One of the most popular mass extinctions is the one that occurred 65 million years ago, which wiped out most large living things, including dinosaurs.
Although scientists agree that this catastrophe did not occur overnight, but lasted thousands of years, there was consensus that it was a large rock from space that produced a cataclysm at levels worldwide, given its enormous size (ten kilometers in diameter).
But new research published in the prestigious journal Science posits as a highly probable option that the asteroid did not cause the mass extinction directly, but indirectly, activating massive volcanic eruptions . A volcanism that, according to the article, would have started in India, half a world from the place of impact, in the Caribbean Sea.
Furthermore, the research sheds light on the huge lava flows that have periodically emerged throughout Earth’s history, and how they have affected the atmosphere, altering the course of life on the planet.
By analyzing rock samples, the researchers have established that the timing of the eruptions was the same across much of the Indian continent. This supports the group’s hypothesis that the asteroid impact triggered earthquakes that caused a strong outbreak of volcanism in India, almost on the diametrically opposite side of the planet from the impact site, the Chicxulub crater in the Caribbean Sea.
According to this research, the coincidental catastrophes have likely dealt a double fatal blow to life on Earth, but the details are unclear. Volcanic eruptions produce many gases, but some, such as carbon dioxide and methane, warm the planet, while others, such as sulfur aerosols, cool it. If anything, the impact itself would have sent dust into the atmosphere that blocked sunlight and cooled Earth , although no one knows for how long.
Both the asteroid impact and volcanism can produce similar environmental effects, but these occurred on different time scales. Therefore, to understand how each agent contributed to the extinction event, timing is key.
Layered lava flows into the Wai Subgroup near Ambenali Ghat, Western Ghats./ Courtney Sprain.
The impact caused ‘simultaneous’ eruptions on the other side of the world
Scientists very accurately date intense volcanic eruptions in India, which coincided with the global mass extinction at the end of the Cretaceous Period . The sequence of eruptions, which lasted millions of years, spewed lava flows at distances of at least five hundred kilometers across the Indian continent called Deccan Traps flows, which can be nearly two kilometers thick.
We pick up the words of the lead author of the study Paul Renne, professor in residence of Earth Sciences and Planetariums at the University of Berkeley: “I would say, with quite high confidence, that the eruptions occurred within fifty thousand years and perhaps thirty thousand years , after the impact moment. That is, they were almost simultaneous, the least, on the scale of the Earth’s age “.
Gases, not lava, could cause climate change
The new dates also confirm previously made estimates that the lava flows continued for about a million years. But the data comes as a surprise: three-quarters of the lava emerged after the impact; while previous studies suggested that around eighty percent of the lava erupted before impact.
If most of the lava from the Deccan Traps had emerged before impact, the gases emitted during the eruptions could have been the cause of global warming in the last four hundred thousand years of the Cretaceous, during which temperatures rose, on average, around eight degrees centigrade. During this warming period, the species would have evolved adapted to the conditions of the greenhouse effect. The cold would have been a shock that most creatures would never have recovered from, completely disappearing from the fossil record – literally, a mass extinction.
But if most of the lava from the Deccan traps emerged after impact, this scenario changes.
According to study co-author Courtney Sprain: “Either the Deccan eruptions had nothing to do with the extinction, which is unlikely, or many climate-modifying gases emerged during the lowest volume cycle of the eruptions.”
The hypothesis that climate-altering volcanic gases frequently seep from underground magma chambers, and not just during eruptions, is supported by evidence from current volcanoes, such as those on Mount Gas. Etna in Italy and Popocatepetl in Mexico.
Today we know that magma below the surface transmits gases into the atmosphere, even without eruptions. That is, according to the results of the study by the California researchers, it is likely that the symptoms of the strong climate change that took place during the mass extinction were present long before the volcanic eruptions.
“We suggest that it is highly likely that many of the gases that come from magma systems that precede eruptions do not necessarily correlate with eruptions,” in the researchers’ words.
Other co-authors of the paper are volcanologist Stephen Self and UC Berkeley graduate student Tushar Mittal, Loÿc Vanderkluysen of Drexel University in Philadelphia, Pennsylvania, and Kanchan Pande of the Indian Institute of Technology Bombay in Mumbai, India. The work was supported by the Ann and Gordon Getty Foundation, the Esper S. Larsen Fund of the University of Berkeley, the Heising-Simons Foundation, the National Science Foundation (EAR-1615021, EAR-1615203 and EAR-1615003) and the Berkeley Center for Geochronology.
