This is something very interesting when just like rainwater dissolves the bedrock on the Earth’s crust and produce sinkholes, melt water on a glacier’s surface can melt ice and form sinkholes too. Sinkholes on glaciers are often called Moulin’s, French for “mill”. Moulin’s form when summer melts water streams on the surface of the glacier uncovers a crevasse or other weak spot in the ice and begins to pour down through the ice. As the water moves downward, its turbulence and heat generates a narrow, tubular and vertical shaft, up to ten meters wide, that can go all the way down to the bottom of the glacier, hundreds of meters deep.
Water entering a Moulin and eventually exits the glacier at base level where it acts alike a lubricating fluid that plays a huge role on how fast the glacier flows. The melting water accelerates the glacier’s flow to the sea, where large chunks break off to form icebergs, leading to further ice loss by speeding disintegration of the ice sheet. Given sufficient water flow, a Moulin can straightforwardly form over the course of just a month. This was once formed; the shaft will stay open as long as there’s melt water to feed the Moulin. If the melt water freezes, the Moulin will start to fill up with snow and close up. Moreover few Moulin’s’ have been observed to be present in the similar spot for numerous years; however the spot will continually move forward with the flow of the ice.