What’s the difference between the glacier per se and the ice cap?
We see ice is spilling over off the plateau above Petermann like foam spilling over a too-full glass of beer.
The ice cap is a big scoop of ice cream cone on top of the plateau between fjords. It is sort of a smaller version of an ice sheet (Greenland, West Antarctica, East Antarctica ar ice sheets). All of these are glaciers in the sense of being moving ice (non-moving ice might be called a permanent snowfield), but the term glacier is customarily often to imply flowing ice along a channel. An ice cap or ice sheet might flow radially or in a broad swath from a high-elevation “ice divide”, but it might also have outlet glaciers that drain its center through narrow canyons. Petermann Glacier is an outlet glacier to the Greenland Ice Sheet. The center of the Greenland Ice Sheet is below sealevel. Most of Petermann Glacier is below sealevel. It is thought (but still not completely clear) that the connection between Petermann and the ice sheet is continuously below sealevel.