Crawford Lake | |
---|---|
Kionywarihwaen (Wyandot) | |
Location | Regional Municipality of Halton, Ontario |
Coordinates | 43°28′05″N79°56′55″W / 43.46806°N 79.94861°W [1] |
Type | Meromictic |
Primary inflows | Unnamed creek |
Basin countries | Canada |
Max. length | 270 m (886 ft) |
Max. width | 130 m (427 ft) |
Surface area | 2.4 ha (5.9 acres) |
Max. depth | 22.5 m (74 ft) |
Surface elevation | 286 m (938 ft) [2] |
Crawford Lake (Wyandot : Kionywarihwaen [3] [4] ) is a lake near the community of Campbellville, in the town of Milton, Regional Municipality of Halton, Ontario, Canada. [1] [5] It is located within Crawford Lake Conservation Area, a Regionally Environmentally Sensitive Area, an Ontario Area of Natural and Scientific Interest, and part of the Niagara Escarpment World Biosphere Reserve. [6]
The primary inflow to the lake is an unnamed creek.
Crawford Lake is meromictic, [6] which means it has sequentially deposited seasonal sediment laminations called varves at the bottom; these allow for accurate dating of sediment cores and make Crawford Lake a prime site for archeological and geochemical studies.
Using pollen analysis of the lake, reconstruction of the history of the area over several hundred years was possible. The analysis revealed the agricultural history of the native Iroquoians and a pre-European contact village, through the presence of corn and squash pollen motes. [7] The Wendat-Huron village has been reconstructed in the conservation area based on many years of work by archaeologists, historical references, and First Nations oral traditions.
Further analysis revealed evidence of European colonists through sawdust and ragweed pollen from the construction of nearby settlements. [7]
Crawford Lake developed over thousands of years ago in Southern Ontario as water filled in a limestone cliff sinkhole. [3] Due to its meromictic attributes, the lake is separated into two layers: its upper layer is mixed with external factors such as wind, and its bottom layer is undisturbed, leading to sediment accumulating at its bottom. [3] When temperatures and acidity are high during summers, the water produces calcite that forms a white layer over the lake bed's sediment layer. [3]
Stratigraphic evidence using charcoal analysis of Crawford Lake's sediments showed a record of increased charcoal accumulation, when pollen analysis showed a change between northern hardwoods to a white pine and oak forest. [8]
In 2009, the Anthropocene Working Group of the Sub-commission on Quaternary Stratigraphy began debating on a candidate for the Anthropocene Global Boundary Stratotype Section and Point (GSSP), where the area had to preserve, in good condition, changes of human impacts on the environment. [3] [9]
Geochemical analysis of sediment cores has allowed for the reconstruction of the environmental history (e.g. human impact, pollution) of the area. This analysis has revealed the trends and sources of air pollution over approximately 150 years. [10] The well-distinguished stratigraphy led to the lake becoming a candidate for determining the start date of the proposed Anthropocene epoch, with a base date at 1950 CE. [3] [11] [12]
Crawford Lake was chosen in July 2023 to represent the "key site that shows we're in a new climate epoch". [13] The lake has been described as the "golden spike" showing the global human impact on earth. [14] The first age of the Anthropocene could be named the "Crawfordian," after the lake. [11]
The Anthropocene was a rejected proposal for a geological epoch following the Holocene, dating from the commencement of significant human impact on Earth up to the present day. This impact affects Earth's oceans, geology, geomorphology, landscape, limnology, hydrology, ecosystems and climate. The effects of human activities on Earth can be seen for example in biodiversity loss and climate change. Various start dates for the Anthropocene have been proposed, ranging from the beginning of the Neolithic Revolution, to as recently as the 1960s. The biologist Eugene F. Stoermer is credited with first coining and using the term anthropocene informally in the 1980s; Paul J. Crutzen re-invented and popularized the term. However, in 2024 the International Commission on Stratigraphy (ICS) and the International Union of Geological Sciences (IUGS) rejected the Anthropocene Epoch proposal for inclusion in the Geologic Time Scale sparking significant disagreement from scientists working in the field.
The Oak Ridges Moraine is an ecologically important geological landform in the Mixedwood Plains of south-central Ontario, Canada. The moraine covers a geographic area of 1,900 square kilometres (730 sq mi) between Caledon and Rice Lake, near Peterborough. One of the most significant landforms in southern Ontario, the moraine gets its name from the rolling hills and river valleys extending 160 km (99 mi) east from the Niagara Escarpment to Rice Lake, formed 12,000 years ago by advancing and retreating glaciers during the last glaciation period. Below the approximately 200 metre thick glacial derived sediments of the moraine lies thick bedrock successions of Precambrian rocks and up to 200 metres of Ordovician aged rock, capped by a regional unconformity of erosion and non-deposition to the Quaternary period. Rivers and lakes scatter the landscape and are important for creating habitat for the rich diversity of species of animals, trees and shrubbery. These are also the supply of fresh water to aquifers in the moraine through complex subterranean connections. Construction development nearby, and with expansion of communities around the moraine in need of potable water, it is a contested site in Ontario, since it stands in the path of major urban development. Conservation of the moraine is thus an important step for keeping aquifers in a safe drinkable condition while also protecting the natural ecosystems surrounding and within the moraine. This region has been subject to multiple decades of scientific research to study the origins of formation, and how early communities used the land. A larger focus currently is how to source potable water without removing the aquifer entirely.
The Sudbury Basin, also known as Sudbury Structure or the Sudbury Nickel Irruptive, is a major geological structure in Ontario, Canada. It is the third-largest known impact structure on Earth, as well as one of the oldest. The structure, the eroded remnant of an impact crater, was formed by the impact of an asteroid 1.849 billion years ago in the Paleoproterozoic era.
A meromictic lake is a lake which has layers of water that do not intermix. In ordinary, holomictic lakes, at least once each year, there is a physical mixing of the surface and the deep waters.
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 has a "masterpiece" golf course designed by Robert Trent Jones very early in his career. Green Lake itself 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.
Round Lake National Natural Landmark lies within Green Lakes State Park, which lies a few miles east of the city of Syracuse, New York and adjoining the village of Fayetteville. Round Lake itself and the adjoining 59 acres (24 ha) of old-growth forest were designated a National Natural Landmark in 1973 by the U.S. Department of the Interior. Hubert W. Vogelmann, a professor of botany at the University of Vermont, wrote the evaluation to the National Park Service that concurred with the recommendation of National Natural Landmark status for the region around Round Lake. Vogelmann's evaluation noted the "outstanding virgin mesophytic forest" adjoining Round Lake on its southwestern side; this text became part of the citation when the landmark was created. Vogelmann also noted Round Lake's importance as an extremely rare, "meromictic" lake. It shares this distinction with Green Lake, which lies a few hundred meters to the east.
Lake Fidler is a meromictic lake beside the Gordon River in the Tasmanian Wilderness World Heritage Site area of the west coast of Tasmania, Australia. The lake has a layer of fresh water overlying an anoxic salt water layer. The meromictic lakes and ponds of the Gordon River were discovered by D. A. Hodgson and Professor Peter Tyler.
Crawford Lake Conservation Area is a conservation area owned and operated by Conservation Halton near the community of Campbellville in Milton, Halton, Ontario, Canada. It is categorized as a regional environmentally sensitive area, an Ontario Area of Natural and Scientific Interest, and part of the Niagara Escarpment world biosphere reserve. The conservation area contains Crawford Lake, a reconstructed Iroquoian village, and several hiking trails.
Conservation Halton, also known as the Halton Region Conservation Authority, is a conservation authority established under the Conservation Authorities Act of Ontario. It forms a partnership with the Province of Ontario, the Ministry of Natural Resources and the regional municipalities of Halton, Peel, The County of Wellington, and surrounding municipalities.
Tephrochronology is a geochronological technique that uses discrete layers of tephra—volcanic ash from a single eruption—to create a chronological framework in which paleoenvironmental or archaeological records can be placed. Such an established event provides a "tephra horizon". The premise of the technique is that each volcanic event produces ash with a unique chemical "fingerprint" that allows the deposit to be identified across the area affected by fallout. Thus, once the volcanic event has been independently dated, the tephra horizon will act as time marker. It is a variant of the basic geological technique of stratigraphy.
Paleolimnology is a scientific sub-discipline closely related to both limnology and paleoecology. Paleolimnological studies focus on reconstructing the past environments of inland waters using the geologic record, especially with regard to events such as climatic change, eutrophication, acidification, and internal ontogenic processes.
Rattlesnake Point is an eco-tourism area located in Milton, Ontario, Canada and is owned and operated by Conservation Halton. Spanning roughly one hundred square kilometres across and near the Niagara Escarpment in Halton Region, the Rattlesnake Point area is home to many golf courses, country markets and equestrian training and boarding facilities. It is a popular scouting area.
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Crawford Lake Conservation Area is in Halton, Ontario, Canada.
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