The Mesozoic era ended 66 million years ago with a mass extinction event that eliminated all the dinosaurs except birds. Along with them went some marine reptiles such as the ‘mosasaurs’, ‘ichthyosaurs’, and ‘plesiosaurs’, as well as all the flying reptiles known as ‘pterosaurs’.
In 1980, a team lead by the Nobel Prize-winning physicist Luis Alvarez and his Walter Alvarez discovered that the sedimentary layer found all over that the Cretaceous-Palaeozne boundary contain concentration on Iridium, a hundred times higher than normal.
Iridium is highly dense and has an affinity for Iron, thus into the Earth’s core while the Earth was still molten. The team suggested the Alvarez Hypothesis proposing the mass extinction was caused by a large asteroid hitting the Earth.
The size of the asteroid was at least 10km wide. Such large was the impact that would have released approximately 100 million megatons of energy which is about 2 million times greater than the most powerful thermonuclear bomb ever tested. The Chicxulub crater formed due to the impact of the asteroid has a diameter of 150 km, is located offshore near the Chicxulub tow, Mexico.
Around the same time, a large volcanic eruption occurred in southern India releasing 200,000 cubic miles lava and climate-altering gases into the atmosphere. Two of the five biggest mass extinctions were caused due to severe warming from volcanic carbon dioxide, including The Permian-Triassic mass extinction, 252 million years ago, caused due to the ancient eruptions in Siberia wiped out 96 per cent of marine life and about three of every four species on land.
Researchers have long wondered as to did the asteroid wipe out the dinosaurs or the volcanic eruption that caused the Deccan Traps in southern India also contributed to the devastation of life?
The Deccan Traps could have impacted lives on Earth 66 million years ago, in two major ways. On a shorter timescale, the sulphur dioxide released from the eruption could have cooled the planet and encouraged acid rain. Over time, the carbon dioxide released would have led to steady warming, imbalanced the ecosystem.
In the new study, Alessandro Chiarenza (researched while studying PhD in Imperial College, London) and his colleague Alexander Farnsworth, a climatologist at the University of Bristol, built computer models to recreate Earth’s ancient climate. They ran 14 different catastrophic scenarios, that included asteroid and volcanic eruptions, and both the events combined.
These simulations revealed that perhaps the asteroid alone made the Earth’s atmosphere inhabitable for all dinosaurs. The volcanic eruptions of the Deccan Traps counter intuitively made Earth sustainable for lives.
“The relative roles of these two potential kill mechanisms on the timing and magnitude of the extinction have been fiercely debated for decades,” the study said.
“Could it (the volcanic activity) have played a smaller role by making it harder for dinosaurs to thrive prior to the asteroid impact? No, we show that Deccan Traps activity, if anything, might have buffered the ‘negative effects’ of the impact on climate, potentially boosting the recovery after the extinction event,” Chiarenza said.
All the models showed that the Deccan eruption could not have alone caused the elimination of the dinosaurs. The asteroid impact scenarios were horrific too. In some, average land temperatures dropped from more than 68°F (20°C) to below zero, and precipitation declined by between 85 per cent and 95 per cent. When the virtual Chicxulub impact dimmed sunlight by 15 per cent or more, no habitat anywhere on Earth could support non-avian dinosaurs.