High Quality Content by WIKIPEDIA articles! Glacial Lake Passaic was a prehistoric proglacial lake that existed in northern New Jersey in the United States at the end of the last ice age approximately 13,000 years ago, which was formed of waters released by the melting of the retreating Wisconsin Glacier that had pushed large quantities of earth and rock ahead of its advance, blocking previous natural drainage. The area of this drainage basin today is called Passaic Meadows and includes Great Swamp, Black Meadows, Troy Meadows, Hatfield Swamp, Lee Meadows, Little Piece Meadows, Great Piece Meadows, Bog and Vly Meadows. The lake was formed on the western side of the Watchung Mountains by a blockage of the Passaic River at Moggy Hollow from a moraine left by the retreat of the glacier. The river had previously passed through the Watchungs on a northerly course near present-day Summit and Chatham and turning eastward at what is called the Short Hills Gap that separates the present day communities of Short Hills and Summit.