All glaciers move, though very slowly, like huge solid rivers. These glaciers, called icebergs, are floating mountains of ice, commonly found on the coast of Greenland up to the North American Coast which are very cold regions.
These glaciers cannot stop moving due to excessive pressure of the masses of ice behind them. They, thus slide into the sea, moving ahead, till they meet warm currents, where they break up and gradually melt.
Below Icebergs info from Wikipedia (Read More):-
An iceberg is a large piece of freshwater ice that has broken off from a snow-formed glacier or ice shelf and is floating in open water.[1] It may subsequently become frozen into pack ice. Alternatively, it may come to rest on the seabed in shallower water, causing ice scour (also known as ice gouging) or becoming an ice island.
http://en.wikipedia.org/wiki/Icebergs
