Things should start at the beginning of the 20th century.
Find a map of the world and study the shapes of the continents carefully. You may find that the coastlines on both sides of the Atlantic are very similar. If we do a jigsaw puzzle to put the coastlines of the Atlantic Ocean together and embed the protruding part of the eastern end of Brazil into the Gulf of Guinea on the west coast of Africa, then the entire coast of Brazil will coincide with the west coast of Africa without leaving much gap in between. Although the map has been around for a long time, few people paid attention to such a “coincidence” in the past. It was not until 1910 that a German meteorologist named Wegener discovered this “miracle” by accident. This discovery aroused his keen interest, and he was determined to explore this issue to the end.
After two years of intense research and investigation, Wegener put forward a bold hypothesis in 1912. He proposed: In ancient times, there was only a whole piece of land on the earth. Later, this continent split and drifted on the sea like floating ice, and it gradually formed the current continents. In 1915, he collected a large amount of evidence on stratigraphic structure, paleontology, paleo-climate, etc., made a systematic discussion on the issue of continental drift, and wrote the famous book “The Origin of Land and Sea”, which put forward a complete theory of continental drift. .
The proposal of the theory of continental drift caused a sensation in the field of geosciences. Traditional earth tectonics believes that the crustal movement is mainly vertical movement, and the relative position of the land and the sea is fixed. Wegener’s theory of continental drift actually believed that the earth’s crust had large-scale horizontal movement, and the continent could float like a ship. This naturally met with opposition from many orthodox scholars. Due to the limitation of scientific conditions at the time, Wegener failed to provide a satisfactory answer to the way and dynamics of continental drift. Therefore, with the premature death of Wegener in 1930, the theory of continental drift gradually declined under the siege of deep-rooted traditional forces. Up.
The ever-expanding seabed
Whether people admit it or not, the continent is drifting after all. In 1960, a group of British geophysicists independently confirmed that the continent had drifted based on their study of paleomagnetism, and the drift trajectory obtained was quite consistent with Wegener’s inference that year. In 1965, someone used a computer to compare the contours of the continental slopes on both sides of the Atlantic Ocean, and the result was an almost perfect picture. The ingenious cooperation between the study of ancient geomagnetism and the boundary of the continental slope has injected new vitality into the theory of continental drift that has been silent for many years. The continental drift is said to have begun to recover.
In the early 1960s, American scholars further proposed the theory of seafloor expansion from the perspective of horizontal crustal movement pioneered by the theory of continental drift, which provided a new mechanism and the strongest evidence for the theory of continental drift, and made the theory of horizontal crustal movement in In the confrontation with fixed theory, an overwhelming advantage was finally achieved.
Earlier, people always thought that the seabed was relatively flat. It was not until the invention of echo sounding in the early 20th century that oceanographers discovered that the seabed was also rough. In the mid-1950s, through the comprehensive ultrasonic sounding of the oceans, it was discovered that the ocean floor of the oceans around the world runs through a continuous submarine mountain called the mid-ocean ridge. The mid-ocean ridges of the oceans are connected end to end, endless, with a total length of 64 000 kilometers, which is equivalent to more than one and a half circle of the earth. Along the axis of the mid-ocean ridge, a fault valley splits the mid-ocean ridge. This kind of central rift valley is widely distributed in the mid-ocean ridges and is called the global rift system. In addition to the mountains and valleys at the bottom of the ocean, there are many deep and steep narrow trenches at the edge of the ocean. The deepest Mariana trench is 11,000 meters deep, which is the deepest place in the world. Almost all the strongest volcanoes and earthquakes on the earth are located near the trenches. In addition, people have also discovered that the age of the ocean floor is much younger than the ocean itself. This is a weird phenomenon that cannot be explained in any way with the traditional view.
Faced with such new discoveries, the theory of seabed expansion proposed that the ocean floor of the ocean is formed by the outflow of mantle material under the crust. Mid-ocean ridges and rift valleys are the outflow outlets for mantle material to rise. The mantle material that gushes out condenses into a new seafloor and pushes the formed seafloor to expand to both sides. In different sea areas, there can be two situations of seabed expansion: one situation is that the expanding ocean floor simultaneously pushes the continents on both sides together with their adjacent seabeds. As new seabeds continue to grow, the new oceans continue to open. The continents on both sides gradually drifted away. The current Atlantic Ocean was created in less than 200 million years due to the expansion of the ocean floor. Another situation is that when the ocean floor expands and reaches the trench, it subducts and returns to the depths of the earth’s crust. At this time, the ocean floor does not push adjacent continents to drift to both sides, but constantly renews itself. For example, the ocean floor of the Pacific Ocean is in the process of continuous regeneration, expansion and subduction. Calculated based on the expansion speed of the Pacific Ocean floor, it only takes about 200 million years to update the entire ocean floor at once.
According to the expansion of the ocean floor, the entire earth is like a monster with two blood basins and big mouths constantly swallowing and vomiting the substance in the abdomen: a big mouth is a global rift system extending along the top of the mid-ocean ridge, and it keeps spitting out new The bottom of the sea; a big mouth is a deep and narrow trench, which constantly sucks the old bottom of the sea.
Because the ridge is the place where the old seabed returns to the depths of the earth’s crust, the movement and collision of the earth’s crust are violent and unstable, so most of the earthquakes and volcanoes are concentrated near the trench; because the seabed is constantly renewing, its age Nature is much younger than the ocean itself. The theory of submarine expansion simply and clearly explains the problems that are difficult to explain by traditional views.
In just a few years after the submarine expansion theory was put forward, research work on submarine magnetic anomalies, mid-ocean ridge conversion faults, and deep-sea drilling have successively made fruitful progress, providing strong quantitative evidence for the submarine expansion theory. Therefore, in 1967, the theory of submarine expansion had achieved a fully established position in the geosciences community.
Since the concept of submarine expansion eventually broke the traditional view that the position of the sea and land is relatively immobile, fixed continents have become drifting land masses, and local specific geological phenomena have been summarized into the global evolution model. Therefore, more and more People began to admit that the rise of the theory of continental drift and submarine expansion has brought about a “revolution in earth science.”
A fascinating disciplinary revolution
The revolution did not end here. Later, the theory of continental drift and submarine expansion was further extended and developed, and the theory of plate tectonics appeared.
According to the theory of plate tectonics, the surface of the earth is a lithosphere with an average thickness of 70 to 100 kilometers. Under the lithosphere, due to the increase in temperature and pressure, the earth’s material softens and melts, forming a layer of asthenosphere that can flow. The lithosphere is very hard. It is divided into several huge plates along mid-ocean ridges and trenches, such as the Pacific plate and the Eurasian plate. The plates are very large, including both land and sea floor. They float on the asthenosphere, drifting constantly with the convection of the asthenosphere material.
The theory of plate tectonics is a magical theory, which can explain and explain many problems. It is like an indescribable magic weapon.
The theory of plate tectonics can not only explain how the oceans are formed, why the ocean floor has extremely magnificent ridges and trenches, why the ocean floor is so young, but also explain why the Himalayas uplift, why there are many volcanoes in Japan, and why strong earthquakes occurred in Greece and Italy. Go to the North African continent to find out why. Plate activities provide an endless source of metal deposits, and also provide very favorable conditions for the generation and storage of oil, bringing hundreds of billions of tons of oil to mankind. The theory of plate tectonics can explain why oil and natural gas are abundant in Alaska and the North Sea in the cold climate, and coal seams are also buried in the frozen Antarctic region, guiding people where they can find mineral deposits. Biologists are also interested in the theory of plate tectonics, because it is plate activity that promotes the evolution of organisms and clearly explains why organisms on different continents are related. The emergence of plate tectonics has enabled us to discover many peculiar facts.
At present, the Amazon River in South America originates from the Andes on the westernmost edge of South America and flows eastward into the Atlantic Ocean. However, in ancient times when South America and Africa were connected, the Amazon River originated in Africa and flows westward into the Pacific Ocean. Plate activity created the Andes and caused the Amazon River to flow backwards. Even the rampant crabbing is also related to plate activity.
In the field of geosciences, no comprehensive theory can explain so many facts so simply and clearly. No wonder the vast majority of geoscientists are now leaning toward the theory of plate tectonics, fascinated by it.
The doctrine of good knowledge of the past and the future
There is another unique feature of the theory of plate tectonics, that is, it has certain predictive and quantitative properties.
According to the measurement of the magnetic anomaly of the ocean floor, the age of the ocean floor can be inferred. According to the age of the ocean floor, the expansion rate of the plate can be measured. According to the expansion speed of the plate and the known law of plate movement, a quantitative depiction of the global image of plate movement can be made. Through the calculation of the ancient latitude of the rock and the position of the paleomagnetic pole, a certain quantitative description of the magnitude and speed of continental drift can also be made, so as to further infer the past hundreds of millions of years ago and predict the future hundreds of millions of years later. Good knowledge of the past and the future. The argument at the beginning of this article is calculated in this way.
We can also look at our earth in a larger time scale: the seven continents today are formed by the division and drift of the ancient joint ancient land, and the joint ancient land does not exist since ancient times, but is separated from each other by several The continents of China have gradually collided and “welded” together. In the Paleozoic, Europe, North America, and Siberia were all independent plates. About 400 million years ago, North America and Europe met and “welded” into the European and American continent. About 200 million years ago, Africa and North America collided, Europe and Siberia collided, and this roughly formed the United Ancient Land. Prior to this, the primitive Chinese mainland was once an isolated land free from other continents.
Besides, in the future, one day, “the Himalayas will exceed 10,000 meters above sea level”, “New York and Portuton may form volcanoes”, “the Pacific Ocean will lose the crown of the’world’s largest ocean’ and may disappear completely. The Asian continent will eventually disappear. “Welded” with the American continent, an extremely magnificent mountain range will rise between them. China has become a landlocked country, and in other places new oceans will be formed. The sea, land, and mountains of the entire world will be completely different”… …
In short, as the expansion of the ocean floor is confirmed and the theory of plate tectonics is accepted, a new situation in earth science is emerging. In people’s minds, all parts of the earth are no longer static and isolated, but are born and die, are constantly in motion, and are full of infinite vitality.
For more than a century, the theory of continental drift has gone through a process of affirmation, negation, and negation of the rise and development of the theory of submarine expansion and plate tectonics from birth, decline to recovery, and then to the theory of new drift. Today, although the new theory still has such problems as the power source of plate activity and many specific processes of plate activity, further research and exploration are needed. However, we already have a lot of evidence to prove that the continent is indeed drifting. The new doctrine covers such a wide range of fields, and the research results obtained are so exciting, which has had an extremely far-reaching impact on the earth sciences.