How are fossils formed? How are fossils formed?

Fossils are the relics of ancient creatures buried in the strata. The most common fossils are formed from teeth and bones. After the death of ancient animals, the internal organs, muscles and other soft tissues of the corpse will quickly decay, and the teeth and bones can be preserved for a longer time because there is less organic matter and more inorganic matter.

If the body happens to be buried in sediment, cut off from the air, the process of decay slows down. There is slow-flowing groundwater in the sediment voids. On the one hand, the water dissolves the minerals in the rock and sediment, and on the other hand, the excess minerals in the water precipitate or become crystals, which gradually seep into the bones buried in the sediment and fill the space left by the decay of the organic matter of the teeth and bones.

If the conditions are right, the minerals that seep into the bones from the outside can effectively replace the original organic matter of the bones before they decay and disintegrate, and the teeth and bones are preserved as fossils. Because a large number of minerals in fossils are slowly replaced by extremely careful organic matter, the original shape of teeth and bones can be preserved intact, and even the shape of tissues that can be seen by electron microscopy can be preserved as they are. Over time, the weight of the bones increases, and the original teeth and bones become stones that still preserve the original shape and internal structure of the teeth and bones, a process called "petrification".

In addition to teeth and bones, the feces of some animals can also be fossilized. For example, some carnivores eat meat with broken bones, and there are many undigested broken bones in the feces, which are not easy to decay, so they can become fossils. Footprints can also become fossils.

People or animals step on the mud and sand, causing footprints. When the sediment dried, the footprints were filled with other substances. Both substances are preserved by the petrification of minerals that later seep in, but the properties of the two substances are different, the hardness is different, and the degree of weathering or destruction is also different.

When one substance is weathered or destroyed, the other appears as fossilized footprints.

To put it simply, a fossil is a stone that turns the remains or remains of a creature that lived in the distant past into stone. In the long geological time, there have been countless creatures living on the earth, and many of the remains of these creatures after death or the traces left by life were buried by the sediment of the time. In the years that followed, the organic matter in the remains of these creatures was decomposed, and the hard parts such as the shells, bones, branches and leaves, along with the surrounding sediment, were petrified and turned into stone, but their original form, structure (and even some subtle internal structures) remained; In the same way, the traces left by those creatures when they lived can be preserved in this way.

We call these petrified biological remains and relics fossils. From the fossils, you can see the appearance of ancient animals and plants, so that you can infer the living conditions and living environment of ancient animals and plants, you can infer the age of the formation of the strata where the fossils are buried and the changes they have undergone, and you can see the changes of organisms from ancient times to the present, and so on.

If you go to the encyclopedia, the fossils and the formation process in it are explained in great detail.

Fossils are formed by petrification in the process of sediment compaction and consolidation after the remains of organisms or other living activities in the historical period of the earth are buried by sediments.

According to the different characteristics of fossil preservation, there are four types: solid fossils, molded fossils, relic fossils and chemical fossils. Among them, the more in-depth research and significance comparison are solid fossils. Among solid fossils, it is very rare for the remains of an organism to be preserved as fossils, and it is more common that only a certain part of the organism is preserved, such as a tooth, a bone, a shell or a leaf.

In the process of fossil fossilization, the original components of the biohard may be partially or completely replaced by minerals in groundwater, or the less stable nitrogenous and oxygen-containing substances volatilize and disappear through decomposition and lifting, leaving only the carbonaceous part with high stability, such as the fossilized leaves of plants are usually carbonaceous and filmy.

Due to the harsh conditions required for the formation and preservation of fossils, the fossils preserved in rock formations were actually only a very small part of the living things at that time, which is the incompleteness of the biological history record.

The land of ancient times.

On the compound ball, there is a lot of growth.

Make exotic flora and fauna. bai a flood, du buried them. After hundreds of millions of daos

For a long time, they did not disappear, but became one with the rocks, waiting for us to discover them one day. This is a precious fossil.

Fossils refer to the remains and remains of organisms preserved in rock formations from various geological historical periods. The types of fossils can be divided into: solid fossils, such as mammoths that survived 25,000 years ago found in the Quaternary permafrost of Siberia; Molded fossils, impressions of plant leaves, impressions of shells, etc.; Fossils of relics, such as fossils of footprints, fossils of fish dung, etc.

Fossils are the remains of an animal or plant that have died for a long time without decay and become part of the earth's crust after a few years. The organism itself is well preserved, or an impression in a sedimentary rock, or a trace left by its survival (called a relict fossil). Fossils, usually after the death of animals and plants, are quickly buried by aqueous sediments, resulting in a chemical reaction, and then the minerals plus humans or organisms are excreted.

If this process does not take place, the organism will be temporarily preserved, but will not become a fossil.

The bones were buried in the earth for a long time and then petrified.

The formation and preservation of fossils are mainly related to the following conditions:

Whether the organism has a hard body (such as shells, bones, etc.) composed of chemically stable substances, and organisms with hard bodies are more likely to be preserved as fossils;

whether the physical and chemical conditions of the environment where the biological remains or relics are located are suitable for preservation, and the water environment with strong wave action is not conducive to the preservation of biological remains and relics; When the pH value of the environmental medium is less, the biological hardware composed of calcium carbonate is easy to be dissolved, so it is not conducive to the preservation of biological remains. Oxidation conditions are not conducive to the preservation of organic matter;

Whether the organism is buried quickly after death, if the body of the organism can be buried quickly and for a long time after death, it is easier to form fossils;

The type of sediment also has an important impact on the formation and preservation of fossils; Fossil formation is more likely if the remains are buried by chemical sediments (e.g., CAC3) or sediments of biotic origin;

In the process of fossil consolidation of sedimentary rocks, strong compaction and recrystallization are not conducive to the formation and preservation of fossils.

In the fossilization process, the original components of the bio-hardware may be partially or completely affected by minerals in the groundwater.

Specialized replaced, or stabilized.

It is a low qualitative nitrogen-containing and oxygen-containing substance that volatilizes and disappears through decomposition and lifting, leaving only a carbonaceous part with high stability, such as the leaf fossils of plants are usually carbonaceous and filmy. Due to the harsh conditions required for the formation and preservation of fossils. Therefore, the fossils preserved in the rock formations are actually only a very small part of the living things at that time, which is the incompleteness of the biological history record.

Nevertheless, the study of fossils can reveal an overview of the biological world in different geological periods.

In layman's terms, fossils refer to the remains of ancient organisms and traces of life activities preserved in rock formations. In the long geological time, there have been countless organisms living on the earth, and the organic matter in the remains of these organisms has been decomposed over the long years, and the hard parts (such as shells, bones, branches and leaves, etc.) and the surrounding sediment have been retained and buried with the sediment. After a long geological period, the material components of the organism itself are filled or replaced by minerals, becoming as hard as rocks, but their original form and structure are preserved.

After tectonic movements in the earth's crust, rocks and paleontological fossils are exposed, and finally discovered, which is what we call "fossils".

The formation process and preservation conditions of fossils.

1.The condition of the organism itself.

Organic matter must possess hard parts such as shells, bones, teeth, or woody tissue. The shells of invertebrates and the bones of vertebrates are mainly made of minerals, which can resist various destructive effects for a long time. In addition, organisms with cuticle, fibrous and chitin films, such as the leaves of plants and the body walls of pen stones, are easily damaged but do not dissolve easily and can be carbonized into fossils at high temperatures.

Soft bodies such as animal internal organs and muscles are susceptible to oxidation and corrosion, and are generally difficult to become fossils except under very special conditions.

2.Burial conditions.

Creatures must be avoided from destruction immediately after death, and are quickly buried by something that hinders decomposition. Often, the remains of marine animals can be fossilized because they sink to the bottom of the sea and are covered in soft mud after they die. Soft mud becomes shale or limestone in later geological epochs.

3.The time factor.

Biological remains, or their hard parts, must undergo prolonged burial before they can be petrified into fossils by the diagenetic processes of the surrounding sediments. However, there are some fossils preserved in older rock formations that have been destroyed due to deformation and metamorphism of the rock layers.

4.Diagenesis of sediments.

The compaction and crystallization of sediments during consolidation and diagenesis will affect the formation and preservation of fossils. Among them, the compaction of clastic sediments is more significant, so the fossils in clastic sedimentary rocks can rarely maintain their original three-dimensional state.

There are two kinds of fossils, one is that after the death of organisms on the earth, the body is buried by sediment, the organic part of the body is decomposed, and the hard part such as the shell, bones, branches and leaves are preserved, and petrified together with the surrounding sediment and turned into stone, thus forming.

The other is the traces left by those creatures, which are also formed by petrifying and turning into stone. In general, fossils take hundreds of millions of years to form. It retains the form and structure of those organisms that once lived on the earth, allowing modern people to understand the ecological environment hundreds of millions of years ago and the changes of organisms from ancient times to the present.

In fact, for a long time, fossilization was considered to be a simple "petrification", and it was only later that humans gradually understood the principle of fossil formation. It is a very complex process, a combination of three phenomena: biological, physical, and chemical. And the formation of fossils requires some special conditions:

First, dead organisms are quickly buried in sand, silt, or river mud without decomposing.

The bottom of the sea and the bottom of the lake are very conducive environments, as are the grasslands and deserts. Second, the organism does not decay, but gradually replaces the organism's organic matter with minerals. Finally, for fossils to remain unchanged for millions of years, they must be petrified without undergoing any geological changes.

The formation of fossils is a very complex process, a combination of biological, physical and chemical phenomena. To put it simply, in a long geological time, the remains or traces of life of ancient creatures were buried by sediment, and the organic woolly material in the body was carefully decomposed, and the hard parts such as shells, bones, branches and leaves, etc., were petrified into stone together with the surrounding sedimentary sediments, but their original form, structure (and even some subtle internal structures) were still retained. We call the remains and remains of petrified organisms that are formed in this way fossils.

For a long time, people thought that the formation of fossils was petrification, but in fact, this petrification process is quite complex, and it is a combination of biological, physical, and chemical phenomena. It takes a long time and there are many specific conditions for fossils to form. To put it simply, the remains or traces of life of ancient creatures are buried by sediment, and the organic matter in the remains is decomposed, and the hard parts such as shells, bones, branches and leaves, etc., are petrified into stone together with the surrounding sediment, but their original form, structure (and even some subtle internal structures) are still preserved.

This is the formation of what we know as fossils.

While whether or not an organism can form fossils depends on many factors, there are five factors that are fundamental, and the five basic factors of fossil formation are as follows:

1) Organic matter must have hard parts, such as shells, bones, teeth, or woody tissue. However, under very favorable conditions, even very fragile organisms, such as insects or jellyfish, are able to turn into fossils.

2) Creatures must be avoided from destruction immediately after death. If a creature's body parts are crushed, decayed, or severely weathered, this may alter or eliminate the possibility of the organism becoming fossilized.

3) Organisms must be quickly buried by something that hinders decomposition. And the type of material that is buried usually depends on the environment in which the organism lives. The remains of marine animals are often fossilized because they die and sink to the bottom of the sea, covered in soft mud.

Soft mud becomes shale or limestone in later geological epochs. Fine-grained sediments are less likely to damage the remains of living organisms. In certain fine-grained sedimentary rocks of the Jurassic period in Germany, fossils of fragile organisms such as birds, insects, jellyfish, etc., are well preserved.

4) The buried corpses of organisms must also undergo a long period of petrification before they can form fossils. Sometimes, after death, the organism is quickly buried, but it is soon destroyed due to various factors such as erosion, and fossils cannot be formed. There are some fossils preserved in older rock formations, which have been destroyed by deformation and metamorphism of rock formations.

5) In the process of sediment consolidation and rock formation, compaction and crystallization will affect the petrification and preservation of fossils.