Historical story

New evidence in dino murder case

Did the dinosaurs die out or not because of a meteorite impact? Opinions are still divided, but improved dating methods support the impact theory.

Will the debate over the cause of the dinosaurs' extinction finally be settled? Probably not, but the proponents of the impact theory did good business this week. According to these scientists, the impact of a huge meteorite at the end of the Cretaceous period, about 66 million years ago, killed the dinosaurs.

The meteorite impact happened simultaneously with the start of the extinction wave, a group of earth scientists writes today in Science, and thus an important condition for the impact scenario has been met. It would appear from new dating with improved techniques, which are more accurate than ever before.

Troubled

It was a turbulent period on Earth, between 68 and 65 million years ago. The warm climate began to show periods of strong cooling. Near India, enormous masses of magma rose to the earth's surface, accompanied by volcanic eruptions and the release of large amounts of volcanic gases. A meteorite hit Mexico's Yucatán, leaving a crater 180 kilometers in diameter. And many plants and animals, including the terrestrial dinosaurs, became extinct.

The cause of this extinction wave was the meteorite, many Earth scientists believe. This must have caused tsunamis and earthquakes, and probably caused so much dust that it was dark for months. However, this theory is disputed by a small group of skeptics. According to these scientists, the Chicxulub crater in Yucatán would have been created more than 180,000 years after the start of the extinction wave, so that the impact could not have been the cause of the disappearance of the dinosaurs.

Dates

However, new dating of tektites, tiny droplets of molten rock created by the impact, and volcanic ash from strata deposited shortly after the extinction show that this is not true. The mass extinction and impact of the Chicxulub meteorite happened simultaneously. The difference is at least within the measurement error, which is smaller than ever with the new techniques. “It is the first time that the impact and the end of the Cretaceous have been shown to be of the same age,” says Klaudia Kuiper, earth scientist at both Utrecht University and VU University Amsterdam, who participated in the study.

Last move

Volcanism near India, which in total spilled about 1.5 million cubic kilometers of lava over the Earth's surface and created the Deccan Traps, started several hundred thousand years before the dinosaurs died, the researchers further concluded. This must have caused extra periods of cooling, due to the emission of dust that blocks the sun. It is possible that the dinosaurs were already considerably weakened by this, and received the last push due to the consequences of the comet impact, causing them to disappear from the face of the earth. “But we actually have no evidence for that,” explains Jan Smit, professor of event stratigraphy at the Vrije Universiteit, who also participated in the research. “That is pure speculation.”

More about dinosaurs on Kennislink

More about the end of the Cretaceous period

  • Another impact on the Cretaceous-Tertiary border (Knowledge link article)
  • Hello Obamadon (Article Science 24 )

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