When mentioning volcanic eruptions, people naturally think of it as the self-explosion of the earth's crust, with the earth rumbling and spewing fire... Volcanoes can be divided into dormant and active ones. Volcanoes that are still erupting or have erupted in historical records are called active volcanoes, while so-called dormant volcanoes not only formed a long time ago, but also have been proven to be unlikely to erupt again in the foreseeable future. Different countries have different time limits for defining active volcanoes. A more common criterion is to call volcanoes that have had eruptive activities since the Holocene (about 12,000 years ago) active volcanoes. In some countries with many volcanoes (such as Japan), volcanoes that have had eruptive activities in the past 2,000 years are considered active volcanoes. In different regions, the activity cycles and frequencies of different volcanoes vary. Some erupt once and then stop; others erupt repeatedly, with short intervals between eruptions and resuming eruptions after a period of rest. Volcanoes that are relatively dormant but still likely to erupt are called dormant volcanoes and belong to the category of active volcanoes. For example, before the eruption of Mount St. Helens in the western United States in 1980, there were nine pulse activities, each lasting from 5,000 years to less than 100 years; and the major eruption in 1980 occurred after 123 years of dormancy, starting on March 27 and ending on April 11 of the following year, with multiple eruptions and pauses in between. Mount Pinatubo in the Philippines erupted on June 2, 1991, after being dormant for more than 500 years, lasting for more than 10 hours. Its volcanic ash reached an altitude of 35 kilometers in the atmosphere, covering an area of thousands of square kilometers, with a maximum accumulation thickness of 200 meters, making it the largest volcanic eruption of the 20th century.
The Earth appears to be calm, but it actually contains huge energy that can cause partial melting of rocks in some areas. Volcanoes erupt because magma is ejected to the surface along weak areas of the Earth's crust under certain geological conditions. The Earth's surface is composed of plates, and the edges of these plates are weak areas, especially when one plate subducts beneath another. The subduction zone is prone to convection and melting of materials within the Earth, producing magma and making volcanic eruptions more likely. The Pacific Ring of Fire is the edge of a plate and a subduction zone, where more than two-thirds of the world's volcanoes are located, making it known as the "Fire Chain" of the Earth. There are also some volcanoes formed within plates, often in continental rift systems such as the East African Rift, the East Asian Continental Rift, and the Rhine Graben; there are also hotspots or mantle plumes within plates, which are like boils on the Earth, and the magma ejected from these areas forms volcanoes.
Some people compare the Earth to a living, hot organism, with volcanoes as its nostrils, magma as its blood, and earthquakes as its pulse. Earthquakes and volcanoes often occur together. There are volcanoes where there are earthquakes, but there are not necessarily volcanoes where there are earthquakes. Volcanic activity is a symbol of the Earth's vitality.