What special weather does China have? (Don’t look for geography books on cold waves, typhoons, sandstorms, plum rains, etc.)
A volcanic eruption is the release of magma and other eruptions from a volcanic crater to the surface in a short period of time. Because the magma contains a large amount of volatile components, and the confining pressure of the overlying rock formations, these volatile components are dissolved in the magma and cannot escape. When the magma rises close to the surface, the pressure decreases and the volatile components are released sharply, thus forming a volcanic eruption. Volcanic eruption is a peculiar geological phenomenon, a manifestation of crustal movement, and the strongest display of the earth's internal thermal energy on the surface.
Edit the type of volcanic eruption in this paragraph
Due to the influence of various factors such as the nature of magma, the pressure in the underground magma chamber, the shape of the volcanic channel, and the volcanic eruption environment (on land or underwater) , which makes the forms of volcanic eruptions very different, generally divided into the following categories:
Fissure eruptions
Magma overflows to the surface along huge cracks in the earth's crust, which is called a fissure eruption. This type of eruption does not have a strong explosive phenomenon. The ejected material is mostly basic magma, which often forms a lava platform covering a wide area after condensation. For example, the Permian Emeishan basalt distributed in the junction area of Sichuan, Yunnan and Guizhou provinces in southwest China and the Tertiary Hannuoba basalt north of Zhangjiakou, Hebei are both fissure-type eruptions. Modern fissure-type eruptions are mainly distributed at mid-ocean ridges on the ocean floor. Only Iceland can see such volcanic eruptions on the continent, so they are also called Icelandic volcanoes.
Central eruption
Underground magma erupts to the surface through a tubular volcanic channel, which is called a central eruption. This is the main form of modern volcanic activity, which can be subdivided into three types:
(1) Quiet type: when a volcano erupts. Only a large amount of hot lava quietly overflowed from the crater and slowly flowed down the hillside, just like boiling rice soup pouring out of a rice pot. The overflowing material is mainly basic magma. The magma has a high temperature, low viscosity and is easy to flow. It contains less gas and has no explosion phenomenon. It is represented by Hawaiian volcanoes and is also called the Hawaiian type. People can enjoy this kind of volcano.
(2) Explosive type: When a volcano erupts, a violent explosion occurs, and a large amount of gas and pyroclastic material are ejected at the same time. The ejected magma is mainly medium-acidic magma. On December 16, 1902, the eruption of Mount Pelé in the West Indies shocked the world. The lava it spewed was thick and thick, and it spewed out large amounts of pumice and hot volcanic ash. The eruption that killed 26,000 people fell into this category, also known as the Pelé type.
(3) Intermediate eruption: It is the transitional type between quiet eruption and explosive eruption. This type is dominated by medium-basic lava eruptions. If there is an explosion, the explosive force is not large. It can erupt steadily for several months or even years, and is characterized by intermittent eruptions. Take the Strombod volcano on the Lipari Islands near the west coast of Italy as an example. The volcano erupts approximately every 2-3 minutes, and the flames of the volcanic eruption can still be seen 50 kilometers away at night, so it is known as the "Mediterranean Lighthouse." Also called Stromboli style. Some people think that the Wudalianchi volcano in Heilongjiang Province, my country, belongs to this type.
(4) Penetrating eruption
Edit the stages of volcanic eruption
1. Gas explosion
During a volcanic eruption During the gestation stage, due to the occurrence of gas dissolution and earthquake swarms, the degree of cracking of the overlying rock increases and the pressure decreases. The amount of gas dissolution in the magma continues to increase, the magma volume gradually expands, the density decreases, and the internal pressure increases. When When the internal pressure greatly exceeds the external pressure, a violent explosion of gas occurs in the crack density zone of the overlying rock, breaking the rock and opening the channel for volcanic eruption. First, the fragments are ejected, followed by the eruption of magma.
2. The formation of the eruption column
After the gas explosion, the gas sprayed the rock debris and deep magma in the channel high into the sky with great ejection force, forming a tall eruption column. . The eruption column can be divided into three zones:
(1) Aeration zone: It is located in the lower part of the eruption column and is equivalent to one-tenth of the height of the entire eruption column. Because the gas rushes out of the crater with great speed and force, although the density of the rocks and other materials ejected is much higher than the density of the atmosphere, it will also be thrown high into the sky. The speed of air rush gradually accelerates as it rises in the volcanic channel. When it erupts from the surface and shoots to high altitude, its speed gradually decreases due to the pressure of the atmosphere and the consumption of jet energy. The magnitude of gravity begins to fall at different altitudes.
(2) Convection zone: Located in the upper part of the gas rush zone, due to the slowdown of the gas rush of the eruption column, the gas in the gas column scatters outward, and the gas in the atmosphere is continuously added to form the eruption column The convection of internal and external gases is therefore called the convection zone. The denser material in this area begins to fall. Materials with a density less than that of the atmosphere continue to rise due to the buoyancy of the atmosphere. The height of the air column in the convection zone is relatively large, accounting for approximately seven-tenths of the total height of the eruption column.
(3) Diffusion zone: Located at the top of the eruption column, the pressure of the eruption column and the upper atmosphere in this area reaches a state of basic balance. The eruption column continues to rise, and the gas and low-density substances in the column diffuse along the horizontal direction, so it is called a diffusion zone. Volcanic ash brought into high altitudes can form volcanic ash clouds. Volcanic ash clouds can float in the air for a long time, which can have a great impact on regional climate and even cause disasters.
The height of the column in this area accounts for about two-tenths of the total height of the column.
3. Collapse of the eruption column
As the eruption column rises, it carries debris of different particle sizes and densities. These debris depend on the gravity. , collapsed at different heights and stages respectively. There are four main factors that determine how quickly an eruption column collapses:
(1) The crater radius is large and the gas impulse is small, so the column collapses faster;
(2 ) If the content of rock debris in the eruption column is high, and the particle size and density are large, the column will collapse quickly;
(3) If there are many solid rock blocks in the eruption column that repeatedly return to the air, the column will collapse The faster it collapses;
(4) If surface water is added to the eruption column, the density of the column can be increased, and the column collapses faster. On the contrary, if the eruption column stays in the air for a long time, it will collapse slowly.
Volcanic eruptions are not uniform. For eruptions like Hawaii's Kilauea volcano, lava has flowed out quietly beforehand. Because the lava flows slowly, it only damages property and does not endanger lives. Pyroclastic eruptions or steam explosions (or violent steam eruptions) like the Krakatau volcano in Indonesia in 1883 caused heavy casualties.
In the process of volcanic eruptions, volatile substances play an important role. They are not only the products of volcanic eruptions, but also the driving force of volcanic eruptions. The activity of volatile substances plays a role in the entire process from the generation of magma to the eruption of a volcano.
British scientists believe that a super volcanic eruption may destroy mankind
British scientists believe that mankind may be destroyed in a super-intensity volcanic eruption. Stephen Self of the University of Great Britain and Northern Ireland said in an answer to a reporter from an electronic magazine that there is currently no way to prevent this disaster. Currently, scientists are busy formulating various strategies to resist "external threats", such as how to prevent asteroids from colliding with the earth, but they rarely consider that the main danger may come from the interior of the earth.
Geophysicists assert that some volcanic eruptions are hundreds of times more powerful than in the past, and that the earth experienced such a large-scale disaster not long before civilization emerged.
American geologists had earlier discovered a not too deep volcanic ash dead layer in Yellowstone National Park, and believed that its formation was caused by a super volcanic eruption that occurred 620,000 years ago. The result is still there today. You can also see some large funnel-shaped craters here, which are calderas formed after devastating volcanic eruptions.
The consequences of this super volcanic eruption were described in detail in a report to the British government's natural disaster task force - a large area will be covered with lava and spread into the atmosphere The dust and ashes will prevent a lot of sunlight from reaching the earth's surface, which will undoubtedly cause global climate changes.
According to Michael Rampino of New York University, the extremely powerful eruption of the Sumatra volcano that occurred 74,000 years ago caused global cooling and the destruction of three-quarters of the plants in the northern hemisphere. There is a rapid discharge between one part of the charged cloud layer and another part of the cloud layer with a different type of charge, or the charged cloud layer on the earth. This rapid discharge process produces intense lightning and a loud sound. This is what we see as lightning and thunder.
Of course, the discharge between clouds is mainly harmful to aircraft and has no great impact on buildings, people and livestock on the ground. The discharge of clouds on the earth is harmful to buildings, electronic and electrical equipment and The harm to humans and animals is great.
Usually there are three main forms of lightning strikes: One is a rapid discharge phenomenon between charged clouds and a certain point on the earth, which is called "direct lightning strike". The second is that the charged cloud layer causes a certain area of the ground to be charged with a different type of charge due to electrostatic induction. When a direct lightning strike occurs, the electrification of the clouds quickly disappears, and in some areas on the ground due to the large dispersion resistance, local high voltages appear, or during the discharge process of direct lightning strikes, strong pulse currents produce electromagnetic induction on surrounding wires or metal objects. The phenomenon of high voltage causing lightning strikes is called "secondary lightning" or "induction lightning". The third is the "spherical mine".
Edit this paragraph about the power of lightning
The average lightning current is about 20,000A (or even greater), and the lightning voltage is about 10 to the power of 10 volts (the safe voltage for the human body is 36 volts ), a lightning strike lasts about one thousandth of a second, and the average power emitted by a lightning strike reaches 20 billion kilowatts (generally the power of a rice cooker is less than 1,000 watts).
The Three Gorges Hydropower Station, the world's largest hydropower station built by our country, has a total installed capacity of 18.2 million kilowatts, which is only one thousandth of the power of a lightning strike.
Of course, although the electrical power of lightning is very large, due to the short discharge time, the electrical power of the lightning current is not very large, about 5555 degrees at a time.
There are more than 100 lightning phenomena every second in the world. The total electrical energy released by lightning in a year is about 1.75 billion kilowatt hours.
If the electricity fee per kilowatt hour is 0.30 yuan, the value of lightning in the world for a year is 5.25 trillion yuan. This is a huge wealth. However, due to the extremely short duration of lightning, humans have not yet been able to capture this kind of lightning. Electric energy, currently there is no method to utilize lightning electric energy in the world.
Edit this paragraph about the hazards of lightning
There are millions of lightning strikes in nature every year. Lightning disasters are one of the ten most serious natural disasters announced by the United Nations International Decade for Disaster Reduction. The latest statistics show that the losses caused by lightning have risen to the third place among natural disasters. Lightning strikes cause countless casualties and property losses around the world every year. According to incomplete statistics, there are 3,000 to 4,000 casualties in my country every year due to lightning strikes and negative effects of lightning strikes, and property losses range from 5 billion to 10 billion yuan.
Lightning disasters affect almost all walks of life. One of the negative effects of the rapid development of modern electronic technology is the reduction of its ability to withstand lightning surges. Advanced electronic equipment such as measurement, monitoring, protection, communication, and computer networks with large-scale integrated circuits as core components are widely used in electric power, aviation, national defense, communications, radio and television, finance, transportation, petrochemicals, medical care, and other fields of modern life. , these electronic devices composed of large CMOS integrated components generally have the disadvantage of weak tolerance to transient overvoltage and overcurrent. Transient overvoltage will not only cause malfunction of electronic equipment, but also cause greater direct damage. economic losses and widespread social impacts.
There are four main types of hazards caused by lightning strikes:
(1) Direct lightning strikes
The charged clouds produce a violent discharge at a certain point on the earth. It's called a direct strike. Its destructive power is very huge. If it cannot be discharged into the earth quickly, it will cause serious damage or damage to objects, buildings, facilities, people and animals in the discharge channel - fire, damage to buildings, destruction of electronic and electrical systems, Even endangering the lives of humans and animals.
(2) Lightning wave intrusion
Lightning does not discharge directly on the building and equipment itself, but on the cables laid outside the building. Lightning waves or overvoltages on cables spread along the cable lines almost at the speed of light, invading and endangering various systems such as indoor electronic equipment and automation control. Therefore, often before hearing thunder, our electronic equipment, control systems, etc. may have been damaged.
(3) Induced overvoltage
Lightning strikes occur near equipment, facilities or lines, or lightning does not discharge directly to the ground, but only discharges between clouds. Lightning discharges electrical charges and induces overvoltages in power and data transmission lines and metal supports on metal pipes.
When lightning strikes a building with lightning protection facilities, the lightning wave is discharged to the earth along the air terminal (lightning protection belt, lightning protection wire, lightning protection net or lightning rod) and down conductor on the top of the building. , a strong transient magnetic field will be formed around the down-conductor, which may cause interference to electronic equipment, loss of data, malfunction or temporary paralysis; in serious cases, it may cause component breakdown and circuit board burnout, causing the entire system to collapse. paralysis.
(4) System internal operating overvoltage
Caused by changes in the internal state of the system such as the operation of circuit breakers, the input and removal of heavy power loads and inductive loads, system short-circuit faults, etc. Changes in system parameters cause the transformation of electromagnetic energy within the power system, resulting in internal overvoltage, that is, operating overvoltage.
Although the amplitude of operating overvoltage is small, the probability of occurrence is much greater than lightning induced overvoltage. Experiments have proven that whether it is induced overvoltage or internal operating overvoltage, it is a transient overvoltage (or instantaneous overvoltage), which ultimately endangers electronic equipment in the form of electrical surges, including damaging printed circuit traces, components and insulation. Premature aging shortens the service life, damages the database or causes software misoperation, causing some control components to go out of control.
(5) Ground potential counterattack
If lightning directly hits a building or facility with a lightning protection device, the ground potential of the grounding grid will be raised by several microseconds. Tens of thousands or hundreds of thousands of volts. Highly destructive lightning current will flow from the grounded part of various devices to the power supply system or various network signal systems, or it will break down the earth insulation and flow to the power supply system of another facility or various network signal systems, thereby counterattacking damage or damage electronic equipment. At the same time, in wire circuits where equipotential bonding is not implemented, high potential may be induced, resulting in the risk of spark discharge.
Edit this paragraph Benefits of lightning
When lightning strikes, part of the oxygen in the air is excited into ozone. Thin ozone is not only odorless, but also absorbs most cosmic rays, protecting organisms on the earth's surface from the harm of excessive ultraviolet radiation. The high temperature generated during lightning can kill more than 90% of bacteria and microorganisms in the atmosphere, making the air purer, fresher and more pleasant.
According to statistics, more than 3.1 billion lightning flashes occur above the earth every year, an average of 100 times per second. Each time it is discharged, its electrical energy is as high as 100,000 kilowatt hours, which cannot be compared with even the largest power installations in the world. In addition, the atmosphere also contains 78% free nitrogen that cannot be directly absorbed by crops. During lightning, the current reaches up to 100,000 amperes, and the gas molecules in the air are heated to more than 30,000 degrees, causing the inactive nitrogen in the atmosphere to combine with oxygen and become nitrogen dioxide. Heavy rains dissolve nitrogen dioxide into dilute nitric acid, which then falls to the ground to combine with other substances and become nitrogen fertilizer that crops can directly absorb. It is estimated that 2 billion tons of nitrogen fertilizer are "synthesized" by thunderstorms in the world every year.
These 2 billion tons of nitrogen fertilizer falling from the sky are equivalent to the combined output of 200,000 fertilizer plants with an annual output of 10,000 tons!
Edit this paragraph’s prevention skills
1. Six major methods for lightning protection in units
(1) Units should regularly conduct inspections by qualified professional lightning protection testing institutions Detect lightning protection facilities and evaluate whether the lightning protection facilities meet the requirements of national regulations.
(2) The unit should set up a person responsible for preventing lightning disasters, be responsible for lightning protection safety work, establish various management regulations for lightning protection and disaster reduction, and implement regular testing of lightning protection facilities, inspections after thunderstorms, and daily maintenance .
(3) When designing and constructing lightning protection facilities, construction units should comprehensively consider factors such as geology, soil, meteorology, environment, characteristics of protected objects, and lightning activity patterns, and adopt safe, reliable, and Technologically advanced, economically sound design and construction.
(4) Lightning protection equipment, devices, and equipment whose technology and quality meet national standards should be used, and non-standard lightning protection products and devices should be avoided.
(5) Redesign and build the lightning protection system when new construction and installation equipment are used.
(6) When a lightning disaster occurs, the situation should be reported to the Municipal Lightning Protection Office in a timely manner so that it can be dealt with promptly and avoid another lightning strike.
2. Ten tips for personal lightning protection
(1) You should stay indoors and close the doors and windows; people working outdoors should hide in buildings.
(2) It is not suitable to use TVs, stereos and other electrical appliances without lightning protection measures or with insufficient lightning protection measures, and it is not suitable to use faucets.
(3) Do not touch antennas, water pipes, barbed wire, metal doors and windows, building exterior walls, and stay away from wires and other live equipment or other similar metal devices.
(4) Reduce the use of telephones and mobile phones.
(5) Do not swim or engage in other water sports. It is not suitable to engage in outdoor ball games. Leave the water and other open spaces and find a place to take shelter.
(6) Do not stand on top of a mountain, on a rooftop, or near other highly conductive objects.
(7) Never handle flammable items in open containers.
(8) If you cannot hide in a building with lightning protection facilities in the wilderness, you should stay away from trees and masts.
(9) It is not advisable to hold an umbrella in an open space, or to carry badminton, golf clubs, etc. on your shoulders.
(10) It is not suitable to drive a motorcycle or ride a bicycle.
Edit this paragraph first aid for lightning strikes
1. Main symptoms
The skin is burned, the eardrum or internal organs are shattered, ventricular fibrillation, cardiac arrest, respiratory failure Muscle paralysis.
2. First Aid
1. The injured person lies down on the spot and loosens clothes buttons, bra, belt, etc.
2. Immediately perform mouth-to-mouth breathing and external chest compression until the patient wakes up.
3. Use hand guidance or acupuncture at Renzhong, Shixuan, Yongquan, Mingmen and other points.
4. Send to hospital for emergency treatment.
3. Prevention
1. Do not walk outside or take shelter under big trees during thunderstorms. Take off the metal on your body and squat down to protect yourself from lightning strikes. Turn off the TV, radio, and unplug the antenna.
2. During thunder, stay away from lights and power sources, and do not get close to pillars and walls to prevent induced electricity.
3. When you are in a high-rise building, you must enter the house quickly, when you are in a high mountain, you must get down quickly, and when you are swimming, you must go ashore quickly.
4. Close doors, windows, home appliances, televisions and turn off electric doors.
5. If you feel your hair standing on end, skin tingling, and muscles trembling when you are outdoors, you are in danger of being struck by lightning. You should lie down or stay in place immediately to avoid lightning strikes.
Extratropical cyclones are approximately elliptical air vortices that appear in mid-to-high latitudes and have a central air pressure lower than the surrounding areas. They are one of the important weather systems that affect large-scale weather changes. The average diameter of extratropical cyclones is 1,000 kilometers, with small ones ranging from hundreds of kilometers to large ones up to 3,000 kilometers or more. The cyclone moves eastward with the high-altitude westerly airflow, with a warm front in the front and a cold front in the rear. The south side of the fluctuation at the junction of the two is the warm area. The entire life history of an extratropical cyclone from formation to development to death generally takes 2-6 days. Sometimes 2-5 extratropical cyclones will form one after another on the same front, moving forward from west to east, which is called a "cyclone family". Extratropical cyclones have an important impact on weather changes in mid- and high-latitude areas. It is windy and rainy, sometimes accompanied by heavy rain or strong convective weather, and sometimes the maximum wind near the ground can reach level 10 or above.
Some extratropical cyclones are formed by the degeneration of tropical cyclones after they enter high latitudes. The nature of the cyclone has changed from the original warm center to a cold center.
The evolution process of extratropical cyclones can be roughly divided into the initial stage, the development stage, the mature stage (imprisonment stage) and the extinction stage.
(1) Initial stage:
Originally there was a stationary front on the ground. To the north of the front was cold air, to the south of the front was warm air. The cold air moved from east to west, and the warm air moved from east to west. Moving from west to east, when the cold air inserts under the front to the south, the warm air lifts to the north, and 1 to 2 closed isobars appear.
(2) Development period
As the wave develops, the air pressure further drops, the closed isobars increase, the cold air advances further south, and showers or snow showers appear near the cold front. Precipitation also occurs before the warm front, and the precipitation area expands. As the cyclone develops, low-level disturbances gradually develop toward upper levels, the airflow rises in a spiral, and the high-altitude low trough gradually deepens.
(3) Confinement period
When the cyclone develops to its peak, it has become a circular closed circulation from the ground to a height of 500 millibars. The cold front on the ground gradually catches up with the warm front and lifts the warm air on the ground, and the cyclone begins to trap. At this time, the range of clouds and rain is the largest, the intensity is strengthened, the wind is increasing, and the weather changes are the most dramatic. However, because the ground has been occupied by cold air and turned into a cold vortex, the cyclone begins to weaken.
(4) Extinction period
In the final stage of cyclone development, warm air only remains in the southeast corner of the ground. The convergence of the entire cyclone center in the lower levels is strengthened, and the ground is pressurized, turning it into cold air. Sexual vortex, the low pressure center begins to be filled. The closed circulation from the ground to about 500 millibars weakens, the upward motion disappears, and the cyclone weakens or even disappears.
These stages are the life history of a single cyclone. It takes an average of 2 days from birth to death, and it can take up to 6 days in some cases. The development process of frontal cyclones in East Asia and my country generally takes about 3 days, with the shortest one taking about 1 day, and the long one taking 4 to 5 days.