts, and the icy river glides along the mountain slope, as your skates at the rink.