Perennial Lakes, Cirques, Ponds [PLCP]: A lake is a natural body of fresh or saline water > 8 ha (20 ac) that is completely surrounded by land, holds water year round, and remains relatively unchanged across years. A cirque is a body of standing water that occurs where valleys are shaped into structures resembling amphitheaters by the action of freezing and thawing ice. These formations are usually found in the upper portion of a glaciated area in mountains and always contain water. A pond is a natural or artificial body of standing water usually < 8 ha (20 ac) and characterized by a high ratio of littoral (shallow) zone relative to open water.