The origin of the earth

The Origin of the Earth

Every year, everyone grows older. One year is a relatively long time for all of us, but in the history of the earth, it is simply an insignificant moment. Geologists have discovered that the layers of rock formations covering the original crust are a "big book in stone" left behind by the evolution and development of the earth over billions of years. In geology, they are called strata. The strata start from the oldest geological time and reach the surface layer by layer. Generally speaking, the strata formed first are on the bottom, and the strata formed later are on top. The closer to the upper part of the strata, the shorter the age of formation.

The stratum is like a book recording the history of the earth, and the rocks and fossils in the stratum are like the words in this book. Using modern scientific methods to measure ancient rocks, people know that the earth has existed for 4.6 billion years.

So what scientific methods do people use to estimate the age of the earth? At present, science uses the method of measuring the content of radioactive elements in rocks and the isotopes generated by their transformation as a "timer" to determine the age of the earth.

People use the characteristics of the transformation of radioactive elements to calculate the age of rocks. When radioactive elements transform, their speed is very stable and is not affected by external conditions. Within a certain period of time, there is an exact number of how many parts of a certain amount of radioactive elements are split and how many new substances are generated. For example, 7.4 billionths of a gram of uranium fission into lead and helium over the course of a year. So we can work out the age of a rock based on how much uranium and how much lead it now contains. The Earth's crust is made of rock, so we can tell how old it is. Some people calculate it to be 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 has to go through a period of molten surface. Adding this period, the age of the earth is estimated to be about 46 years. Billions of years. This is a big number. But in the universe, there are many planets older than the earth.

Geological scientists say the earth is at least 4.6 billion years old. The recorded history of mankind only lasts a few thousand years. So, how do we know the age of the Earth?

To estimate the age of the earth, there are mainly rock formation methods, fossil methods and the transformation method of radioactive elements. According to identification, the oldest rock on earth is the Amizok gneiss discovered in the Gothab area of ??western Greenland, which is approximately 3.8 billion years old. The debris of the solar system are all 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 also be divided into five "generations" since its formation. From ancient times to the present, they are: Archean Era, Proterozoic Era, Paleozoic Era, Mesozoic Era and Cenozoic Era. Some eras are further divided into several "epochs". For example, the Paleozoic Era is divided into the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian from far to near; the Mesozoic Era is divided into the Triassic, Pyrrhic Luoji and Cretaceous; the Cenozoic is divided into the Tertiary and Quaternary. This is the roughest division of the earth's historical periods, which we call "geological ages." People in different geological ages have different characteristics.

In the Archaean Era 2.4 billion years ago, primitive lithosphere, hydrosphere and atmosphere had formed on the surface of the earth. But at that time, the earth's crust was very unstable, volcanic activity was frequent, magma overflowed everywhere, the ocean area was vast, and the land was full of bare mountains. This was an important era for the formation of iron ore, and the lowest primitive life began to emerge.

The Proterozoic Era, 2.4 billion to 600 million years ago. At this time, most of the Earth was still covered by oceans. In the later period, large areas of land appeared on the earth. "Proterozoic" means the era of primitive organisms, when marine algae and marine invertebrates appeared.

The period between 600 million and 250 million years ago is the Paleozoic Era. "Paleozoic" means the age of ancient life. At this time, thousands of species of animals appeared in the ocean, and marine invertebrates were more prosperous than ever. Later, fish-shaped animals appeared, and fish multiplied in large numbers. A kind of fish that crawled with fins appeared and landed on land, becoming the ancestor of land vertebrates. Amphibians also appear. Ferns appear on land in the northern hemisphere, some reaching a height of more than 30 meters. These tall and dense forests later turned into large coal fields.

The Mesozoic Era, which lasted about 250 million to 70 million years ago, lasted about 180 million years. This was the age of reptiles, when dinosaurs once dominated and primitive mammals and birds also appeared. Ferns declined and were replaced by gymnosperms. The lush plants and huge animals of the Mesozoic era later turned into many huge coal fields and oil fields. Many metal deposits were also formed during the Mesozoic Era.

The Cenozoic Era is the latest stage in the history of the earth and the shortest, only about 70 million years ago. At this time, the appearance of the earth was basically similar to today's situation. The Cenozoic angiosperms developed greatly, and various herbivorous and carnivorous mammals flourished unprecedentedly. The great development of biological life in nature eventually led to the emergence of humans. Ancient apes gradually evolved into modern humans. It is generally believed that humans appeared in the Quaternary Period, about 2.4 million years ago.

The earth where humans live has evolved step by step until now, gradually forming what it looks like today.