A huge volcano, and not an asteroid, could kill the dinosaurs

The Deccan Traps - also called the Deccan stairs -, a place in India where there was great volcanic activity in the past, could hold the key to extinction.


Strata formed by lava flows on which the research has been carried out. COURTNEY SPRAIN

They find the best preserved fragments of the asteroid world that killed dinosaurs

Two opposing positions relate the great extinctions of the Cretaceous with extreme climatic phenomena of different origin

The Deccan Traps - also called the Deccan stairs -, a place in India where there was great volcanic activity in the past, could hold the key to the extinction of dinosaurs . It all depends on when they were formed and if they did it before the asteroid of Chicxulub, Mexico, hit Earth. To it is attributed, to date, the massive disappearance of Cretaceous species. Of previous and having a devastating effect on the climate of the planet, everything would point out that terrestrial life succumbed sooner than previously thought and for other reasons.

Was it because of a volcano or an asteroid? The debate has been on the table of scientists for 15 years. But, this Thursday, it has reopened with the publication in the Science magazine of two studies on the dating of these geological formations of the center west of India. It is the largest volcanic area on Earth , it covers 500,000 square kilometers and has a thickness of 2,000 meters.

The results of the two studies lead to completely contrary conclusions, so the controversy is served, since both investigations are totally valid . The difference between them is in the degree of error of each method used. When it comes to events that happened so long ago, the inaccuracy of the techniques is measured in thousands or millions of years, so the uncertainty is high.

One of the works has been directed by Blair Schoene, a researcher at Princeton University, USA. He and his team have used the Uranium-Lead dating method (U-Pb). They went to the area and collected samples of lava and volcanic ash layers containing zirconium (a common mineral when magma cools). They measured the decay of uranium and its transformation into lead. Thus they calculated the age at which zirconium was formed upon cooling and crystallization. It is a precise technique, but it is wrong in ± 40,000 years.

The results of the Schoene group indicate that in the Deccan Traps there were four volcanic periods of great magnitude. They lasted about 100,000 years and occurred tens of thousands of years before the Chicxulub crater originated. They suggest that volcanic activity released enormous amounts of magma and greenhouse gases into the environment capable of transforming the planet's climate. These emissions could have caused massive extinctions long before the impact of the asteroid.

"Given that our U-Pb data are significantly more accurate, we can place the record of the eruption with more confidence and argue that one of the large eruptions began before the impact of Chicxulub," Blair Schoene told EL MUNDO.

The other study is led by geoscientist Courtney Sprain of the University of Liverpool and geologist Paul Renne, director of the Geochronology Center at the University of California, Berkeley. The dating technique they have used is that of argon-argon (40Ar / 39Ar). What they have measured is the gas released by the samples after irradiating them and the proportion that is established between the radiogenic argon (40Ar) and the argon produced by neutron flux (39Ar).

According to his analyzes, the eruption of more than 75% of the lava of Deccan occurred 600,000 years after the mass extinction of the Cretaceous-Paleogene. For this research group, magmatism did not have a leading role in that event.

Experts explain the differences

The technique of (40Ar / 39Ar) is less precise. However, it does not have some of the limitations of U-Pb dating. "In fact, the two methods are very reliable, in the case of Ar / Ar there may be gas loss, but the analytical method used allows us to know the quality of the sample and discard those that lack precision," he said. Inés Galindo, geologist specialized in volcanic activity. Galindo, who is not part of this research, is head of the Las Palmas de Gran Canaria Unit of the Geological and Mining Institute of Spain.

"The two models are characterized by an amount of uncertainty that is quantified by a plus sign and a minus sign, and within this uncertainty there is room for subtle differences in interpretation, both of which reach reasonable conclusions based on their data sets." , has explained to this newspaper Seth Burguess, geophysicist of the Center of Sciences of Volcanoes of the Geological Service of the United States (USGS, for its acronym in English), who has published this Thursday, also in the journal Science , a review of the two jobs. "The fact that these interpretations differ indicates that we need more accurate and precise dates," he added. "These two studies teach us something more about extinction and what could have triggered it, but they also show us that there is still a lot to learn."

Theories for the extinction of dinosaurs

In what all the scientists of the world agree is that at the end of the geological period known as the Cretaceous, 66 million years ago, there was the disappearance of a large number of species and was the end for the animals that dominated the Earth at that time , the non-avian dinosaurs. This event is known as the mass extinction of K / Pg, by the acronym in German of the boundary between the Cretaceous (last period of the secondary era) and the Paleogene (first period of the tertiary era).

Several hypotheses explain the facts. The best known is that formulated by Spanish-Americans Luis Álvarez and his son Walter Álvarez. After observing the unusual amount of iridium of certain rocks, both formulated in 1981 the theory that explains that the impact of a large asteroid caused the extinction of dinosaurs. The 180-kilometer diameter crater of Chicxulub , Mexico favors this theory since it had to be produced by an asteroid at least ten kilometers in diameter. If one, or several objects (as other scholars say) of such dimensions had hit the Earth, the climatic consequences could have been triggers of the catastrophe.

Scientists do not rule out, in any case, that it is not the only factor. To the possible climatic change of the end of the Cretácico they would contribute volcanic phenomena like those of the Traps of the Deccan in India, now backed by the two new studies. It would remain to see which one comes closest to reality and clears the doubt of what happened before.

"There is definitely no need to exclude the impact of Chicxulub or the Deccan Traps, both occurred and both probably played a role in the event of extinction, " Schoene said.

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REF: https://www.elmundo.es/ciencia-y-salud/ciencia/2019/02/21/5c6efdd6fdddffc3a48b45b1.html