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| Fossils of marine animals show that extinctions occur every 60 million years. (Credit: Shutterstock) |
The fossils show that the marine biodiversity of the oceans of the planet falls every 60 million years. It's a cycle that has been going at least 500 million years and his reason was a mystery - until now. A theory formulated by the physicist and astronomer Adrian Melott of the University of Kansas, says that these extinctions are caused by a "pulse" on Earth, what happens with the same periodicity. The pulses would increase the continents, would leave the shallower seas and kill many species.
His conclusion came from a study on the amount of strontium-87 found in marine fossils. The substance is one of four stable isotopes of strontium, although less common than others - it represents only 7% of the total found on the planet. However, Adrian Melott found that the concentration of strontium-87 compared to strontium-86 in fossil marine rises every 60 million years, coinciding with the periods of extinction in the oceans.
The most common way to produce strontium-87 is the radioactive decay of other chemical, rubidium, material common in rocks of the continental crust. The scientist's conclusion was that something should happen to these rocks every 60 million years, to release the substance in the seas.
It was from here that Melott developed his thesis: the continents should be going through a kind of elevation, since this type of rock is the bottom-most layers of the earth. In the new time, they could erode and mix with water. The scientist faced periodic elevation of the continents as evidence of a "heartbeat" of the planet, possibly caused by movements in the Earth's core. The study shows that the conclusion will be published in March in the Journal of Geology.
Source Galileu.
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