The above outlines the life of the Earth. Everyone will inevitably have this question in their mind: How do you know about the past events that happened hundreds of millions of years ago? Not to mention the past events hundreds of millions of years ago, hundreds of years or even decades ago, if they are not recorded, they will be easily lost. Unknown. After the formation of the earth, it took more than 4 billion years for humans to appear. Who will record its history?
It is the earth itself, and the history of the earth is recorded in those rocks.
Almost 1,000 years ago, Chinese scholar Shen Kuo (1031-1095) first scientifically explained many natural phenomena on the earth's surface in "Mengxi Bi Tan". For example, he talked about the erosion and sedimentation of running water, inferring that the sediment on the surface of the North China Plain was deposited by rivers in the western mountainous areas; he also inferred from the fossils of marine snails and clams found on the cliffs of the Taihang Mountains that it is now about a thousand miles away from the sea. The place used to be a seaside in ancient times; he was the first person in our country to recognize and name "oil". Many rocks are formed by the accumulation of sediment underwater. They are called sedimentary rocks. The appearance of layers is a characteristic of sedimentary rocks. The snail and clam shells in the rock are what geology calls fossils. Fossils are the remains or relics of living things. If a living thing is quickly buried by sand after death and is placed in an underwater environment isolated from oxygen, it may not completely decay. The shell or bones of the living thing are absorbed by the minerals in the water. It gradually penetrates and replaces, becomes solid and still retains its original form, becoming a special component in the rock - fossil (fossil).
More than 400 years after Shen Kuo of the Song Dynasty, the famous Italian artist and knowledgeable scholar L. da Vinci (1452~1519) also made his own judgment: marine life found on the Apennine Mountains Fossil shells were originally creatures that lived on the seashore. The rivers brought mud to bury them and seep into their interior. He also theorized that the terrain here later rose, so the remains of these sea creatures would appear on the mountain. Both Shen Kuo and Leonardo da Vinci realized that today's mountains can be the seas of the past, and the rock formations in the mountains and fields are relics of the earth's history. In 1669, N. Steno (1638-1686), who was born in Copenhagen, concluded that there are the following rules between these rock layers: after the formation of sedimentary rock layers, if they are not affected by strong crustal movements, they will be reversed. In its original position, it should be deposited first at the bottom, then at the top, maintaining a nearly horizontal state, and then gradually pinching out as it extends to the distance. This is called the law of superposition of strata. It allows us to identify the order of creation of the earth's history through those seemingly chaotic rock formations. Rock strata have the meaning of time here, forming an important basic concept in geology - stratum. Strata are rock layers or combinations of rock layers that have time significance. Each stratum represents a certain period of time. This not only refers to layered sedimentary rocks, but also includes all other rocks produced during this time. Without the concept of unified understanding of time and space, it would be impossible to understand the history of the earth. Strata formed in different periods can be divided into stratigraphic units such as universes, realms, systems, systems, and stages based on the length of time they represent. They have the same upper and lower time limits as the epochs, generations, epochs, epochs, and periods in geological time. , that is, the stratum formed during the period of "Europe" is called "Yu", the stratum formed during the period of "Genesis" is called "Jie", and so on. The geological time scale (Table 21) is a manifestation of the combination of time and space.
"For example, if you accumulate salary, you will come from behind." Ancient Chinese sages have had this understanding for a long time. Unfortunately, they only use it to explain people and things, and do not use it to observe rocks in the mountains. Nor did they even think about the observations they needed to make about nature. Because "there is no way to measure things in the world, and the ability to measure things can only be done in the body and mind"; because "not only the animals and plants, but also the heaven and the earth are of the same body with me, and the ghosts and gods are also of the same body with me." This means that as long as you sit there and think hard, you can find the answer to all your questions within yourself. Before the introduction of geology established in the West, no Chinese scholar was more knowledgeable than Shen Kuo.
The West caught up later. The Englishman J. Hutton (1726-1797), based on his actual experience in field investigations and the understanding of predecessors, vividly expressed the geological thinking of the unity of time and space as "In the current structure of the earth, it can be Seeing the ruins of the old world” (Treatia terrestrialis, 1785). He told people that all past changes on Earth were caused by the slow action of existing processes. Later, Hutton's compatriot, C. Lyell (1797~1875) used more abundant facts to demonstrate and clarify this law, which was summarized as "discussing the present against the past", or the principle of realism (Actualism). His famous saying is: "Today is the key to understanding the past." His masterpiece "Principles of Geology" made geology truly a science and entered the stage of history. The principle of realism is a thinking method that is particularly valued by geology (the study of the earth's evolutionary history).
Table 2-1 Geological Time Table
Note: This table is mainly based on International Commission on Stratigraphy, UNESCO & IUGS, 2004; some international scholars suggest that the Quaternary Period be merged into the Neogene Period. This table is temporarily Keep it; the Proterozoic Eon is divided according to the domestic plan.
With the weapon of geology, the unknown history recorded on the earth itself has been revealed bit by bit. The material composition of the rocks in the formation, that is, their lithology and lithofacies, can also tell us about the environment we were in. Today, rivers carry sediment into the sea, depositing it in an orderly manner from coarse to fine, from near to far. Based on this, it can be inferred that the changes from coarse to fine rock composition materials appearing in the same group of strata in the same area on the ground today are outlining the depth of the water and the distance from the shore when it was deposited. According to today's changes, traces of the past can be found in the rock formations, including the original "waves rolling over the lake bottom, wind forming sand dunes, cracks in the land, and rain hitting the beach" (Figure 2-2).
However, it is obviously not enough to interpret the history of the earth simply from the nature and location of the rock formations themselves. Because sediments are not accumulating all the time and everywhere, and old rock formations are still being damaged and removed, as has been the case a lot historically. Therefore, it is impossible to leave a complete record of the strata we see in one area in all periods. Only by comparing strata distributed around the world can we piece together a relatively continuous and complete stratigraphic series. We also see that after the formation of rock formations, there are still changes, sometimes very strong. The originally nearly horizontal strata will become crooked, or may fracture and move away from their original positions.
Figure 2-2 Ripple marks (A), wind-induced cross-bedding (B), mud cracks (C) and rain marks (D)
How can we combine this How can we sort out the messed up history of the earth? Fossils can play a key role in determining the relative order of times and have unique advantages. Because the development of organisms always evolves from simple to complex, from low-level to high-level, this is called the progress of biological evolution. At the same time, biological evolution also has stages and irreversibility. As long as the creature that formed the fossil can be identified, it can be compared with fossils in other strata to determine their order. The self-taught British canal engineer W. Smith (1769-1832) obtained a large number of fossils in the process of digging the canal. After his sorting and research, he found that each stratum has its own specific fossils, and he formulated a plan accordingly. The world's first systematic stratigraphic table not only scientifically organizes the British stratigraphic sequence, but is also of great reference value for the division of European strata. Since then, there has been another law of fossil sequence to help us examine the history of the earth.
Fossils are not only useful for determining the sequence, but also reflect the environmental conditions at that time. For example, modern corals like warm and clear water, and animals in cold areas have thick long hairs; therefore, containing corals The fossil strata were not formed in cold areas. The appearance of long-haired rhino and elephant fossils indicates that their living environment at that time was not as hot as Africa today. The limestone formed in ancient times contains a large number of algae fossils, which strongly proves that these limestones were formed in the ocean. Creatures in the ocean generally do not become fossils in freshwater lakes on land; plant fossils that are only found on land are generally not easy to find in ancient marine strata.
The results of paleontological research provide strong support for the division of strata. After studying the structure and function of a large number of animal organs, the French paleontologist D.G. Cuvier (1769-1832), who was proficient in anatomy, discovered that various forms of animal bodies are a unified system, and every part of this system is They are mutually adaptable in structure and function, so understanding the parts can infer the whole. Cuvier's "Organ Correlation Law" allows us to deduce its body structure and habits from the animal remains preserved in fossils, reshape its original image, and gain more knowledge about the environment and life activities in the history of the earth. learn. He also noticed the close relationship between fossils and strata, and believed that "without this relationship, we would never have thought that there had been successive periods in the formation of the earth." His work played a positive role in promoting the development of geology.
Therefore, the value of fossils cannot be estimated in terms of money. As early as April 2, 1956, the State Council of my country issued a decree prohibiting the sale and purchase of "keel bones", that is, vertebrate fossils, to protect fossils. . In recent years, more comprehensive and detailed regulations have been made.