A small lake less than an hour from Canada's largest city, Toronto, is one of a handful of sites around the world that could embody humanity's entry into a new geological period: the Anthropocene. For years, geologists have been trying to establish the right spot, called the "golden spike" that best defines this new geological epoch, reflecting the significant impact of human activity on the planet. Because of its unique composition, Crawford Lake holds layers of sediment in its depths that have remained unaltered for thousands of years, mirroring the various suspended substances in the region and beyond, including human pollution. "In the 1950s, the United States started doing more atomic bomb testing", explains Paul Hamilton from the Canadian Museum of Nature. "So we started to map the amount of plutonium that's in the atmosphere, that got down in the sediment, into the core, into our small lake." IMAGES AND SOUNDBITES ARRANGED IN SEQUENCES