1, active volcano
Refers to a volcano that is still active or erupts periodically in modern times. This volcano is at the peak of its activity. For example, Mount Merapi in Zhaotu Island has been erupting every two or three years since this century. The recent volcanic activity in China is most famous in Qixing Mountain, the main peak of Datun Volcano Group on the island of Taiwan Province Province. On the mainland, only six years ago, the Caldarcy Volcano Group in Yutian, the western section of Kunlun Mountain in Xinjiang, recorded volcanic eruption. Volcanic eruption formed a flat-topped volcanic cone with an altitude of 100004 1m, a height of 25746 1m, a base diameter of 656655m, a top diameter of 254688524m and a crater depth of 9659885m m.
2. extinct volcano
Refers to a volcano that erupted in prehistoric times but has never been active in history. This volcano has lost its ability to move. Some volcanoes remain intact, while others have weathered and eroded, leaving only incomplete volcanic remains. There are 99 isolated volcanic cones in the area of about 1230 square kilometers in Fiona Fang, among which the height of the volcanic cone of Langwoshan is nearly19000m.
3. dormant volcano
Refers to a volcano that has erupted in history but has been relatively static for a long time. This kind of volcano has preserved a complete volcanic male body and still has volcanic activity ability, or it cannot be concluded that it has lost its volcanic activity ability. For example, China Baitoushan Tianchi erupted twice in 1327 and 1658, and there were many activities before that. Although there is no eruption activity at present, some unfathomable blowholes on the hillside keep spewing high-temperature gas, indicating that the volcano is currently in a dormant state.
It should be noted that there are no strict boundaries between these three types of volcanoes. Dormant volcanoes can be resurrected, and dead volcanoes can also be "resurrected", and they are not static. In the past, Mount Vesuvius was always considered as an extinct volcano. At the foot of the volcano, many towns and vineyards were built on the hillside of the volcano. However, in 26 AD, Vesuvius erupted suddenly, and the high-temperature volcanic eruption in Attack and Capture created two unsuspecting ancient cities, Pompeii and Heragonom. Cities and residents were destroyed and killed.
(two) according to the type of volcanic eruption.
Volcanism is influenced by factors such as magma properties, underground magma chamber pressure, volcanic channel shape and volcanic eruption environment (land or underwater), which makes volcanic eruption have the following types.
1, fissure eruption
Magma overflows the surface along a huge crack in the earth's crust, which is called fissure eruption. There is no strong explosion phenomenon in this eruption, and the ejecta are mostly basic molten slurry, which often forms a lava platform with a wide coverage after condensation. For example, the Permian Emeishan basalt distributed in the border area of Sichuan, Yunnan and Guizhou in southwest China and the Tertiary Hannuoba basalt north of Zhangjiakou in Hebei belong to fissure eruption. Modern fissure eruption is mainly distributed in the mid-ocean ridge at the bottom of the ocean. Only Iceland can see this kind of volcanic eruption on the mainland, so it is also called Icelandic volcano.
2. Central eruption
Underground magma is ejected from the surface through a tubular volcanic passage, which is called central eruption. This is the main form of modern volcanic activity, which can be subdivided into three types:
Quiet type: When the volcano erupts, only a large amount of hot magma quietly flows out of the crater and slowly flows along the hillside, just like white rice soup cooked in a rice cooker. Overflow is mainly alkaline molten slurry with high temperature, low viscosity and easy flow. Less gas, no explosion, Hawaii volcano is its representative, also known as Hawaiian type.
Explosive; When the volcano erupts, it explodes violently, and at the same time, it ejects a lot of gas and pyroclastic materials, and the molten slurry ejected is mainly medium-acid molten slurry. 1568 On June 25th, Mount Pere in the West Indies erupted, also known as the Pere type.
Intermediate type: it belongs to the transitional type between calm eruption and explosive eruption. This type is dominated by intermediate-basic lava eruption. If there is an explosion, the explosive force is not great. It can erupt smoothly for months or even years and is characterized by intermittent eruption. Take stron Boulder Volcano on the Lipari Islands near the Italian west coast as an example. The volcano erupts about every 2-3 minutes, and its flame can still be seen 669 kilometers away at night. So it is also called Stromboli style.
3. Infiltration eruption
Magma penetrates the earth's crust and overflows the surface in a large area, which is called penetrating eruption. This is an ancient way of volcanic activity, which no longer exists in modern times. Some scholars believe that the Archean crust is thin and the underground magma temperature is high, which often causes penetrating magma ejection.
2. Knowledge about volcanoes
Active Volcanoes Generally speaking, only active volcanoes will erupt.
Volcanoes that are erupting and are expected to erupt again can of course be called active volcanoes. Those dormant volcanoes, even if they are alive, are not going to erupt now, and those that may erupt again in the future can also be called active volcanoes.
Those volcanoes whose last eruption was a long time ago and proved not to erupt in the foreseeable future are called extinct volcanoes or extinct volcanoes. So far, there is no strict scientific standard to judge whether a volcano is "dead" or "alive".
Experientially or traditionally, volcanoes with historical eruption or records of historical eruption are called active volcanoes, but there are 534 such volcanoes in the world. However, the history or historical records of each country and region can be very different, some are only three or four hundred years, and some can reach three or four thousand years or longer.
In those remote areas where there are no people, even modern active volcanic eruptions may be unknown and have no historical records. For example, an explosive eruption occurred about 1600 years ago at Jinlong Dingzi volcano, 40 kilometers west of Jingyu, China, but no historical record has been found so far.
Obviously, the definition of active volcano based on historical or historical records is very incomplete and unrealistic. Therefore, according to the statistics of the eruption interval of a large number of active volcanoes and the last eruption time of dead volcanoes, some volcanologists put forward an improved definition of active volcanoes with certain time constraints, that is, those volcanoes that erupted once in the past 10000, 5000 or 2000 are called active volcanoes.
According to the specific situation of different countries and regions, 10000, 5000 or 2000 is allowed. This improved definition of active volcano still allows exceptions, requiring that when evaluating a specific active volcano, evidence of whether there is an active magma chamber system under the volcano can be provided.
But the "dead" or "alive" of a volcano is relative. Some "dead" volcanoes that haven't erupted in 10000 or even longer may resurface and erupt due to deep structure or magmatic activity.
For example, most of the volcanoes in China Wudalianchi Volcano Group erupted before 100000 years, but the volcanoes of Laoheishan and Yamakaji erupted in1719-1721year. Therefore, whether there is an active magma system under the volcano becomes the key to judge whether a volcano is "dead" or "alive". How can we know that there is an active magma system under the volcano? Generally, it can be preliminarily judged according to the following phenomena: (1) There is hydrothermal activity or jet in the active volcanic area; (2) In the small area centered on the volcano, the microseismic activity is obviously higher than its peripheral area; (3) There are some observable surface deformations in the volcanic area.
The above phenomena are all due to the specific activities of the magma system below the volcano, so it is necessary to establish a long-term earthquake-deformation observation network in this volcanic area and use other geophysical, physical and geochemical methods to detect them. This is the basic monitoring and detection research that should be carried out after the volcano is confirmed as a dangerous volcano.
According to the above, we can get the general concept of active volcano: that is, volcanoes that are erupting or have erupted in historical periods and recently 10000 are called active volcanoes. When there is an active magma system or magma chamber under the volcano, it is considered that the volcano has eruption risk and should be placed in the modern volcano monitoring system.
The formation of volcanoes involves a series of physical and chemical processes. At a certain temperature and pressure, the rocks in the crust and upper mantle are partially melted and separated from the parent rocks, and the molten body moves upward through pores or cracks, and gradually enriches in some parts, forming magma sacs.
With the continuous supply of magma, the excess pressure of magma in the magma sac gradually increases. When the strength of the crust cover is not enough to stop the magma from moving upward, the magma rises to the surface through the weak zone.
In the process of rising, the volatiles dissolved in magma gradually dissolve out and form bubbles. When the volume fraction of bubbles exceeds 75%, the bubbles trapped in the liquid will be released quickly, leading to explosive eruption. After the gas is released, the viscosity of magma drops to a very low level and the flow becomes turbulent. If the viscosity of magma is low or volatile matter is less, it will only overflow quietly.
The difference of a series of physical and chemical processes from partial melting to eruption has formed a * * * * shaped volcanic activity. That is, volcanoes that are erupting or have erupted in historical period and in recent 10000 years are called active volcanoes.
When there is an active magma system or magma chamber under the volcano, it is considered that the volcano has eruption risk and should be placed in the modern volcano monitoring system. /view/6893 1 .
3. Volcanic eruption Why are the types of volcanic eruptions different?
Terrain change. Before volcanic eruption, underground magma was active, which produced in-situ stress and changed the ground fluctuation. For example, before the eruption of Katmai volcano in Alaska in 19 12, many ground fissures suddenly appeared around it, even more than ten kilometers away, from which gas and dust were emitted. 1978 Before the eruption of Kabbah volcano in Ardu in Djibouti's Afar Triangle, a protrusion as high as 100 meters suddenly appeared. 1979 Before the eruption of San hellens volcano, a dome appeared on its northern slope. By 1980, the height of the dome increased rapidly, with the fastest increase of 45 cm per day. Finally, on May 18 of that year, it broke through this dome and broke out. However, before the eruption of Crafra volcano in Iceland in 1980+00, the ground subsidence occurred, which was also related to magma migration. The ice and snow on the volcano melted. Many tall volcanoes are above the snow line all the year round. Before the eruption, the ice and snow on the volcano melted due to magmatic activity and rising ground temperature, which indicates that it will erupt. Such as San hellens, Couto Paxi, Ruiz and other volcanoes have this phenomenon, and snowmelt water even causes mudslides or flash floods. Animal abnormality. Similar to earthquakes, some animals will show uneasy expressions. The volcano rumbled. Due to the expansion of magma and gas, the noise it made before it rushed out of the crater indicates that the eruption is coming. Seismic instrument monitoring. There are often microseisms before volcanic eruptions, which can be detected by seismographs set there. There are seismic stations around active volcanoes. For example, there are 13 around Mount St. hellens, 47 around Kilauea and 6 around Mount Merapi. For example, before the eruption of San hellens volcano in May 1980, there were as many as 30 earthquakes of magnitude 3 per day, and before the eruption of Soufriere volcano in April/978, the number of sensible earthquakes reached 15 per hour. Analyze volcanic gases. Gas samples are often taken near the volcano for analysis, and the increase of abnormal gases indicates that some volcanic gases have "advanced" before the volcanic eruption. Monitoring of water temperature and ground temperature near volcano. Before the volcanic eruption, the temperature generally rose and could be measured. Through the above signs, people can use it to predict volcanic eruption.
It smells lovely!
4. Volcano knowledge and related popular science, 2000 words, with pictures.
Hello, I'm a loyal solver of Tencent. Let me answer for you: British scientists believe that super volcanic eruption may destroy mankind. British scientists believe that human beings may be destroyed in a super volcanic eruption.
Stephen cerf of the University of Great Britain told an e-magazine reporter that there was no way to stop the disaster. At present, scientists are busy making various strategies to resist "external threats", such as how to prevent asteroids from colliding with the earth, but rarely consider that the main danger may come from the inside of the earth.
Geophysicists assert that the eruption intensity of some volcanoes is hundreds of times that of the past, and the earth experienced such a large-scale disaster not long before the emergence of civilization. American geologists discovered the shallow volcanic ash dead layer in Yellowstone National Park earlier, believing that its formation was caused by the super volcanic eruption 620,000 years ago. Therefore, some funnel-shaped craters can still be seen here, which are all craters formed after destructive volcanic eruptions.
In the report to the British working group on natural disasters, the consequences of this super volcano eruption are described in detail-a large area will be covered by lava, and dust and ash scattered into the atmosphere will prevent a lot of sunlight from reaching the earth's surface, which will undoubtedly change the global climate. According to the research of Michael Ram Pi Nuo of new york University, 74,000 years ago, the super eruption of Sumatra volcano caused global cooling and destroyed 3/4 plants in the northern hemisphere.
China Volcano Eruption The earliest recorded active volcano in China is Haotian Temple in Julebao, Datong, Shanxi Province, which was still erupting in the Northern Wei Dynasty (5th century AD) (according to Shan Hai Jing). The five Lianchi volcanoes in Northeast China erupted violently from 17 19 to 172 1. The scene is: "Fireworks are soaring into the sky, and the sound is like thunder. They are heard day and night, five or six miles away. The people who flew out were all black stone sulfur and so on, and the hot air pressed for more than 30 miles "(according to In 19 16, 1927, the submarine volcano in the eastern waters of Taiwan Province Province erupted twice, showing" half seawater and half flame ",which was spectacular; 195 1 In May, a volcano erupted in the middle of Kunlun Mountain, south of Yutian, Xinjiang. At that time, smoke was billowing, flames were soaring, rocks were flying and thunder was rumbling, which lasted for several days and nights, and a cone with a height of 145 meters was piled up. As for Qixing Mountain, an active volcano with an altitude of1130m in the north of Taiwan Province Province, a lot of sulfur fever is still erupting. Volcanic eruption and dinosaur extinction The gas produced by volcanic eruption may be the cause of dinosaur extinction.
According to the latest scientific findings published in London on March 20th, the gas produced by volcanic eruption may be the reason for the extinction of a large number of species including dinosaurs in the past 545 million years. India's volcanic eruption zone is the product of a series of volcanic eruption activities.
The volcanic eruption 65 million years ago filled the air with sulfur, which had a devastating impact on the earth's climate. Large-scale volcanic eruption also formed "flood basalt", which is one of the two main reasons for periodic mass extinction in history.
Another reason is the influence of asteroid activity, which is considered to be the most important reason for the extinction of dinosaurs 65 million years ago. In the past, researchers have been suspicious of the lethality of volcanoes because they don't know how much toxic gas can be released by volcanic eruption.
However, in the study of Deccan Rock, a British expedition found a crucial clue, which unveiled the mystery of the gas composition of primitive volcano. They wrote in the journal Science that the gas containing a lot of sulfur and chlorine released by volcanic eruption is likely to have a "serious" impact on the environment.
StephenSelf, a former volcanologist at the Open University in Britain and now a senior volcanologist at the National Nuclear Regulatory Commission (NRC), said: "This discovery can certainly support our conclusion, but it has not been finally proved." "At the same time as a huge basalt flood formed, many species mysteriously disappeared."
The amount of sulfur released into the air by volcanic eruption every year is 10 times that produced by coal burning and other industrial activities, which leads to large-scale acid rain and the formation of suspended sulfuric acid droplets in the air. This makes the surface temperature drop and the normal circulation mode is destroyed.
The most powerful and spectacular volcanic eruptions often occur in subduction zones. The volcano here may erupt again after hundreds of years of silence, and once it erupts, its power is particularly fierce.
This kind of volcanic eruption often brings disasters to mankind. A large amount of volcanic ash and volcanic gas emitted during volcanic eruption have a great influence on the global climate.
Because in this case, dark days, storms and even mud rain will bother local residents for months. Volcanic ash and gas are sprayed high into the air, and they will spread far away with the wind.
These volcanic materials will block the sunlight and cause the temperature to drop. In addition, they will filter out some wavelengths of light, making the sun and the moon look like they are covered with a halo or have strange colors, especially at sunrise and sunset, which can form a strange natural landscape.
The combination of a large amount of volcanic ash and heavy rain caused by environmental damage can destroy roads and bridges, flood nearby villages and cities and make countless people homeless. Mud formed by soil and rock fragments can flood the whole city.
Although the rocks are covered by volcanic ash clouds, when the volcano just erupted, you can still see huge rocks spewing into the air. The eruption of the revived volcano has a far-reaching impact on the natural landscape.
Land is the most precious resource in the world, because it can breed all kinds of plants to support everything. If volcanic eruption can cover farmland with volcanic ash less than 20 cm thick, it is really a blessing for farmers, because these volcanic ash are rich in nutrition and can make the land more fertile.
1. After the lava disintegrated, weeds and liverworts began to appear. 2. Pteridophytes grow on the hillside where rope-like lava flows.
Volcanic ash enriches the surrounding land, and the local grapes are harvested every year.