How did the dinosaurs become extinct?

 

SCIENTISTS have come up with evidence of how at least 70% of the dinosaur population was wiped out in a study at Yale University, in which palaeontologist Dr Laia Alegret (pictured), took part.

The researcher from the Aragón Institute of Environmental Science, part of Zaragoza University, was one of the team which has concluded that the dinosaurs were largely wiped out by an asteroid.

In a debate spanning generations, researchers have never been able to agree on whether these giant reptiles became extinct because of a volcanic eruption and the global warming that came with it, or whether they were struck by an asteroid hitting the earth.

But the Yale team believes both factors came into play – although the asteroid was the main cause of extinction.

According to the article published in Science magazine, the volcanic eruptions which led to planetary warming started before, and finished after, the asteroid incident.

It is known that, around 66 million years ago between the end of the Cretacean era and the start of the Tertiary period, an asteroid of 10 kilometres (6.25 miles) in diameter crash-landed on the Yucatán peninsula in eastern México, giving off a massive amount of gases and molten mass into the atmosphere, which caused acid rain and huge quantities of acid in the surface of the oceans – a natural disaster of which the effects went on at least for days, but possibly even for years.

This led to a sharp increase in global temperature in the decades that followed, which gave rise to a nuclear winter that went on for many years.

Meanwhile, intense volcanic activity in India was generating enormous amounts of lava and gases – a factor which was originally blamed for the dinosaurs' dying out.

Researchers in Yale, including Dr Laia Alegret, took climate registers, biotic data and information on carbon cycles obtained from sediment and fossils, and compared these with various scenarios of volcanic eruption and asteroid impact.

They then presented the most detailed reconstruction ever compiled to date on global temperature during this period, and used models to ascertain the moment, magnitude and composition of the volcanic gas emissions, comparing these with the effects of an asteroid's impact on climate and life.

Their conclusion was that the impact of the asteroid was the only event that coincided with the mass wipe-out of the dinosaurs.

With 70% of them having died out, they were now near enough extinct, but new species evolved from those remaining.

The volcanic activity in India may have contributed to the slow recovery of ecosystems following the asteroid.

Dr Alegret's extensive experience allowed her to reach these conclusions along with the rest of the team.

She has been a member of the Royal Academy of Physics, Natural and Exact Sciences since March, and in 2017, took part in the international expedition to Zealand, the 'new' continent found submerged beneath the Pacific Ocean, discovered because only its highest mountains were visible above the sea – these mountains being New Caledonia and New Zealand.

She is also due to travel to New Zealand tomorrow (Friday) to compare notes with the rest of the scientists who took part in the expedition in order to publish their findings in the next few weeks.

 

Photograph: ServiMedia