In the bowels of the earth is almost the entire periodic table. Chemical elements form compounds with each other that make up natural minerals. One or more minerals may be included in the rocks of the earth. In the article we will try to deal with their diversity, properties and meaning.
What are rocks
For the first time this term was used by our Russian scientist Severgin in 1978. The definition can be given as follows: rocks are a combination into a single whole of several minerals of natural origin, which has a constant structure and composition. Rocks can be found everywhere, as they are an integral part of the earth's crust.
If you study the description of rocks, then they all differ in features:
- Density.
- Porosity.
- Color.
- Strength.
- Resistant to severe frosts.
- Decorative qualities.
Depending on the combination of qualities, they are used.
Rock diversity
The division of rocks into different types is based on the chemical and mineral composition. The name of the rocks is given independing on their origin. Consider what groups they are divided into. A common classification might look like this.
1. Sedimentary rocks:
- clastic rocks;
- organogenic;
- chemogenic;
- mixed.
2. Igneous:
- volcanic;
- plutonic;
- hypabyssal.
3. Metamorphic:
- isochemical;
- metasomatic;
- ultrametamorphic.
Next, consider in more detail the characteristics of these breeds.
Sedimentary rocks
Any rocks, being under the influence of various factors and external processes, can be deformed, change their shape. They begin to collapse, fragments are carried, they can be deposited on the bottom of the seas and oceans. As a result, sedimentary rocks are formed.
It is difficult to classify rocks of sedimentary origin, since most of them were formed under the influence of many processes, and therefore it is almost impossible to attribute them to a specific group. Currently, this type of breed is divided into:
- Clastic rocks. There are different examples: gravel or crushed stone, sand and clay, and many others that are familiar to everyone.
- Organogenic.
- Chemogenic.
Let's dwell a little more on each type of breed.
Clastic rocks
They appear as a result of the formation of debris. If we classify them withtaking into account their structure, they distinguish:
- Cemented rocks.
- Not cemented.
The first variety has a connecting component in its composition, which can be represented by carbonates, clays. The second variety does not have such substances, therefore it has a loose structure.
It can be further clarified that clastic rocks often include traces and remains of plant and animal organisms. These include mollusk shells, preserved fossilized parts of the stem, insect wings.
Clastic rocks are best known. Examples confirm this. Clastics include well-known sand and clay, crushed stone and gravel, as well as many others. All of them are widely used in the construction industry.
Chemogenic rocks
This group is the product of chemical reactions. S alts, such as potassium s alts, and bauxites can be attributed to them. The process of formation of this type of rock can go in two ways:
- Gradual process of concentration of solutions. The influence of radiation from the sun is not excluded here.
- Combining several s alts at low temperature.
The structure of such breeds will depend on the place of their appearance. Those that form on the surface of the earth are in the form of a layer, while the deep ones are completely different.
Rocks from this group are very widely used, examples only confirm this. Chemogenic rocks include:
- Mineral s alts.
- Bauxites.
- Limestones.
- Dolomite and magnesite and manyothers.
In nature, there are quite often breeds, in the formation of which various natural processes took part. The name of the rocks that originated in this way is mixed. For example, you can find sands mixed with clay.
Organogenic sedimentary rocks
If clastic rocks sometimes include the remains of living organisms in their composition, then this group only consists of them. It consists of:
- Oil and shale.
- Bitumens.
- Phosphate rocks.
- Carbonate compounds, such as chalk used to write on a blackboard.
- Limestones.
If we talk about the composition, then limestone and chalk almost entirely consist of the remains of shells of ancient mollusks, foraminifera, corals, and algae are also part of them. Given that different organisms can give rise to an organogenic rock, they are divided into several varieties:
- Bioherms. This is the name of the accumulation of living organisms.
- Thanatocenoses and taphrocenoses are the remains of organisms that lived in these places for a long time or were brought by water.
- Planktonic rocks were formed from organisms living in water bodies.
Grain size of sedimentary rocks
This feature is one of the characteristics of the structure of sedimentary rocks. If you look at the rocks, they can be divided into homogeneous and with inclusions. In the first variant, the whole breed is perceived as a homogeneous mass, and in the second one can consider individualfractions, grains and their shape and ratio.
If we consider the size of fractions, we can distinguish several groups:
- The grains are quite visible.
- Hidden-grained visually appear structureless.
- In the third group, it is impossible to see the granularity without special equipment.
The shape of the inclusions may be one of the criteria by which these rocks are separated. There are several types of structures:
- Hypodiomorphic. In this type, the crystals obtained from the solution act as grains.
- Hipidioblast type refers to an intermediate structure in which substances are redistributed in an already hardened rock.
- Granoblastic, or leaf, has irregularly shaped crystals.
- Mechanoconforous type is formed as a result of mechanical action of grains under the pressure of those layers that are located above.
- Non-conformally granular has the main feature in the form of different grain outlines, which leads to the appearance of voids and porosity.
In addition to the structure, they also highlight the texture. The division is based on layering:
- Gradation. Its formation is carried out at great depths under water.
- Interlayer occurs in some layers of water, this type can be attributed to clay smudges, layers of sand in clay.
- Interleaved occurs when the layer thickness is large, you can observe a change in the color gamut of the layers. An example is the alternation of clay and sand.
One could give many more classifications, but let's stop here.
Representatives of sedimentary rocks
We have already considered sedimentary clastic rocks, examples of them have also been given, and now we will focus on others that are also widespread in nature.
- Gravelites. They are sedimentary rocks in the form of gravel. They include fragments of rocks and minerals of various sizes.
- Sand rocks. This includes sands and sandstones.
- Silty rocks are somewhat reminiscent of sandstones, only in their composition they have more stable minerals in the form of quartz, muscovite.
- Siltstone is characterized by fracture roughness, and the color depends on the cementing material.
- Loams.
- Clay rock.
- Argillites.
- Marls are a mixture of carbonates and clay.
- Limestones that are composed of calcite.
- Chalk
- Dolomites resemble limestones, only instead of calcite they contain dolomite.
All these rocks are widely used in construction and other sectors of the economy.
Metamorphic rocks
If you remember what metamorphosis is, it will become clear that metamorphic rocks appear as a result of the transformation of minerals and rocks under the influence of temperature, light, pressure, water. The most famous of this group are: marble, quartzite, gneiss, schists and some others.
Since different types can undergo metamorphosisbreeds, then the classification depends on this:
- Metabasites are rocks that result from the transformation of igneous and sedimentary rocks.
- Metapelites are the result of the transformation of acidic sedimentary rocks.
- Carbonate rocks such as marble.
The shape of the metamorphic rock is preserved from the previous one, for example, if the rock was previously located in layers, then the newly formed one will have the same shape. The chemical composition, of course, depends on the original rock, but under the influence of transformations it can change. The mineral composition can be different, and it can include both one mineral and several.
Igneous rocks
This group of rocks makes up almost 60% of the entire earth's crust. They arise as a result of the melting of rocks in the mantle or in the lower part of the earth's crust. Magma is a molten substance, partially or completely, enriched with various gases. The formation process is always associated with a high temperature in the bowels of the earth. Geological processes occurring inside the earth constantly provoke magma to rise to the surface. In the process of uplift, cooling and crystallization of minerals occurs. This is how the formation of igneous rocks looks like.
Depending on the depth at which solidification occurs, rocks are divided into several groups, the table of varieties may look like this:
| Plutonic | Volcanic | Hypabyssal |
| Such rocks are formed in the lower partthe earth's crust. | Formated when magma erupts to the surface. | Rock appears when magma fills cracks in existing rocks. |
Igneous rocks differ from detrital ones in that they do not contain the remains of dead organisms. Rock granite is one of the most famous among this group. It consists of: feldspar, quartz and mica.
When a volcano erupts, the magma, leaving the surface of the earth, gradually cools down and forms rocks of a volcanic type. They do not contain large crystals, since the temperature decrease occurs rather quickly. Representatives of such rocks are bas alt and granite. They were often used in ancient times to make monuments and sculptures.
Clastic volcanogenic rocks
In the process of volcanic eruptions, not only granite rock is formed, but also many others. In addition to the outpouring of lava, a large amount of debris flies into the atmosphere, which, together with clots of hardening lava, fall to the surface of the earth and form tephra. This pyroclastic material is gradually eroded, part of it is destroyed by water, and what remains is compacted and turns into strong rocks - volcanic tuffs.
At the fault of these rocks, you can see fragments, the gaps between which are filled with ash, sometimes clay or siliceous sedimentary substances.
Rock weathering
All rocks, being in nature, are exposed to many factors,resulting in weathering or destruction. Depending on the influencing influence, several types of this process are distinguished:
- Physical weathering of rocks. It occurs due to temperature changes, as a result of which the rocks crack, water gets into these cracks, which can turn into ice at low temperatures. This is how the destruction of the rock gradually occurs.
- Chemical weathering is carried out under the action of water, which enters the cracks of the rock and leaches, dissolves it. Marble, limestone, s alt are most susceptible to such an effect.
- Biological weathering is carried out with the participation of living organisms. For example, plants destroy the rock with their roots, the lichens that have settled on them secrete some acids, which also have a destructive effect.
It is almost impossible to avoid the process of rock weathering.
Meaning of rocks
It is impossible to imagine the national economy without the use of rocks. Such an application began in ancient times, when a person learned to process stones. First of all, rocks are used in the construction industry. Examples include:
- Marble.
- Limestone.
- Chalk
- Granite.
- Quartzite and others.
Their use in construction is based on strength and other important qualities.
Some breeds find their application in the metallurgicalindustry, e.g. refractory clay, limestone, dolomites. The chemical industry is inseparable from rock s alt, tripoli, diatomaceous earth.
Even light industry uses rocks for their needs. Agriculture cannot do without potassium s alts, phosphorites, which are an important part of fertilizers.
Thus, we have considered the rocks. And we can conclude that at present they are indisputable and necessary helpers of a person in almost every industry, from everyday life to construction. That is why the most commonly used concept is not a rock, but a mineral, which exactly expresses the significance of these natural deposits.
