"Volcano" The Unquiet Earth PPT Courseware 4

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"Volcano" The Unquiet Earth PPT Courseware 4

extinct volcano

Extinct volcanoes refer to volcanoes that have erupted in prehistoric times but have never been active during human history. This type of volcano has lost its ability to move because it has not erupted for a long time. Some volcanoes still maintain their complete volcanic form, while others have been weathered and eroded, leaving only incomplete volcanic remains. Mount Kilimanjaro in eastern Africa and the Datong Volcanic Group in Shanxi, China are all extinct volcanoes. Among them, the Shanxi Datong Volcanic Group has two isolated volcanic cones distributed within a radius of about 50 square kilometers. Among them, the Langwoshan Volcanic Cone Nearly 120 meters high.

active volcano

Active volcano: A volcano that is currently erupting and is expected to erupt again. Dormant volcanoes, even those that are active but are not about to erupt now and may erupt again in the future, can also be called active volcanoes. Volcanoes that last erupted a long time ago and are proven not to erupt in the foreseeable future are called extinct or extinct volcanoes. Generally speaking, only active volcanoes erupt.

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. It is the release of magma and other eruptions from the 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.

A volcanic eruption is the release of gaseous (water vapor, sulfur dioxide), solid (volcanic ash, volcanic bombs), liquid (magma) and other eruptions from the 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.

eruption type

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), the volcano

volcanic eruption scene

The forms of eruptions vary greatly and are generally classified as follows.

central eruption

When underground magma erupts to the surface through tubular volcanic channels, it is called a central eruption. This is the main form of modern volcanic activity, which can be subdivided into three types:

(1) Quiet style: When a volcano erupts, only a large amount of hot lava quietly overflows from the crater and flows slowly along 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, few volatile components 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 eruption

(2) Explosive type: When a volcano erupts, a violent explosion occurs and a large amount of gas and pyroclastic material are ejected. The magma ejected is mainly medium-acidic magma. Generally speaking, the intensity of a central eruption is mainly related to the viscosity of the magma and the volatile components contained in it. High viscosity and many volatile components will lead to violent eruptions. 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.

(3) Intermediate type: It is the transitional type between quiet and explosive eruptions. This type is dominated by medium-basic lava eruptions. If there is an explosion, the explosive force will not be 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.

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Update Time: 2024-09-09

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