Several kilometers in a few minutes: crack in the ice shelf breaks speed record. Ice from glaciers raises sea levels as it flows into the ocean.
If large pieces of ice shelf break off particularly quickly, this can increase the flow speed of a glacier - and thus also accelerate sea level rise. About ten percent of the mass of the West Antarctic Ice Sheet is found in the Pine Island Glacier System. The condition of the glacier is crucial to the question of how much sea level rises globally (you can read more about this here)