Explain: Until 12/10/2014 6am there is nothing to see on the ice sheet between Hutchinson Island and Cronenwell Island at Antarctica, then 1 hour later on 12/10/2014 7am the shadow of an enormous medieval castle becomes visible on the same spot.
Something went wrong with the Google Earth image processing or the appearance of the shadow is a mysterious and unexplained holographic projection from the past when it used to be ice-free until about 34 million years ago, before it became covered with ice.
Here are the coordinates: 76°52'13.87"S 149°59'14.52"W