Every year, everyone will grow up by one year. A year is a long time for all of us, but it is a negligible moment in the history of the earth. Geologists have found that the layers of rocks covering the original crust are a "stone book" left by the evolution and development of the earth for billions of years, which is called stratum in geology. The stratum starts from the oldest geological age and reaches the surface layer by layer. Generally speaking, the stratum formed first is below, and the stratum formed later is above, and the stratum formed closer to the upper part of the stratum is shorter. The stratum is like a book that records the history of the earth, and the rocks and fossils in the stratum are like the words in this book. By measuring ancient rocks with modern scientific methods, people know that the earth has existed for 4.6 billion years. So what scientific methods do people use to calculate the age of the earth? At present, in science, the method of measuring the isotopic content of radioactive elements and their transformation in rocks is used as a "timer" to measure the age of the earth. People use the characteristics of radioactive elements to calculate the age of rocks. Radioactive elements deteriorate at a stable speed and are not affected by external conditions. In a certain period of time, there is an exact amount of radioactive elements, how much they split and how many new substances they produce. For example, one gram of uranium splits into lead and helium in one year. Therefore, we can calculate the age of rocks according to the contents of uranium and lead in rocks now. The earth's crust is made of rocks, so we can know its age. Some people calculate that it is about 3 billion years. The age of the earth's crust is not equal to the actual age of the earth, because before the formation of the earth's crust, the earth generally went through a period when the surface was in a molten state, and during this period, the age of the earth was estimated at about 4.6 billion years. This is a big number. But in the universe, there are more planets older than the earth. Geological scientists say that the earth is at least 4.6 billion years old. The recorded history of mankind is only a few thousand years. So, how do we know the age of the earth? There are several methods to calculate the age of the earth, such as rock formation method, fossil method and radioactive element disintegration method. According to the identification, the oldest rock on the earth is Amizok gneiss found in St. Gotha, western Greenland, with an age of about 3.8 billion years. The debris of the solar system is between 4.5 billion and 4.7 billion years old. Therefore, it is believed that most members of the solar system, including the earth, were formed at the same time. According to the method of dividing dynasties in human history, the earth can be divided into five generations from its formation to the present: Archean, Proterozoic, Paleozoic, Mesozoic and Cenozoic. Some generations are further divided into several "periods", for example, Paleozoic is divided into CAMBRIAN, Ordovician, SILURIAN, Devonian, Carboniferous and Permian from far to near; Mesozoic is divided into Triassic, Jurassic and Cretaceous; Cenozoic is divided into tertiary and quaternary. This is the roughest division of the earth's historical period, which we call "geological age". People in different geological ages have different characteristics. The primitive lithosphere, hydrosphere and atmosphere were formed on the earth's surface 2.4 billion years ago. But at that time, the crust was very unstable, volcanic activity was frequent, magma was everywhere, the ocean was vast, and the land was all bare mountains. This is an important era of iron ore formation, and the lowest primitive life began to appear. From 2.4 billion years ago to Proterozoic 600 million years ago. At this time, most of the earth is still covered by oceans. Later, a large area of land appeared on the earth. "Proterozoic" refers to the primitive era, when algae and marine invertebrates appeared. 600-250 million years ago was Paleozoic. "Paleozoic" refers to the era of ancient life. At this time, thousands of animals appeared in the ocean, and marine invertebrates flourished unprecedentedly. Later, fish-shaped animals appeared, and fish multiplied in large numbers. A fish crawling on its fins appeared and landed on land, becoming the ancestor of terrestrial vertebrates. Amphibians also appeared. Ferns have appeared on the land in the northern hemisphere, some as high as 30 meters. These tall and dense forests later became big coalfields. Mesozoic, from 250 million years ago to 700 million years ago, lasted about 65438+800 million years. This is the era of reptiles. Dinosaurs once ruled for a while, and then primitive mammals and birds appeared. Ferns are decreasing and being replaced by gymnosperms. The lush plants and huge animals in Mesozoic later turned into many huge coalfields and oil fields. Many metal deposits were also formed in Mesozoic. Cenozoic is the latest stage in the history of the earth, with the shortest time, only about 70 million years. At this time, the face of the earth has been basically similar to today's situation. A new generation of angiosperms has developed greatly, and all kinds of herbivorous and carnivorous mammals have flourished unprecedentedly. The great development of nature creatures finally led to the emergence of human beings, and the ancient apes gradually evolved into modern people. It is generally believed that human beings appeared in the Quaternary, about 2.4 million years ago. The earth where human beings live has evolved step by step to the present and gradually formed today's face. There is also a long article. If you are interested, please look at the content resources at the following address:

/3zrkx/dqls.htm Question: What "Ji" do I want to answer? A: Late Paleozoic, the late stage of Paleozoic. The strata formed in this period are called Upper Paleozoic. Late Paleozoic is divided into Devonian, Carboniferous and Permian. In the Late Paleozoic, with the expansion of land area and the change of geographical environment, it brought new changes to the development of biology. Plants and vertebrates developed rapidly from aquatic to terrestrial, forming a new situation of vivid land and great development of plants in late Paleozoic. A group of gymnosperms appeared on the land. Spore plants flourished, and gymnosperms appeared in the late Permian. Late Paleozoic is the development period of terrestrial vertebrates. In the history of the earth, the Late Paleozoic is called the Age of Fish and Amphibians. Among marine invertebrates, there are ammonites, foraminifera and bamboo stones. There have been two extinctions of biota: ① the sudden change of biomass and the replacement of ecosystem between the late Devonian Frazier period and Famen period. (2) At the end of Permian, most families and genera of Tetracorals, Bedplate corals, trilobites and brachiopods became extinct, which became the symbol of dividing Paleozoic and Mesozoic. In the Late Paleozoic, the global lithospheric plates continued to move. Due to the collision and splicing between the northern hemisphere plates and the connection with Gondwana continent, a joint ancient land was formed at the end of Permian. It is widely distributed in glaciers in the southern hemisphere in the middle and late Late Paleozoic. The famous minerals are oil and natural gas related to reefs, and potassium salt related to evaporites. The prosperity of terrestrial plants has caused a large-scale accumulation of coal and oil shale in geological history. Paleozoic is divided into seven periods (the oldest is at the bottom of the table). The sources and names of these periods are listed as follows: Permian-named after the Pennsylvanian epoch in Perm province of the Soviet Union-named after the Mississippi epoch)-the period in Pennsylvania of the United States-named after the upper Mississippi valley (the term Carboniferous used by European geologists includes the Pennsylvania epoch in North America). Devonian-a sequence of geological chronological units named after Devon, England. The latest time unit is at the top of the histogram, while the earliest time unit is at the bottom of the graph. Geology: the study of the origin, composition, structure and history of the earth and its inhabitants. The name comes from the Greek geo plus logos, and the field of geology is very extensive, which makes it divided into two branches: physical geology and historical geology. Physical geology studies the composition and structure of the earth, various movements in and on the crust, and now the Silurian is being made on the surface of the earth-named after the Cambrian of the ancient British tribe, and named after the Latin Cambrian. It means that the Mesozoic era of the well and its name comes from: Cretaceous-from Latin Creta, which means Jurassic-named Triassic in Jura Mountains between France and Switzerland-from Latin Trias, which means that the name of Cenozoic comes from an outdated classification system, which divides all rocks and rocks on the earth into three parts. The following two periods are the two surviving periods still in use in the system: the fourth order-meaning the fourth derivative, and the third order-meaning the third derivative.

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