How microorganisms formed the earth's crust

2024 Author: Seth Attwood | [email protected]. Last modified: 2023-12-16 15:55

The mountains look especially impressive against the backdrop of the endless Mongolian steppe. Standing at the foot, one is tempted to reflect on the colossal power of the earth's bowels that have piled up these ridges. But already on the way to the top, a thin pattern covering the rocky ledges catches the eye. This rainwater slightly corroded the porous skeletons of the ancient archaeocyate sponges that made up the mountain, the real builders of the mountain range.

Little giants of big construction

Once, more than half a billion years ago, they rose from the bottom of a warm sea as a bright reef of a volcanic island. He died, covered with a thick layer of hot ash - some archaeocyates were even burned out, and cavities were preserved in the frozen tuff.

However, many skeletons, which had grown together during their lifetime and were "frozen" into the rock by winding layers of sea cement, remain in their usual places even today, when the sea has been gone for a long time. Each such skeleton is smaller than a little finger. How many are there?

The skeletons of tiny radiolarians form the siliceous rocks of the mountain ranges.

Having estimated the volume of a low mountain (about a kilometer across at the foot and about 300 m in height), we can calculate that about 30 billion sponges took part in its construction. This is a grossly underestimated figure: many skeletons have long been rubbed into powder, others have completely dissolved, without having time to be covered with protective layers of sediment. And this is only one mountain, and in the west of Mongolia there are entire ranges.

How long did it take for small sponges to complete such a grandiose "project"?

And here is another cliff nearby, smaller, and not white, limestone, but reddish-gray. It is formed by thin layers of siliceous shale, rusty due to the oxidation of iron inclusions. At one time, these mountains were the seabed, and if you correctly split along the layers (hit hard, but carefully), then on the surface that opens you can see myriads of needles and crosses of 3-5 mm.

These are the remains of sea sponges, but, in contrast to the whole calcareous skeleton of archaeocyates, their base is formed from separate silicon elements (spicules). Therefore, having died, they crumbled, strewn the bottom with their "details."

The skeleton of each sponge consisted of at least a thousand "needles", about 100 thousand of them are scattered on each square meter. Simple arithmetic allows us to estimate how many animals it took to form a 20-meter layer on an area of at least 200 x 200 m: 800 billion. And this is just one of the heights around us - and only a couple of rough calculations. But already from them it is clear that the smaller the organisms, the greater their creative power: the main builders of the Earth are unicellular.

Openwork calcareous plates of unicellular planktonic algae - coccoliths - are combined into large coccospheres, and when they crumble, they turn into chalk deposits.

On land, in water and in the air

It is known that in every 1 cm³Writing chalk contains about 10 billion fine calcareous scales of planktonic algae coccolithophorids. Much later than the time of the Mongolian seas, in the Mesozoic and the present Cenozoic era, they erected the chalk cliffs of England, the Volga Zhiguli and other massifs, covered the bottom of all modern oceans.

The scale of their construction activities is amazing. But they pale in comparison with other transformations that her own life has made on the planet.

The salty taste of the seas and oceans is determined by the presence of chlorine and sodium. Neither element is required by sea creatures in large quantities, and they accumulate in aqueous solution. But almost everything else - everything that is carried out by rivers and comes from the bowels through hot bottom springs - is absorbed in an instant. Silicon is taken for their ornate shells by unicellular diatoms and radiolarians.

Almost all organisms need phosphorus, calcium and, of course, carbon. Interestingly, the creation of a calcareous skeleton (like that of corals or ancient archaeocyates) occurs with the release of carbon dioxide, so the greenhouse effect is a byproduct of building reefs.

Coccolithophorides absorb not only calcium from water, but also dissolved sulfur. It is required for the synthesis of organic compounds that increase the buoyancy of algae and allow them to stay close to an illuminated surface.

When these cells die off, the organics disintegrate, and the volatile sulfur compounds evaporate along with the water, serving as a seed for the formation of clouds. A liter of seawater can contain up to 200 million coccolithophorids, and each year these unicellular organisms supply up to 15.5 million tons of sulfur to the atmosphere - almost twice as much as land volcanoes.

The sun is capable of giving the Earth 100 million times more energy than the planet's own bowels (3400 W / m² against 0.00009 W / m²). Thanks to photosynthesis, life can use these resources, gaining power that exceeds the capabilities of geological processes. Of course, much of the sun's heat is simply dissipated. But all the same, the flow of energy produced by living organisms is 30 times higher than the geological one. Life has controlled the planet for at least 4 billion years.

Native gold sometimes forms bizarre crystals that are more valuable than the precious metal itself.

Forces of light, forces of darkness

Without living organisms, many sedimentary rocks would not have formed at all. Mineralogist Robert Hazen, who compared the variety of minerals on the Moon (150 species), Mars (500) and our planet (more than 5000), concluded that the appearance of thousands of terrestrial minerals is directly or indirectly related to the activity of its biosphere. Sedimentary rocks accumulated at the bottom of water bodies.

Sinking to a depth, over millions and hundreds of millions of years, the remains of organisms formed powerful deposits, which remained to be squeezed out to the surface in the form of mountain ranges. This is due to the movement and collision of huge tectonic plates. But tectonics itself would not have been possible without dividing rocks into a kind of "dark" and "light matter".

The first is represented, for example, by basalts, where minerals of dark tones predominate - pyroxenes, olivines, basic plagioclases, and among the elements - magnesium and iron. The latter, such as granites, are composed of light-colored minerals - quartz, potassium feldspars, albite plagioclases, rich in iron, aluminum and silicon.

Dark rocks are denser than light rocks (on average 2.9 g / cm³ against 2.5-2.7 g / cm³) and form oceanic plates. When colliding with less dense, "light" continental plates, oceanic ones sink under them and melt in the bowels of the planet.

The bright banding of the iron ores reflects the seasonal alternation of dark siliceous and red ferruginous layers.

The oldest minerals indicate that it was "dark matter" that appeared first. However, these dense rocks could not sink into themselves to set the plates in motion. This required the "bright side" - minerals, which are in short supply in the immobile crust of Mars and the Moon.

It is not without reason that Robert Hazen believes that it was the living organisms of the Earth, transforming some rocks into others, that ultimately led to the accumulation of the "light matter" of the plates. Of course, these creatures - for the most part unicellular actinomycetes and other bacteria - did not set themselves such a super task. Their goal, as always, was to find food.

Ferrous metallurgy of the oceans

In fact, the basalt glass erupted by the volcano is 17% iron, and each cubic meter of it is capable of feeding 25 quadrillion iron bacteria. Existing at least 1.9 billion years, they skillfully transform basalt into a “nanoshet” filled with new clay minerals (in recent years, such a mechanism has been recognized as a biogenic factory of clay minerals). When such a rock is sent to the bowels for melting, new, "light" minerals are formed from it.

Probably the product of bacteria and iron ores. More than half of them were formed between 2, 6 and 1.85 billion years ago, and the Kursk magnetic anomaly alone contains about 55 billion tons of iron. Without life, they could hardly accumulate: for oxidation and precipitation of iron dissolved in the ocean, free oxygen is required, the appearance of which in the required volumes is possible only through photosynthesis.

Acidovorax bacteria stimulate the formation of green rust - iron hydroxide.

Life is able to carry out the "processing" of iron and in the dark, oxygen-deprived depths. The atoms of this metal, carried away by underwater sources, are captured by bacteria capable of oxidizing ferrous iron to form ferric iron, which settles to the bottom with green rust.

A couple of billion years ago, when there was still very little oxygen on the planet, this happened everywhere, and today the activity of these bacteria can be seen in some oxygen-poor water bodies.

Precious microbes

It is possible that large deposits of gold would not have appeared without the participation of anaerobic bacteria that do not need oxygen. The main deposits of the precious metal (including in the Witwatersrand in southern Africa, where the explored reserves are about 81 thousand tons) were formed 3, 8-2, 5 billion years ago.

Traditionally, it was believed that the local gold ores were formed by the transfer and washing of gold particles by rivers. However, the study of Witwatersrand gold reveals a completely different picture: the metal was "mined" by ancient bacteria.

Dieter Halbauer described strange carbon pillars framed by particles of pure gold back in 1978. For a long time, his discovery did not attract much attention until microscopic and isotopic analysis of ore samples, modeling of ore formation by colonies of modern microbes and other calculations confirmed the geologist's correctness.

Apparently, about 2.6 billion years ago, when volcanoes saturated the atmosphere with hydrogen sulfide, sulfuric acid and sulfur dioxide with water vapor, acid rains washed away the rocks containing scattered gold and carried solutions to shallow water. However, the precious metal itself came there in the form of the most dangerous compounds for any living creatures, like cyanide.

Averting the threat, microbes “disinfected” the water, reducing toxic gold salts to organometallic complexes or even to pure metal. The glittering particles settled on the bacterial colonies, forming casts of multicellular chains, which can now be viewed with a scanning electron microscope. Microbes continue to precipitate gold even now - this process is observed, for example, in hot springs in New Zealand, albeit on a very modest scale.

Both the Witwatersrand and, probably, other deposits of the same age were the result of the vital activity of bacterial communities in an oxygen-free atmosphere. The Kursk Magnetic Anomaly and related iron ore deposits were formed at the beginning of the oxygen epoch. However, more deposits of this scale did not appear and are unlikely to ever begin to take shape again: the composition of the atmosphere, rocks and ocean waters has changed many times since then.

But during this time, countless generations of living organisms have also changed, and each of them managed to take part in the global evolution of the Earth. The thickets of sea sponges and treelike horsetails of the land have disappeared, even herds of mammoths are a thing of the past, leaving a trace in geology. The time has come for other beings and new changes in all the shells of our planet - water, air and stone.