Periglacial processes: phenomena that take place near glaciers
In tundra environments, subsurface soil is permanently frozen. Shrubs, mosses, lichens, and polygons characterize the "muskeg terrain" surface.
Polygons form a "patterned ground". In cross section the edges of the polygons look like wedges. The wedges are about 2 meters from top to bottom. Reverse-graded bedding: Coarse sediment at the top of the wedges grades into finer sediment at the bottom.
Angularity of ponds that form the headwaters of the Peconic reflect this patterned ground. Swan Pond is the thirs largest pond on Long Island.
NYS DEC gave permits for the golf course at Swan Pond, based on the erroneous claim that the wetlands there wer artificial. They stated that a human presence there would maintain the dikes that impound the wetlands. However, old maps indicate that the wetlands existed prior to the dikes. The dikes were built to enable cranberry farmers to control water levels.
Is Swan Pond a kettle? Lake Ronkonkoma, which is the type kettle put forth by Fuller(1914) has an upside-down helmet shaped cross section, but Swan Pond and other coastal plain ponds have more of a frying pan shaped cross section, so it appears unlikely that they are kettles. The maxmum depth of Swan Pond is about 4 feet. Most likely, these ponds result from secondary ice that melted, allowing the ground above them to collapse.
The Calverton Ponds are the site of the highest concentration of rare, threatened and endangered species of plants and animals in New York State. Thread-leaved sundew, pitcher plants, and bladderworts are insectivorous and occur at coastal plain ponds. Insects stick to the hairs on the leaves of the sundews and are then digested by the plant. The insects supplement the plants' diet with nitrates. The Peconic headwaters, as are the remainder of the Pine Barrens, are low in nitrates and other nutrients.
Near Jones Pond, the Peconic is jagged and angular. Nearby, there are perfectly round ponds. Sears and Bellows Ponds are flat-bottomed. Deeper ponds exist around Scuttlehole south of Sag Harbor.
Wildwood lake is the fourth largest lake on Long Island. Parts of the shoreline are jagged, and other parts are rounded. This body of water may be composed of kettles, but shows some tundra-like characteristics.
Patterned ground may be the result of alternate freezing and thawing over thousands of years. Streams may be captured by the polygonal pattern. This can expain the jagged appearance of parts of the Peconic River. Little round ponds appear at the junctions of polygons. The larger jagged depressions formed where entire polygons collapsed that had become underlain by thick ice. This ice may have resulted from an abundance of moisture cause by the presence of a captured meltwater stream in the channel that now contains the Peconic. The stream had been captured by the polygonal pattern.
Sea level rise is probably responsible for a gradual rise of the water table that eventually filled these depressions.
Sea level rise is also responsible for the existence of stumps of Atlantic White Cedar in the intertidal zone at Hubbard County Park. It has also resulted in traces of freshwater peat on the beach at Hubbard. The white cedar grew at the freshwater-saltwater interface. Habitats associated with the shoreline are transgressive habitats on Long Island. Individual coastal plain ponds are relatively young, but the habitat type is old, and has migrated as sea level has risen.
Continued global warming will cause sea level to continue to rise, and the habitats will continue to migrate.
Last modified December 4, 1997