Mass extinctions of land animals follow a cycle of 27 million years

Sixty-six million years ago, 70% of all species on land and seas, including dinosaurs, suddenly became extinct as a result of the disastrous consequence of the collision of a large asteroid or comet with Earth. Later, paleontologists discovered that such mass extinctions of marine life, in which up to 90 percent of species disappeared, were not random events; Instead, it follows a cycle of about 27 million years, according to a new study.

The study by scientists at the University of Newyork also suggests that these mass extinctions line up with major asteroid impacts and devastating volcanic lava spills called basalt flood eruptions.

Michael Rampino, a professor in the Department of Biology at New York University, said: “It appears that large-body impacts and pulses from Earth’s internal activity creating a flooded basalt volcanism may be marching at the same rate of 27 million years as extinctions, perhaps at the rate of our orbit in the Galaxy. “.

Based on the examined records of mass extinctions of land animals, scientists concluded that they coincided with extinctions of ocean life. After performing statistical analyzes of the extinctions of terrestrial species, the scientists showed that these events followed a similar cycle of approximately 27.5 million years.

What could be causing the periodic mass extinctions on land and in the seas? Mass extinctions aren’t the only events that occur in cycles: the ages of impact craters, created by asteroids and comets colliding with the Earth’s surface, also follow a cycle that lines up with the extinction process.

Astrophysicists hypothesize that periodic comet showers occur in the Solar System every 26 to 30 million years, producing cyclical impacts that result in periodic mass extinctions. The Sun and the planets traverse the crowded midplane of the Milky Way approximately every 30 million years. During these times, comet showers are possible, causing large impacts on Earth. The impacts can create conditions that would stress and potentially kill terrestrial and marine life, including widespread darkness and cold, wildfires, acid rain, and ozone depletion.

Rampino said, “These new findings of sudden and coincidental mass extinctions on land and in the oceans, and the common cycle of 26 to 27 million years, lend credence to the idea of ​​periodic global catastrophic events as triggers for extinctions. It is already known that three of the massive species killings on land and at sea occurred at the same time as the three largest impacts of the last 250 million years, each capable of causing a global disaster and causing mass extinctions. “

Scientists found another possible explanation beyond asteroids for mass extinctions: basalt flood eruptions or giant volcanic eruptions that cover vast areas with lava.

The eight coincident mass deaths on land and in the oceans coincided with the times of the flood basalt eruptions. These eruptions would have created severe conditions for life, including brief periods of intense cold, acid rain, ozone destruction, and increased radiation; In the longer term, eruptions could lead to lethal greenhouse warming and more acid and less oxygen in the ocean.

Rampino said, “The global mass extinctions were caused by the largest cataclysmic impacts and massive volcanism, perhaps sometimes working together.”

Magazine reference:
  1. Michael R. Rampino et al. An underlying periodicity of 27.5 m detected in non-marine tetrapod extinction episodes. DOI: 10.1080 / 08912963.2020.1849178