Scientists have shed new light on the timing and probable cause of major volcanic events that occurred millions of years ago and caused such climatic and biological upheavals that they triggered some of the extinction events the most devastating in the history of the Earth.
Surprisingly, the new research, published today in the journal Scientists progresssuggests that a slowdown in continental plate motion was the critical event that allowed magma to rise to the Earth’s surface and produce devastating impacts.
Earth’s history has been marked by major volcanic events, called Large Igneous Provinces (LIPs) – the largest of which have caused large increases in atmospheric carbon emissions that have warmed Earth’s climate, driven changes without precedent in ecosystems and led to mass extinctions on land and in the oceans.
Using chemical data from ancient mudstone deposits obtained from a 1.5 km deep borehole in Wales, an international team led by scientists from the School of Natural Sciences at Trinity College Dublin has was able to connect two key events from around 183 million years ago (the Toarcian period). .
The team found that this period, which was characterized by some of the most severe climatic and environmental changes ever, directly coincided with the onset of major volcanic activity and the release of greenhouse gases. associated in the southern hemisphere, in what is now called southern Africa. , Antarctica and Australia.
Upon further investigation – and more importantly – the team’s plate reconstruction models helped them uncover the key fundamental geological process that appeared to control the timing and onset of this and other large-scale volcanic events. .
Micha Ruhl, assistant professor at the Trinity School of Natural Sciences, led the team. He said:
“Scientists have long believed that the onset of rising molten volcanic rock, or magma, from deep within the Earth’s interior, in the form of mantle plumes, was the instigator of such volcanic activity, but the new evidence shows that the normal rate of continental plate movement of several centimeters per year effectively prevents magma from entering the Earth’s continental crust.
“It appears that only when the speed of continental plate motion slows to near zero can magmas from mantle plumes actually rise to the surface causing major volcanic eruptions in large igneous provinces and their climatic disturbances. and associated mass extinctions.
“Essentially, further assessment shows that a reduction in continental plate motion likely controlled the onset and duration of many major volcanic events throughout Earth’s history, making it a fundamental process in the control of the evolution of the Earth’s climate and life on the surface throughout the history of this planet.”
Studying past global change events, such as in the Toarcian, allows scientists to disentangle the various processes that control the causes and consequences of global carbon cycle change and to constrain the fundamental Earth system processes that control points shift in the Earth’s climate system.
The research was carried out as part of the International Continental Drilling Program (ICDP) Early Jurassic Earth System and Timescale (JET) project and financially supported by the SFI Research Center in Applied Geosciences (iCRAG), the Natural Environment Research Council UK ( NERC), the National Science Foundation China and the EU Horizon 2020 program.