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SELFtalks
Geology by its very nature,
The main thing is to study those that not only we have not experienced,
And it's a process that no one has ever experienced.
So to unearth the final, ultimate truth, it takes a lot of effort.
Zhai Mingguo, Academician of the Chinese Academy of Sciences
Science gurus talk about science | Beijing 2021
Hello everyone, I am Zhai Mingguo. The title of my lecture today is "The Mysterious Earth and the Mission of Mankind."
The earth is the place where we all live and should be the most familiar. But in fact, a lot of knowledge about the earth is unfamiliar to everyone, so it is a mysterious planet.
In recent years, earth science and related issues can be said to be "internet celebrities", such as "Jurassic Park" about the extinction and reproduction of dinosaurs, and "Wandering Earth" about the flight of human beings to the universe. Compared with other countries, the continent's popularization of earth knowledge is not good enough, and it is necessary to arouse everyone's desire for earth knowledge. After understanding the earth, we know that human beings have a sacred mission to the earth.
Part.1
Mysterious Earth
When people meet, they often ask: Who are you? How old is it? Where are you from? Where are you going? There is also a question that we Chinese more taboo: where will you go? For The Planet, these same problems exist.
The Earth is in the universe. The universe is the sum of time, space, matter (energy), and is a very large system. The solar system is a galaxy in the universe, and the earth is in the solar system.
▲ In order: Early Chaotic Earth Early began to stratify
Modern Blue Earth Future Earth?
Like everything else, the earth has past, present, and future. It was originally called "Chaotic Earth", chaotic, chaotic, no heaven, no earth. Later, there was gradual stratification, with the core, mantle and crust, and the atmosphere, hydrosphere and biosphere, which we call the Blue Earth. Will the Blue Earth live forever? It will also evolve and eventually become an unknown Earth.
It is 4.6 billion years since the birth of the Earth. During this period, it underwent earth-shaking, earth-shaking, or earth-making changes. Understanding the formation and evolution of the earth, especially the continents, is the core and crown of the natural sciences, which is a very profound knowledge.
▲ Structure of the Earth
The earth itself has circles, so we say that the earth is round. Its structure is like the picture above, from the center of the earth to the surface of the earth, in order of the core, mantle and crust. The circles are not static and dead, but move with each other and are alive. There is magma in the interior of the Earth that can be spewed out by volcanoes. Where a volcano erupts, it means that there is movement between the circles.
For example, eggs also have "circle layers": the inside is the yolk and egg white, and the outside is the eggshell. The structure of the egg is not rigid: the egg core can slowly give birth to new life, suck nutrients from the protein, and finally hatch the chicks.
The basic form of all things is the circle layer. We stand on the surface of the earth, so the most important thing we should know is the crust.
How thick is this crust? Its average thickness is about 17 km, of which the continental crust is larger, averaging about 35 km. The crust of the earth in the alpine and plateau areas is thicker, reaching up to 70 km. The continental crust can be divided into the lower crust and the upper crust, the lower layer is basalt, is basic, and the silica content is relatively low; the upper layer is granite, acidic, and the silica content is high.
So what is the continental crust made of? It is made of rocks. There are three types of rocks, one is called hydrogenetic rocks, also called sedimentary rocks, as well as igneous rocks and metamorphic rocks, of which igneous rocks include volcanic rocks and intrusive rocks. Metamorphic rocks are new types of rocks that have been transformed by the earth's internal forces (temperature, pressure, etc.). Hydroclavonic, igneous and metamorphic rocks can all be metamorphic. These stones "run" from the shallow layer of the earth's crust to the depths, below 10 km, below 20 km, under 30 km, under 40 km, and change again, no longer the original structure, but become another mineral. Metamorphic rocks record earth-shaking changes in rocks on earth's surface.
Rocks, in turn, are made up of minerals. Minerals come in different colors, including diamonds, rubies, sapphires, emeralds, etc. that we all love. Some minerals are also important cutting-edge materials that are very difficult for us to synthesize and can be applied to high-precision high-tech manufacturing.
The earth's crust is divided into the oceanic crust and the continental crust. The bottom below the ocean, as we all know it, is the shell of the ocean. The continent we are on is the continental crust. The ratio of continents to oceans is about 3:7, with the former concentrated in the northern hemisphere. The bottom of the ocean is as potholed as the continents, with ridges and depressions. The Hawaiian Islands are some of the peaks in the underwater mountains, with a maximum of more than 10,000 meters, which is much higher than Mount Everest, the highest peak on land where humans live.
Part.2
The movement of the earth and the movement of the earth
The circles are mutually moving and alive. So we call the Earth the Earth in motion. There is magma, there is fluid, and there is water in constant motion and movement. The sea can become mountains, and mountains can become seas. Tectonic movements cause earthquakes and can even allow an entire continent to drift to another place.
The movement of the earth also has a profound meaning: the earth is not a dead planet, it is alive, and it is getting old day by day from its birth. I wrote a book, Motion: The Code of Life on Earth, which introduced the motion of the Earth.
The ancestors were aware of the movement of the earth. For example, in the "Left Biography", it is contained that "the high shore is the valley, and the deep valley is the mausoleum", which refers to the high shore becoming a deep valley, and the deep valley becoming a large earth mountain. There are also stories of the vicissitudes of sangtian and Magu offering life. Magu said she had seen the East China Sea turn into a mountain three times and an ocean three times. The ancients all knew the truth that mountains turned into seas and seas became mountains. So when you climb the mountain and see that the stones on the top of the mountain contain fish fossils, it is not surprising at all. Because that place used to be the sea many, many years ago, and then it became land.
The ancients also had a long understanding of "ground movement", but did not fully unlock the secrets, and many ancients wrote excellent articles to explore, such as Qu Yuan's "Heavenly Question" there is "eight pillars what to do, southeast what to lose". Meaning: Why is the sky not as high, the west side is high, and the east side is low? The solution is that the east pillar fell. Why did the pillar fall? In the past, we had a myth called "The Wrath of Co-Workers Can't Touch the Mountains", which tells you that the earth is in motion.
▲ Earth "changing face"
In addition to the big movements, the Earth has smaller movements. We gave the earthquake a word, "change face." After the earthquake, everyone saw that the original mountain had become lower, there were original trees, trees fell, there were original bridges, bridges were broken, and the original road was wrongly cut off for dozens or even hundreds of meters... It's all a face-changing of the planet.
The photos were taken on the 1st anniversary of the Wenchuan earthquake.
▲ Japan Earthquake
As you probably know, the 2011 earthquake in Japan triggered a tsunami that caused a nuclear disaster.
Earthquakes are an activity on Earth, and magma eruptions are the most seen. Earthquakes are equivalent to the pulse of the earth, and magma eruptions are equivalent to the blood of the earth. When the earth is no more earthquake, there is no pulse, and the earth is frozen. So what we fear is not earthquakes, but that the earth will one day freeze to death.
People have been groping for the laws of the earth's movement, including the continental drift hypothesis proposed by Wegener. Wegener, a German meteorologist, is said to have stumbled through the world map while smoking cigars in his house, drinking coffee, and stumbling through the world map: the west coasts of Europe and Africa were far from the east coasts of North and South America, and their outlines were very similar; if the two continents were cut off from the map, they could be spliced together into a roughly consistent whole. He wondered if they had been together and then separated, and he suggested that the continent had drifted.
After this hypothesis was proposed, it was ridiculed by the world and criticized by scientists. He didn't have any more knowledge reserves, just saw this phenomenon and made an image decryption. Later, Wigener was killed by a snowstorm during an expedition to the Arctic. 50 years later, the theory of plate tectonics was created based on the theory of continental drift.
▲ Supercontinent - Pangea (left) and present (middle)
Plate tectonic theory is like a clever puzzle. 250 million years ago, the continents were basically connected, but then they gradually separated, drifted apart, and became different continents, which is what they are now.
Some scientists believe that in another 250 million years, based on the current rate of plate drift, the continents will converge again, as indicated in the chart above.
Of course, this is a hypothesis, and it needs to be confirmed. But this confirms that we can't see, and we can't see it 250 million years ago. But this speculation is not nonsense, it is based on current observations and records. How fast are the Eurasian plates moving? Equivalent to us not cutting nails for a year, the length of the new long part is equivalent to the distance of the annual movement of the Eurasian plate.
Profound principles of plate tectonics include mantle convection and ocean floor expansion. Just like the picture on the left, red magma continues to spew out and go to both sides, forming an ocean floor that expands. In the upper right is the subduction of the plate, and in the lower right is a continuous mountain range that once existed in Europe and North America.
Plate theory was one of the greatest contributions to the natural sciences of the 1960s and 1970s, and it continues to develop today. From it we can know that the earth has three major scientific problems:
First, what is the tectonics of the Earth's plates? When are there plate tectonics? Did the Earth exist as a continent, or did it exist later? Will this plate structure always exist? What would be the structure if it were not for the plate tectonics in the future? Second, has the mainland always existed? How did it grow to be so big? Third, when did water and oxygen form? When was Earth's current environment shaped?
These three major scientific problems are very cutting-edge in earth science research, and scientists around the world are paying attention. Among these questions, I have specifically brought up a question: how continents evolved. Continental evolution is so important that in the earth science white papers of various countries, the first topic is how continents are formed, when they are formed, and how they evolve.
Part.3
How continents evolved
Why is the continent important? Because we live on the continent. Without continents, we might have become aquatic animals. Moreover, only continents can record the history of Earth's evolution. Although there is also a crust under the ocean, the oceanic crust cycles every 200-300 million years, and the cycle of the ridge shell mantle formed by subduction disappears and becomes new. The continental crust has been preserved since its birth, and if we want to understand the history of the earth, we must study the continents.
▲ Jack Mountain Zircon (Part 1)
Quartz conglomerate (bottom)
By studying the rocks, we can discover the age of the continents. The earliest stone in China is 3.8 billion years old; the world's earliest stone came from Mount Jack in Australia, where there is a mineral called zircon, which can be used for isotopic studies to determine its age.
What is its age? 4.4 billion years, so the continent formed 4.4 billion years, because that's when the scale of the continental crust was formed. The age of the earth still needs to be pushed forward by one or two hundred million years, and 4.6 billion years is the age of the earth as we know it now.
So then there is a new question: when did the continents form, and when did the oceans form? The answer is no. Because the current science does not have enough evidence to prove whether there is a land or an ocean first.
▲ Magma ocean stage, 4.4 billion years ago?
If there is a ocean first, we assume a silicate ocean, like the red "ocean" in the figure, of which silica accounts for about 40%-52%. If this ocean can be divided into a crust on top and a mantle on the bottom, it can explain the cause of the crust. But this model is not good on Earth, but it can be used for the moon. Because the crust above the Moon is obliquely long and the Earth's continent is granite, it does not work.
Suppose there is a crust first, and then partially melts when the crust dives to a certain depth, and the part that melts out becomes the continental crust. Partial melting means melting part, easy to melt melt, not easy to melt. But this also encounters great difficulties, and there are problems with the calculation mode.
So far, how the continent was formed is still a mystery that needs to be solved. In fact, there are many hypotheses and evidence, I don't have time to expand on them, they are also published in the world's top magazines.
In fact, except for the continents of 4.4 billion years, there are many mysteries at every stage of the earth since 4.6 billion years.
▲ Geological chronology
Now we understand the basic history of the earth through the geological chronology: 4.56 billion to 3.8 billion years ago this period is called the Pluto, 3.8 billion to 2.5 billion years ago was the Archean, 2.5 billion to 545 million ago is called the Proterozoic, from 545 million ago to the present is called the Phanerozoic. Every stage, every event, is being studied and tracked by scientists.
The Phanerozoic stage can now record strata with fossils, which is the distribution of geological epochs we see, from trilobites all the way to the extinction of dinosaurs.
What will happen to the earth from land cores to continents, from plateless tectonics to plate tectonics, from anaerobic to aerobic to currently aerobic? Will it become anaerobic? That's all about people talking about. So we say that the evolution of the whole earth is from hot to cold, and when the earth is completely cold, the earth will "die". When the earth is particularly hot, there are no creatures, and they do not begin to have creatures until they reach the right temperature; and when they continue to be cold, there are no more. This is the evolutionary history of the Earth.
Part.4
What will be the fate of the earth?
The evolutionary history of the Earth leads to the fate of the Earth. The earth is alive, what is its destiny? When I was a child, I heard people say that the earth is getting hotter and hotter, and in the future it will explode. Now I know that the earth is not getting hotter and hotter, but getting colder, and the fate of the earth is not to explode, but to freeze.
When talking about the fate of the earth, we must put the earth into the universe and into the solar system. There are many planets in the solar system, the sun is a star, there are many planets, and some planets have their own moons, such as the moon on the earth.
What is a planet? Planets are planets that can move and revolve around stars, and we can divide them into two categories: terrestrial planets and Jupiter planets. Terrestrial planets are much the same as Earth , for example , they may also have nuclei , mantles , and outer shells , with silicates as the main composition. Jupiter is a gas planet, Jupiter and Saturn are typical Jupiter-like planets.
Among the eight planets, Mercury, Venus, Earth, and Mars are terrestrial planets, and here I also introduce the Moon as a planet. The moon we study the most is because it is a satellite of the Earth, the closest to the Earth, and it is very similar to the Earth. Whether we understand the planets or the moons, it is all to better understand the earth, study how the earth evolves, and predict what the earth will become in the future, which is a very important task for mankind.
Let's not talk about how important the earth is for human survival, just to say that a person living on the earth does not know what the earth is like, does not know how old the earth is, does not know the structure of the earth, then living on the earth is too confused. So we have to understand the planet, understand the planet, understand the earth.
▲ Mars
Mars is relatively close to the Sun and is the 7th largest planet. Mars is currently a planet of more concern to human beings, it also has gas on it, but the gas is very thin, only 1% of Earth. It looks gentle and pale in color because it has less energy and less light. Mars is very dry and very cold, with an average surface temperature of only minus 63 degrees. Whether it's water, carbon dioxide, or other gases, they will become solid on Mars, so there can be no higher life on Mars. I saw some articles that said: Let's study Mars well, in the future the earth can not survive, we will sit on rockets, everyone to Go to Mars to live. This story can be told on April Fool's Day, after all, Mars has long been more unlivable than Earth.
▲ Venus
Venus is the closest planet to Earth, everyone likes it, Westerners call it Venus, Chinese call it Taibai Star. Venus, second only to the Moon in brightness, appears in the eastern sky before dawn and is called "Enlightenment"; appears in the western sky after dusk and is called "Chang Gung". Its energy is very large, the temperature is very high, and the surface temperature can reach more than 480 degrees. Not to mention the higher life, no life can survive in such a high temperature. So Venus is a hot, impenetrable planet, and its outer surface is all sulfuric acid clouds.
▲ Moon - an old photograph of the Earth
Our favorite thing to see and learn the most is the moon. The Moon has no energy at all, and the moonlight comes all from the Sun. The moon is beautiful when it's bright, but it's just a "zombie."
▲ Earth-moon impact theory
How did the Moon form? There is a theory called earth-moon impact: one day in geological history, an object the size of Mars hit the earth, and after the collision, their material spreads in space and is partially connected, you have me, I have you, and then eventually separated, resulting in the moon. This doctrine is still in the mainstream.
Why do we study the Moon? Can it inform the evolution of the Earth? Although the moon is now "dead," it is the equivalent of an old photograph of Earth.
The Moon is also layered , with a mantle , a lunar core , and a lunar crust , but it is very different from Earth. It is not an ocean-land structure, but an impact crater structure, and the black circle we see is formed by the impact. The white part is the "land" of the moon, called the oblique rock highland; the black part is the "ocean", which is the sea formed by the melting of the moon mantle and the magma eruption after the meteorite hits down.
▲ Lunar surface impact process: meteorite impact on the lunar surface
Many of the impacts occurred more than four billion years ago, when the lunar surface was hot and the craters that were knocked out were red, and then gradually cooled to the way they are now. Now meteorites are still constantly impacting, the moon will hit the sea when there is life, and after there is no life, there will only be impact craters, that is, the craters of the moon that we see.
▲ The oldest rock on the moon
So what is the age of the Moon? Its oblique rock crust is 4.4 billion years old, the same as the oldest granite on Earth.
▲ Lunar rock samples
There is a difference between the rock samples of the Moon and the rock samples of the Earth. In addition to the oblique rock, it also has basalt. Basalt is more common, and everyone can see it when you go to Wudalianchi and Changbai Mountain. But the Moon and Earth can not see the Klipp Rock, which is a rock with potassium and rare earth elements. In addition, the Moon does not have the most important type of crust rock on Earth, granite.
Although the Moon has a close relationship with Earth, their evolutionary history is very different. The Moon is an impact tectonic, with no oceans, no continents, and naturally no plate tectonics.
We see phase after phase of meteorites hitting the moon, which is the evolution of the moon in one phase after another. Later impact craters covered the front, and scientists explored them to calculate when the moon "died" through the youngest lunar sea.
China's Chang'e-5 took a sample of lunar soil and calculated that its age was 2 billion years ago. In the past, it was thought that the moon died about 3.1 billion years ago, so this time the age is set, and it may not die until 2 billion years. What is the concept of lunar "death"? That is, there is no life, no energy, no earthquakes, no magma, and there is no activity.
Next, let's look at the "life-to-death" process of the planets, where I think of the moon as a planet. The moon grew too "anxious", and because the energy inside was exhausted, it completely died 2 billion years ago.
Below is mars about to fall into wood, dim in color, and has no atmosphere or water.
The Earth is in its prime, with water and oxygen, and is full of life. How long will it take to reach the state of the Moon? About 4.5 billion years. A journey like this from birth to death is the fate of the earth.
Looking further back at Venus, we can say that Venus is a "cataclysmic planet." It's young, it's still hot, and it may slowly cool down and become another Earth in the future. But there is also a theory that Venus experienced a cataclysmic event 800 million years ago, and the original atmosphere and oceans escaped. So we study Venus in two directions: whether Venus can continue to evolve, becoming cooler and more suitable for survival; if it is cataclysmic, how to look at the occurrence of cataclysmic events? This provides us with some new ground and information for early warning of the Planet.
Part.5
Will the earth be habitable forever?
The Earth is the luckiest planet in the solar system, with "four onlys": the only planet with macroscopic water and oxygen for all things to grow; the only planet that has fully evolved into its current state; the only planet with life, trees and trees, and the only planet with higher animals that can control the world, human beings.
There was no oxygen in the early days of the Earth, so when was the oxygen produced? There was no water in the early days, where did the water come from? This is something that the earth sciences need to seriously study.
▲ Two major oxidation events in the history of the Earth
It is now recognized that the Earth had two major oxidation events, one is the GOE (Paleoproterozoic oxidation event), which occurred about 2.35 billion to 2.2 billion years ago, and the other is called NOE (Neoproterozoic oxidation event), which occurred 600-700 million years ago. These two great oxidation events allowed oxygen on Earth to develop to its current levels.
▲ The face of the earth in history has changed dramatically
Where does oxygen come from? How can it suddenly rise? There are many hypotheses, one of which is called the snowball hypothesis. 700 million years ago, the earth was called Snowball Earth, and it was covered with ice and snow from the equator to the poles, and then the carbon dioxide changed, and the ice melted and led to the emergence of oxygen.
▲ The blue stage on the right is the Snowball Earth period
This catastrophe brought good fortune to the earth, and more than 500 million years ago there was a cambrian explosion of life, which gradually evolved into the prosperity of the earth now. Earlier, the first major oxidation event led to the birth of eukaryotes.
This is a process of earth evolution, and oxygen is first and foremost the evolution of the earth itself. Deep evolutionary relationships: from the core to the mantle, the hydrogen-oxygen material is gradually brought to the surface of the Earth. It is also possible that cataclysms, such as the impact of other planets, cause water and oxygen. The reason should not be single, there must be different sources: for example, like nitrogen, how can the deep part decompose such a large amount? It is not possible to fully calculate it at present, and this number is always wrong after it is calculated and added up, and there may be such and such a problem, that is, they must have different sources, there are deep parts, and there must be celestial collisions.
Two major oxidation events in Earth's history brought the planet to its present prosperity, and changes in oxygen concentrations caused animal evolution. Animals are constantly emerging, from the earliest microbes all the way to advanced life, is this evolving forever and constantly? How does this evolve every day? No, it's a leap forward. After having a relatively advanced life, there will also be a sudden decrease and rise in oxygen, which has been associated with many mass extinctions of life in the history of the earth, such as the mass extinction of dinosaurs.
▲ Changes in oxygen concentrations and extinctions
The mass extinction of higher organisms is due to changes in the earth's environment, and changes in the earth's environment are also a manifestation of the evolution of the earth. The cause of change can be that, like Mars or other planets, it is affected by some changes in the solar system; in addition, changes in the structure of the Earth itself and the magma tectonic activity can be caused.
▲ The origin and evolution of water
So where does the water come from? The role of water was found in zircons 4.4 billion years ago, but it is not known that macroscopic water is not known. In the lower right picture, you can see thick rock formations, which are all rocks that have sunk in the water, so there was macroscopic water at that time, and macroscopic water 3.9 billion years ago. We still have to study macroscopic water, study the evolution of the earth: the evolution of structure, the evolution of minerals, and the evolution of living things, and evolution is an important scientific frontier on earth.
▲ The evolution of minerals and microorganisms with the times
The evolution of the Earth, like other terrestrial planets, follows an objective law of evolution: the law of the consumption of the Earth's internal energy is also affected by the movement of the solar system. Man cannot fundamentally change this evolutionary process. The Earth itself has followed an evolutionary pattern from unlivable to livable to uninhabitable. There is no planet in the solar system that is more habitable or more habitable than Earth. In the 4.6 billion-year-old evolution of the Earth, the Ezoogens were only 500 million years old, while late Homo sapiens appeared about 50,000 years ago. Humanity has enough time to understand the earth, continue to explore, and master more scientific knowledge.
Part.6
Our sacred responsibility and mission
After understanding how the earth has evolved, what are our sacred responsibilities and missions?
The demand and consumption of human beings from the earth has brought about three major problems: human living environment, human resource problems, geological disasters and man-made disasters. This has led to the formation of a new science- the relationship between man and land.
First of all, we must understand the objective laws of the earth, follow the objective laws of the earth, and finally rationally use the earth's resources on the basis of following the objective laws to protect the earth's surface environment within the scope of human beings.
People live on the earth, survival and development are inseparable from the earth's resources, this can not be changed. Human history has experienced the Stone Age, the Bronze Age, the Iron Age, and then developed into the Energy Age and the Electronic Age, and it is difficult to walk without nature.
Human activities always have an impact on the earth's environment. For example, the oxygen consumption process of human activities is an example, if the oxygen consumption is too much, the air is not fresh, you are uncomfortable.
Therefore, the mission and responsibility of the earthlings is: to understand the evolution of the earth, especially the laws of the future, the future geology will be the crown of natural science; then we must rationally use the earth's resources; we must rationally and scientifically protect the earth's environment; we must also adhere to the concept of international development of peaceful coexistence.
I hereby appeal to everyone to love science, advocate science, learn science, and engage in science. Science is the study of approaching the knowledge of objective things, and to truly understand the world, we must grasp the truth, and nothing can be done against the truth.
I would like to conclude with a quote from Engels's Anti-Dühring: Geology, by its very nature, consists mainly of the study of processes which not only we have not experienced, but which no one has experienced, so it takes a great deal of effort to unearth the final, ultimate truth.
Earth science is very important, and Engels said that earth science is the ultimate truth. I hope that everyone can learn the knowledge of earth science well and fulfill their responsibilities for our common home, the earth.
Thank you!
Source: Gezhi Dao Pulpit
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