Shelf ice

Shelf ice is ice that forms when a portion of a lake surface freezes. It is often then washed upon the shore. The phenomenon is common within the Great Lakes.Southern Lake Michigan beach in winter at Indiana Dunes National ParkAn unbroken stretch of shelf ice at Indiana Dunes National ParkRidges of shelf ice along Lake Michigan's southern shore at Indiana Dunes National Park Shelf ice is ice that forms when a portion of a lake surface freezes. It is often then washed upon the shore. The phenomenon is common within the Great Lakes. Shelf ice forms from float ice. Float ice is like drift ice, but seldom becomes large enough to support humans or large animals. The cold temperatures freeze small areas of the open lake, forming float ice. Similar ice will form along the shoreline when the lake is calm. Over time, the ice will build up from continued freezing on the open lake and from snow accumulation on the surface. The surface of the Great Lake seldom remains calm enough for the entire surface to freeze. Note: The smaller lakes, Lake St. Clair, Lake Erie, and Lake Ontario will freeze over more often than the larger upper lakes. The wind pushes the float ice and creates waves which also move the ice. Over time, the ice will accumulate on the leeward shores of the lake. Like sand, which is moved by the wind and the waves, the ice begins to accumulate along the east and southern shore of Lake Michigan. When pushed onto the beach, it remains and over time, the ice accumulates on top of the beach and the ice already pushed ashore.