Types of volcanic eruptions
Due to the nature of the magma, the pressure of the underground magma reservoir, the shape of the volcanic channel, the eruption environment (on land or underwater) and other factors, so that the form of the eruption is very different, there are generally some of these classifications:
Fissure eruption
Magma along the crust of the earth's huge cracks on the overflow of the earth's surface, called the fissure eruption. fissure eruptions. This type of eruption is not a strong explosive phenomenon, most of the ejected material is basal lava, condensation often form a wide area covered by lava terrace. Such as the distribution in southwest China, Sichuan, Yunnan, Guizhou, the junction of the three provinces of the Permian Emeishan basalt and Hebei Zhangjiakou north of the Tertiary Hannaoba basalt are fissure type eruption. Modern fissure eruptions are mainly distributed in the ocean floor at the mid-ocean ridge, only Iceland on the continent can see such eruptive activity, so it is also known as Iceland-type volcano.
Central eruption
Underground magma through the tube-like volcanic channel out of the surface, called the central eruption. This is the main form of modern volcanic activity, and can be subdivided into three kinds:
(1) quiet type: the eruption. Only a large number of hot lava from the caldera quiet overflow, along the mountain slopes flow slowly, as if the boiling rice soup from the rice pot boiling out of the same. Overflow to the base of the lava is mainly, lava temperature is high, viscosity is small, easy to flow. Containing less gas, no explosion phenomenon, the Hawaii volcanoes as its representative, also known as Hawaii type. This type of volcano people can enjoy.
(2) explosive: when the volcano erupted, resulting in violent explosions, while spewing out a large number of gases and volcanic debris material, spewing out of the lava to the acidic lava-based. December 16, 1902, the West Indies Pele volcano eruption shook the whole world. It spewed out viscous magma, as well as large quantities of pumice and fiery ash. This eruption, which killed 26,000 people, was of this type, also known as the Pele type.
(3) intermediate: belongs to the quiet and explosive eruptions between the transitional type. This type of lava eruption in the base is mainly. If there is an explosion, the explosive force is not large. Can be continuous for several months, or even a few years, a long period of smooth eruption, and characterized by intermittent outbursts. Near the west coast of Italy on the Liparic Islands Strombolian volcano as a representative. The volcano erupts about every 2-3 minutes, at night in 50 kilometers away from the volcano can still be seen in the eruption of the light flame, so known as the "Mediterranean lighthouse". It is also known as the Stromboli style. Some people believe that China's Heilongjiang Province, Wudalianchi volcano belongs to this type.
(4) melt-through eruption
Edit this section of the phases of volcanic eruption
1, the explosion of gas
In the gestation phase of the eruption, due to the gas out of the dissolution and the occurrence of shock group, the degree of fissuring of the overlying rock increased, the pressure is lowered, and the amount of magma in the body of the gas out of the dissolution continues to increase, the magma volume gradually expanding, the density decreases, and the internal pressure increases, when the internal pressure greatly exceeds the external pressure. When the internal pressure greatly exceeds the external pressure, in the overlying rock fissure density band gas explosion, so that rock fragmentation, and open the channel of volcanic eruption, the first broken pieces of spray, followed by the eruption of magma.
2, the formation of the eruption column
After the gas explosion, the gas to a great jet of force will be channeled to the debris and deep magma sprayed into the air, the formation of a tall eruption column. Eruption column can be divided into three areas:
(1) gas rush area: it is located in the lower part of the eruption column, equivalent to one-tenth of the height of the entire eruption column. Because the gas from the crater rushed out of the speed and force is very large, although the density of the ejected rock and other materials far more than the density of the atmosphere, but it will also be thrown into the high altitude. The speed of the gas rush, rising in the volcanic channel gradually accelerated, when it is sprayed out of the surface shot to high altitude, due to the pressure of the atmosphere and the consumption of the energy of the jet, its speed gradually decreases, was gas rushed to the high altitude of the material, according to the magnitude of its gravity at different heights began to land.
(2) convection zone: located in the upper part of the gas rush area, because of the slowdown in the speed of the eruption column gas rush, the gas in the gas column outward scattering, the gas in the atmosphere continues to join the formation of the eruption column inside and outside of the gas convection, and therefore called the convection zone. Substances of high density in this zone begin to fall. Substances less dense than the atmosphere continue to rise by the buoyancy of the atmosphere. The height of the convection zone gas column is large, accounting for about seven tenths of the total height of the eruption column.
(3) diffusion zone: located in the top of the eruption column, this area of the eruption column and the pressure of the atmosphere to reach a basic balance of the state. The eruption column is rising, the column of gas and small density material is along the horizontal direction of the diffusion, so it is called the diffusion zone. Volcanic ash brought into the high altitude can form volcanic ash clouds, which can drift in the air for a long time and have a great impact on the regional climate, or even cause disasters. The height of the column in this area accounts for about two-tenths of the total height of the column.
3. the collapse of the eruption column
The eruption column in the process of rising, carrying different particle size and density of debris, these debris according to the size of gravity, respectively, in different heights and different stages of the collapse. There are four main factors that determine how fast an eruption column collapses:
(1) If the radius of the caldera is large, the gas impulse is small, and the column collapses fast;
(2) If the content of rock debris in the column is high, and the particle size and density are large, the column collapses fast;
(3) If the solid rock pieces in the column are repeatedly returned to the air, the column collapses fast;
(4) If there is surface water in the eruption column, it can increase the density of the column, and the column will collapse faster. Conversely, the eruption column in the air to stay a long time, the collapse of the slow.
Volcanic eruptions are not uniform, like the eruption of Hawaii's Kilauea volcano, beforehand lava has been quietly outflow, due to the slow flow of lava, and thus only the destruction of property and did not jeopardize life. And like the 1883 Krakatoa volcano in Indonesia, such as the eruption of volcanic debris or steam explosion (or steam eruption), but caused significant casualties.
In the volcanic eruption process, volatile substances play an important role, it is not only the product of volcanic eruption, but also the power of volcanic eruption. From the generation of magma to the entire process of volcanic eruption, the activity of volatile substances are not playing a role.
British scientists believe that a super-volcanic eruption could destroy the human race
British scientists believe that: the human race is likely to be destroyed in a super-intense volcanic eruption. Stephen Selph of the University of Great Britain's Public **** in a reply to a question from an e-magazine reporter said that there is no way to prevent such a catastrophe at the moment. Currently, scientists are busy developing strategies to combat "external threats", such as how to prevent asteroids from colliding with the Earth, but little thought is given to the possibility that the main danger could come from within the planet.
Geophysicists assert that some volcanic eruptions are hundreds of times more intense than in the past, and that the Earth has experienced catastrophes of this magnitude not long before civilization emerged.
U.S. geologists had earlier discovered not-so-deep layers of dead volcanic ash in Yellowstone National Park, attributed to a super-volcanic eruption that took place 620,000 years ago, and the result is that large, funnel-shaped craters can be seen here to this day, broken craters formed by those destructive volcanic eruptions.
The consequences of such a super-volcanic eruption were described in detail in a report to the British government's Natural Disasters Task Force - a large area would be covered in lava, and the dust and ash that would be spread into the atmosphere would prevent much of the sunlight from reaching the Earth's surface, which would undoubtedly lead to global climate change. This will undoubtedly lead to global climate change.
According to Michael Rampino of New York University, the super-intense eruption of the Sumatra volcano, which occurred 74,000 years ago, led to global cooling and the destruction of three-quarters of the plants in the northern hemisphere. A rapid discharge between one part of a charged cloud and another part of a cloud with a different charge, or a charged cloud against the earth. This rapid discharge process produces a powerful flash of lightning accompanied by a loud sound. This is what we see as lightning and thunder.
Of course, the discharge between clouds is mainly harmful to aircraft, and does not have a significant impact on buildings, people and animals on the ground, whereas the discharge of clouds on the earth is very harmful to buildings, electrical and electronic equipment, and people and animals.
Usually there are three main forms of lightning strikes: one is a charged cloud and a point on the ground between the rapid discharge phenomenon, called "direct lightning". The second is a charged cloud due to electrostatic induction, so that a range of the ground with a heterogeneous charge. When the direct lightning occurred, the cloud charged quickly disappear, and some range of the ground due to the high resistance of the scattering current, resulting in local high voltage, or due to the direct lightning discharge process, a strong impulse current on the surrounding wires or metal objects produced by electromagnetic induction of high voltage and the phenomenon of flash, called "secondary lightning" or called "Induction lightning". The third is "spherical lightning".
Edit the power of lightning
The average lightning current is about 20 000 A (or even greater), lightning voltage is about 10 times 10 square volts (human safety voltage of 36 volts), a lightning time is about one thousandth of a second, an average of a lightning issued by the power of 20 billion kilowatts (the general power of the rice cooker is less than 1,000 watts).
China's construction of the world's largest hydroelectric power plant - the Three Gorges hydroelectric power plant, the total installed capacity of the power plant is 18.2 million kilowatts, only one thousandth of a lightning power.
Of course the electrical power of lightning is very large, but because of the short discharge time, so the electrical power of the lightning current is not very large, once about 5555 degrees.
In the world, there are more than 100 lightning phenomena per second, and the total electrical energy released by lightning in a year is about 1.75 billion kilowatts.
If one degree of electricity for 0.30 yuan, the world's annual value of lightning for 5.25 trillion yuan, which is a huge wealth, but due to the lightning time is very short, mankind has not been able to capture this kind of electricity, the world has not yet studied the use of lightning power method.
Editing the hazards of lightning
There are millions of lightning flashes in nature every year. Lightning is one of the ten most serious natural disasters declared by the United Nations International Decade for Disaster Reduction. The latest statistics show that the damage caused by lightning has risen to the third place of natural disasters. Every year, lightning strikes cause countless casualties and property losses around the world. According to incomplete statistics, China's annual lightning strikes as well as the negative effects of lightning strikes caused by casualties amounted to 3,000 to 4,000 people, property losses in the 5 billion to 10 billion yuan.
The scope of lightning disasters involved in 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 resist lightning surges. Large-scale integrated circuits as the core components of the measurement, monitoring, protection, communications, computer networks and other advanced electronic devices are widely used in electric power, aviation, defense, communications, broadcasting, finance, transportation, petrochemicals, medical care and other areas of modern life, large CMOS integrated components composed of these electronic devices generally exist on transient over-voltage, overcurrent tolerance ability is weak, transient over-voltage will not only cause the electronic equipment, but also the ability of overcurrent. Transient overvoltage will not only cause electronic equipment to produce misoperation, but also cause greater direct economic losses and a wide range of social impact.
There are four main hazards caused by lightning:
(1) direct hit mine
Charged clouds on the earth at a point where a violent discharge phenomenon, known as direct hit mine. Its destructive power is very huge, if it can not quickly diarrhea into the earth, will lead to discharge channel objects, buildings, facilities, people and animals suffered serious damage or damage - fire, building damage, destruction of electronic and electrical systems, and even endanger the lives of people and animals.
(2) lightning wave intrusion
Lightning is not directly discharged in the building and the equipment itself, but on the cables placed on the outside of the building discharge. Lightning wave or overvoltage on the cable spreads almost at the speed of light along the cable line, invading and endangering indoor electronic equipment and automation control and other systems. Therefore, often before hearing the sound of thunder, our electronic equipment, control systems, etc. may have been damaged.
(3) Induced overvoltage
Lightning strikes occur in the vicinity of equipment and facilities or lines, or lightning does not discharge directly to the ground, but only in the cloud to cloud discharge phenomenon. Lightning releases an electrical charge and generates an overvoltage inductively on power and data transmission lines and metal piping metal supports.
Lightning discharge in buildings with lightning facilities, lightning waves along the top of the building flashing device (lightning belt, lightning rod, lightning net or lightning rod), the process of lead wires leaked into the earth, will be in the lead wires around the formation of a strong transient magnetic field, the light is caused by the interference of electronic equipment, data loss, resulting in malfunctions or temporary paralysis; serious cases can cause components to break through and circuit boards The whole system will be paralyzed.
(4) system internal operation overvoltage
Due to the operation of circuit breakers, heavy loads of electricity and inductive loads into and out of the system, system short-circuit faults and other changes in the internal state of the system parameters change, caused by the internal electromagnetic energy conversion of the power system, resulting in an internal overvoltage, that is, the operation of the overvoltage.
The amplitude of the operational overvoltage is small, but the probability of occurrence is much greater than the lightning induction overvoltage. Experiments have shown that both the induction overvoltage or internal operation overvoltage, are transient overvoltage (or transient overvoltage), and ultimately to the electrical surge of the way to jeopardize the electronic equipment, including the destruction of printed circuits printed lines, components and insulation premature aging life shortening, damage to the database or make the software malfunction, so that some of the control elements out of control.
(5) ground potential counterattack
If lightning strikes directly on a building or facility with lightning protection, the ground potential of the grounding network will be raised tens or hundreds of thousands of volts within a few microseconds. Highly destructive lightning current will flow from the grounded portion of various devices to the power supply system or various network signaling systems, or break through the earth's insulation and flow to the power supply system of another facility or various network signaling systems, thus counteracting the destruction or damage to electronic equipment. At the same time, the danger of spark discharges may be induced by high potentials in conductor circuits where equipotential connections are not practiced.
Editing the benefits of lightning
When lightning strikes, some of the oxygen in the air is excited into ozone. The thin ozone is not only odorless, but also absorbs most of the cosmic rays, saving life on the earth's surface from the hazards of excessive ultraviolet radiation. The high temperature generated during the lightning process can kill more than 90% of the bacteria and microorganisms in the atmosphere, thus making the air more pure and fresh and pleasant.
According to statistics, lightning occurs more than 3.1 billion times per year over the Earth, an average of 100 times per second. Each discharge, its electricity up to 100,000 kilowatt-hours, even the world's largest power plant can not be compared with it. In addition, the atmosphere contains 78% free nitrogen that cannot be directly absorbed by crops. Lightning, the current up to 100,000 amperes, the molecules of the gas in the air is heated to more than 30,000 degrees, resulting in the atmosphere of inactive nitrogen and oxidized together, into nitrogen dioxide. Heavy rain and nitrogen dioxide dissolved into dilute nitric acid, and with the rain down to the ground and other substances into the nitrogen fertilizer can be directly absorbed by crops. According to estimates, the global annual thunderstorms and "synthetic" nitrogen fertilizer has 2 billion tons. This 2 billion tons of nitrogen fertilizer from the sky, equivalent to 200,000 annual output of 10,000 tons of fertilizer plant production!
Edit Preventive Techniques
1, the unit of lightning six ways
(1) the unit should be regularly by a qualified professional lightning detection agencies to test lightning protection facilities, to assess whether the lightning protection facilities in line with national norms.
(2) The unit should set up a person responsible for lightning disaster prevention, responsible for lightning safety work, the establishment of various lightning mitigation management regulations, the implementation of regular testing of lightning protection facilities, inspection after thunderstorms and routine maintenance.
(3) construction units in the design and construction of lightning protection facilities, should be based on geology, soil, meteorology, the environment, the characteristics of the protected object, the law of lightning activity and other factors for comprehensive consideration, the use of safe and reliable, technologically advanced, economically rational design and construction.
(4) should be used technology and quality are in line with national standards of lightning protection equipment, devices, equipment, to avoid the use of non-standard lightning protection products and devices.
(5) new construction and new additions to the installation of equipment application of lightning protection system redesign and construction.
(6) lightning disaster should be reported to the City Lightning Protection Institute in a timely manner in order to deal with the situation in a timely manner to avoid another lightning strike.
2, personal lightning top ten tips
(1) should stay indoors, and close the doors and windows; people working outdoors should hide in the building.
(2) You should not use TVs, stereos and other electrical appliances without lightning protection or with insufficient lightning protection, and you should not use water faucets.
(3) Do not touch the antenna, water pipes, barbed wire, metal doors and windows, building facades, and stay away from electric wires and other energized 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, should not play outdoor ball games, leave the water and other open space, looking for a place to hide.
(6) Do not stand on the top of a hill, on the roof of a building, or near other objects with high conductivity.
(7) Do not handle flammable materials in open containers.
(8) Stay away from trees and masts in the wilderness if you are unable to take shelter in a building with lightning protection.
(9) In the open field should not play umbrellas, should not be badminton, golf clubs, etc. on the shoulders.
(10) It is not advisable to drive a motorcycle or ride a bicycle.
Edit First Aid for Lightning Strike
I. Main Symptoms
The skin is burned, the tympanic membrane or internal organs are cracked, ventricular fibrillation, heart stops beating, and the respiratory muscles are paralyzed.
Second, first aid
1. The injured person lies down on the ground, loosening the buttons of the clothes, bra, belt and so on.
2. Immediately mouth-to-mouth respiration and extrathoracic cardiac compression, insist until the patient wakes up.
3. Hand-guided or needle puncture Renzhong, Xixuan, Yongquan, and Vital and other points.
4. Send the patient to the hospital for emergency treatment.
Third, prevention
1. Thunderstorms do not walk outside or under a tree to avoid the rain, take off the body of the metal, squatting to prevent lightning strikes. Turn off the TV, radio, unplug the antenna.
2. Stay away from lights and power sources when thunder strikes, and don't get close to columns and walls to prevent induced electricity.
3. In the high building must be fast into the room, in the mountains fast down, under the swimming fast ashore.
4. Close the doors, windows, home appliances, TV sets and electric doors.
5. In the outdoors feel hair erect, skin tingling, muscle shivering, that is, there will be a risk of being struck by lightning, should immediately lie down or in situ, can avoid lightning strikes.
Temperate cyclones are air vortices that appear in middle and high latitudes and have a center pressure lower than that of the surrounding near-elliptical air vortex, and they are one of the most important weather systems affecting a wide range of weather changes. Temperate cyclones have an average diameter of 1,000 kilometers, the smaller ones have several hundred kilometers, and the larger ones can reach 3,000 kilometers or more. The cyclone moves eastward with a westerly flow at high altitude, with a warm front at the front and a cold front at the back, and a warm zone on the south side of the fluctuations at the interface between the two. The entire life history of a temperate cyclone, from formation, development to extinction, is generally 2-6 days. Sometimes 2-5 temperate cyclones are formed one after another on the same front, moving forward in sequence from west to east, which is called a "cyclone family". Temperate cyclones have an important impact on the weather changes in the middle and high latitudes, more rain and wind, sometimes accompanied by heavy rain or strong convection, sometimes the maximum wind near the ground up to 10 or more.
Some temperate cyclones are tropical cyclones that enter high latitudes and then degenerate. The nature of the cyclone has changed from the original warm center, to a cold center.
The evolution of temperate cyclones can be roughly divided into the incipient, development, maturity (captivity) and demise.
(1) incipient:
Originally, there was a stationary front on the ground, the front north of the cold air, the front south of the warm air, cold air movement from east to west, warm air movement from west to east, when the cold air inserted into the front to the south, the warm air to the north to lift, and the emergence of 1-2 closed isobaric pressure lines.
(2) Developmental period
With the development of fluctuations, the air pressure drops further, the closed isobars increase, the cold air pushes further to the south, showers or snow showers appear near the cold front, and precipitation occurs in front of the warm front, and the precipitation area expands. With the development of the cyclone, the low-level disturbance gradually develops to the upper level, the airflow makes a spiral upward, and the upper-air trough is gradually deepened.
(3) Imprisonment period
During the peak period of cyclone development, the cyclone has become a circular closed loop from the ground to the height of 500 millibars. The ground cold front gradually catch up with the warm front, and the ground warm air uplift, the cyclone began to imprison. At this time, the range of clouds and rain is the largest, the intensity is strengthened, the wind increases, and the weather changes are the most dramatic. But because the ground has been occupied by cold air, become cold vortex, so the cyclone began to weaken.
(4) extinction period
The final stage of cyclone development, warm air remains only in the southeast corner of the ground, the entire cyclone center convergence in the lower levels strengthened, the ground is pressurized, has become a cold vortex, and the low-pressure center part began to be filled. From the ground to about 500 millibars of the closed circulation weakened, the upward movement has disappeared, the cyclone weakened to extinction.
These stages are the life history of a single cyclone. From the first born to the beginning of the demise of an average of 2 days, the longest up to 6 days, East Asia and China's frontal cyclone development process, generally about 3 days, the shortest about 1 day, the longest about 4 to 5 days.