How did volcanoes form?

How did volcanoes form? Volcano is a very dangerous existence. In the history of the earth, volcanic eruptions have occurred countless times. Volcanoes are mainly distributed along the Pacific coast, so Indonesia has the most volcanoes in the world. Let's share how volcanoes are formed.

How did volcanoes form? 1 volcano formation

According to the theory of plate tectonics, the movement of plates is caused by thermal convection in the asthenosphere inside the earth. When plates push each other, one side with higher density will fall below the other side, which is called subduction, and the belt area where subduction occurs is called subduction zone or convergent plate boundary. The high temperature underground will melt the hidden plates and form magma. Magma rises slowly by buoyancy, and finally converges into a magma chamber, and magma chamber is the place where magma is stored at the bottom of the volcano.

When the gas pressure in the magma accumulates to a certain extent, the volcano erupts. For example, most volcanoes in the Pacific Rim are of this type. Some volcanoes are distributed at the boundary between plates, that is, the belt-shaped area where the two plates are separated. In this area, high-temperature mantle material will rise and form submarine volcanic mountains, which are called mid-ocean ridges.

The movement of hot spots forms a chain of volcanic islands, and some volcanoes are not located at the junction of plates, such as the Yellowstone composite crater in the United States and the Hawaiian Islands. Volcanologists call these volcanoes "hot spots".

At present, the mechanism of hot spots is not clear, but scientists generally believe that hot spots are caused by "hot columns" rising at the bottom of the mantle. When the plate moves horizontally on a hot spot, a series of volcanoes will be produced. After this continuous action, a series of volcanic islands will be formed, and the farther away from the hot spot, the older the volcano is.

Volcanic eruption process

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 various volcanic activities.

The process of volcanic eruption

The process before the volcano erupts from the surface can be summarized into three stages: magma formation and initial rising stage, magma sac stage and magma sac leaving the surface stage.

1, magma formation and initial rising stage

Magma must have two processes: partial melting and separation of molten body from parent rock. In fact, these two processes cannot be independent of each other, and the separation of molten body and parent rock may have occurred at the beginning of melting. Partial melting is the * * * existing state of liquid (magma) and solid (crystal), which is produced with the increase of temperature, the decrease of pressure and the decrease of solidus. When some molten substances rise with the mantle flow, liquid-solid separation will also occur in the flow, which will lead to the movement and even aggregation of liquid, which is called melting away.

2. Magmatic capsule stage

Magma sac is an area filled with magma below volcano, and it is a place where magma is relatively enriched in the rock medium of crust or upper mantle. It is generally considered to be a high-temperature fluid in rock pores (or fractures) similar to oil reservoirs, and it is generally considered that magma only accounts for 5%-30% of the total volume in the mantle plume. A part can be considered as a collection of liquids with relative circulation inside. Magma is a mixture of molten magma, volatiles and crystals.

3. From magma sac to surface stage

The rise of magma from the magma source to the near surface is related to the overpressure of magma sac, the formation and penetration of channels, the crystallization and degassing process of magma rise. When the tensile stress or shear stress in the crust is greater than the local rock fracture strength, it may form tensile stress or shear stress cracks. If these faults are interconnected, they can be used as channels for magma eruption.

Volcanic eruption conditions

Whether a volcano can form in a place mainly depends on whether the following conditions are met:

1, the formation of partial melting must have high geothermal energy (self-accumulation or external boundary conditions), or uplift and decompression process, or dehydration to lower the solidus;

2. The enrichment of magma in the earth's crust, or the location where magma sacs are formed, is related to the depth of neutral buoyancy surface, which in turn is related to the rheological discontinuity of the earth's crust;

3. Physical and chemical processes in magma chamber are mainly fractionation and interaction of crystals, volatiles and fluids, and magmatic eruption plays a role in promoting or inhibiting. The existence of magma sac in the crust has played a role in intercepting and transforming the magma rising from the mantle. It is also an important condition for the formation of explosive volcanic eruption.

4. The existence of magma sac can promote the formation of magma channel, and the tensile stress field produced by tectonic activity is the main reason for the formation of magma channel.

5. The rise of magma after leaving the magma sac is driven by pressure gradient and buoyancy.

How did volcanoes form? How powerful is the volcanic eruption?

The volcanic eruption is powerful enough to destroy the surrounding cities; Volcanic eruption will directly destroy the surrounding ecology and climate.

When a volcano erupts, it will fall into darkness.

Dark days, violent storms and even muddy rain will haunt local residents for months. When volcanic ash and gas are sprayed into the sky, they will spread far away with the wind. These volcanic materials will block sunlight and filter out some wavelengths of light, making the sun and the moon look like rings or strange colors.

After the volcano erupts, it will be very cold.

When the temperature drops, especially at sunrise and sunset, it will form a strange natural landscape. A large amount of volcanic ash combined with the rainstorm caused by volcanic eruption can form mudslides, which can destroy roads and bridges, flood nearby villages and cities and make countless people homeless. Mud formed by mud, rocks and debris can flood the whole city like a flood. Volcanic eruption has a profound impact on the natural landscape. Volcanic eruptions will also release carbon dioxide, which may offset the cooling effect caused by volcanic ash and atmospheric particles, but people will also be cooked.

Volcanic eruption will destroy the ecology and climate of the surrounding areas.

A large amount of volcanic ash will seriously affect the breathing of people and animals and plants, resulting in a large number of animal and plant deaths. A large number of volcanic ash particles produced by volcanic eruption will enter the stratosphere and stay there for several years.

Volcanic ash will block the sun's rays that shine on the earth for a long time, thus reducing the temperature of the earth.

The third is the impact on living things. A large amount of sulfur dioxide, carbon dioxide and other substances formed by volcanic eruption interact with moisture in the atmosphere to form acid rain, which enters the soil and ocean. Acidification of soil and seawater will affect the growth and reproduction of organisms and even lead to the extinction of some species.

Fourthly, trace metals such as phosphorus and iron released by volcanic ash and volcanic eruption are beneficial to plant growth. After several years of volcanic eruption, the areas covered by volcanic ash are usually extremely lush with plants. However, if it is excessive, it may form a dead zone in some sea areas.

The most terrible volcano in China.

Speaking of volcanoes, people first think of Japan, which is a country with many volcanoes and earthquakes. It is said that Japan is also the country with the most earthquakes, but in fact, there are terrible volcanoes in China. The most terrible volcano in China is the Tianchi volcano in Changbai Mountain, which is also very famous. It is said that it is the best preserved multi-genetic compound volcano in China.

Although this volcano has not erupted for hundreds of years, there have been several eruptions in history. It is said that when it erupted, there was volcanic ash along the east coast of North Korea, which was the most terrible volcano in China.

Tianchi volcano in Changbai Mountain

Tianchi volcano in Changbai Mountain is a scenic spot in Antu, Yanbian Korean Autonomous Prefecture, with beautiful scenery. This is a tourist attraction that many people like. Although Tianchi volcano in Changbai Mountain is a volcano, it hasn't erupted for hundreds of years, so the vegetation on the mountain is very beautiful.

It is said that Tianchi volcano in Changbai Mountain was the biggest volcanic eruption in the world from 1 199 to 120 1 in 2000, when the volcanic ash even reached the Sea of Japan and northern Japan, so it was considered as the most terrible volcano in China.

Is Tianchi Lake in Changbai Mountain an active volcano?

Although Tianchi Lake in Changbai Mountain has not erupted for hundreds of years, it is actually a dormant active volcano, which is very famous. It is said that it broke out during the Song and Ming Dynasties in China, but now it is dormant, so it is not an extinct volcano. Although it has been dormant for about 300 years, there are still many volcanoes in the world that have been dormant for hundreds of years.