Scientists have learned more about the timing and most likely cause of major volcanic events that happened millions of years ago and changed the climate and ecosystems so much that they caused some of the worst mass extinctions in Earth’s history. Unexpectedly, the new research, which came out in the journal Science Advances, says that a slowing of the continental plate movement was the key event that made it possible for magma to rise to the surface of the Earth and cause the disasters.
Throughout Earth’s history, major volcanic eruptions known as Large Igneous Provinces (LIPs) have occurred; the largest of these have resulted in significant increases in atmospheric carbon emissions, which have warmed the Earth’s climate, caused unprecedented changes to ecosystems, and caused mass extinctions on land and in the oceans.
Using chemical information from ancient mudstone deposits found in a 1.5 km-deep borehole in Wales during the Toarcian period, an international team led by scientists from Trinity College Dublin‘s School of Natural Sciences was able to connect two important events that happened about 183 million years ago.
The research team found that this time period, which was marked by some of the most extreme climatic and environmental changes ever, directly corresponded with the occurrence of major volcanic activity and associated greenhouse gas releases in the southern hemisphere, in what is now known as southern Africa, Antarctica, and Australia.
More importantly, after more research, the team’s plate reconstruction models helped them figure out the key geological process that seemed to control the timing and start of this and other important volcanic events.
The team was led by Micha Ruhl, an assistant professor in Trinity’s School of Natural Sciences. He said,
According to new evidence, the normal rate of continental plate movement of several centimeters per year effectively prevents magma from penetrating Earth’s continental crust. Scientists have thought for a long time that mantle plumes, which are upwellings of molten volcanic rock, or magma, from deep within the Earth, were the cause of such volcanic activity.
“Magmas from mantle plumes don’t appear to be able to effectively reach the surface until the speed of continental plate movement slows down to almost zero, leading to large igneous province volcanic eruptions, associated climatic changes, and mass extinctions.”
“Most importantly, further analysis shows that a decrease in continental plate movement likely controlled the start and length of many of the most important volcanic events in Earth’s history,” the authors write. “This is a key process in determining how the climate and life on Earth’s surface have changed over time.”
Researchers can figure out the causes and effects of global carbon cycle changes by looking at past global change events like the Toarcian. They can also learn about the fundamental Earth system processes that control tipping points in the Earth’s climate system by looking at these events.
The study was carried out as part of the Early Jurassic Earth System and Timescale (JET) project of the International Continental Drilling Programme (ICDP), and it was funded by the EU Horizon 2020 program, the Natural Environment Research Council of the United Kingdom (NERC), the National Science Foundation of China, and the SFI Research Centre in Applied Geosciences (iCRAG).
