Scientists: oxygen levels fell by 0.7% in the last million years,
MOSCOW, September 23 - RIA Novosti . The deep ice samples from Greenland told scientists that the level of oxygen in the Earth's atmosphere has decreased by almost 1% in the last 800 thousand years, the causes of which have not yet fully understood, said in an article published in the journal Science .
The oxygen level in the world, despite the opinion of ordinary people, is not a constant - in the past geological epochs, its share in the atmosphere could be higher or lower by tens of percent today. For example, during the Carboniferous period, 350-300 million years ago the oxygen level was not 21% as it is today, and 35%, so that the world lived and flourished meter predatory dragonflies, three-meter poisonous centipedes and giant spiders the size of a dog.
In another era, for example, at the end of the Permian period the oxygen concentration could fall sharply due to the different geological phenomena that caused mass extinctions and ecosystem adjustment.
Daniel Stolper (Daniel Stolper) from Princeton University (USA) and his colleagues found that on Earth right now is something similar, investigating popular today, the idea that the level of oxygen is gradually reduced, in particular due to the burning of fossil hydrocarbons and other forms of fuel.
For this Stolper and his colleagues carried out an expedition in Greenland and Antarctica, where there are glaciers, formed more than 800 thousand years ago. Scientists have extracted samples of ice, cut them into thin layers and examined the contents of the small air bubbles, "immured" in ice thickness.
By studying and comparing the chemical and isotopic composition of ancient air, Princeton chemists have found that 0.7% more that 800 thousand years ago, the proportion of oxygen in the Earth's atmosphere was not 20.95% as it is today, and 21.10%.
Even such a small difference indicates that some natural or biological processes has led to the fact that the lithosphere, hydrosphere and atmosphere absorb about 2% more oxygen than they gave him, over the last million years.
Scientists can not yet say exactly what led to a decrease in the proportion of O 2 in the atmosphere, but they believe that a certain role in this process could play a retreating and advancing ice during the onset and end of ice ages, whose movement has led to the fact that they were naked large areas of pyrite and sedimentary rocks of organic origin, well absorb oxygen. Another possible reason - the global cooling of the ocean waters, which enabled him to absorb more O2.
Both of these processes, to all appearances, is still ongoing, as many observation stations are fixed very slight but significant decrease in the concentration of oxygen in the atmosphere in recent decades. When this process is over, we do not know, and therefore the fate of oxygen and all life on Earth is not yet clear, reveal that as the authors believe, will help to further research how the oxygen concentration fluctuated in the past.
No comments:
Post a Comment