A Brief Natural History of Lake Champlain
 Geology and Geologic History
The rocks and landforms of the Lake Champlain valley are a geologist’s dream. The oldest fossil coral reef in the world, an internationally famous example of a thrust fault, and the excavation site of a 10,000-year-old beluga whale are just three examples of the Lake's many geologic delights.
While nearly all of the Vermont shoreline (and the New York shoreline at the northern end of the Lake) is composed of sedimentary rocks (limestones, dolostones, quartzites) which formed in shallow tropical seas about 500 million years ago, the New York shoreline from the vicinity of Port Kent south is ancient "basement" rock, which once lay below the mountains where the Adirondacks now stand. These rocks, which have been exposed to tremendous amounts of heat and pressure are over 1 billion years old!
Successive block faulting associated with the stretching of continents developed a deep canyon about 200 million years ago forming what is now the Broad Lake. Although they are made of ancient rock, the Adirondacks are only about 5 to 50 million years old. The rock that composes the Adirondacks (and is exposed along much of the New York shoreline) is old, yet the mountains themselves are relatively young.
More recently, from about 3 million to about 12,000 years ago, as the Pleistocene glaciers overrode the area as far south as Long Island, ice ploughed the Lake Champlain canyon out even more. With subsequent climatic warming, the glaciers receded northward, and massive amounts of meltwater flowed south into the Hudson River drainage.
Melting ice dropped "glacial erratics"—boulders carried from the northwest—onto what are now the shores of the Lake. Debris dams to the south dammed up the glacial meltwater, forming a huge glacial lake, "Lake Vermont", which achieved a surface elevation of about 600 feet (around 500' above the current level!). When the dams broke, the water drained out.
Since the landmass was below sea level (as a result of the huge weight of the ice), as glacial ice receded north of the St. Lawrence Valley, ocean waters flowed in to form an inland arm of the Atlantic Ocean (which geologists refer to as the Champlain Sea). Subsequent rising of landforms brought the Lake elevation above sea level, and gradually, saltwater flushed out, replaced by fresh water brought in by tributaries.
 Aquatic and Terrestrial Plant Communities
Aquatic Zone: The Lake supports many native species of aquatic plants that provide shelter and cover for invertebrates and fish, and food for waterfowl.
Wetland Areas: In 1994, a Lake Champlain Basin Program Study identified 166 major wetlands, at least 50 acres or larger, with a direct hydrological connection to Lake Champlain. Wetlands have special soils and conditions that favor unique plants and animals, providing habitat for more threatened and endangered species. Many of the Lake’s shoreline wetlands have been created by fluctuating Lake levels over thousands of years. Wetlands improve water quality by filtering sediments, pollutants and nutrients. They also protect groundwater and drinking water supplies, control flooding, stabilize shorelines and prevent erosion.
These wetlands support extensive wildlife and fisheries resources. Shoreline wetlands and yearly fluctuations in water levels support the early life stages of many organisms. There are many wetland types: deep rush marshes, shallow emergent marshes, cattail marshes, lakeshore grasslands, lakeside floodplain forests, and riverine floodplain forests, to name a few. Buffer areas around wetlands are important for maintaining the functions and values of a wetland. Shoreland development and invasive species are present-day threats to Lake Champlain’s remaining wetland areas.
Upland Shores: In addition to numerous wetland types with their associated plant communities, the upland shorelines of the Lake support a diverse array of natural plant communities. The diversity of river shores, cliffs, rocky outcrops, and sand and cobble beaches – in addition to the largely calcareous bedrock and soils of the region – create a variety of natural communities high in plant diversity.
Animal Populations
Invertebrates: The diverse aquatic community of invertebrates from microscopic zooplankton to macroscopic insect larvae and mussels are an important if poorly understood part of the Lake Champlain ecosystem. All of the Lake’s invertebrates are food for a huge variety of larger animals and along with tiny plants known as phytoplankton, form the base of Lake Champlain’s food web.
Fish: Eighty-one species of fish have been identified in Lake Champlain. About twenty of these species are popular among anglers, and these include walleye, northern pike, large and smallmouth bass, brown bullhead, channel catfish, yellow perch, lake trout and landlocked salmon.
 Not much is known about the distribution of many species of non-game minnows, darters, and sculpins. Several species found in the Lake are disjunct and at the eastern extent of their range, being more abundant in the Great Lakes and St. Lawrence drainages. These include the bowfin, long-nose gar, and freshwater drum. The Lake is also home to several species listed as threatened or endangered in New York and Vermont including the lake sturgeon and the eastern sand darter.
Amphibians and Reptiles: Twenty-one species of amphibians and twenty species of reptiles have been identified in the vicinity of the Lake. Of these, many are abundant, in water, wetlands and shorelines. Some of the more commonly encountered amphibians are the green frog, northern leopard frog, gray tree frog (more often heard than seen), and red-spotted newt. More commonly encountered reptiles are the garter snake, and painted turtle.
The Lakeshore is also home, however, to several regionally rare or endangered species including the eastern spiny soft-shell turtle, the map turtle, and the striped chorus frog (which, although thought to have been recently extirpated, was rediscovered in the vicinity of Alburg). In the past decade there has been growing concern over certain frog species that show high incidence of malformations.
Birds: Located in the Atlantic flyway, a migratory corridor for waterfowl and other wetland birds, Lake Champlain and its wetlands provide critical resting and feeding sites during the spring and fall migrations. Over 30 species of waterfowl use Lake Champlain annually, including mallards and black ducks, blue winged teal, common goldeneye, common and hooded mergansers, bufflehead, and Canada geese.
 Paddlers may also see common loons, bald eagles, peregrine falcons, common and black terns, and osprey. Ring-billed and herring gulls are abundant as are double-crested cormorants, a newly arrived species which many consider a nuisance for their harmful effect on island ecology and potential for impacting portions of the Lake's fishery resources.
A frequent and beloved site is the great blue heron flying over or standing in the shallows. Black-crowned night herons are sometimes observed in riparian zones as well. When paddling, keep your eyes peeled – you may see something unusual such as a group of oldsquaw. If not, you will certainly be treated to the many beautiful, more abundant species. Shoreline corridors and islands also provide important habitat for migratory songbirds.
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