March 28, 2016 -

A glacier table. A boulder perched on a pedestal of ice. The boulder protects the ice from ablation during sunny weather. Around the boulder the ice surface ablates and, therefore, is lowered, whereas the boulder remains at the original level. While the pedestal becomes higher and higher in relation to the glacier surface, the sun shines further under the boulder from the south (in the northern hemisphere). Consequently the pedestal gets ablated on its southern side, and the boulder will eventually fall off the pedestal, usually on its southern side (in the northern hemisphere). After this a new cycle of table growth and destruction may begin.