expected for plunge pools, the lakes are fairly deep in comparison to their area. For example, Round Lake is deep, and has a diameter of about . The color of the lakes 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 (see photo) 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. Climate history and Green Lakes Nearly all lakes undergo mixing of their deepest waters with their surface waters at least once a year. This mixing does not occur for Green Lake and Round Lake. They are rare, meromictic lakes. Waters deeper than about 55 feet (18 m) do not mix with the surface waters; as a consequence, they are essentially devoid of oxygen, and are rich in calcium, magnesium, and sulfur. The meromictic character of the lakes is due both to their relative depth compared to their area, and to the influx of mineral rich ground waters. Because of this lack of physical mixing, as well as the absence of growing plants or crawling animals in their oxygen-depleted depths, the deep bottoms of the lakes have relatively undisturbed annual layers of sediment (or varves) that preserve a historical record, somewhat like tree rings do. These varves are being used to study the climate of this area of New York over the last several thousand years. References External links New York State Parks: Green Lakes State Park, official State of New York website for the park with contact and camping reservation information. Green Lakes State Park Golf Course webpage with contact information, times and fees. "The Underwater World of Green Lakes", video obtained using a robotic submarine by Dr.