Scientists: life on Earth exists today, by happy coincidence

© Photo : Museum of paleontology Orlovaca the artist imagined life on Earth in the Precambrian eraScientists: life on Earth exists today, by happy coincidence© Photo : Museum of paleontology Orlova

. Life on the Earth exists thanks to a happy coincidence, a series of super volcanic eruptions, melt about 570 million years ago a giant ice sheet that covered the entire planet, according to a paper published in the journal Nature Geoscience.

«In order to reconstruct the full history of the Earth at that time, we had to perform a huge number of crystals of zircon, formed in different geological epochs. This allowed us to find the most powerful greenhouse gases in Earth’s history, which occurred just before the Cambrian explosion, the most important event in the evolution of life on Earth,» said Chad Deering (Chad Deering) from the University of Michigan in Houghton (USA).

The Earth’s atmosphere before the first plants and microbes is almost entirely composed of nitrogen, carbon dioxide, methane and other greenhouse gases. Oxygen it began to appear only about 2.2 billion years ago, after the so-called «great oxygen catastrophe», when the first photosynthetic microbes began to absorb atmospheric CO2 and saturate it with oxygen.

As a result, the strength of the greenhouse effect weakened, and, as scientists believe today, approximately 850-600 million years ago the Earth turned into a kind of «snowball» – the temperature on earth has declined so much that its oceans began to freeze to the equator. How the Earth got out of this glaciation, scientists still argue.

Dearing and his colleagues found that the Earth got rid of chains of ice by happy coincidence, studying samples of the oldest rocks on the planet, was found on the West coast of Antarctica at the points where the glaciers are no longer present on its surface.

Inside of these rocks, says Deering, there are so-called zircons – microscopic crystals occur in the igneous rocks at very high temperatures. The chemical composition of these crystals is not changed after their formation, allowing them to be used as reliable indicators of the age of rocks and the conditions in which they appeared.

Using these crystals, the scientists were trying to find the very interesting question – did the frequency of eruptions and the magma and gases they have emitted into the atmosphere at the beginning and at the end of the era of «planet-snowball.»

As the scientists explain, the amount of greenhouse gases emitted by the volcano into the atmosphere very much depends on where he is and what he is spewing magma. For example, mount Etna in Italy and Erebus in Antarctica emit ten times more CO2 than most of the other volcanoes of the Earth, despite its modest size and low frequency of eruptions.

Their high productivity, according to the geologist, is that their magma was formed from alkaline rocks found in the Earth are rare. Studying zircons, formed 700-500 million years ago, Deering and his colleagues tried to understand how often met such volcanoes in the Precambrian era.

Their composition indicated a very strange and interesting coincidence. Around 570-550 million years ago the Earth began to produce large quantities of the alkaline magma, for which the contribution to the planet’s surface led to the release of gigantic quantities of CO2, sulphur compounds and other greenhouse gases in the atmosphere. This is supported by the fact that the proportion of carbon isotopes in the atmosphere at that time has changed dramatically, sliding about 20% in 5-10 million years.

At the same time, today scientists believe, began the so-called «Cambrian explosion» – a special period in the history of the evolution of life when in the primary ocean of the Earth appeared the representatives of almost all the modern types of multicellular animals. As scientists assume, the outbreak of volcanic activity that took place 580 million years ago, was a trigger of this explosion and the «Creator» of all modern life on Earth.

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