The mass extinctions of land animals – including amphibians, reptiles, mammals, and birds – follow a cycle of approximately 27 million years that coincides with the previously reported mass extinctions of marine life. This emerges from a new analysis published in the journal Historical Biology.
The study also notes that these mass extinctions are consistent with large asteroid impacts and devastating volcanic outpourings of lava known as flood basalt eruptions.
"It appears that large body impacts and the impulses of internal earth activity that create flood basalt volcanism are marching to the same 27 million year drum beat as extinction that may be caused by our orbit in the galaxy," Michael said Rampino, professor in the Department of Biology at New York University and lead author of the study.
Sixty-six million years ago, 70 percent of all species on land and in the sea, including dinosaurs, suddenly became extinct after a large asteroid or comet collided with Earth. As a result, paleontologists discovered that such mass extinctions of marine life, in which up to 90 percent of the species disappeared, were not random events, but occurred in a 26-million-year cycle.
In their study of historical biology, Rampino and co-authors Ken Caldeira of the Carnegie Institution for Science and Yuhong Zhu of the NYU Center for Data Science examined the records of land animal mass extinctions and concluded that they were related to the ocean extinction collapsed lives. They also performed new statistical analyzes of land species extinctions and showed that these events followed a similar cycle of about 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 age of the impact craters created by asteroids and comets crashing onto the earth's surface also follow a cycle that aligns with the extinction cycle.
Astrophysicists assume that periodic comet showers occur in the solar system every 26 to 30 million years, which cause cyclical influences and lead to periodic mass extinctions. The sun and planets cycle through the crowded central plane of the Milky Way every 30 million years. During this time, comet showers are possible, which have a major impact on the earth. The impacts can create conditions that pollute and potentially kill land and marine animals, including widespread darkness and cold, forest fires, acid rain, and ozone depletion.
"These new insights into the coincidence of sudden mass extinctions on land and in the oceans, as well as the common cycle of 26 to 27 million years, confirm the idea of periodic global catastrophic events as the cause of extinction," he told Rampino. In fact, it is already known that three of the mass exterminations of species on land and in the sea have occurred simultaneously with the three largest effects in the last 250 million years, each of which can cause global catastrophe and the resulting mass extinction. ”
Lichen-covered rivers from the Siberian flood basalts. Photo: Linda Elkins-Tanton
The researchers were surprised to find another possible explanation for the mass extinction beyond asteroids: flood basalt eruptions or huge volcanic eruptions that cover large areas with lava. All eight coincident mass extinctions on land and in the oceans coincided with the times of the flood basalt eruptions. These eruptions would also have created severe living conditions, including short periods of intense cold, acid rain and ozone depletion, as well as increased radiation; In the longer term, eruptions could lead to deadly greenhouse warming and more acid and less oxygen in the ocean.
"The global mass extinction appears to have been caused by the greatest catastrophic effects and massive volcanism that may sometimes work together," added Rampino.