Minerals from the Urals helped foreign geologists uncover the secret of the first mass extinction in the history of the Earth, which happened 550 million years ago thanks to a series of rapid flips of the planet's magnetic axis.
A series of rapid flips in the Earth's magnetic axis about 550 million years ago deprived the planet of the ozone layer, which led to its "bombardment" with ultraviolet light and the extinction of the bizarre Precambrian fauna and its replacement by modern life forms, according to an article published in the journal Gondwana Research.
Before the so-called "Cambrian Explosion of Life", during the Ediacaran period, the oceans of the earth were filled with bizarre forms of life, which have no analogues and relatives today. Around 550-540 million years ago, these multicellular creatures mysteriously disappeared, marking the first mass extinction in Earth's history.
Joseph Meert of the University of Florida in Gainesville (USA) and his colleagues uncovered the cause of this extinction by studying samples of Ediacaran rock from the Ural Mountains. In that era, the Urals did not yet exist - these mountains arose only during the Permian period, and its rocks only began to form during the Ediacaran, gradually rising from the depths of the mantle and freezing.
As geologists explain, when rocks freeze, the iron atoms contained in them record information about which direction the Earth's magnetic field was directed and what strength it had. This allows, by studying the magnetization of thin slices of ancient rocks, to determine how the position of the magnetic axis and the strength of the Earth's "magnetic shield" changed over time.
Studying the Ediacaran deposits in the Urals, Meert and his colleagues found that during that era, magnetic axis flips occurred about 20 times more often than today and in later historical eras. Such coups, according to researchers, happened approximately every 10 thousand years during the Ediacaran extinction.
As a result of this, as the calculations of the authors of the article show, the ozone layer, which protects us from ultraviolet radiation, periodically becomes defenseless and is destroyed by cosmic rays. As a result, the thickness of the ozone layer dropped by 40%, and about twice as much ultraviolet radiation began to fall on the Earth.
This led to two things - the mass death of the Ediacaran fauna, which in general led a sedentary or sedentary lifestyle, as well as to the rapid evolution of animals and the appearance of the main Cambrian innovation - the eyes that helped the inhabitants of the primary ocean move to darker corners of the bottom, less exposed to ultraviolet radiation. … Shells and other hard shells that protected the body of Cambrian animals from radiation could have developed in a similar way.
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In the near future, Meert's group will go on expeditions to other parts of the Earth, where scientists will check whether the Earth's magnetic axis really changed its position frequently during the Ediacaran.