It's for the plastic fragments embedded in the rocks discovered in Hawaii, for the coal dust dating back to the 19th century and buried in the deep layers of the North Pole glaciers, it's mainly for the radioactive elements released into the atmosphere at the time of the nuclear tests. The fact is that the Planet Earth has entered in a new geological era invented by human: the Anthropocene.
A scientific discovery that was announced during the 35th International Geological Congress held in Cape Town, South Africa, where a team of 34 experts from around the world announced, almost unanimously (except the abstention of one member), that our Planet has entered in the Anthropocene era, the modern age marked in all respects by the impact of man on our planet. The term Anthropocene comes from Antropos which in greek means 'man', was coined in the eighties by biologist Eugene Stoermer and adopted in 2000 by the Nobel Prize in chemistry Paul Crutzen to indicate the impact that man has on the balance of Planet, but only recently, international geologists organizations are considering the adoption of the term for a new geological epoch.
The proposal of the scientists will now have to pass the scrutiny of the International Union of Geological Sciences to become official, but there are various factors that have made this choice favorable: the higher land temperatures, the rising sea levels, the ashes from fossil fuel, plastic waste, a heavy increase in erosion of the rocks, the extinction of several animal species scattered throughout the world and the atomic waste released into the atmosphere from military experiments have affected the rock structure of the Earth and such a radical change deserves a new name. As regards the dividing line between the end of the Holocene (the geological era started 11,700 years ago and in which we still believed to be) and the beginning of the Anthropocene, geologists agree that is to track in the middle of the 20th century with the dispersion of radioactive elements due to the first nuclear tests, the plastic pollution, the cement proliferation and many other traces, not properly positive, left by the past generations.