Earth’s history has been marked by huge volcanic eruptions, some of which produced such climatic and biological upheaval that they drove some of the planet’s most catastrophic extinction events.
Now, scientists have shed new insight on the timing and probable cause of these occurrences that took place millions of years ago.
A recent study from Trinity College Dublin finds that a slowing of continental plate movement was the crucial factor that allowed magma to climb to the top of the Earth and cause terrible knock-on effects.
Chemical data from ancient mudstone deposits extracted from a mile-deep Welsh borehole led to the astonishing discovery.
Dr. Micha Ruhl of Trinity College Dublin, the study’s principal author, stated, “Scientists have long believed that the commencement of upwelling of molten volcanic rock, or magma, from deep within the Earth’s interior, as mantle plumes, was the cause of such volcanic activity.”
‘However, fresh evidence demonstrates that the normal rate of continental plate movement, several centimeters per year, successfully prevents magma from accessing the continental crust of the Earth.
Magmas from mantle plumes can only effectively reach the surface when continental plate movement slows to near zero, generating significant big igneous province volcanic eruptions and their associated climate perturbations and catastrophic extinctions.
Large Igneous Provinces are the locations of the world’s largest volcanoes (LIPs).
These include the Siberian Traps in Russia, which cover more than 1,000,000 square miles and were the site of epic volcanic activity for about a million years.
The largest eruptions have led to significant increases in atmospheric carbon emissions, which have warmed the planet’s climate, triggered dramatic changes in ecosystems, and caused mass extinctions on land and in the seas.
The worldwide team was able to correlate two significant occurrences that occurred during the Toarcian epoch, around 183 million years ago, in their study.
This historical period was characterized by some of the most severe meteorological and environmental shifts ever recorded, which precisely coincided with the occurrence of significant volcanic activity and the subsequent release of greenhouse gases in the southern hemisphere.
Computer models of reconstruction revealed that the slowing of continental plate movement was the primary geological process that appeared to regulate the time and beginning of this and subsequent major volcanic events.
Dr. Ruhl stated that a reduction in continental plate movement likely controlled the onset and duration of many of the major volcanic events throughout Earth’s history, making it a fundamental process in determining the evolution of climate and life on Earth’s surface throughout the planet’s history.
In the past 600 million years, there have been five significant mass extinctions. Some are well-studied, while others are more mysterious.
Near the end of the Ordovician Period (about 445 million years ago), the Devonian Period (from 385 to 355 million years ago), and the Permian Period, the first three mass extinctions occurred (252 million years ago).
The most catastrophic of these occurrences was the end of the Permian epoch, which wiped out around 96% of all marine life and approximately 70% of all known species on Earth.
Never-before-seen volcanic eruptions occurred on an unprecedented scale, with other repercussions including a runaway greenhouse effect caused by the release of methane from clathrates on the seafloor. Recovery lasted around 10 million years.
Approximately a third of marine species became extinct during the end of the Triassic, approximately 201 million years ago, as a result of an extinction event. Some species of reptiles also became extinct on land.
The last great extinction occurred 66 million years ago when a city-sized asteroid struck the Gulf of Mexico. It eradicated the dinosaurs.
The work assists in disentangling the various processes that regulate the global carbon cycle and climate system tipping points.
It may have repercussions for the present, as a sixth mass extinction is already believed to be occurring because of human-caused global warming.
