What is the principle of fountains and volcanic eruptions?

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. Due to the influence of 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), the forms of volcanic eruptions vary greatly. Generally, they are classified as follows: 1. Fissure type The eruption of magma spilling out of the surface along huge cracks in the earth's crust is called a fissure eruption. This type of eruption does not have a strong explosion 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 ??the three provinces of Sichuan, Yunnan and Guizhou in southwest my country 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. 2. Central eruption: Underground magma erupts to the surface through tubular volcanic channels, which is called a central eruption. This is the main form of modern volcanic activity, which can be subdivided into three types: 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. 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 magma ejected is mainly medium-acidic magma. On December 16, 1902, the eruption of Mount Pelé in the West Indies shocked the world. The lava it erupts is viscous, and it also spews out large amounts of pumice and hot ash. The eruption that killed 26,000 people fell into this category, also known as the Pelé type. Intermediate type: Belongs to the transitional type between quiet and explosive eruptions. This type is dominated by medium-basic lava eruptions. If there is an explosion, the explosion 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 "Lighthouse of the Mediterranean." Also called Stromboli style. Some people think that the Wudalianchi volcano in Heilongjiang Province, my country belongs to this type. 3. Penetrating eruption: The magma penetrates the crust and overflows the surface over a large area, which is called a penetrating eruption. This is an ancient form of volcanic activity that no longer exists in modern times. Some scholars believe that in the Archaean period, the earth's crust was thinner and the underground magma had greater heat, which often caused penetration-type magma eruptions. Volcanic eruptions can be divided into three stages: 1. Gas explosion. In the gestation stage of volcanic eruptions, due to gas dissolution and the occurrence of earthquake swarms, the degree of cracking of the overlying rock increases and the pressure decreases, while the amount of gas dissolution in the magma continues to increase. As the magma volume increases, the volume of the magma gradually expands, the density decreases, and the internal pressure increases. When the internal pressure greatly exceeds the external pressure, a violent explosion of gas occurs in the fissure 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 areas: (1) Gas flush area: As shown in the figure, area A is located at 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: It is located in the upper part of the gas rush zone. Because the speed of the gas rush of the eruption column slows down, the gas in the gas column scatters outward, and the gas in the atmosphere is continuously added, forming convection of the gas inside and outside the eruption column, so it is called It is the convection zone (zone B in the figure). The denser material in this area begins to fall. Materials that are less dense than 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 between 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 area (area C in the figure). 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 with different particle sizes and densities. These debris collapse at different heights and stages depending on the gravity. There are four main factors that determine the speed of collapse of an eruption column: (1) If the radius of the crater is large and the gas impulse is small, the column will collapse faster; (2) If the content of debris in the eruption column is high and the particle size is The higher the density, the faster the column will collapse; (3) If there are more solid rock blocks that repeatedly return to the air in the eruption column, the column will collapse faster; (4) If there is surface water added to the eruption column, it can increase the The density of a large cylinder causes the cylinder to collapse quickly. 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 the Kilauea volcano in Hawaii, lava has flowed out quietly beforehand. Because the lava flows slowly, it only damages property but 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. International Online News 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 large-scale disasters 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. As a result, some funnels can still be seen here. These are large craters formed by devastating volcanic eruptions. The consequences of such a supervolcano 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 the dust and ash thrown into the atmosphere will cause A lot of sunlight cannot reach 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.

A fountain is a combination of water or other liquids with a specific shape that is sprayed through a nozzle under a certain pressure. The water pressure is generally provided by a water pump. After years of development, it has gradually developed into several categories: musical fountains; program-controlled fountains. ; Music program-controlled fountains; laser water screen movies; fun fountains, etc., coupled with specific lighting and control systems, can purify the air and beautify the environment. The fountain was originally a natural feature, a ground outcrop of pressurized water. Fountains in gardens are generally artificially constructed decorative water spray devices for the purpose of landscaping. Fountains can moisten the surrounding air, reduce dust, and lower temperatures. The tiny water droplets in the fountain collide with air molecules, which can produce a large amount of negative oxygen ions. Therefore, fountains are beneficial to improving the appearance of the city and improving the physical and mental health of residents.