New study points the finger at Deccan traps for extinction event

men 1980, American scientists Luis and Walter Alvarez published their theory about an extraterrestrial body impacting Earth, causing the mass extinction that marked the end of the Reptile Age. The discovery of the Chicxulub crater in the Gulf of Mexico, the “smoking gun” evidence in the 1990s added credence to this theory put forward by the father and his team.

Recent studies of the asteroid belt between Mars and the outer planets led scientists to deduce that the fate of the dinosaurs was sealed in the Jurassic when an impact between huge asteroids sent a huge chunk of space rock hurtling. collision. with the earth

New evidence from scientific study

Now a second team of US scientists has challenged the asteroid/meteor theory and proposed that massive volcanic eruptions in India caused the demise of the dinosaurs and around 65% of all life on Earth. New studies of the huge basaltic lava flows of western and central India, known as the Deccan Traps, indicate that the most violent and devastating eruptions date very close to the mass extinction event.

Volcanic activity on this scale would have spewed huge volumes of carbon dioxide and sulfur dioxide into the atmosphere, drastically changing the world’s climate and causing entire ecosystems to collapse.

Deccan Traps is one of the largest volcanic provinces on the planet. Basaltic lava flows that occurred around 70-65 million years ago, cover an area of ​​over 500,000 square kilometres, this is twice the size of the whole of the UK. In some parts, the basalt is more than 2 kilometers deep. Plate movements and other tectonic factors have broken up lava deposits, some scientists estimate that volcanic activity at the end of the Cretaceous deposited enough lava to cover 1,500,000 square kilometres, this would have covered half of India.

It has been accepted for some time that these huge eruptions would have had a devastating effect on Earth’s climate. In addition to the damage caused by the eruptions themselves, the smoke and ash clouds would have been enormous and would have disturbed the weather. Sulfur dioxide pumped into the air would have caused acid rain, and carbon dioxide and other gases, in addition to being toxic to life, would have caused global warming. This new study by the US team dates the most massive volcanic activity just against the KT boundary and as a result the research team has published a paper stating that it was these eruptions and not the asteroid impact that caused the destruction.

Volcanic eruptions

The main period of eruptions has been linked chronologically to the estimated date for the start of the extinction phase, during this period geologists estimate that ten times more climate-changing gases would have been released compared to the Chicxulub impact event. So it was probably volcanic activity that did for Earth’s climate, although the huge alien impact couldn’t have come at a worse time and added to the environmental chaos. As with other impacts (some scientists believe there were two such impacts, just 300,000 years apart, in very close geological time to each other, a real double whammy.

Previous dating techniques involved paleomagnetic signatures of crystals formed in the lava as it cooled. These indicated that the main eruptions occurred around 800,000 years before the geological boundary between the end of the Mesozoic and the beginning of the Cenozoic. More recent studies measuring the radioactive decay of argon and potassium isotopes in the lava deposits placed the longest period of volcanic activity within 300,000 years of the KT boundary. However, US researchers believe that evidence from small marine microfossils proves that volcanic activity is a direct cause of the mass extinction.

Mass extinction event manager

Scientists are confident that soon after the mass extinction event, one of the first signs that ecosystems began to recover was the establishment of new types of planktonic foraminifera (similar to the animals that helped form the White Cliffs of Dover). Analysis of deposits in the Bay of Bengal region of the Deccan Traps has shown that marine sediments were deposited on top of basaltic lava from the most active phase of the trap formation. In these marine deposits, evidence of foraminifera microfossils has been found, indicating that these marine deposits were deposited almost immediately after the extinction event. Therefore, it is logical to deduce that the lava deposits that immediately preceded the marine sediments must have been deposited at the time of the death of the dinosaurs and the disappearance of much of life.

The US team’s paper has already received support from a number of leading academics in Europe. It was previously presented at the annual meeting of the Denver Geological Society and has received widespread comment and review. The sheer magnitude of volcanic activity certainly played a role in climate change, but this study of microfossils places the worst of the eruptions immediately before the mass extinction, as if these eruptions triggered the extinction event.

The US team has cited a number of other studies that support their conclusions, saying their work sheds light on an anomaly that supporters of the Chicxulub impact theory have been unable to resolve. Analysis of other sites around the world along the KT boundary and of sediments deposited thousands of years after the alien impact show that life on Earth took a long time to recover. Microfossils do not enter the fossil record until 300,000 years after the asteroid/meteorite collision. The fact that the marine environment shows no signs of recovery for about 300,000 years after the impact can be explained by looking at the telltale lava deposits on marine deposits in the Bay of Bengal. These younger lava deposits were deposited after the mass extinction event, but still caused enough disruption to delay the recovery of life on Earth. According to American researchers, the last period of eruptions from the Deccan Trap occurred in the early Paleocene (Danian faunal stage) about 280,000 years after the end of the Mesozoic. It was these eruptions that caused the delay in the recovery of life forms and the construction of ecosystems.

Evidence from the fossil record

The fossil record indicates that there have been a series of mass extinction events in the history of life on Earth. It is true that the KT boundary represents a period of dramatic environmental change. The dual effect of the formation of the Deccan Traps together with asteroid impacts would explain the mass extinction, the extinction of non-avian dinosaurs, marine reptiles, pterosaurs, certain birds, ancient crocodiles and many types of invertebrates could be due to a number of factors. This is not in doubt, what remains in dispute is the contribution to the mass extinction that each of these factors played.