Rocks heat up faster than snow and ice because of their darker color. . This is clearly visible in the following two images. Although the weather is bad and there is almost nothing to see on the normal photo, the picture taken with the thermal imaging camera shows the shield and the rock very clearly.
This temperature difference causes more ice to melt around the rock. The dark rock heats up even in diffused light and also gives off the heat at night. This creates a gap between the ice and the rock, the so-called edge gap.