Welcome to plastic age - pollution left behind in fossil record
Deposits of plastic double every 15 years
Plastic pollution is now in the fossil record - a discovery that may mean this period becomes known as the plastic age, scientists say.
Deposits of plastic have increased exponentially since the end of World War II, doubling around every 15 years, the researchers said after combing through 200 years of sediment in California's Santa Barbara Basin.
"We all learn in school about the Stone Age, the Bronze Age and Iron Age - is this going to be known as the plastic age?" asked lead author Jennifer Brandon, from the Scripps Institution of Oceanography at the University of California San Diego.
"It is a scary thing that this is what our generations will be remembered for."
Most plastics were invented in the 1920s, but it was not until after World War II that they were used widely.
Scientists found microplastics - most of which were from clothing fibres - in reasonable quantities in all layers of the core after 1945.
"Our love of plastic is actually being left behind in our fossil record," Dr Brandon told 'The Guardian'. "This study shows that our plastic production is being almost perfectly copied in our sedimentary record."
Scientists found that by 2010, people were depositing 10 times as much plastic in the basin as they were before World War II.
The post-war period also showed an increase in the diversity of plastics - including plastic bag materials and plastic particles, as well as fibres. The study, published in 'Science Advances', is the first to look at the accumulation of plastic in one location.
Researchers chose to study Santa Barbara Basin because the waters are still and there is a near total absence of oxygen, helping to preserve sedimentary layers.
Each 5mm of sediment translates to two years of history and scientists were able to sample sediments dated back to 1843.
Previous research by Scripps found microplastics at depths of up to 1,000 metres off Monterey in California. In April, an explorer visited the Mariana Trench in the western Pacific Ocean - the deepest natural trench in the world - and found plastic bags.
Scientists estimate that between 4.8 million and 12.7 million tonnes of plastic waste enter the ocean every year.
"Our results demonstrate that such an increase is now detectable not only in surface ocean water but also in a benthic ecosystem [the lowest level of a body of water], as recorded in the sedimentary record," researchers wrote in the paper.
Scientists say they "predict that this growing rate of plastic deposition will continue to increase in the future, barring marked changes in policy or waste management".
Earlier this year, scientists from the Marine Biological Association and the University of Plymouth found there had been a "significant increase" in larger plastic items found in the ocean from 1957 to 2016.
Plastic objects such as bags, rope and netting were among those retrieved from oceans. This rubbish already causes more than €11bn in economic damage to marine systems each year.
If these trends continue, marine plastic is set to outweigh fish by 2050.