Evidence links Cretaceous Mass Extinction to Deccan Traps Eruptions

Disastrous amounts of sulphur dioxide pumped high into the Earth’s atmosphere by the enormous volcanic eruptions taking place in what was to become western India led to the Cretaceous mass extinction according to new research.

New evidence from a team of geologists studying the basaltic lava flows of the region known as the Deccan Traps, suggests that the millions and millions of tonnes of sulphur dioxide thrown up into the atmosphere as a result of huge volcanic eruptions led to dramatic climate change.

Discharging of hundreds to thousands of teragrammes* of sulphur dioxide per year, would have led to global climatic cooling, seriously damaging ecosystems and leading to the collapse of food chains and mass extinction.

Teragrammes* – a measure of weight equivalent to 1 million metric tonnes

The research team has speculated that this was the real cause behind the death of the dinosaurs, marine reptiles, pterosaurs and a number of other animal and plant families 65 million years ago.  The meteor/asteroid impact (Chicxulub) in the Yucatan peninsula in the Gulf of Mexico may have played only a secondary role in the mass extinction event.  Ironically, the strata within the Yucatan region are heavily laden with sulphur, a huge impact such as the Chicxulub event would probably have thrown vast amounts of sulphur dioxide into the atmosphere, contributing to this “overdose of sulphur” and consequent environmental instability.

To read more about the Deccan Traps: Blame the Deccan Traps

Research team member, geologist Stephen Self of the Open University (United Kingdom), commenting on the mass release of poisonous gases due to the volcanic activity stated:

“A semi-persistent gas release of hundreds to thousands of teragrammes of (sulphur dioxide) per year can be envisaged for each Deccan eruption.  There’s plenty of it, and it would be pumped into the atmosphere.”

Yet today, with all the research into global climate change, scientists have little knowledge regarding the behaviour of sulphur dioxide in the Earth’s atmosphere.  Whilst carbon dioxide (one of the main so called greenhouse gases); tends to persist for many years, acting as a climate blanket warming the Earth, sulphur dioxide in massive amounts may behave differently.  The sulphureous gas could reflect sunlight back into space, this would lead to global cooling.  Sulphur compounds tend to be less persistent than carbon compounds in an atmosphere so the effect would not have been sustained.

An additional problem caused by the excessive amounts of sulphur in the atmosphere could be acid rain.  The sulphur particles would combine with moisture in the atmosphere and fall back down to earth as dilute sulphuric acid.  This would have had a devastating effect on vegetation which could have led to the collapse of terrestrial food chains.  Acid rain falling on the oceans could have acidified the seas, leading to the collapse of coral based ecosystems and other calciferous based life forms such as zoo-plankton populations and shelled animals such as the Ammonites.  In this way, the ecosystems in the oceans would also have been seriously disrupted.

The largest of the Deccan Traps volcano’s spewed basalt lava east across the continent and into the sea. The volcanic activity at the end of the Cretaceous was extremely intense.  To gain an idea of the strength of the massive volcano, the 1991 Mount Pinatubo volcano on the Philippines was 1000 times less powerful commented Self.

To read more about the Chicxulub impact: Geologists get to the Bottom of the Chicxulub Crater

More information about Chicxulub: End of Dinosaurs set in Motion by Asteroid Collision in Mid Jurassic

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