How did plate movement and orogeny occur?

On the earth, the land area only accounts for about 29% of the earth's surface area. However, in this small part of the land area, the mountains and plateaus above 2000 meters above sea level account for 1 1% of the landing area. As for the mountainous area above 1000 meters above sea level, it actually occupies more than 28% of the total landing area, covering an area of about 42 million square kilometers. This area is also exactly equivalent to the area of the whole of Asia. Coupled with some low mountains and hills, the earth's land can be said to be full of mountains.

So, why are there so many mountains on the earth? According to the geomechanics theory of geologists, the main driving force of orogeny is the horizontal compression of the crust. Generally, there are two kinds of compressive forces: ① the east-west horizontal compression caused by the change of the earth's rotation speed; ② Crustal compression in equatorial direction caused by different linear velocities of the earth's rotation at different latitudes. These two kinds of compressions, combined with the distortion caused by the uneven stress on the earth's crust, form mountains with various trends.

Generally speaking, when the earth's crust moves, the relatively hard part of the earth's crust often breaks, rising or falling on both sides of the break, and sometimes mountains can be formed. But many times it is a large-scale uplift, the altitude can be very high, and the terrain is relatively flat; However, in some weak areas of the earth's crust, violent folds and uplifts are often prone to occur, becoming endless mountains. How many mountains in the world are formed in this way. In many mountains, we can see that the rock strata have become crooked, which proves that this kind of fold change has happened here. Under the action of strong and weak forces, the strata in the earth's crust can have certain plasticity and become curved from the original almost horizontal state. The formation of mountains is caused by crustal movement, but the crustal properties there also play a decisive role.

After the ground is uneven caused by crustal movement, the running water on the ground has obtained a place to move freely. The greater the topographic difference, the stronger the fluidity of flowing water and the faster the erosion of the raised part of the ground. The general trend is to flatten this protruding part, and the wind and glaciers are also doing this work. As a result, some mountains on the earth have been lowered and even become almost calm. However, because the crustal movement has not stopped, for example, the Himalayas were formed during the Cenozoic Tertiary Himalayan movement 2 million years ago and are still rising. So now our earth has gone through a huge orogeny, for example, the Himalayas passed through Central Asia to the Alps, all of which were formed in the recent uplift of the earth's history, so there are many mountains on the earth at this stage.

In the process of running water scouring the ground, due to the different properties of ground rocks, their anti-scouring strength is different, and the scouring ability of running water is also different. In some places, in a certain period of time, not only did it not play the role of flattening, but it carved the ground up and down. This effect of glaciers is also significant. Although the basic reason for the formation of many mountains is crustal movement, mountain shapes like this are processed by running water and glaciers. Due to these complicated reasons, there are not only many mountains on the earth, but also many mountain images. Who would believe that Chinese mainland is made up of many plots? However, this is indeed a fact. This matter should start with the magnetism of "guiding blind fish".

Fish guide

In the Northern Song Dynasty, there was a military book called "General Theory of the Martial Classics", which mentioned that when marching on a cloudy day, it was dark, and blind fish could be used to identify the direction. The book also describes how to make a guide fish: cut a thin piece of iron into the shape of a fish, put it on a charcoal fire to burn it red, then face the head south, let it cool, float on the water after cooling, and the head will point south. Now it seems that the guide fish can guide because the fish-shaped thin iron sheet is magnetized by the earth's magnetic field during the cooling process and becomes a magnet.

In ancient times, the fiery magma from volcanic eruption was magnetized by the earth's magnetic field at that time when it cooled, and also formed magnetic rocks. Especially basalt with more iron. This magnetism is called fossil magnetism or remanence. A rock with fossil magnetism is like a small fish, but it now points not to the South Pole, but to the ancient magnetic pole when the rock was formed. According to the angle (dip angle) between the magnetic direction of fossils and the horizontal plane, the latitude of rock formation can be calculated (the higher the latitude, the greater the dip angle at the equator, which is 0 and the poles are 90). When geologists detect some magnetic rocks, they often find that the latitudes of some magnetic rocks are very different from those when they are collected now. This shows that the place where these rocks are now is not the original place where they were formed, but drifted from a distance.

The study of fossil magnetism not only shows that Chinese mainland did drift, but also finds that about 300 million years ago, the central part of the North China block and the central part of the South China block were separated by about 20 latitudes (more than 2,000 kilometers), which is much farther than their present distance. Geologists have discovered ancient ocean floor rocks, ophiolite and marine sediments in the Qinling Mountains between North China and South China. It can be seen that there used to be a Wang Yang between North China and South China. More than 200 million years ago, these two plots were close to each other, and the ancient ocean sandwiched between them disappeared. The sediments and rocks in the ancient ocean were squeezed, folded and uplifted, forming the magnificent Qinling Mountains and Dabie Mountains.

Evidence such as paleontology also shows that in ancient times, North China and South China were not the same land. Between 500 million and 800 million years ago, the stratigraphic and biological characteristics in southern China were completely different from those in northern China, but very similar to those in Australia. For example, both South China and Australia have found glacial deposits that existed only in the very harsh climate 600-800 million years ago, but not in North China. The study of fossil magnetism proves that South China may have been connected with Australia for a period of time, and then it was pieced together with the North China block after a long-distance drift.

The same evidence also shows that Tibet, Tarim, Qaidam and Junggar were once isolated blocks separated by ancient oceans. More than 300 million years ago, South China was located in the tropics, but cold-loving creatures lived in Tibet. 65438+ billion years ago, freshwater mussels from South China entered Tibet, reflecting that two plots far apart had been put together. Most of the above plots were spliced with each other about 200 million to 300 million years ago, forming the embryonic form of Chinese mainland; The folded mountain between blocks is the splicing line. At the beginning of Mesozoic more than 200 million years ago, the North China-Tarim block was still spliced with Siberia, thus forming the ancient Asian continent. As for India's collision with Tibet to the north and the formation of modern Asia, it was the Cenozoic era more than 40 million years ago.

On mountains, China's classic Shan Hai Jing is a great early work in the world. "Mountain Classic" takes mountains as the center, describing the natural landforms of the vast areas from south to South China Sea in Guangdong, Yinshan Mountain in Inner Mongolia in the north, Qinghai Lake in the west and Zhoushan Islands in the east. The geographical location, hydrology, flora and fauna, minerals and even myths and legends of each mountain have different detailed descriptions. This is a very valuable scientific attempt, but apart from myths and legends, there is little about the cause of this mountain. In China, it was not until the Song Dynasty that Shen Kuo and Zhu Cai made a guess that "the mountain is a valley and the deep valley is a tomb" according to the fossils of aquatic animals and plants on the mountain.

After all, later generations are smarter than the ancients, and modern geologists have found the motive force for building mountains from the movement of rock plates caused by the earth's pulsation. Today's science has developed to not only give a well-founded analysis of the history of each mountain, but also reach an outline understanding of the formation of the global mountain pattern.

Sanqingshan Mountain is located at the junction of Dexing City and Yushan County in the northeast of Jiangxi Province. Its geographical location is 28 54' north latitude and118 03' east longitude, which is close to zhejiang-jiangxi railway trunk line. In ancient times, it was a meeting of Rao, Xin and Qu, but now it is a bright pearl on the East China Tourism Network and a national key scenic spot.

Sanqingshan is 44 kilometers east of Quzhou/KLOC-0 in Zhejiang, 5 kilometers south of Wuyishan1KLOC-0 in Fujian, 78 kilometers west of Shangrao and 263 kilometers north of Huangshan in Anhui. The total area of the scenic spot is 220 square kilometers, the central scenic spot is 7 1 square kilometers, and the highest main peak, Yujing Peak, is 18 16.9 meters above sea level. Sanqingshan is 12.2km long from north to south and 6.3km wide from east to west. Its plane is lotus leaf-shaped and inclines from southeast to northwest.

Due to frequent and intense orogeny, Sanqingshan Mountain is densely covered with faults, joints are developed and the mountain is constantly rising. After a long period of weathering and erosion and the disintegration of gravity, a spectacular mountain scene with strange peaks and rocks and numerous pieces has been formed. The beauty of Sanqingshan lies in its simplicity and naturalness, and its wonder lies in its combination of form and spirit, vivid fairy spirits, inviting it to swim in the ethereal land and lingering in the clouds. It was a Taoist paradise in ancient times. There are countless strange peaks and rocks on the mountain, and the clouds are lingering, which is amazing and rare in the world. Lingquan Waterfall is comparable to single crystal jade liquid, and the caves in the valley are the places where Teng Jiao raises the phoenix and Crouching Tiger hides the dragon. The palace buildings of past dynasties are integrated with the unique natural landscape, and Zhong Ling has beautiful scenery, so it has the reputation of "the first fairy peak in the world and the blessed land of chinese odyssey".

The magical and magnificent landscape of Sanqingshan Mountain is closely related to the suitable geological climate, which is the product of the long-term change of crustal movement on geological action. Sanqingshan Mountain has experienced1400 million years of geological historical vicissitudes, with three transgressions and many geological tectonic movements.

The first seawater immersion occurred in Mesoproterozoic1400 million years ago. At that time, the crustal movement in Sanqingshan area was in the stage of "geosyncline" subsidence, and the seawater eroded for 400 million years, and the marine clastic rocks of Shuangqiao Mountain Group flysch with a thickness of several thousand meters were deposited, mixed with submarine volcanic eruption. After the "Jinning Movement", the history of geosyncline subsidence ended, the crust began to rise gradually, and the water came out as land, and the Sanqingshan area entered a relatively stable "platform" stage. Since then, the crust has still fluctuated, but the settlement speed is moderate and the range is wide.

Sanqingshan

At the end of Sinian 600 million years ago, the second sea immersion took place, which lasted for 65.438+0.6 billion years and lasted until the end of Ordovician. More than 4,000 meters of shallow sea sand shale and carbonate rocks were deposited, including marine paleontological fossils such as trilobites, graptolites and sponges. The above two trips into the sea turned Sanqingshan headquarters into the sea of Wang Yang. After the "Caledonian first act" orogeny at the end of Ordovician, Sanqingshan was completely separated from the seawater environment and no longer accepted sedimentation.

In the early Silurian 440 million years ago, although there was a third sea immersion, the seawater only reached the edge of the southeast corner of Sanqing Mountain. Until10.8 billion years ago, during the Late Jurassic, Cretaceous and Sanqingshan periods, an unusually strong orogenic movement, namely Yanshan Movement, accompanied by large-scale acid magma immersion activities, laid the geological foundation of Sanqingshan landscape.

In the years from 20 million to 30 million years ago, Himalayan orogeny, that is, neotectonic movement, broke out one after another, and the mountains rose sharply, accompanied by strong downward cutting of hydraulic erosion, which made the terrain height difference disparity. Because the geological environment of Sanqingshan Mountain is in an area where orogeny is frequent and intense, faults are dense and joints are developed, especially vertical faults and joints. The mountain is constantly rising, long-term weathering and erosion, coupled with gravity disintegration, forming a strange landform with peaks in the sky and valleys in the deep. The formation of Sanqingshan Scenic Area can be said to be a masterpiece of nature.

Global plate structure and its movement

In the late 1960s, based on the theories of continental drift and submarine spreading, Morgan of the United States, Lei Bixiong of France and Mackenzie of Britain put forward the theory of lithospheric plate tectonics. The research results of seismology support the theory of plate tectonics, which makes more and more people accept and recognize this theory. Therefore, the relative movement of lithospheric plates is considered as the cause of lithospheric continental tectonics, and the plate tectonic theory is also considered as a new global tectonic theory.

According to the lithospheric plate theory, a rigid lithosphere can be divided into several rock plates according to its geological structure characteristics. Through the research of geologists, the lithosphere tends to be divided into seven plates and seven small plates, and each plate can be divided into several blocks. There are three major tectonic systems at the plate boundary: global ridge tectonic system, continental neoorogenic belt tectonic system and island arc-trench tectonic system. These three tectonic systems are all obvious deformation and fracture zones with strong activity. Therefore, most earthquakes and volcanoes in the world occur at plate boundaries. Plate boundaries are the edges of some plots. The geological tectonic system of the block margin is the old fold belt tectonic system, continental rift tectonic system, stable continental margin tectonic system, ocean floor ridge tectonic system, continental fault zone tectonic system and ocean floor fault zone tectonic system. These seven plates are Pacific plate, Eurasian plate, Indo-Australia plate, Africa plate, North America plate, South America plate and Antarctic plate.

The Pacific plate is an ocean plate composed of a single ocean lithosphere. The board has 9 diagrams.

The Eurasian plate is mainly composed of continents. China lies in the Eurasian plate. The internal structure of Eurasia plate is the most complex. There are 24 blocks in Eurasia plate.

The Indo-Australian plate has nine blocks.

The African plate is mainly the African continent. Part of the Atlantic Ocean is also divided into this plate. The African plate has 9 blocks.

The North American plate includes most of the North American continent and the Arctic Ocean basin, with 14 blocks.

The South American plate is mainly the South American continent with six blocks.

The Antarctic plate has nine blocks.

The earth has been moving. Because of the earth's rotation, there is relative motion between the inner circles of the earth, and these seven plates rotate westward relative to the inner circles of the earth as a whole. In addition, there is a depolarization movement in the lithospheric plate. The plates in the northern hemisphere move in the equatorial direction, and the plates in the southern hemisphere also move in the equatorial direction, but the plates in the northern and southern hemispheres move in opposite directions. Therefore, the movement of the whole lithospheric plate relative to the inner ring is the synthesis of these two movements. In addition to the overall movement of lithospheric plates, there are also relative movements between plates. There are three forms of relative motion between lithospheric plates: plate separation, plate convergence and plate translation. At present, most of the relative motion rates of the global lithospheric plates have been determined. According to these three forms of plate relative motion, their boundaries can be called separation plate boundary, convergence plate boundary and translation plate boundary.

Plate separation generally occurs on the fault zone of the older continental block. The result of the separation movement will produce a new ocean basin.

The convergence movement of plates is manifested as collision and extrusion between plates. This relative movement is closely related to the global large-scale orogeny.

The characteristic of plate translation is that two plates slide past each other in a simple way. In many cases, plate translation occurs along some form of twisted tectonic belt, which is closely related to the separation and convergence of plates.

Global neoorogenic tectonic system

If the Himalayas rose from the ancient sea, it seems incredible. How does the roof of the majestic world covered with snow connect with the sea? However, the facts have proved the correctness of the theory. When we climb the steep cliffs in the Himalayas, or in deep valleys, we can find many fossils of ancient marine animals and plants, including trilobites, graptolites, gastropods, brachiopods, nautilus, ammonites, petabranchia, corals, bryozoa, sea urchins, lilies, ostracods, foraminifera, algae and ichthyosaurs. It can be proved that this used to be the sea of Wang Yang, and the Himalayas emerged from the ancient sea.

Then, how did the vast ancient sea suddenly become the most magnificent mountain range in the world? This is the result of the rise of the earth's crust. At the altitude of 5700~5900 meters on the northern slope of Mashan, Xixia State, the fossils of Quercus alpine and Quercus felta, which grew 6,543,800 years ago, were found. These plants are still growing in the vast area of southwest China at an altitude of 2,200-3,000 meters. Although the climatic conditions before 654.38+million years and the growing environment and height of these plants are not exactly the same as now, it can be roughly estimated that the area has increased by about 3000 meters in the past 654.38+million years, with an average increase of about 30 meters per 1 10,000 years. According to similar data, a place in the south of Dingri County, Tibet, China has risen by about 500 meters in the past 200,000 years, which shows how strong the crustal uplift is here. The Himalayas rose from the sea to become the "roof of the world", and it is still rising, but the speed of rising is a bit slow, which is not easy to be noticed.

The so-called neoorogenic belt refers to the folded mountains formed in the late geological period, that is, since Mesozoic, and it is also a zone where large-scale orogeny is taking place in the lithosphere. The neoorogenic belt is basically located in two narrow zones, namely the Pacific Rim Orogenic Belt and the Alps-Himalayan-Southeast Asia Orogenic Belt. The circum-Pacific orogenic belt passes through the Philippines, Japan and Alaska, as well as the Rocky Mountains and Andes on the western edge of the American continent, and finally extends to Antarctica. The Alps-Himalayas-Southeast Asia orogenic belt runs through Alps, Himalayas, Indonesia, and finally connects with New Guinea, roughly spanning North Africa, Europe and Asia.

The North American plate, located in the east of the Pacific plate, moves from northeast to southwest relative to the inner circle of the earth. The collision and compression between the western North American plate and the Pacific plate made a part of the eastern Pacific plate participate in orogeny and was annexed by the North American plate, forming a huge folded mountain system on the western edge of the North American continent. The movement direction of the South American plate is west to north. Because the South American plate is close to the equator and part of it is on the equator, the movement of the South American plate to the west is better than that to the north, and its western edge collides with the Pacific plate, which also produces a huge wrinkled mountain system in the west of the South American plate. The North American plate is connected with the folded mountains from north to south on the western edge of the South American plate, and becomes a part of the folded mountains around the Pacific Ocean. In the eastern part of the North American plate and the South American plate, a winding and broken coastal shape is formed.

The Eurasian plate is mainly composed of continents, moving from northeast to southwest and advancing westward relative to the Indo-Australian plate. The Indo-Australian plate includes the Indian Peninsula, the eastern floor of the Indian Ocean, Australia and its surrounding parts. Of the nine blocks in the Indo-Australian plate, five are in the southern hemisphere, two are in the northern hemisphere, and the other two cross the equator. Most of them are in the southern hemisphere, and a few areas are above the equator. As a whole moving plate, the Indo-Australian plate moves from southeast to northwest. The Indo-Australian plate and the Eurasian plate are compressed in parallel, forming an east-west folded mountain system. The Himalayas and Suleiman Mountains, the roof of the world, constitute a part of the Alps-Himalayas-folded mountains in Southeast Asia in the Eurasian plate. A large number of continental crust islands have been formed in the northern part of Eurasia plate. The southern part of Indo-Australia Plate separates Australia Island from New Zealand Island, forming Tasman Basin.

In a word, the Pacific Rim orogenic belt and the Alps-Himalaya-Southeast Asia orogenic belt are thus formed, which can generally be considered as a global continuous orogenic system.