It is really one ice shelf, nominally divided by Berkner Island. Berkner Island is actually an ice rise, where bedrock below sea level makes the ice dome upward. Like much of Antarctica, the Filchner and Ronne Ice Shelves were named by and for explorers. But the Kaiser renamed it Filchner. This place-name confusion was fixed by treaty in 1968.
Ice shelves are part of a cycle.
When a large piece of ice shelf calves into the ocean it does not drop and splash down into the water, because the front of the ice shelf was already floating on water. The top 150 m of ice came from snow and glaciers, but the bottom 80 m of ice came from the water below. This bottom layer is clear and bubble-free. The top layer is hard but snowy and bubbly. The annotated 1973 image shows such a crevasse, called the Grand Chasms.