Green Lakes State Park is a New York State Park located east of Syracuse in the Town of Manlius. The park is strikingly scenic, and is perhaps the most studied meromictic lake—one in which layers of water do not mix—in the world. The park preserves the largest stand of old growth forest in Central New York, and Round Lake has been designated as a National Natural Landmark by the U.S. Department of the Interior.

The park is centered on two small lakes, Green Lake and Round Lake, which have an unusual blue-green color. These lakes lie at the base of a gorge that is somewhat longer than a mile in length. The lakes and the gorge are remnants of the ice ages, and exemplify some of the unusual geology of upstate New York. Green Lake has a surface area of 65 acres and a maximum depth of 195 feet. Round Lake has a surface area of 34 acres and a maximum depth of 170 feet.

Nearly half of the water that enters the lakes comes directly through the bedrock in which the lakes are embedded. This water contains a heavy load of dissolved minerals that are not present in water that enters through the surface from rain and snow. The high concentration of sulfur in the deep waters had already been reported by 1849; the lakes' waters also have a high concentration of calcium and magnesium. This mineral concentration leads to "whiting" events each year in which small crystallites of calcite and other minerals precipitate from the water. At these times of year the lakes appear particularly green, and the small crystallites are deposited in a layer underneath the lakes' waters. The notable shoreline "reef" at Deadman's Point on Green Lake was built up by this precipitation over thousands of years. Underneath Deadman's Point there are some extremely rare aquatic mosses and sponges.

Green to Round Lake Trail

Easy

Route type: Loop

Length: 2.9 miles