highest point above sea level long island
(Bald Hill, Farmingville, is the highest point along the moraine.) The glaciers also formed Lake Ronkonkoma, a kettle lake. The island's tallest natural point is Jayne's Hill near Melville, with an elevation of 400.9 feet (122.2 m) above sea level. Long Island is separated from the mainland by the East River, not in fact a river, but a tidal strait. Long Island Sound forms the northern boundary of the island.