Questions for the future of humanity: What geological imprint will we leave behind?

Eyon was born at a scientific conference in Mexico, in 2000. It was casually thrown into space by Paul Krutzen, one of the most respected scientists in the world. The name of the Dutch scientist had already gone before him as a prophet of wrath who warned that a worldwide nuclear war would cause a "nuclear winter" that would kill the world of flora and fauna on Earth. Even earlier, Krutzen won bNobel Prize in Chemistry About research that dealt with another man-made global threat: the destruction of the ozone layer that envelops the earth.

In Mexico, the experts discussed the evidence for the changes that occurred in the global environment during theHoloken, a distinct geological period that began, according to geologists, 11,700 years ago and continues to this day. He listened to the discussion with increasing displeasure and at one point his patience ran out and he interrupted the discussion by exclaiming: "No! We are no longer in the Holocene. We are in..." - Here he stopped for a moment and immediately continued - "We are inAnthropocene! "

There was silence in the hall. It seemed that the concept hit the mark, and it came up again and again at the conference. In the same year Krutzen wrote an article together with Eugene Stormer (who has since passed away), an expert in the class of microscopic algae known as molluscs (Diatoms), who coined the term "anthropocene" a few years before [from the words: anthropo" - human, "ken" - new]. The evidence is unequivocal, the two experts claimed in the article: the industrialized world created by humans has changed the composition of the atmosphere and oceans of our planet and has also affected the Earth's landscape and its biosphere, including the population of algae. We live on a new earth that is controlled by man, a world completely different from the one we were familiar with in the past. Thanks to Krutzen's prestige and his fluid and persuasive writing, the term "Anthropocene" was quickly adopted by the thousands of scientists who participated in the international program for the study of the geosphere and biosphere (IGBP), under whose auspices the conference was held in Mexico, and in a short time the term entered the scientific discourse and began to appear in scientific journals around the world.

But is it really a geological change - a change so profound that its signals are evident in geological layers on the surface of the entire planet? Is it possible for humans to bring about dramatic changes like those that took place during the ten thousand years from 18,000 years ago to 8,000 years ago, during the transition period between the Pleistocene and the Holocene, when the retreat of the giant glaciers that covered large areas on Earth and their melting caused a rise of 120 meters in the level of the oceans? Are the consequences of our actions on the ground under our feet so far-reaching that they set in motion processes no less powerful than those that caused the period ofPleistocene 2.66 million years ago, a period during which there was a prolonged ice age on Earth? And is there any place at all to compare human influences on the Earth that are only a few hundred years old to the great changes that our planet has known in its turbulent geological past, when time units were measured in millions of years and even billions of years?

The idea is not new. Back in the 19th and early 20th centuries, scholars such as the clergyman and the Italian geologist usedAntonio Stopani and the American naturalist Joseph La Conte in concepts like "the anthropozoic era” (the era of man) and “the era”. the psychozoic” (The Age of the Intelligent Man), but the geologists dismissed these concepts with disdain and even contempt: how can human activity, however impressive, be compared to tremendous transformations such as the formation and destruction of oceans and mountain ranges, massive volcanic eruptions or terrible impacts of meteorites on the Earth? Faced with events of this magnitude, human activity is dwarfed and seems short-lived and fleeting.

But this is not the only problem. Geological terms such as the Jurassic period, the Cretaceous period, the Pleistocene period or the Holocene period are not just nicknames. These are scientific names for time units defined in the complex geological timetable, the division into which describes the vicissitudes of the earth's development throughout its more than 4.6 billion years. These names were given official scientific approval only after decades of gathering evidence and discussionsThe international committee לStratigraphy. The "periods" and "eras" to which they are associated have technical meanings Specificity and geologists take them seriously. Declaring a new era is a step from which it can be understood that enough evidence has accumulated that humans are indeed changing the course of the Earth's evolution.

But the term Anthropocene did not stand up to any such scientific assessment. And with all the recognition that Krutzen has received, his area of ​​expertise is atmospheric chemistry and his research deals with the study of environmental stress conditions. He is not a geologist nor an expert in the study of rock layers. And even so, the term that penetrated the scientific discourse became common in professional literature, as if it were an official geological period, as my friends saw Committee on Stratigraphy of the Geological Society of London in 2008. The London Society therefore decided that it should start a fight against the use of the term.

This conservative group of scientists, who carefully economize their steps, usually meet in the council room at Burlington House in London. The walls of the room, which emits aromas of the old world, are decorated with portraits of serious personalities, and it was previously used as a hostel for the great scientists of the Victorian era, including Charles Darwin. Against the background of this impressive historical setting, the scientists began the geological evaluation of the term Anthropocene. Perhaps to their own surprise, most of them agreed that the term is actually justified and that it is appropriate to consider it as a possible official unit in the accepted geological time schedule. the geologist Philip Gibbard - who, among other things, served as chairman of the subcommittee for stratigraphy of the Quaternary period in the International Committee for Stratigraphy, a committee with the authority to make decisions regarding the geological time table - proposed to appoint Work group, and is still dealing with the burning of the issue ever since.

To justify the term, scientists must show that human activity will leave a clear mark, which will be preserved as a fossil in rock layers, and which geologists in the distant future will be able to recognize even after tens or hundreds of millions of years. Layers are very important in this context. For geologists, geological layers represent geological time. The key idea is a "rock-time" unit - a geological layer that can be hit with a hammer, taken samples from or dug into (to find dinosaur bones, for example), and which defines a new period in the history of the earth. For us to attribute such a deep geological meaning to the Anthropocene and for the term to have any chance of gaining official status, it needs to have its own unit of rock time. Do we have enough evidence to allow the Anthropocene to stand the test? Well, there is certainly evidence to support this.

Rocks, oxides and hydroxides

Let's start with minerals, the building blocks of rock. Metals, for example, almost always appear in different compounds: oxides, carbons (carbonates) Or Silicates (Although there are unusual minerals such as gold). Humans learned to separate these compounds and extract metals from them in huge quantities. Since World War II, we have produced more than 5000 million tons of aluminum, enough to cover the entire USA with aluminum foil. The billions of cans, electrical appliances, wrappers from cigarette boxes and other waste that we throw around us or put in landfills leave deposits of pure aluminum in new layers of sedimentary rocks.

The last time in Earth's history when there was a very significant increase in the variety of minerals and their distribution in sedimentary rocks occurred approximately 2.5 billion years ago, when the Earth's atmosphere became saturated with oxygen. This process created a series of oxides and hydroxides, including rust, which changed the color of the soil and landscape from gray to reddish. Recently, there has again been a significant increase in mineral concentrations in the soil, and this time, by humans, who produce mineral compounds and create a variety of new compounds, for example, tungsten carbide, which is common in the use of various tools and ballpoint pens. But it seems that the most interesting invention in this field is the "Mineraloids” (mineral-like materials), such as glass and plastic. Before World War II, the use of plastic materials was limited to a limited number of products such as varnish, Bakelite וrayon (artificial silk), but after the war the production of plastic products soared, and today it reaches a huge volume of 3000 million tons of plastic products every year - a mass equal, more or less, to the total body mass of all humanity. The very useful properties of the plastic materials - stability over time and resistance to weathering - are the ones that keep these materials preserved and remain in the environment for many years.

The geological imprint that plastic waste leaves on the ground is significant enough, but the piles of plastic piled up in the oceans have a much more far-reaching geological significance. Many of the creatures living in the sea eat the plastic materials and eventually, upon their death, most of these materials sink to the bottom of the sea, the first step on the way to the formation of fossils. Tiny, invisible plastic particles, such as fibers shed from synthetic clothing, are even more common. Researchers have found thousands of such fibers in every square meter of sediment on the ocean floor even in the most remote and remote areas from land.

Man-made rocks are also everywhere. The most prominent of them in terms of volume are the concrete blocks. So far, humanity has produced about half a trillion tons of concrete, about a kilogram of concrete for every square meter of the earth's surface. Concrete is a basic component in the buildings, roads and dams we build, and today you can find many fragments of concrete in the excavated ground below our city. These concrete blocks, along with the bricks and ceramic products we produce, are already a unique rock layer of the Anthropocene. The upper layer of the Earth's crust is saturated with the huge rock masses we created, and we repeat and scatter these rocks even when we dig into the ground with large machines to erect buildings on it or when we stick the plow blade into it to grow crops for food. In fact, the amounts of sediment materials that humans move from place to place today are greater than those that are moved by natural forces such as river drift or the wind.

chemical fingerprint

In about the last hundred years, the burning of mineral fuels has driven most of the accelerated production of new sedimentary materials, such as aluminum, plastic and concrete, and these leave their mark in new layers of sedimentary rocks. The amount of by-products of burning fossil fuels is so great that they also leave a variety of chemical signals in sedimentary rocks around the world. The increase in the concentration of carbon dioxide in the atmosphere since the beginning of the Industrial Revolution is occurring at a rate approximately 100 times higher than it was during the period when the glaciers began to retreat at the beginning of the Holocene. The emitted carbon dioxide is trapped in air bubbles trapped in layers upon layers of snow and ice that freeze in the polar caps.

Combustion of materials also creates smoke: tiny, chemically inert particles that have not been fully burned. These particles fall to the ground and leave an indelible geological imprint of smoke around the world. The fires ignited by a giant meteorite hitting the Earth tens of millions of years ago - an event that defines the boundary between the Cretaceous and Tertiary periods - left similar traces in the rock. The carbon that comes from burning fossil fuels is rich in carbon-12 (12C), the light stable isotope of the element, which is easily absorbed by plants and animals, and these life forms will turn into fossils after their death and leave behind a permanent imprint: the carbon-12 imprint of the Anthropocene.

Extensive agriculture also leaves its own chemical traces on the earth. Humans began cultivating the land approximately 10,000 years ago, but only since the beginning of the 20th century have farmers fertilized their fields with huge amounts of nitrogen fertilizer, extracted from the air using a method known as the Haber-Bosch process, as well as with phosphorus extracted from the soil. These are far-reaching changes that leave a clear chemical imprint in the soil, water and air. These substances, carried with the wind from distant agricultural areas, pollute lakes at high, very northern and very southern latitudes, in areas near the poles. Fertilizer-saturated sludge originating from agricultural fields finds its way into streams and rivers and is washed through them into the open sea, where the fertilizers excessively accelerate the growth of plankton colonies. When the plankton boom season ends and the masses of tiny organisms die and decompose, they create "Dead areas” across hundreds of thousands of square kilometers every year and suffocate life on the seabed. The story of the destruction of marine life will be told by the fossils that will be preserved in future geological layers.

Other chemical traces leave behind organic pollutants that remain in the environment, such as insecticides and toxic industrial chemicals, in which Dioxins, which give their signals in the sedimentary rocks already today. Some of these materials may remain for a long time even on a geological scale, similar to the long chains of carbon compounds formed by algae in ancient times and which paleontologists use today to trace the climate of the Earth tens of millions of years ago.

Tiny radioactive particles scattered around the world after each nuclear explosion also leave traceable traces. Only two atomic bombs have so far been dropped during a war, but since then more than 500 nuclear bombs have exploded in the atmosphere in nuclear tests conducted by various countries between the mid-40s and the late 90s. The radioactive particles penetrated the soil, the ice at the poles and the sediments at the bottom of the sea and were absorbed by the bodies of animals and plants on the surface. This radioactive layer is one of the hallmarks of the Anthropocene.

Metamorphoses are fossilized in the rock

There is no doubt that we humans have also left a clear mark on the biological landscape of the planet. Even though until a few thousand years ago the human species was only a marginal player among the multitude of living creatures on our planet, today it is the dominant predator on land and sea. We use up about a quarter of the Earth's total biomass for our needs. As a result, our share of the mass of all terrestrial vertebrates reaches approximately one third (in terms of body weight only), and the handful of animal species that we inhabit as a source of our food make up most of the other two thirds. The wild animals, pushed to the margins, occupy only 5% of the mass of vertebrates or even less than that. With our settlement in ever-growing areas of our planet, we have completely changed the distribution of wild animal populations, or what is left of them, and caused, intentionally or unintentionally, the migration of animals and plants to remote areas across the globe and thus the formation of a more uniform biological landscape in the entire world. And if that's not enough, we are destroying so many species with our own hands that the biological diversity of the planet may absorb within a hundred or two hundred years a similar damage to the one that wiped out the dinosaurs from the face of the earth. These transformations will be reflected in the distant future in the layers of sedimentary rocks, where the transition from one group of fossils to another will be clearly visible.

In the meantime, humans are bringing the amount of geological evidence of their activity to unprecedented levels. Similar to the footprints left behind by the dinosaurs or the burrows dug by sea worms, we also produce "fossil traces". Our mines and boreholes penetrate miles deep into the bowels of the earth, so deep that the traces left by this activity scar our planet forever. The cities we have built on Earth and the urban landscape that has changed its face beyond recognition are reflected as if in a mirror image underground in the underground foundations of the buildings we have built, in the pipelines branching under them and in the subway systems.

Eternal or transitory change?

In general, we humans leave behind us a very long line of geological fingerprints. But will human activity indeed forever change the map of the earth's geological layers and reshape the course of history, and thus define a new period that will be officially recognized scientifically in the geological timeline? Or with the disappearance of the human race from the face of the earth, the earth will renew its days as before and wear down the structures we have erected, and their fate will be like the fate of the mighty empire founded by the Egyptian king Ozymandios In the well-known sonnet bearing his name written by the English poet My Percy Bish? It's still too early to tell.

Fortunately, four billion years of geological strata teach us quite a bit about what lies ahead. Well, it turns out that when the earth's crust rises, as in places where mountain ranges are formed, the forces of nature erode structures on the surface and their remains are carried away as sediment particles to distant seas and oceans. When the earth's crust sinks - as happens in many of the largest delta areas in the world - in the layers piled up below the surface, even seemingly ephemeral traces such as leaves, twigs and footprints are often preserved. The San Francisco area, pushed up by tectonic forces, will likely undergo weathering processes and be eroded to dirt. On the other hand, New Orleans, Shanghai and Amsterdam will leave behind an abundance of traces - the remains of the massive buildings that adorn them, alongside sedimentary materials such as aluminum, plastic and ceramics - as well as skeletons including teeth with metal fillings and artificial joints. When in the distant future, in millions of years, tectonic forces will push these layers upwards, the new sedimentary rocks will reveal a distinct geological layer, the Anthropocene layer.

Part of the answer to the question of whether the current change will be preserved as a distinct geological period is also found in the preservation of fossils and the long-term consequences of our activity, humans. The meteorite impact that brought the Cretaceous era to an end happened in an instant, and the shock wave it created subsided within a few hours. But the consequences of this event reshaped the biological environment for millions of years, and its long-term impact is still evident today. It is quite possible that if a meteorite had not hit the earth, the dinosaurs would have continued to rule our planet and man would not have appeared on earth at all.

Human activity may also affect the Earth quickly (even if not as suddenly as a meteorite impact) and cause far-reaching changes in it that will be evident long after the human race no longer inhabits it. Many of the processes of change are occurring at an accelerated rate, but some, such as species extinction, global climate change and sea level rise, are only in their early stages. Regardless of when the end of the age of fossil fuels comes, its influence will not fade soon and it will leave its mark for millions of years. (And human civilization, which developed in the stable environment of the Holocene period, will be forced to adapt to an unstable global environment that will be subject to constant changes for many generations to come.)

We may leave behind a long-lasting mark in another sense as well. Human activity is a much more complex, changing and multifaceted force than a meteorite impact or retreating glaciers. Our impressive geological power is driven by the power of our intelligence, our ability to execute, and our developed social relationships, through which we pass on acquired knowledge to our own kind. These features allowed us to develop the technology that sustains us, and which itself develops at an accelerated pace, year after year.

This is the genesis of Technosphere (as the retired Duke University professor calls it Peter Huff) which can be considered the result of the biosphere. It has its own dynamics over which we have only partial control, and it holds the possibility that it will develop artificial intelligence that soon you will be able to compete with our own intelligence. Of all the global changes taking place today that are expected to shape the geological future of our planet, the technosphere is by far the great loser. It may create a different anthropocene, perhaps a more advanced one, but one in which humans will not necessarily run things. For now, scientists can only determine the characteristics of the present. Does the earth on which humans are creating rapid and far-reaching changes that will leave their mark forever worthy of scientific recognition as representing a new period in the geological timeline?

The geologists discussing this have not yet reached a decision. They must first answer a series of weighty questions. For example: where is the boundary line that defines the beginning of the Anthropocene period? The proposed answers to the question begin in ancient times, thousands of years ago, when human activity first gave its signals on the Earth's landscape, and reach into the distant future when its full impact will be realized. For practical reasons, it seems appropriate to set the boundary line at the point where the "Great Acceleration" began, the extraordinary increase in the rate of population growth, energy use and industrialization in the middle of the 20th century. From this point in time onwards, the geological layers are characterized by a considerable increase in concrete, plastic and plutonium sediments and the remains of a deep biological transformation.

The geologists are trying to locate such a "gold nail": a reference point that will be carefully chosen and will serve as a global landmark for the beginning of a new era. Will the answer be provided by the radioactive fallout particles of nuclear fissions or the carbon particles trapped in the snow and ice layers of Greenland and Antarctica, in the sedimentary layers of lakes and fjords far away and deep in the seabed? Or will it be some other marker? Perhaps the telltale traces of biochemical changes preserved in tree rings and annual growth bands of coral colonies? The search for answers to these questions is still ongoing.

For more articles in the series:

• Questions for the future of humanity: How will climate change change us?
• Questions for the future of humanity: who will prosper and who will be left behind in a world of 10 billion people?
• Questions for the future of humanity: Will we survive the economic disparities?
• Questions for the future of humanity: Will we defeat aging?