Since the late 1980s, scientists have tried to establish a three-dimensional three-dimensional image of the mantle, and found that under Africa and the Pacific Ocean, there is a huge hot plume upwelling from the bottom of the mantle, and below Asia, there is a huge cold plume downflow caused by the sinking plate material falling into the bottom of the mantle. Scientists have been inspired by this, and the original driving force that makes the plates move is the convection of this hot and cold substance.
The latest earth science shows that the earth is closely linked to the evolution of life. The discovery of the mantle plume column is a significant addition to the tectonic theory of plate tectonics. From a new theoretical perspective, combined with new biological discoveries, people have sketched a new view of the earth. Let's take a new look at the 6 epoch-making events in the history of the earth and their ins and outs.
<h1 class= "pgc-h-center-line" > 4.6 billion years ago, the primordial Earth was born</h1>
Earth was born about 4.6 billion years ago by the repeated collisions and mergers of many planets. It took an estimated 3,000 years from the initial growth of a few kilometer-diameter microplanets to the size of the earth now. Some scientists believe that after the end of the Earth's growth, perhaps a Planet the size of Mars hit the Earth, and as a result of this collision, the scattered debris merged around the Earth to form the Moon.
When a planet collides with a primordial Earth at a speed of more than 10 kilometers per second, its energy is converted into heat, causing the material of the planet or primitive planet to melt or evaporate. Through the melting of the material, the dense metal iron components sink into the center of the primordial Earth, forming the core of the Earth. On the other hand. Substances that evaporate easily become gases, constituting the primordial atmosphere. As a result, the Earth's core and atmosphere are largely simultaneously generated along with the Earth's growth.
The final stage of the Earth's formation process was the birth of the ocean. The primordial atmosphere contains a large amount of water vapor brought by the microplanet, and once the number of impacts of the microplane on the Earth is reduced, the temperature of the primordial atmosphere drops, and the water vapor becomes water and falls to the surface, a process that forms the primordial ocean.
The composition of the original atmosphere or ocean is also gradually changing. The primordial atmosphere contained a lot of hydrogen. However, due to the small density, it gradually escaped to the cosmic space, and the atmospheric composition gradually evolved to be dominated by nitrogen, and the marine component evolved to be dominated by water.
<h1 class= "pgc-h-center-line" > 4 billion years ago, life was born</h1>
The first life on Earth was born about 4 billion years ago. At this time, the Earth's impact on the planet gradually decreased, and the Surface of the Earth cooled and hardened sufficiently, forming a plate. Where the mantle rises, the oceanic plates split. It forms the longest extending mountain range on Earth, the Mid-Ocean Ridge. At the mid-ocean ridge where the mantle rises, a new oceanic crust of basalt nature is formed. Plates form and move in the mid-ocean ridge, sinking under another plate in the trench, and since then the plates have begun to move. When the oceanic crust sinks to the bottom of the mantle, the sunken oceanic crust partially melts, forming the granite composition that makes the continental crust. The magma of the granite composition rises. It began to form an island arc of land as a marine area (similar to the island arc formed by today's Japanese archipelago, Taiwan island, and Philippine archipelago).
In the middle of the ocean ridge also forms a place called "hot water vent" that spews out hot water. Seawater seeps into the ground from cracks in the earth's crust. By heating the magma, it becomes hot water, and the hot water dissolves the surrounding metal components in large quantities and gushes out of the hot water spout with the magma. In such places, certain organic matter may use nutrient salts dissolved in seawater to produce their own mechanisms of reproduction, thus evolving into the original life.
< h1 class= "pgc-h-center-line" > 2.7 billion years ago, a strong geomagnetic field was formed</h1>
From its birth until 2.7 billion years ago, the Earth's surface was exposed to radiation from the sun or high-energy particles falling from the universe. High-energy particles can destroy an organism's DNA and cause it to die. Therefore, the creatures at that time could only survive in the deep sea where high-energy particles could not radiate.
2.7 billion years ago, a strong magnetic field gradually formed on the earth, and the reason for this formation is still not clear. Scientists have simply speculated that due to plate movement, the plates that sink into the ground 2.7 billion years ago were excited to generate a strong geomagnetic field by falling into the outer nucleus. Plates that originally sank into the Earth's interior from trenches accumulate at about 670 kilometers above the surface. Due to the difference in the hardness of the mantle and the variety of minerals at this depth, a boundary separating the outer and inner layers of the mantle is formed. Above this depth, the outer layer of the mantle is a hard and cold lithosphere, and below the lithosphere is an asthenosphere, where the material is plastic and the internal temperature is high. Therefore, in the lower part of the lithosphere bordering the upper part of the asthenosphere, some locally melted rock makes the lithosphere there slide more easily, which is the main factor causing the earth's land change.
Taking 2.7 billion years ago as the dividing line, the previous mantle convection was carried out separately in the outer and inner layers of the mantle. However, 2.7 billion years ago, the accumulated plate material suddenly sank down to the earth's outer core, thus forming a full mantle convection throughout the mantle. Since the metal fluid with iron as the main component sinks into the field core, its temperature is lower than the temperature of the field core, which is like dripping cool material on the surface of the boiling field core, so that the fluid metal of the field core begins a regular and strong convection. An electric current is generated through the flow of fluid metals, which as a result creates a strong magnetic field on Earth.
The formation of a strong geomagnetic field intercepts the radiation of high-energy particles from the sun or the universe, making the shallow sea less terrifying to living things, and living things begin to enter the shallows to live. In the shoals, clusters of bacteria called fissile algae were born, releasing oxygen into the atmosphere through photosynthesis.
<h1 class = "pgc-h-center-line" > the earliest Lauren ancient land appeared on Earth 1.9 billion years ago</h1>
The greater the mantle convection, the greater the change of the plates on it. Mantle convection 2.7 billion years ago made the emergence of the paleocontinental possible. 1.9 billion years ago, the earliest Lauren ancient land appeared on Earth.
Scientists estimate that in the early days of the Earth, there were about 1,000 small plates (or small islands) on the Earth's surface, which existed in the form of arc-like archipelagos. The repeated collisions and mergers of the arc archipelagos, and by 2.8 billion years ago, before the formation of the mantle convection, a number of small continents appeared, but the number of plates was still very large, and it was difficult to merge with each other to form a supercontinent. By 2.7 billion years ago, due to the beginning of mantle convection, the plates rapidly became larger and smaller through mergers. After 800 million years of consolidation, 1.9 billion years ago, the earliest Lauren ancient land appeared, which was comparable in size to the current North American continent. Why do continents come together? This is because the oceanic plates sink under another in the trench and become so-called cold plumes, i.e. the mantle descending stream into the depths of the mantle. The plume has the property of pulling the upper layer of material downwards. So the plates carrying the continent are constantly dragged together by the sinking cold feather column, moving until the cold feather column merges into a large downdraft, and some of the plates carrying the continent do not sink into the ground, but concentrate to form a super continent.
< h1 class= "pgc-h-center-line" > 600 million years ago, the continent of Gondwana split. Causes a great development of species</h1>
After the formation of the Lauren Ancient Land 1.9 billion years ago, there were repeated continental divisions and mergers on the earth. After the division of the Lauren ancient continent, supercontinents were formed 1.5 billion years ago and 1 billion years ago, respectively, and 600 million years ago, the gondwana continent was formed.
The continent of Gondwana concentrated what is now North America, Antarctica, Australia, and Siberia as a whole. Under the rising action of the hot plume column, the continents on the surface were opened and split, and the Pacific Ocean formed shortly in the middle of the split plate. When divided, seawater is poured along the rift valleys formed between the respective continents, forming shallow seas. The shallow sea is a warm environment rich in nutrient salts. As has been called the "Cambrian (from about 570 million years ago to 500 million years ago) species explosion", many large multicellular molluscs have evolved dramatically. In the Burgess Shale of the Canadian Rocks, strange fossils have been found, which are the representative creatures of that time. That place was actually the place where North America split with Australia and Antarctica.
Correspondingly with those organisms, the concentration of oxygen in the atmosphere has increased, rapidly approaching the current value (about 20% of the atmosphere). 440 million years ago, the ozone layer formed, and for organisms, harmful ultraviolet rays no longer poured heavily onto the surface, life activity on land became possible, and eventually plants began to penetrate deep into the land.
<h1 class="pgc-h-center-line" > 250 million years ago, the division of the Pancontinent caused a mass extinction</h1>
After the division of the continent of Gondwana, it became 9 continents 400 million years ago and scattered throughout the earth. By 300 million years ago, a huge cold plume column fell into the mantle beneath the current Asian continent. As if dragged by the fall of the cold feather column, the 8 continents were rapidly concentrated in Asia, forming the ancient continent of Lauya in the northern hemisphere, while the southern hemisphere was the lonely gondwana continent. 250 million years ago, the Lauya ancient continent in the northern hemisphere and the gondwana continent, which was still dividing between the north and the south, stuck together near the Mediterranean Sea, forming a pan-continent.
Corresponding to the decline of the cold plume column located below the Asian continent, there is a hot plume pillar rising below Africa. As a result, the Pancontinent began to split again. At this time, because the hot plume column brought the material from the depths of the mantle to the surface, in the place where the Pan continent split, causing intense volcanic activity, the mantle magma rich in gasification components spewed out of the surface and turned into dust scattered in the atmosphere.
This upheaval in the environment led to the human-scale extinction of plankton and corals. As volcanic eruptions block sunlight and inhibit photosynthesis, plankton or coral reefs known as oxygen generators die. There are many symbiotic algae near corals, as well as other organisms that inhabit coral reefs, which form a biological pyramid structure of food chains based on the photosynthesis of algae. Due to the extinction of the coral, many creatures that depended on it also died in large numbers, directing a biological mass extinction.
Each of these six upheavals in earth's history has had a profound impact on the planet, lasting hundreds of millions of years. When human beings look back at these changes, they will be amazed by the magic and ingenuity of nature.