Discover a small lake with a big story as Crawford Lake: Layers in Time opens at ROM

TORONTO, September 17, 2025 – A remarkable little lake in Ontario that has intrigued archaeologists, biologists, and geologists for decades holds an extraordinary record of our impact on the planet – and a potential global marker for the start of the Anthropocene.

Crawford Lake – a uniquely significant natural site located near Milton, Ontario – reveals a comprehensive 1,000-year record of human impacts in the new ROM-original exhibition Crawford Lake: Layers in Time, opening September 27, 2025, and running until September 13, 2026.

Situated on the high plateau near the Niagara Escarpment, Crawford is a rare meromictic lake – where the water layers don’t mix – given its small size but great depths (75 feet). Study of the lakebed has led to its consideration as a site for a proposed new epoch on the geologic time scale – the Anthropocene. In 2023, Crawford Lake was selected from among other potential global sites as a "golden spike" – a physical marker definitively indicating where one epoch ends and another begins.

ROM-led research beginning in 1970 examined the lake’s sediment and led to archaeological work uncovering adjacent Indigenous villages that thrived from the late 1200s CE to around 1500 CE. Through such work, researchers have unearthed intimate details of the region’s history by examining individual layers of sediment. 

“While ROM’s involvement in the study of this unique body of water has been ongoing for more than 50 years, its recent moment in the spotlight as a potential marker of the Anthropocene starting date is a testament to the critical role – and perseverance – of museum researchers in advancing our understanding of the world," says Josh Basseches, ROM Director & CEO. "This exhibition offers a fascinating glimpse into how nature chronicles humankind’s impact on our planet – and how the decisions we make today impact future generations.”

Through the examination of varves – the annual layers of sediment deposits that, much like the rings of a tree, show the passage of time – the direct impact of human activity since the late 1200s CE can be observed in great detail. While the exhibition focuses on the timespan that records human activity, Crawford Lake’s unique lakebed sediments are so deep that researchers able to study deposits that go back thousands of years. 

Central to the exhibition is a dynamic display enabling visitors to view in fine detail the timeline represented by the layers, with key markers highlighting environmental change at the lake. Animations show how the layers formed over the years as different types of material were deposited.

“Crawford Lake’s records highlight over 30 generations of activity and illustrate how humans have altered the world – whether considering traces of plutonium isotopes scattered across the planet with the advent of nuclear weapons, or actions we have taken repeatedly over time to improve the environment,” says Dr. Soren Brothers, ROM’s Allan and Helaine Shiff Curator of Climate Change.

To give visitors a sense of what being at Crawford Lake is like, a stunning large-scale video installation showcases sweeping drone-camera views of the area through all four seasons, capturing the natural vistas and wildlife. Another video highlights researchers’ painstaking process as they extract a frozen sediment core from the bottom of the lake.

“Analysis of various plants’ pollen, brought up from the lakebed, is like looking through a microscopic window into the past,” says Deborah Metsger, ROM’s Assistant Curator, Botany, and Acting Curator, Green Plant Herbarium. “Year after year, through the annual layers of sediment, Crawford Lake shows that nature and humans are inextricably intertwined.”

The oldest clear signs of human impact around the lake are from Indigenous farming beginning in the late 1200s CE with crops containing sunflowers and corn. The exhibition includes 500-year-old grinding stones, pot fragments, and even burnt corn from the Indigenous villages near Crawford Lake, demonstrating the long history of agriculture in the area.  

The Crawford Lake Conservation Area now includes three reconstructed longhouses to help educate visitors about the area’s Indigenous history through programs, exhibits, gardens, and workshops developed with Indigenous partners in the region.

The lake sediments show that activity by the Crawford family, who moved into the area in the early 1800s and built a sawmill by the lake in 1874, produced a colour change in the sediments, aligning with a decrease in pine pollen (a tree that was initially targeted for logging), and an increase in ragweed pollen (a common ecological response to the clearing of forests).

While local conditions around the lake have changed over time, some markers that show up at Crawford Lake also occurred globally. For instance, the varve of 1945 records the detonation of the first plutonium-based nuclear bomb at Los Alamos on July 16. This event and subsequent nuclear explosions occurring up until a 1963 nuclear test ban treaty have left such a clear human signal in sediments globally that these atomic signatures are being considered as a primary marker for a potential Anthropocene epoch.

In the varves from the 1950s, further changes are noted in the composition of lake deposits – a result of rapid global increases of population, energy production, and industrialization. They show the introduction of Dutch elm disease, and also how fly ash – a byproduct of coal-burning – traces the growth of the region’s steel industry.

Many more environmental lessons were learned in subsequent decades – including reasons for optimism indicated by the very thin varves formed during the years when acid rain was a pressing environmental issue. Through concerted efforts by government and industry following public concerns, pollutants that cause acid rain and lake acidification were reduced, and the varves regained their prior thickness. 

But taking steps to care for land and water is not new – the exhibition showcases a replica Dish with One Spoon wampum belt made by Ken Maracle from Six Nations of the Grand River, which represents environmental stewardship, diplomacy, and warnings against greed. The belt, representing a treaty associated with the Great Peace of Montreal in 1701, is a reminder to care for each other and future generations by keeping the land and waters clean, only taking what is needed, and never depleting our resources. 

Recently, Crawford Lake has been central to the discussion over whether the Anthropocene should be formally recognized as a geological epoch – and if a date could be determined for its start. A new epoch would mark the end of the Holocene, which began with the end of the last ice age 11,700 years ago.

In 2023, Crawford Lake was put forth as the site – out of a shortlist of 12 global locations – with the clearest record to mark the beginning of the Anthropocene. That this vaunted location happens to be in the Greater Toronto Area may come as a surprise, but research into Crawford Lake goes back to 1970, when ROM curator Jock McAndrews requested permission from Conservation Halton to take sediment cores from the lake for his research on the history of Ontario’s forests and climate.

The submission that proposed Crawford Lake as a site to mark the start of the Anthropocene was led by Brock University Earth Sciences professor Dr. Francine McCarthy (a former student of ROM’s McAndrews), along with a team of researchers from ROM, Brock University, the Canadian Museum of Nature, Carleton University, Queen’s University, Conservation Halton, and others. Two core samples taken as part of this research have been kept frozen to preserve the scientific data – one housed at ROM and the other at the Canadian Museum of Nature.

Although an Anthropocene epoch has not been formally accepted by the International Commission on Stratigraphy, the term is already commonly used to describe the profound changes humans have made – and continue to make – to our planet. Crawford Lake: Layers in Time is a compelling look at the record of human life on Earth as told through one small but significant lake.
 

This exhibition is generously supported by the Royal Exhibitions Circle with additional support from ROM’s Women's Initiative.

Image Credit: Crawford Lake © ROM