Coal- this is a solid, exhaustible, non-renewable mineral that a person uses to obtain heat by burning it. According to the classification, it belongs to sedimentary rocks.

What it is?

Coal as a source of energy, people began to use in antiquity along with firewood. The “flammable stone” was found on the surface of the earth, later it was purposefully mined from under it.

Coal appeared on Earth about 300-350 million years ago, when tree-like ferns flourished in primeval swamps and the first gymnosperms. Huge trunks fell into the water, gradually forming thick layers of undecomposed organic matter. Wood with limited access to oxygen did not rot, but gradually sank deeper and deeper under its weight. Over time, due to the displacement of layers earth's crust, these layers sank to a considerable depth and there, under the influence of great pressure and elevated temperature, a qualitative change took place in wood into coal.

Types of coal

mined today different kinds coal.

• Anthracites are the hardest grades with great depth and maximum combustion temperature.
• Hard coal - many varieties mined in mines and open way. It is widely used in many areas of human activity.
• Brown coal - formed from the remains of peat, the youngest type of coal. Has the most low temperature combustion.

All types of coal lie in layers and their locations are called coal basins.

Coal mining

At first, coal was simply collected at the places where the seam came to the surface. This could have happened as a result of the displacement of the layers of the earth's crust.

Often after collapses in highlands such exits of the deposit were exposed, and people got the opportunity to get to the pieces of "combustible stone".

Later, when primitive technology appeared, coal began to be developed in an open way. Some coal mines plunged to a depth of more than 300 meters.

Today, thanks to the complex modern technology, people descend underground into mines, more than a kilometer deep. From these horizons, the highest quality and valuable coal is mined.

Where is coal used?

All types of coal can be used to generate heat. When burned, it releases much more than can be obtained from wood or other solid fuels. The hottest grades of coal are used in metallurgy, where high temperatures are needed.

In addition, coal is a valuable raw material for chemical industry. A lot of necessary and useful substances are extracted from it.

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For almost 200 years, humanity has been using reserves that have been formed for hundreds of millions of years. Such wastefulness will someday lead us to collapse and an energy crisis, until we begin to take better care of our resources. For a better understanding, it would be worth knowing how coal was formed and how many years the proven reserves will last.

The need for energy

All industries need constant source of energy:

• Energy is released during the combustion of hydrocarbons. In this regard, oil and gas are irreplaceable resources.
• It is possible to obtain the proper amount of energy due to nuclear power plants. The splitting of the atom is a promising industry, but a couple of disasters pushed this option into the background for a long time.
• wind, sun and even water currents can provide electricity. With a proper approach to the issue and the construction of modern structures.

Some new and promising industries today almost never develop and humanity is forced to continue to burn coal, smoke the sky and receive crumbs of energy. This state of affairs is beneficial to large corporations that receive huge incomes from the sale of combustible fuels.

Perhaps in the coming decades the situation will change at least a little and promising projects, in part alternatives energy, will give " green light". So far, one can only hope for the prudence of large investors who will prefer saving from energy crisis in future.

Where did coal come from?

Regarding the formation of coal, there is accepted scientific theory:

1. Somewhere around 300-400 million years ago, much more organic matter was growing on Earth. It's about plants, giant green plants.
2. Like all living things, plants died. Bacteria, at that stage, could not cope with the task complete decomposition these giants.
3. In the absence of oxygen access, entire layers of compressed and rotting ferns were formed.
4. Over the passing millions of years, epochs have changed, other formations were layered on top, the original layer lay deeper and deeper.

There is an opinion that gradually all this substance was transformed into peat, which later turned into coal. Similar transformations are taking place or may still be taking place, with theoretical point vision. But only in the presence of already formed peat, there is no longer a sufficient number of plants for the formation of new layers on the Earth. Not that era, not those climatic conditions.

It is worth noting that volume has changed dramatically.. Losses during the transition from peat to coal alone are 90%, and it is still unknown what the initial volume of dead plants was.

Properties of hard coal

All coal properties can be divided into significant for nature and for humans:

But still, the main and most interesting for us is the fact that a sufficient amount of energy is released during the combustion of coal. Approximately 75% of what can be obtained by burning the same amount of oil.

Defenders of nature are concerned about a completely different property - the ability to release carbon dioxide when burned . Burn a kilogram of coal and get almost 3 kg of emissions carbon dioxide in atmosphere. The global volume of consumption is already estimated at billions of tons of minerals, so the numbers are not funny at all.

Coal mining

In some countries, coal mines have long been closed:

• Low profitability. Today it is much more profitable to pump and sell oil and gas. Less cost, less possible consequences.
• High risk of accidents. Mine disasters are not uncommon in modern world even if all precautions are taken.
• Almost complete development of existing reserves. If a country started mining as early as the century before last and all the time "fed" from one coal basin, one should not expect much from it in our time.
• Availability of an alternative. It's about not only about oil and gas, nuclear energy has also taken its niche. Are being introduced solar panels, windmills, hydroelectric power stations. The process is slow but inevitable.

But someone is still forced to descend into the mine:

1. Mining occurs at a depth of up to 1 km, as a rule.
2. The cheapest way is to mine coal no deeper than 100 m, in which case it can be done using an open method.
3. Shifts of miners equipped with tools and respirators are constantly descending into the face.
4. Role manual labor decreased significantly, most of the work is done by mechanisms.
5. Despite this, miners are constantly at risk of being buried under rubble and buried in a makeshift common grave.
6. Constant exposure to dust causes problems with the respiratory tract. Pneumoconiosis officially recognized as an occupational disease.

To a certain degree such work is compensated by solid salaries and early retirement.

How did coal come about?

It took hundreds of millions of years to form coal.

Here is how the process of its formation on Earth went:

• Massively bred plants on the surface, due to favorable climatic conditions.
• Gradually they died, and microorganisms did not have time to completely process the remains.
• The organic mass formed a whole layer. In some areas, there was no access to oxygen, especially in swampy areas.
• Under anaerobic conditions, specific microorganisms continued to take part in the processes of putrefaction.
• New layers were layered on top, increasing the pressure.
• Thanks to organic basis With large quantity carbon, decay, constant pressure and hundreds of millions of years the formation of coal took place.

This is how scientists see the whole process, based on modern methods study.

Perhaps this picture will still be amended in the future, time will tell. In the meantime, we can only believe her or voice some of our assumptions. But to be taken seriously, they have to be proven.

It is not necessary to know how coal was formed in order to enjoy all the delights scientific and technological progress. But for general development worth checking out.

Video about the appearance of coal on Earth

In this video, geologist Leonid Yaroshin will tell you how and where coal was formed, how it is mined and where it is currently used:

Stuart E. Nevins, MS.

Accumulated, compacted and processed plants form a sedimentary rock, which is called coal. Coal is not only a source of huge economic importance, but also a breed that has a special appeal to the student studying the history of the earth. Despite the fact that coal forms less than one percent of all sedimentary rocks of the earth, it has great value for geologists who trust the Bible. It is coal that gives the Christian geologist one of the strongest geological arguments in favor of the reality of the global Noah's Flood.

Two theories have been proposed to explain the formation of coal. Popular theory The theory held by most uniformitarian geologists is that the plants that make up coal accumulated in huge freshwater swamps or peat bogs over many thousands of years. This first theory, which assumes the growth of plant material at the site of its discovery, is called autochthonous theory .

The second theory suggests that the coal seams accumulated from plants that were quickly transported from other places and deposited under flooding conditions. This second theory, according to which there was a movement of plant debris, is called allochthonous theory .

fossils in coal

The types of fossil plants that are found in coal are obviously do not support the autochthonous theory. Fossil trees of club mosses (for example, Lepidodendron and Sigillaria) and giant ferns (especially Psaronius) characteristic of Pennsylvania coal deposits may have had some ecological tolerance to swampy conditions, while other fossil plants of the Pennsylvania Basin (for example, conifer tree Cordaites, wintering giant horsetail Calamites, various extinct fern-like gymnosperms) in accordance with their basic structure must have preferred well-dried soils rather than swamps. Many researchers believe that anatomical structure fossil plants indicates that they grew in tropical or subtropical climates (an argument that can be used against the autochthonous theory), since modern swamps are the most extensive and have the deepest accumulation of peat in cooler climatic conditions more high latitudes. Due to the increased evaporative power of the sun, modern tropical and subtropical areas are the poorest in peat.

Often found in the corner marine fossils, such as fossil fish, molluscs, and brachiopods (brachiopods). Coal seams are found to be balls of coal, which are rounded masses of crumpled and incredibly well-preserved plants, as well as fossil animals (including marine animals) that are directly related to these coal seams. small marine ringed worm Spirorbis is generally found attached to European coal plants and North America that belong to the Carboniferous period. Since the anatomical structure of fossil plants shows little evidence that they were adapted to sea swamps, the occurrence of marine animals along with non-marine plants suggests that mixing occurred during movement, thus supporting the allochthonous theory model.

Among the most amazing types of fossils that are found in coal layers are vertical tree trunks, which are perpendicular to the bedding often intersect tens of feet of rock. These vertical trees are often found in seams that are associated with coal deposits, and in rare cases they are found in the corner itself. In any case, sediment must accumulate quickly in order to cover the trees before they deteriorate and fall.

How long does it take for layers of sedimentary rocks to form? Take a look at this ten meter petrified tree, one of hundreds discovered in the coal mines of Cookeville, Tennessee, USA. This tree starts in one coal bed, goes up through numerous layers, and finally ends in another coal seam. Think about this: what would happen to top tree for thousands of years required (according to evolution) for the formation of sedimentary layers and coal seams? Obviously, the formation of sedimentary layers and seams of coal had to be catastrophic (rapid) in order to bury the tree in an upright position before it rots and falls. Such "standing trees" are found in numerous places on the earth and at different levels. Despite the evidence, long periods of time (required for evolution) are squeezed between the layers, for which there is no evidence.

One might get the impression that these trees are in their original growth position, but some evidence indicates that this is not the case at all, and even vice versa. Some trees cross the layers diagonally, and some are found upside down. Sometimes vertical trees appear to have taken root in a growth position in layers that are completely penetrated by a second vertical tree. Hollow trunks of fossil trees, as a rule, are filled with sedimentary rock, which differs from the nearby adjacent ones. rocks. Applicable to the examples described, the logic indicates the movement of these trunks.

fossil roots

The most important fossil that has direct relation to disputes over the origin of coal, is stigmaria- Fossil root or rhizome. Stigmaria it is most commonly found in seams that lie beneath coal seams and is generally associated with vertical trees. It was believed that stigmaria, which was studied 140 years ago by Charles Lyell and D.W. Dawson in the Carboniferous coal sequence in Nova Scotia, is unambiguous evidence that the plant grew in this particular place.

Many modern geologists continue to insist that stigmaria is a root that formed in this place, and which goes into the soil below the coal marsh. The coal sequence of Nova Scotia was recently re-examined by H.A. Rupke, who found four arguments in favor of allochthonous origin of stigmaria obtained on the basis of the study of sedimentary deposits. The fossil found is usually detrital and rarely attached to the trunk - this indicates a preferred orientation of its horizontal axis, which was created as a result of the action of the current. In addition, the stem is filled with sediment that is unlike the rock surrounding the stem, and is often found at many levels in strata that are completely pierced by vertical trees. Rupke's research cast serious doubts on the popular autochthonous explanation of other strata in which stigmaria.

Cyclothemes

Coal usually occurs in a sequence of sedimentary rocks called cyclotheme .idealized Pennsylvania cyclotheme may have strata deposited in the following ascending order: sandstone, shale, limestone, underlying clay, coal, shale, limestone, shale. AT typical cyclotheme, as a rule, one of the constituent layers is missing. At each site cyclothemes each deposition cycle is usually repeated dozens of times, with each deposition resting on the previous deposition. In Illinois is fifty sequentially arranged cycles, and more than a hundred such cycles occur in West Virginia.

Although the coal seam that forms part of a typical cyclothemes, usually quite thin (typically one inch to several feet thick) the lateral arrangement of coal has incredible dimensions. In one of the recent stratigraphic studies4, a relationship was drawn between coal deposits: Broken Arrow (Oklahoma), Crowberg (Missouri), Whitebrest (Iowa), Colchester Number 2 (Illinois), Coal IIIa (Indiana), Schultztown ( Western Kentucky), Princess Number 6 (Eastern Kentucky), and Lower Kittanning (Ohio and Pennsylvania). They all form one, huge coal seam that extends for hundreds of thousands of square kilometers in the central and eastern United States. No modern swamp has an area that even slightly approaches the size of the Pennsylvania coal deposits.

If the autochthonous model of coal formation is correct, then very unusual circumstances must have prevailed. The entire area, often comprising tens of thousands of square kilometers, would have to simultaneously rise above sea level in order for the swamp to accumulate, and then it would have to sink in order to be flooded by the ocean. If the fossil forests rose too high above sea level, the swamp and its antiseptic water needed to accumulate peat would simply evaporate. If the marsh was invaded by the sea during the accumulation of peat, the marine conditions would destroy the plants and other sediments and the peat would not be deposited. Then, according to the popular model, the formation of a thick coal seam would indicate the maintenance of an incredible balance over many thousands of years between the rate of peat accumulation and sea level rise. This situation seems the most improbable, especially if we remember that the cyclotheme is repeated in a vertical section hundreds of times or even more. Or perhaps these cycles can best be explained as accumulation that occurred during the successive rise and retreat of the flood waters?

Shale

When it comes to the cyclotheme, the underlying clay is of most interest. The underlying clay is a soft layer of clay that is not arranged in layers and often lies beneath the coal seam. Many geologists believe that this is a fossil soil on which a swamp existed. The presence of underlying clay, especially when found in it stigmaria, often interpreted as enough proof autochthonous origin of coal-forming plants.

However, a recent study has questioned the interpretation of the underlying clay as fossil soil. No soil characteristics that were similar to those of modern soil have been found in the underlying clay. Some of the minerals found in the underlying soil are not the types of minerals that should be found in the soil. On the contrary, the underlying clays, as a rule, have rhythmic layering (larger granular material is located at the very bottom) and signs of the formation of clay flakes. it simple characteristics sedimentary rocks that would form in any layer that accumulated in the water.

Many coal layers do not rest on the underlying clays, and there are no signs of soil existence. In some cases, coal seams rest on granite, slate, limestone, conglomerate, or other rocks that do not resemble soil. Underlayment clay without an overlying coal seam is common, and underlayment clay often overlies the coal seam. The absence of recognizable soils below the coal seams indicates that no type of lush vegetation could grow here and supports the idea that coal-forming plants were moved here.

Structure of coal

The study of the microscopic structure and structure of peat and coal helps to understand the origin of coal. A.D. Cohen initiated a comparative structural study of modern autochthonous peat formed from mangrove trees and a rare modern allochthonous coastal peat from south Florida. Most autochthonous peats contained plant fragments that had a disordered orientation with a predominant matrix of more fine material, while the allochthonous peat had an orientation formed by water flows with elongated axes of plant fragments, which were located, as a rule, parallel to the coastal surface with a characteristic absence of a finer matrix. Poorly sorted plant debris in autochthonous peat had a large structure due to the intertwined mass of roots, while autochthonous peat had a characteristic microlayering due to the absence of ingrown roots.

In conducting this study, Cohen noted: "In the course of the study of allochthonous peat, one feature was revealed, which was that vertical sections of this material, made using a microtome, looked more like thin sections of coal than any autochthonous sample studied". Cohen drew attention to the fact that the characteristics of this autochthonous peat (orientation of elongated fragments, sorted granular structure with general lack finer matrix, microlayering with no entangled root structure) are also characteristics of coals of the Carboniferous period!

Lumps in the coal

One of the most impressive external features coal is the presence in it of large blocks. For more than a hundred years, these large blocks have been found in coal seams around the world. P.H. Price conducted a study in which he studied large blocks of the Sewell coal deposit, which is located in West Virginia. The average weight of 40 boulders collected was 12 pounds, and the largest boulder weighed 161 pounds. Many cobblestones were volcanic or metamorphic rock, unlike all other rock outcrops in West Virginia. Price surmised that the large boulders could have weaved themselves into the roots of the trees and been transported here from afar. Thus, the presence of large blocks in the coal supports the allochthonous model.

coalification

Disputes regarding the nature of the process of turning peat into coal have been going on for many years. One existing theory suggests that it is time is the main factor in the coalification process. However, this theory fell out of favor because it was found that there was no systematic increase in the metamorphic stage of coal over time. There are several clear inconsistencies: lignites, which are the lowest stage of metamorphism, occur in some of the oldest coal-bearing strata, while anthracites, which represent the most the highest degree metamorphism of coal, occur in young layers.

The second theory regarding the process of turning peat into coal suggests that the main factor in the process of coal metamorphism is pressure. However this theory refuted by numerous geological examples in which the stage of coal metamorphism does not increase in highly deformed and folded seams. Moreover, laboratory experiments show that an increase in pressure can actually slow down chemical transformation peat into coal.

The third theory (by far the most popular) suggests that the most an important factor in the process of coal metamorphism is temperature. Geological examples (volcanic intrusions in coal seams and underground fires in mines) show that fever can cause carbonation. Laboratory experiments were also quite successful in confirming this theory. As a result of one experiment, using a rapid heating process, an anthracite-like substance was formed in just a few minutes, while most of heat was generated as a result of the transformation of the cellulose material. Thus, the metamorphism of coal does not require millions of years of exposure to heat and pressure - it can be formed as a result of rapid heating.

Conclusion

We see that a lot of corroborating evidence decisively proves the truth of the allochthonous theory and confirms the accumulation of multiple coal layers during Noah's Flood. Upright fossil trees inside coal layers confirm the rapid accumulation plant residues. Marine animals and terrestrial (rather than growing and living in a swamp) plants found in coal imply their movement. The microstructure of many coal seams has a specific particle orientation, sorted grain structure, and microlayering, which indicates movement (rather than in situ growth) of plant material. The large blocks present in the coal testify to the processes of movement. The absence of soil under many coal seams confirms the fact that coal-forming plants floated with the flow. Charcoal has been shown to form systematic and typical portions cyclothemes, which obviously, like other rocks, were deposited by water. Experiments to study the change in plant material show that coal-like anthracite does not need millions of years to form - it can be formed quickly under the influence of heat.

Links

*Professor of Geology and Archaeology, Christian Heritage College, El Cajon, California.

Coal is a sedimentary rock that forms in the earth's seam. Coal is an excellent fuel. It is believed that this is the most ancient view fuel, which was used by our distant ancestors.

How coal is formed

For the formation of coal, it is necessary great amount plant mass. And it is better if the plants accumulate in one place and do not have time to decompose completely. The ideal place for this is swamps. The water in them is poor in oxygen, which prevents the vital activity of bacteria.

Vegetation mass accumulates in swamps. Not having time to completely rot, it is compressed by the following soil deposits. This is how peat is obtained - the source material for coal. The next layers of soil, as it were, seal the peat in the ground. As a result, it is completely deprived of access to oxygen and water and turns into a coal seam. This process is lengthy. So, most of the modern reserves of coal were formed in the Paleozoic era, that is, more than 300 million years ago.

Characteristics and types of coal

(Brown coal)

The chemical composition of coal depends on its age.

The youngest kind brown coal. It lies at a depth of about 1 km. There is still a lot of water in it - about 43%. Contains a large number of volatile substances. It ignites and burns well, but gives little heat.

Hard coal is a kind of "middling" in this classification. It occurs at depths up to 3 km. Since the pressure of the upper layers is greater, the water content in coal is less - about 12%, volatile substances - up to 32%, but carbon contains from 75% to 95%. It is also highly flammable, but burns better. And due to the small amount of moisture, it gives more heat.

Anthracite is an older breed. It occurs at depths of about 5 km. It has more carbon and almost no moisture. Anthracite is a solid fuel, does not ignite well, but specific heat combustion is the highest - up to 7400 kcal / kg.

(Anthracite coal)

However, anthracite is not the final stage of transformation organic matter. When exposed to harsher conditions, coal transforms into shuntite. With more high temperatures get graphite. And when subjected to ultra-high pressure, coal turns into diamond. All these substances, from plants to diamonds, are made up of carbon, only molecular structure different.

In addition to the main "ingredients", the composition of coal often includes various "rocks". These are impurities that do not burn, but form slag. Contained in coal and sulfur, and its content is determined by the place of formation of coal. When burned, it reacts with oxygen to form sulfuric acid. The less impurities in the composition of coal, the higher its grade is valued.

Coal deposit

The place of occurrence of coal is called a coal basin. Over 3.6 thousand coal basins are known in the world. Their area occupies about 15% of the earth's land area. The largest percentage of deposits of the world's coal reserves in the United States - 23%. In second place - Russia, 13%. China closes the top three leading countries - 11%. The largest coal deposits in the world are located in the USA. This is the Appalachian coal basin, whose reserves exceed 1600 billion tons.

In Russia, the largest coal basin is Kuznetsk, which is in Kemerovo region. The reserves of Kuzbass amount to 640 billion tons.

The development of deposits in Yakutia (Elginskoye) and in Tyva (Elegestskoye) is promising.

Coal mining

Depending on the depth of the coal, either a closed mining method or an open one is used.

Closed, or underground mining method. For this method, mine shafts and adits are built. Mine shafts are built if the depth of coal is 45 meters or more. A horizontal tunnel leads from it - an adit.

There are 2 closed mining systems: room and pillar mining and longwall mining. The first system is less economical. It is used only in cases where the discovered layers are thick. The second system is much safer and more practical. It allows you to extract up to 80% of the rock and evenly deliver coal to the surface.

The open method is used when the coal is shallow. To begin with, an analysis of the hardness of the soil is carried out, the degree of soil weathering and the layering of the covering layer are ascertained. If the ground above the coal seams is soft, the use of bulldozers and scrapers is sufficient. If the upper layer is thick, then excavators and draglines are brought in. A thick layer of hard rock lying above the coal is blown up.

The use of coal

The area of ​​use of coal is simply huge.

Sulfur, vanadium, germanium, zinc, and lead are extracted from coal.

Coal itself is an excellent fuel.

It is used in metallurgy for iron smelting, in the production of iron, steel.

The ash obtained after burning coal is used in the production of building materials.

From coal, after its special processing, benzene and xylene are obtained, which are used in the production of varnishes, paints, solvents, and linoleum.

By liquefying coal, a first-class liquid fuel is obtained.

Coal is the raw material for producing graphite. As well as naphthalene and a number of other aromatic compounds.

As a result of the chemical processing of coal, more than 400 types of industrial products are currently obtained.

Coal, like oil and gas, is organic matter that has been slowly decomposed by biological and geological processes. The basis of coal formation is plant residues. Depending on the degree of transformation and the specific amount of carbon in coal, four types of it are distinguished: brown coals (lignites), hard coals, anthracites and graphites. AT Western countries there is a slightly different classification - lignites, sub-bituminous coals, bituminous coals, anthracites and graphites, respectively.

Anthracite

Anthracite- the most deeply warmed up at its origin from fossil coals, coal of the highest degree of coalification. It is characterized by high density and gloss. Contains 95% carbon. It is used as a solid high-calorie fuel (calorific value 6800-8350 kcal/kg). They have the highest calorific value, but ignite poorly. They are formed from coal with an increase in pressure and temperature at depths of about 6 kilometers.

Coal

Coal- sedimentary rock, which is a product of deep decomposition of plant remains (tree ferns, horsetails and club mosses, as well as the first gymnosperms). By chemical composition coal is a mixture of high molecular weight polycyclic aromatic compounds with high mass fraction carbon, as well as water and volatile substances with small amounts of mineral impurities, which form ash when coal is burned. Fossil coals differ from each other in the ratio of their components, which determines their heat of combustion. A number of organic compounds that make up coal have carcinogenic properties.

Brown coal- solid fossil coal formed from peat, contains 65-70% carbon, has a brown color, the youngest of fossil coals. It is used as a local fuel, as well as a chemical raw material. They contain a lot of water (43%) and therefore have a low calorific value. In addition, they contain a large number of volatile substances (up to 50%). They are formed from dead organic residues under the pressure of the load and under the influence of elevated temperature at depths of the order of 1 kilometer.

Coal mining

Coal mining methods depend on the depth of its occurrence. The development is carried out by an open method in coal mines, if the depth of the coal seam does not exceed 100 meters. There are also frequent cases when, with an ever-increasing deepening of a coal pit, it is further advantageous to develop a coal deposit by an underground method. Mines are used to extract coal from great depths. The deepest mines in the Russian Federation extract coal from a level of just over 1200 meters.

Along with coal, coal-bearing deposits contain many types of georesources that have consumer significance. These include host rocks as a raw material for the construction industry, groundwater, coal-bed methane, rare and trace elements, including valuable metals and their compounds. For example, some coals are enriched with germanium.