Ice shelves are the floating extensions of a grounded ice sheet. Although a few small ice shelves exist in the Arctic, most occupy bays around the coast of Antarctica. They were once thought to be permanent features of the Antarctic landscape. The largest ice shelf, the Ronne-Filchner, covers an area slightly smaller than Spain. Over many decades, ice shelves find their natural size when the amount of snow falling on the surface, and the amount ice delivered by glaciers, balances the rate of ice loss through melting and iceberg calving. A change in any of these factors will cause an ice shelf to change its size to find a new equilibrium.