A new study led by the University of Southampton has found that stretching of the continents is likely to have caused one of the most abrupt and extreme global warming events in the history of our planet, 56 million years ago. During this episode, the Earth warmed by five to eight degrees Celsius, culminating in the “Palaeocene-Eocene Thermal Maximum” (PETM) that lasted about 170,000 years and led to the extinction of many deep-sea organisms, fundamentally reshaping the course of evolution of life on Earth.
According to the experts, the extensive stretching of the continental plates in the Northern Hemisphere critically reduced the pressures in the Earth’s deep interior, driving a short-lived but intense melting in the mantle. The resulting volcanic activity coincided with – and most probably caused – the release of a massive amount of carbon dioxide in the atmosphere that exacerbated global warming.
“Despite the importance and wider relevance of the PETM to global change today, the underlying cause is highly debated,” said study lead author Thomas Gernon, an associate professor of Earth Sciences at the University of Southampton. “It’s generally agreed that a sudden and massive release of the greenhouse gas carbon from the Earth’s interior must have driven this event, yet the scale and pace of warming is very hard to explain by conventional volcanic processes.”
By using archives of rock drilled beneath the seafloor close to the edge of the Atlantic Ocean, Professor Gernon and his colleagues found evidence of an abrupt and widespread episode of volcanic activity across the North Atlantic Ocean which lasted over 200,000 years – a duration strikingly similar to that of PETM. This discovery prompted the scientists to investigate a broader expanse of the North Atlantic, including today’s Greenland and Faroe Islands. There, they found that the thick piles of lava that started to erupt before the PETM showed an unusual composition, pointing to a massive increase in melting of the Earth’s mantle.
“This finding is significant, because we know that parts of the continental mantle in this region are enriched in carbonates, a major source of carbon,” said Professor Gernon. “This rapid increase in mantle melting likely released a very large volume of carbon – certainly more than we had previously expected.”
According to the researchers, this intense volcanic activity was likely caused by the stretching by plate tectonic forces of the continental landmass uniting Greenland and Europe, with the final phase of stretching causing substantial melting in the Earth’s mantle, and leading to the release of massive amounts of carbon in the atmosphere and fast global warming.
“Such rapid events cause a fundamental reorganization of Earth’s surface environment, altering vast ecosystems,” Professor Gernon concluded.
The study is published in the journal Nature Geoscience.