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Crawford Lake is a small, deep body of water in central Milton, Southern Ontario. The lake is located in a conservation area within the Halton Region and is part of the Niagara Escarpment. The lake’s name derives from the Crawford family, who lived on the site prior to it being bought by the conservation authority. Its Wendat place name, “Kionywarihwaen,” also reflects its history as an Indigenous settlement. For decades, the lake has been the site of various scientific studies.
Physical Features
Crawford Lake occupies a natural sinkhole fed with underground water from its soft bedrock. This unique landscape formed over thousands of years as the last glacial period retreated. The lake is classified as "open" because its waters drain down a stream, ultimately discharging into the Lake Ontario basin. Despite its relatively small size (2.4 hectares), Crawford Lake is quite deep, reaching about 24 meters deep. It is also known as a "meromictic" lake, meaning its lower layers do not mix with the upper surface waters. This unusual feature allows sediments to accumulate undisturbed on the lakebed. While a typical meromictic lake has bottom layers lacking oxygen, Crawford Lake is a rare example where this is not the case. Its groundwater source is said to be oxygenated as it seeps out of the lake’s bedrock. This distinguishing characteristic contributes to the lake's unique ecology and preservation of its historical sediment record.
The natural area adjacent to Crawford Lake consists of a steep glacial valley and mature forest. The areas surrounding it have a protected status and are largely former farmlands. Together, these encompass the Crawford Lake Conservation Area, which Conservation Halton administers. The site is considered an environmentally sensitive area, a provincially designated area of natural and scientific interest, and part of the Niagara Escarpment, a UNESCO-recognized biosphere reserve.
Human Settlements
Various First Nations lived on the lands surrounding Crawford Lake for at least a thousand years before European settlement, and substantial village sites were unearthed as evidence. Remains of woodland structures suggested a village site that belonged to groups of Iroquoian-speaking peoples: the Wendat and the Attiwandaron (see The Neutral Confederacy). Pollen analysis of the surrounding area revealed the site to have been occupied as a seasonal hamlet circa 1300 to 1500 CE. A community of several hundred people lived next to the lake at a time. It was likely that the people of these settlements cleared the lands and cultivated corn that produced the pollen sediments preserved in Crawford Lake. Around the late 1400s, the village was likely abandoned. Indigenous peoples of this area spent significant amounts of time in the woodlands around Crawford Lake until contact with the European settlers.
By the mid-1800s, colonists became interested in the area surrounding the lake for farming and logging (see Milton). In 1883, Crawford Lake was privately owned by the Crawford family, headed by George Crawford. Ownership was transferred to his son a couple of years later. In 1898, the lake's name was changed from Little Lake to Crawford’s Lake. On the south end of the lake, the Crawford family built a lumber mill originally planned for brickmaking. The company was incorporated as Murray Crawford Limited, the namesake of George’s son, who died in 1921. They also operated a hotel.
In 1968, the government acquired Crawford’s lakeside property as a principal feature for a nature conservation program. This prompted the creation of the Crawford Lake Conservation Area shortly after.
Cultural and Scientific Significance
Crawford Lake has been the site of various scientific studies. In 1971, researchers began to analyze the protected lands centred around the lake. Botanist Dr. John H. McAndrews from the Royal Ontario Museum initiated experiments by extracting frozen core sediment samples from the lake bottom. His graduate student, Maria Boyko, later discovered well-preserved, fossilized corn pollen grains embedded in the sediment. From 1973 to 1987, excavations at the site uncovered 10 longhouses and various artifacts from the day-to-day lives of the pre-contact Indigenous peoples.
An Iroquoian village was reconstructed as a replica, built on the exact footprint of longhouse ruins dated between 1434 and 1459. In 1984, the Ontario Heritage Trust recognized this site as a provincial historic landmark by unveiling a commemorative plaque. At the time, it was noted as the most accurately dated prehistoric village in the eastern woodland region of North America. Dr. William D. Finlayson's comprehensive four-volume study, published in 1998 by what is now the Museum of Ontario Archaeology, represented the definitive scholarly work on this prehistoric village, whose inhabitants may have been ancestors of the Wendat people.
Crawford Lake is referred to as “Kionywarihwaen,” which translates to “where we have a story to tell” or “where the matter is lying down” in the Wendat language. Faithkeeper Catherine Tammaro recommended that the name be in Wendat to reflect the site’s ancestral relation and continuing heritage. In 2013, it was agreed upon by community leaders, including the women's council, elders, Conservation Halton board of directors, and scholars while visiting the site during a research project. As of July 2024, the official ceremony to change its name has not taken place yet; however, some have started referring to the site as Kionywarihwaen.
Global Marker Site
Crawford Lake was designated as a global marker site to establish the end of the present geological epoch and the start date of the proposed Anthropocene epoch. Studies of the lake revealed that the deep basin sediments were laminated, meaning there were thin layers with alternating light and dark colours reflecting the year of each deposit. By examining the detailed sediment layers, scientists learned the periodic changes in local and atmospheric chemistry. Analysis showed that the lake holds evidence of significant environmental impact, most notably nuclear fallout, industrial pollution and climate change. Sediment cores from Crawford Lake were placed in the permanent collections of the Royal Ontario Museum and the Canadian Museum of Nature.
In July 2023, an international team of scientists designated Crawford Lake as the "golden spike" — a physical reference point marking the start of the Anthropocene epoch. This new geological time scale is defined by the lasting impact of human activities on Earth's climate and environment. Many geologists believe that humans have significantly altered the planet’s climate and environment, signalling a shift from the previous geological era.
As of March 2024, an expert panel of scientists had rejected the proposed Anthropocene epoch, which would have defined the present age with a base year of around 1950 CE.
