Climatologist Gavin Schmidt of NASA and astrophysicist Adam Frank of the University of Rochester (USA) asked the interesting question of whether people can be sure that they are the first civilization in the history of the Earth to master the industrial mode of production? For answers, scientists turned to the geological history of the Earth.
Climatologist Gavin Schmidt from NASA and astrophysicist Adam Frank from the University of Rochester (USA) asked an interesting question: Are we (humanity) sure that we are the first civilization in the history of the Earth to have mastered the industrial mode of production? Frank and Schmidt wrote an article about it that was published this week by the International Journal of Astrobiology.
In recent years, geologists have been talking a lot about the onset of a new geological era in the history of our planet. This era is proposed to be called the Anthropocene. It is distinguished from previous eras by traces of human activity in all the outer shells of the Earth - water, air and stone. If another civilization had reached a similar degree of development before people, it also had to leave a mark, including in the lithosphere. Schmidt and Frank decided to look in the geological annals of the Earth for something that could be interpreted as a product of the activity of a prehuman civilization - and they found it.
The Anthropocene is characterized by abrupt and simultaneous changes in the chemical composition of rocks. The rapid and global warming of the climate is reflected in the change in the proportion of oxygen isotopes. Isotopes of carbon are also redistributed - due to the fact that we get out of the ground and burn hydrocarbons. The fluctuations in the distribution of nitrogen isotopes in the rocks formed in our time reflect our agriculture and the production of nitrogen fertilizers.
Soil erosion is causing rivers to wash more sand into the oceans, including those containing heavy metals; the water in the ocean becomes acidic and the carbonate deposits on the seabed dissolve. Species are dying out faster than usual. The newly formed rocks retain undecomposed particles of plastic and isotopes of plutonium and other heavy elements that have fallen out after nuclear tests.
What traces can tell about the existence of another civilization, Schmidt and Frank asked themselves? The chances of finding chemical "traces" are much greater than the chances of finding an ancient artifact. Scientists also took into account that most of the analytical methods give a scatter of dating in thousands of years, and the changes that humans have made to the structure of the lithosphere have occurred over a period of decades. Therefore, it would be very risky to rely on one factor, it is necessary that several markers speak at once about the activities of a hypothetical ancient civilization, scientists decided.
There were several periods of sharp warming in the history of the Earth - for example, the Paleocene-Eocene maximum (55 million years ago). At this time, the ratio of carbon isotopes in rocks changed sharply, the composition of sedimentary rocks changed, species of animals and plants died out, and the concentration of heavy metals grew. Several similar events occurred during the Cretaceous and Jurassic periods. Usually these events are explained by bursts of volcanic activity; and they took place slowly - for thousands of years. But some parallels with the Anthropocene can be drawn.
Scientists, of course, do not argue that the Finger-Eocene thermal maximum was the result of the activity of a prehuman civilization, or that primitive predatory mammals of the end of the Paleocene, like us, received energy by burning oil. If such a theory is taken as a starting point, one can prove it with countless facts, but all these statements will be impossible to verify. Therefore, the version of a prehuman industrial civilization should not be considered until there is direct evidence. But Schmidt and Frank believe that thinking in this spirit is still useful - if only because we are now looking in ancient rocks for what we expect to find, and sometimes it is useful to look wider.
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The article by Schmidt and Frank has already been called a "blockbuster", but scientists did not stop at a scientific publication and accompanied it with a fantastic story about a young scientist who accidentally finds plastic particles in deposits of 55 million years old.