"Volcano" The Unquiet Earth PPT Courseware 2

Description

"Volcano" The Unquiet Earth PPT Courseware 2

Volcano type

1. Active volcano

Refers to a volcano that is still active or has periodic eruptions. This type of volcano is in a period of peak activity. For example, the Merapi volcano on Java Island and the Cardassie volcano group in Yutian in the western section of the Kunlun Mountains in Xinjiang, my country, had a volcanic eruption record 6 years ago.

2. Extinct volcano

Refers to a volcano that has erupted in prehistoric times but has not been active in history. Such volcanoes have lost their ability to move. Some volcanoes still maintain their complete volcanic form, while others have suffered weathering erosion, leaving only incomplete volcanic remains. The Datong volcano group in Shanxi, my country, is an extinct volcano.

3. Dormant volcano

Refers to the eruptions that have occurred in history. But the volcano has been relatively static for a long time. Such volcanoes all have well-preserved volcanic cone shapes and are still capable of volcanic activity, or it cannot be concluded that they have lost their volcanic activity. For example, although there is currently no eruption activity in Tianchi, Changbai Mountain in my country, high-temperature gases are constantly ejected from some unfathomable fumaroles on the hillside, indicating that the volcano is currently dormant.

Volcanic origin

Scientists have proposed several hypotheses for the formation of volcanoes, mainly the plate theory. It considers that the tectonic units of the lithosphere are plates. The world can be divided into six major plates: Eurasian Plate, Pacific Plate, American Plate, African Plate, Indian Ocean Plate and Antarctic Plate.

Based on this theory, volcanologists believe that when the giant rock plates that make up the Earth's outermost layer collide and grind together, the temperature in the subduction zone rises significantly, even to the extent that the rocks below the Earth's crust are partially melted. This leads to the formation of volcanoes. Since most volcanoes in the world are located on the edges of various plates, this explanation seems reasonable.

Volcano eruption

The process of volcanic eruption

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

1. Magma formation and initial ascent stage

The generation of magma must involve two processes: partial melting and separation of the melt from the parent rock.

2. Magma chamber stage

A magma pocket is an area filled with magma beneath a volcano. It is a place where magma is relatively enriched in the rock medium of the earth's crust or upper mantle.

3. From magma chamber to surface stage

When the tensile or tensile-shear stress in the crust is greater than the local rock fracture strength, tensile or tensile-shear fractures may form. If these cracks are connected to each other, they can serve as channels for magma eruptions. Huge lightning often appears during eruptions.

impact

benefit:

1. Fertile volcanic soil is conducive to crop growth

2. Volcanic eruptions will bring a lot of minerals. 3. As long as magma can stay under the surface, it is a good source of geothermal heat. There are often hot springs or hot springs near volcanoes. This heat source is called geothermal heat.

harm:

Volcanic eruptions and the resulting explosions, volcanic ash and toxic gases, lava flows and pyroclastic flows not only bring serious harm to human life and property, but also have a great impact on the human living environment and can also affect the safety of aircraft and other aircraft. Fly safely.

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Update Time: 2024-10-20

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