Rare and valuable minerals

What are fossils in simple terms?

Fossils, fossil remains of organisms, fossils, fossils – remains or traces of the vital activity of organisms belonging to previous geological eras. They are discovered by people during excavations or exposed as a result of erosion. Fossils provide important information about the organisms of their era, the animals and plants of that time. There are analytical methods that make it possible to approximately determine the time of their formation or preservation. Fossils are usually the remains or impressions of animals and plants preserved in soil, rocks, or hardened resins. Quite often, only hard parts of the animal’s body—teeth and bones—are preserved in this way. Soft tissues decompose, but based on the results of their interaction with the surrounding material (changes in shape or chemical composition), one can judge the soft tissues of a petrified organism. Preserved tracks, such as those of an organism’s feet in soft sand, clay, or mud, are also called fossils.

Fossilization

Ammonites. Fossilized shells Fossilization (lat. fossilis – fossil) – a set of processes of transforming dead organisms into fossils. It is accompanied by the influence of various environmental factors and the passage of diagenesis processes – physical and chemical transformations during the transition of sediment into the rock in which they are included. After the death of the organism, first of all, the destruction of soft tissues occurs, then the filling of the voids of the skeleton with mineral compounds. Sometimes the voids of the skeleton undergo pyritization, ferruginization, and druses and inclusions of calcite, amethyst, fluorite, galena, etc. may appear in them. During fossilization, the skeleton undergoes recrystallization, leading to stable mineral modifications. For example, aragonite shells of mollusks are transformed into calcite shells. There are cases of mineralization when the primary chemical composition of the skeleton changes (pseudomorphoses). Thus, calcareous shells are partially or completely replaced by aqueous silica and vice versa. Phosphatization, pyritization, and ferruginization of mineral and organic skeletons are sometimes observed. During fossilization, plants usually undergo complete destruction, leaving the so-called. imprints and cores, but their remains have been found in fossil form since the Precambrian. Also, plant tissues can be replaced by mineral compounds, most often silica, carbonate and pyrite. Such complete or partial replacement of plant trunks while maintaining the internal structure is called petrification.

Types

Subfossils

Subfossils (lat. under – under, almost) – fossils that have preserved not only the skeleton, but also slightly altered soft tissues. For plant residues, the term “phytoleims” (Greek. python – plant; leimma – remainder). They are represented by varying degrees of modified plant remains that retain their cellular structure. Subfossils include phytoleims from Quaternary deposits – seeds, nuts, conifer cones, wood buried in peat bogs. The subfossils also include unique finds of some animals, such as mammoths, rhinoceroses and birds. Preservatives in such cases are permafrost, various bitumens, volcanic ash, aeolian sands. Previously it was believed that amber was also a good preservative, but it did not preserve soft tissue. Fossil plants and animals in amber completely preserve their shape, which makes it possible to carefully study their external morphology. But an attempt to extract objects ends with all their contents crumbling into dust.

Eufossils

Eufossils, or eufossils (Greek eu – good, real) are represented by whole skeletons or their fragments, as well as imprints and cores. Skeletal remains have a mineral or organic composition. These include shells and skeletons of animals, shells of bacteria and fungi, as well as organic remains of leaves, seeds, fruits, spores and pollen. Skeletons are the main objects of paleontological research. The term “organic-walled microfossils” is sometimes used, which includes the membranes of bacteria and fungi, filamentous cyanobionts, as well as spores and pollen. The size of such fossils is less than 100 microns. Many eufossils retain information not only about the soft parts of the body and its functional systems, such as the circulatory, reproductive, vascular bundles of plants, etc., but also about the lifestyle and biogeochemical processes.

Ichnofossils

Ichnofossils (Greek ichnos – trace) – traces of the vital activity of fossil organisms. Most often they are preserved in the form of imprints, less often in the form of low-volume formations. These include traces of crawling and burrowing of arthropods, worms, bivalves; traces of grazing, burrows, passages and traces of drilling of sponges, bivalves, arthropods; traces of vertebrate movements.

Coprofossils

Coprofossils (Greek kopros – droppings, manure) are formed by waste products of fossil organisms. They are voluminous in nature and are preserved in the form of ridges, nodules, mounds, columns, and sheet bodies. The most typical coprofossils include the final products of digestion of vertebrates and undigested remains of other animals and plants. They are usually represented by rolls and ribbons enriched with calcium, iron, magnesium, potassium and phosphorus. Coprofossils are usually lighter or, conversely, darker, often with a reddish tint, which makes them stand out from the surrounding rock.

Chemofossils

Chemofossils (Greek chemistry – chemistry) are represented by organic fossil biomolecules of bacterial, cyanobiont, plant and animal origin. Usually the chemical composition of biomolecules is preserved, which allows us to determine the systematic position of the fossil organism, but not its morphology. They are the object of study of biochemistry and molecular paleontology.

Chemical composition

См. также

  • petrified wood
  • Paleontology
  • Taphocenosis

references

  • Fossils: Nature’s Guide(Retrieved June 16, 2009)
  • Fossil remains of organisms — article from the Great Soviet Encyclopedia(Retrieved June 16, 2009)

Wikimedia Foundation. 2010.

The great cities and civilization of the 21st century will leave a geological legacy that will last for millennia. But, as the author of this article, David Farrell, tells us, some artifacts will last longer than others.

It seemed as if the whole world below me was encased in concrete. Maybe jetlag was to blame, but the view was sickening: no matter where you looked, the city was spreading out to the horizon. This was Shanghai, one of the largest cities in the world. From the observation deck of Shanghai Tower, the second tallest building in the world, the city looked endless. Skyscrapers scattered in all directions, like ripples on water, merging far, far into the blue haze of residential areas.

The modern urban landscape is as geological as it is urban. If Shanghai is a concrete desert, then New York became the first canyon city, where streets lined with skyscrapers turned into deep gorges, comparable only to the valleys of great rivers, formed over millennia. In one of his later essays Virginia Woolf writes that she flies like a bird over the Hudson Delta, passing Staten Island and the Statue of Liberty, heading further to the concrete crevices of Manhattan. “The city of New York over which I float,” she wrote in 1938, “seems to have been scraped and combed only last night. There are no houses here. The city consists of tall towers, and each one is pierced with millions of holes.”

The first cities reproduced the environment that served as a habitat for people, yesterday’s nomads: shelters and means of life support were concentrated in a limited area in the city. According to the writer Guy Vince, the buildings and infrastructure of the urban landscape mimic “the views from the mountains, the dry shelters of familiar caves, and the fresh water of lakes and rivers.”

If there is a geological component to the character of cities, then this begs the question: what mark will they leave on the stratigraphy of the 21st century? Fossils are a kind of planetary memory of what forms once existed in the world. Now the landscapes of the deep past have not been forgotten – so how will Shanghai, New York and other great cities be imprinted in the geological record of the distant future?

One might assume that cities are too ephemeral to become fossils. “Most buildings are designed to last 60 years,” says Roma Agrawal, a design engineer involved in the construction of London’s Shard skyscraper, “and I always thought that seemed too short because it was comparable to my life.” If you want to build something that will last tens of thousands of years“The forces you have to contend with become titanic,” she explains. Most engineers do not think ahead to such deadlines.

But while a building may not be designed to last for thousands of years, that doesn’t mean it won’t leave a geological mark. According to Jan Zalasiewicz, emeritus professor of palaeobiology at the University of Leicester, the megacity will remain a fossil and that is “a very reasonable, even prosaic, geological prediction.” I asked him where this confidence came from. “As a geologist, you’ve almost asked the question by contradiction,” he replied, “how do you think this can be prevented?” [fossilization of the city – approx. trans.]

He says it all depends on the longevity, occupancy and location of the city. The main components of a modern city are of geological origin, and therefore, albeit in their own way, are very durable. Most of the iron ore on Earth was formed approximately two billion years ago. The sand, crushed stone and quartz that make up concrete are among the strongest substances on Earth. These wear-resistant materials were once found in natural deposits. But whereas previously they were driven only by water, gravity and tectonic activity, today their mobility is driven by a combination of human initiative and hydrocarbon energy.

We live in the greatest urban era in world history. Three hundred years ago there was only one city with a population of more than a million people (Edo, modern Tokyo). Today there are million-plus cities already more than 500, but all of them are simply lost against the backdrop of megacities such as Mexico City (population: 21 million), Shanghai (24 million) and Tokyo (now 37 million). As I learned while researching my book Footprints: In Search of Future Fossils, the urban planning industry uses mind-boggling amounts of materials. Every 100 years, the mining and construction industries move enough rock across the planet to form a new mountain range 40 km wide, 100 km long and 4 km high. Concrete, cast since the end of World War II, would be enough to cover our entire planet, both land and water. According to a study published recently in the journal Nature, the total mass of buildings and communications currently present on the planet exceeds the mass of all trees and shrubs (1100 gigatons versus 900 gigatons).

The specificity of the fossil that remains of a city depends heavily on its location. From a geological point of view, the land is constantly in motion, either rising or falling on a “tectonic elevator.” For example, a city like Manchester in the UK is located in an area that is still rising since the last ice age. Therefore, over time, such a city will be completely destroyed by erosion, leaving only traces of brick, concrete and fragments of plastic that will end up in the Irish Sea. “But many of the world’s largest cities are deeply embedded in estuaries, deltas and coastal plains,” Zalasivic says, “and they are sinking. Deltas flood, that’s their nature.” In many cases, human activity greatly accelerates this process. Since 1900, Shanghai has fallen by 2,5 m due to the extraction of groundwater, as well as the weight of its own buildings pressing on the swampy soil. Add to this the rise in sea level, which 2100 will rise by a meter this year. “But even without taking into account the advance of the sea,” says Zalasivic, “this result is inevitable, since the city is constantly sinking.”

What about a specific building? Shanghai Tower weighs 850 000 tons: it has a 632-meter steel frame, the building has more 20 window panes и 60 cubic meters concrete. How does all this fossilize?

“Suppose the same thing happens to Shanghai that is happening to Amsterdam and some areas of the Mississippi Delta, where river sediment accumulates,” says Zalasivic, “such changes will progress over thousands, hundreds of thousands, millions, and then tens millions of years.”

Shanghai, like other wealthy cities, will actively defend against the advancing sea, but the climate feedback loop is such that sea levels will continually rise over the coming centuries. When it is no longer possible to cope with the water, people will probably begin to gradually leave the city, with the rich leaving first. The poor, with nowhere to go, may adapt to a semi-aquatic existence. Several hundred years will pass, and the upper floors of Shanghai Tower will deteriorate due to weathering and rain. Perhaps they will be undermined by “stalkers” who will steal valuable materials from there. If some of the lower floors of the tower still stand above the water, then only one or two already flooded lower floors will serve as their basis, and everything around will be strewn with rubble, into which the ruins of the upper floors will turn.

Inevitable flooding could occur either due to the advancing sea or due to the collapse of the giant Three Gorges Dam located higher up the Yangtze River. But the flowing water will bring with it a huge mass of silt and other sedimentary rocks that will cover the first floor and underground floors like paraffin. In 500 years, where the tower once stood, there will be only a low-lying island, reddish with rust left over from the four immense steel supercolumns that once held the tower. Her whole real story will be underground.

Shanghai Tower has five underground floors, where shops, restaurants and parking are located, among others. 1 cars. These spaces, buried under a thick layer of silt, will thus be preserved and avoid erosion, and then begin to turn into fossils – “call it the Pompeii effect, if you like,” says Zalasivic.

Water seeping into the lower floors will almost immediately begin to react with calcium-containing components of concrete and form stalactite- and stalagmite-like growths that form in the anthropogenic environment. They will continue to grow for thousands of years, giving the retail space an atmosphere that would fit in a horror movie. If humanity still survives by then, most of the things of value will be taken away before the Tower is completely abandoned – most, but probably not all. Aluminum in the ventilation system, stainless steel in the food court and maybe even a few cars in the parking lot will still remain – and remarkable transformations will occur with them.

At first the car will simply rust, but since iron dissolves well in oxygen-free water, this is exactly what will begin to happen to the metal parts of the car. Or, perhaps, the undercarriage of the car will begin to mineralize, react with sulfides and turn into pyrite. Iron in steel beams or reinforced concrete, kitchen utensils, or even tiny iron inclusions in a cell phone speaker will all take on a golden color. Even entire rooms, such as a food court kitchen with many stainless steel countertops, can be covered fool’s gold.

Plastic, protected from harsh weathering and exposure to ultraviolet radiation, will remain among the most durable materials. “No one knows for sure how long it will last,” Zalasivic says, “but it can be compared to another long-chain polymer.” If the insect got stuck in the molten plastic before the Tower was finally cut off from the world, it could be preserved just like a Jurassic beetle in amber.

Over time, the plastic will carbonize and become brittle. The aluminum sheets in the heating pipes will bind with silicates and slowly turn into kaolin, which will provide an ideal medium for fossilization. A hundred thousand years after the tower is abandoned, the kaolin will have hardened into schists, riddled with the eerie imprints of plastic knife handles, switches, and gear knobs.

The story will continue at even greater depths. The entire Shanghai Tower rests on concrete foundation one meter thick, covering an area of ​​almost 9 sq.m. Underneath it are 000 reinforced concrete piles, each a meter in diameter, driven into 86 m into soft ground. In a few million years, as the subsurface layers are eroded beyond recognition by the weight of water and sediment, some of these piles will crack, twisting within the compressed silt-clay formations like the fossilized roots of a gigantic, long-decayed tree.

As millions and then tens of millions of years pass, such transformations will slow down. Rare earth metals that leak from discarded cell phones and other electronics can form secondary mineral crystals. Car windshields and store windows will undergo devitrification, darkening just like obsidian that has been underground for a long time. By that time, the entire city will be compressed, taking the form of a layer perhaps no more than a few meters thick. All that will remain of Shanghai Tower is a geological anomaly littered with fossil imprints of chopsticks, chairs, SIM cards and hairpins.

All this will go underground, perhaps to a depth of several thousand meters. But geology never stands still. In about a hundred million years, as new mountain ranges begin to form, the compressed remains of the structure once called Shanghai Tower may be pushed up and found again.

“Buildings have their own stories,” writes Roma Agrawal in his book Built. They will tell the stories of those who lived in them, the history of the world for which they were built. The same applies to the remains of Shanghai Tower, even after such a long time. Any future archaeologists, whether representatives of some advanced terrestrial life form or aliens, will be able to recreate in amazing detail what the world looked like in the 21st century – provided that they have at their disposal the same methods that modern geologists have.

Fossils of bicycles or rubber boots will indicate that we were bipedal. A fossilized keyboard will reveal the shape of our hands, and glasses or hearing aids will tell us how we perceived the world. The shape of a denture, a motorcycle helmet, a wheelchair, a neoprene wetsuit, or even a store-bought mannequin will tell us about the shape of our bodies and perhaps even about our sexual dimorphism.

From an archaeological point of view, clothing was not durable for most of human history. But with the advent of plastic, we suddenly acquired super-wear-resistant techno-fur, that’s right – removable techno-fur.

In this way, traces will remain not only of our bodies, but also of our minds. The scale and complexity of our fossil cities will demonstrate that we were social creatures. Perhaps a geologist from the distant future will conclude that humanity was like social insects such as termites, but it is likely that there will also be ample evidence of personal ingenuity and the truly diverse fossil footprints that Zalasivic calls “technofossils”, indicating the opposite. Moreover, the scale of our ingenuity can be judged by the effort required to create a mobile phone: extracting hydrocarbons and metals located at great depths from the earth, and then delivering them from one continent to another, where they are processed in workshops with extremely complex assembly lines.

Like the fossilized burrows and grooves left by ancient creatures, similar fossils from our time (ichnofossils) will show how we moved. As well as the fact that we relied not only on our own locomotion. There are more than 300 km of metro lines. Since the metro will be well protected from erosion, it is possible that entire sections and even a carriage will be preserved. The preserved sections of the tunnels, along with curb stones, ventilation systems, glass shades and copper wiring for lighting fixtures, suggest that there was a network of underground roads the length of 50 million kilometers, which once covered the entire planet. Powerful coal deposits slag in the harbors of the largest port cities (slag in the 19th century was simply dumped from the side of steamships) will be read as nodes on the map of global navigation.

Fossils at the Shanghai Tower site can be compared with those of other high-rise buildings in other cities, painting a picture of a global culture of city dwellers who used the same synthetic materials in construction and used many similar things in everyday life. Such homogeneity will also be expressed in the paleobiology of the future. Fossils of a small handful of the same species will be found again and again on every continent except Antarctica. The “Anthropocene rat” will be the most typical species that lived during the era of great urban development. In landfills around the world, bones will be found mixed with construction waste and plastic. chicken populations, in the amount of 60 million individuals annually consumed by humanity as food.

In fact, it is likely that it is the landfills, rather than the remains of cities as such, that tell the most detailed stories about us. Modern landfills can reach tens of meters in thickness and occupy many square kilometers. They will be found by their wear-resistant neoprene. They will see that it is full of individual plastic bags of waste, serving as a double seal, protecting landfills from the corrosive effects of ultraviolet light, oxygen, water and caustic chemicals. Next to every relict city there will be a shadow city, a vast cultural layer by which it will be possible to judge everything that we threw away.

The stratigraphic record of the future will show that we have not all impacted the planet in the same way. Those who lived close to resource extraction sites made do with much less fuel than city dwellers. The fossils will point to this story about global inequality. They can also show how our actions have impacted generations of descendants who have been forced to deal with the consequences of our carbon addiction.

Perhaps it will be simple there is nobody find or comprehend the cultural layer of our cities. But that doesn’t mean we shouldn’t think about the long-term consequences. We could all benefit from learning to think like geologists. Environmental scientist Marcia Bjornerud calls for cultivating a sense of “timeliness,” which she describes as “a sense of distance and proximity on the geographical map of distant eras.” Her approach encourages us better understand the relevance of reflections about the extent of our impact on the planet, and what kind of history we would like capture in the fossils of the future.

After visiting Shanghai Tower, I took the train to Nanhui, a city now being built on the Pudong coast to help disperse the overcrowded Shanghai. When I got to the shore, the tide was low. Behind me stood a wave-like, curving wall slightly taller than I was, facing the sea. Shanghai is fenced off from the sea with such a barrier, the length of which is 520 km, but sooner or later the ocean will take the city. In 100 or 10 years, where the greatest metropolises once stood, civilization will slowly begin to transform into geology. “Let me show you the tide that will come for us,” wrote Kathy Jetnil-Kijener and Aka Nivyana in their poems Rise, – “and awaken our imagination, turning us into stone.”

  • Popular science
  • The future is here
  • Urbanism

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