Vast undersea eruption contributed to Cretaceous mass extinction

New analysis identifies third major culprit in the event that wiped out three-quarters of life on Earth. Stephen Fleischfresser reports.

Twilight of the dinosaurs. Did a vast undersea magma surge seal the fate of most living creatures?
Twilight of the dinosaurs. Did a vast undersea magma surge seal the fate of most living creatures?

A new analysis might help scientists to find long-debated connections between three of the most significant global events in our planet’s history: the eruption of the Deccan Traps in India, the Chicxulub meteorite impact in Mexico, and the extinction of the dinosaurs.

The Cretaceous-Paleogene (K-Pg) mass extinction 66 million years ago wiped out three quarters of life on the planet, including most dinosaur species. Its exact cause, however, is still debated.

The most well-known idea is that an asteroid or comet impact was mostly responsible, a hypothesis first put forward in 1980 by Nobel prizewinning physicist Luis Alvarez and his geologist son, Walter. The subsequent discovery of a massive crater in Mexico’s Yucatán Peninsula strongly bolstered the idea, clearly demonstrating that an object at least 10km across struck the earth at the same time as the K-Pg extinction began.

Another key event closely tied to the extinction is the eruption of the Deccan Traps in what is now western-central India. The Deccan Traps were originally caused by one of the earth’s largest volcanic eruptions, producing a sea of basaltic lava believed to have covered over a million square kilometres.

Earlier theories held that the Deccan eruption was caused by the Chicxulub impact itself; however, we now know that the eruptions actually predate it. Furthermore, recent research has suggested another cause, although researchers do believe the seismic energy of the Chicxulub impact did effect the Deccan eruptions.

Taking this into account, Joseph Byrnes and Leif Karlstrom of the University of Oregon in the US have now put forward a hypothesis in the journal Science Advances that draws connections between these three events and indicates another.

The pair argue that if Chicxulub impact seismic energy did affect the Deccan eruptions, then other volcanic systems may have been influenced as well.

“The global mid-ocean ridge system is a clear candidate for triggering,” they state.

The system is an interconnected set of tectonic plate boundaries that run for a total of 65,000 kilometres, almost all of it under water. Even today, it remains very volcanically active.

By analysing already available marine topographic and gravitational data to look for changes in the sea floor at roughly the same time as the Chicxulub impact, Byrnes and Karlstrom were able to deduce that the seismic energy of the impact – orders of magnitude greater than even the largest earthquake – rippled out in waves and struck the global mid-ocean ridge system. These ridges, where tectonic plates meet, were pulled apart by the seismic wave to release huge volumes of magma stored beneath.

The resulting vast and global release of magma and associated gases, the authors suggest, contributed to the global environmental disaster and thus exacerbated the mass extinction event already underway.

“This massive but short-lived pulse of marine magmatism should be considered alongside the Chicxulub impact and Deccan Traps as a contributor to geochemical anomalies and environmental changes at K-Pg time,” say the authors.

Not only does this shed light on a new contributing factor in the K-Pg upheaval, but it also helps us to see more clearly the connections between these remarkable events.

Stephen fleischfresser.jpg?ixlib=rails 2.1
Stephen Fleischfresser is a lecturer at the University of Melbourne's Trinity College and holds a PhD in the History and Philosophy of Science.
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