The beginning of the modern era is marked by radioactive residues in ocean elements.

The first time researchers have provided a strong quantitative explanation for the Anthropocene period, because of the radioactive material found in marine sediments. Research in many fields considers Anthropocene a landmark for humanity’s impact on Earth’s environment.
Researchers combined records of nuclear radiation from atomic tests in sea sediments with coral skeletons to create a record of the effects on oceans. These records clearly show that the ocean environment changed before, during, or after a period worldwide of atomic testing. Researchers have identified this as the Anthropocene.

Beppu, southwest Japan’s resort city, is well-known for its beautiful beaches, historic hot springs, and traditional festivals. Professor Yusuke Yokoyama of Ehime University and head of the Beppu Bay research project, along with their colleagues, were there to learn more about the fascinating properties of the local ocean floor. While it may not sound like the beach activity you prefer, they were seeking evidence of plutonium resulting from nuclear bomb tests in the Pacific Ocean over 50 years ago.

“Beppu Bay” is one of the many locations in the Pacific with well-preserved records regarding humanity’s effects on the environment. It is located on the seafloor, and sediments have formed layers. Yokoyama explained that plutonium resulting from nuclear testing has been preserved.
“Our task, from the 1950s to 1963, when testing largely ceased, was to identify clear indicators of fallout. We took core samples of the area.

These showed clear evidence of plutonium from fallouts. We also collected coral skulls from Ishigaki (southwest of Okinawa), which contained the plutonium. Comparing sediments to corals helps us date signatures more accurately in the sediments.
Sediment examples can provide evidence for past environmental changes.

However, they are deposited so randomly that it is easy to disrupt. This is why the team had to cross-reference core with coral. Coral, like trees, grows in such a manner that each year’s growth leaves distinct rings. Both kinds of records are valuable because they capture broad environmental information and lack precision. Corals, with their growth rings, offer greater historical precision but don’t provide as much information on past environmental changes.

This led to clear evidence in Coral skeletons indicating that 1954 was the year of the fallout. Other markers in a coral found in the sediments suggested that this year could also be connected to the wider range of chemical signatures.
Yokoyama is excited to search for chemical and geological evidence of nuclear dropout.

They are part of an initiative to redefine what the modern age means. The Holocene period of history, which spans 12,000 years, is generally known. Researchers in many fields, including biology and history, have attempted to establish a new definition for the post-nuclear age. They call it the Anthropocene.
“It was difficult for us to analyze plutonium from our samples. In the period in question, 3 tons of plutonium went into the sea and the atmosphere. But those 3 tons were dispersed far, far away. Yokoyama explained that they’re looking for very small signatures.
“Nevertheless, this work was important not only to define the Anthropocene but also because the successful application of our method could also be used for improving ocean and climate model, or helping to explore past tsunamis or other geological hazards.”