The seemingly tiny lake crawford, on the outskirts of Toronto (Canada), is unusual. Locals usually go dog walking and eat their famous maple syrup pancakes, but it’s not a special place because of that. The lake seems small, barely 250 meters from end to end, but it hides an extraordinary depth of 24 meters. This is what is technically called a meromictic lake: its surface waters do not mix with those of its bottom, which remains…

The seemingly tiny lake crawford, on the outskirts of Toronto (Canada), is unusual. Locals usually go dog walking and eat their famous maple syrup pancakes, but it’s not a special place because of that. The lake seems small, barely 250 meters from end to end, but it hides an extraordinary depth of 24 meters. This is technically called a meromictic lake: its surface waters do not mix with those of its bottom, which has remained untouched for centuries. Sediment from the atmosphere builds up on the bed every year like layers of lasagna. An international team of scientists announced Tuesday that Crawford Lake is the place in the world where the beginning, around 1950, of a new potential geological epoch is best appreciated: the Anthropocene.

the geologist Francine McCarthy shows a photo of a sediment sample taken from the depths of the lake. It’s a vertical sample of barely 90 centimeters, but it tells the story of the Crawfords since the 13th century, year after year. It is very easy to identify the passage of time. In winter, the lake freezes and dark organic matter settles to the bottom. In summer, the calcium and carbonates dissolved in the water, coming from the limestone rocks of the region, crystallize under the effect of the heat and form a white layer of calcite on the bed. This succession of light and dark lines is a perfect timeline, an underwater history book that shows that in 1950 human impact began to transform everything. This is the so-called Great Acceleration, the time when testing with atomic bombs, the massive burning of coal and oil, and the disappearance of species began to leave a very obvious imprint on the skin of the planet.

Humanity officially lives in the Holocene, a geological epoch that began more than 10,000 years ago, after the last ice age. the dutch chemist paul crutzen, winner of the Nobel Prize in Chemistry for illuminating the destruction of atmospheric ozone, and American biologist Eugene Stoermer suggested in the year 2000 that the impact of human beings on the planet had brought about a new era: l ‘Anthropocene. The idea has since caught on, but the certifying body, the International Union of Geological Sciences, has yet to make a decision. A team of experts, the Anthropocene Working Group, has been investigating since 2009 to find out if humanity has indeed changed eras. In 2016, these researchers proclaimed that the Anthropocene is a geological reality. This Tuesday, the leader of the group, the British geologist Hake Watersannounced in a congress in Lille (France) that Crawford Lake is the best model to observe the beginning of this disturbing era, characterized by human contamination.

The scientific community, through the International Commission on Stratigraphy, chooses reference points which mark the beginning of new geological stages. The beginning of the Holocene is officially represented by an ice cream carrot obtained in 2003, at nearly 1,500 meters deep, in Greenland. This frozen sample, kept at the University of Copenhagen (Denmark), reveals a rapid warming of the climate, associated with a modification of certain chemical elements. The reference points of seven geological stages are found in Spain. In the city of Fuentelsaz (Guadalajara), for example, we identify better than anywhere the beginning of the Middle Jurassic, about 175 million years ago. On the coast of Zumaia (Guipúzcoa) there are two official boundaries between Paleocene stages. All these points are marked with golden nails, which are installed during solemn ceremonies.

Nail dozen places vied for the golden highlight of the Anthropocene, including the remote lake of Sihailongwanlocated in the crater of a Chinese volcano, and the sea mud of Japanese beppu berry, which reached the final votes. “Lake Crawford is where the start of the Anthropocene is best recorded today,” says the geologist Alejandro Cearreta, the only Spanish member of the international working group. “The best indicator is plutonium-239. All the sediments after 1950 contain plutonium, either in the park next to your house or at Crawford Lake”, details Cearreta, professor of paleontology at the University of the Basque Country.

The geological authorities are in no hurry to decree the official beginning of a new era. Cearreta explains the complex protocol, which can take years. The Anthropocene Working Group will submit its final proposal, including Crawford Lake, in the coming weeks. The Quaternary Stratigraphy Sub-Committee will study the findings and, if they agree, pass them on to the next level: the International Commission on Stratigraphy. If at least 60% of its members vote in favor of the proclamation of the beginning of the Anthropocene, the decision will still have to be ratified by the International Union of Geological Sciences. “The process can be truncated at any time,” warns Cearreta.

The Royal Spanish Academy, anticipating the discussion among specialists, already includes the end of the Holocene And the start of the Anthropocene in the Language Dictionary. The College of Geologists harshly rejected it. “The Royal Spanish Academy has always been a serious institution, which has worked with scientific methodology. This foray into geology, no doubt guided by ideological interests, is frankly discouraging.” announced May 30 the College, chaired by the geologist Manuel Regueiro. Some experts, like the Americans Lucy Edwards and Stanley Finneyargue that it is too early to detect human impact on geological strata and believe that there is political pressure to declare the start of the Anthropocene.

Canadian geologist Francine McCarthy she is confident that Crawford Lake will help convince the doubters. His team inserts a “finger of ice” into the bottom, a frozen artifact, with liquid nitrogen near 200 degrees below zero inside, to which the sediment sticks. In these leaves the influence of human beings is evident. Layers from the late 13th century already contain corn pollen, confirming the presence of indigenous tribes in the area. The thickest white line corresponds to the year 1935, the hottest summer of the so-called dust bowl [cuenco de polvo, en inglés], a period characterized by drought and sandstorms caused by deforestation. And from 1950 the radioactivity of atomic bombs and contaminants from the combustion of coal and oil are confirmed. These are irreversible and detectable changes everywhere, as argued by the Anthropocene Working Group. “Each time we extract a core of ice from the bottom of this unique lake, it is like witnessing a birth: they are all beautiful when they first emerge. Knowing that they can reveal so much information to us relevant is overwhelming,” says McCarthy.

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