Classification according to activities
Volcanoes can be divided into active volcanoes, extinct volcanoes and dormant volcanoes according to their activities.
Active volcanoes refer to volcanoes that are still active or periodically erupt. Such volcanoes are in a period of vigorous activity. For example, the Merapi volcano on Claw vomit island, has been erupting at intervals of two to three years on average since the 20th century. Qixing Mountain, the main peak of Datun Volcanic Group on Taiwan Island, is the most famous volcanic activity in recent years in China.
More than 1,500 active volcanoes are known on the world's land (including those that are erupting and have erupted in the last 10,000 years but are now dormant), and more are underwater volcanoes. Some volcanoes erupted, causing great disasters. In 79 AD, the Italian Mount Vesuvius erupted, burying two ancient cities, Pompeii and Heragnum. In 1980, the eruption of Mount St. Lawrence in the United States cut the mountain's height off more than 300 m.
The strength of volcanic eruption is related to the nature of lava, and the eruption time can be long or short, ranging from a few hours to thousands of years.
An extinct volcano is a volcano that has erupted in prehistoric times but has not erupted since the beginning of history. Such volcanoes have lost their ability to move. Some volcanoes remain intact, others have been eroded by weathering, left only with incomplete volcanic remains. The Datong Volcanic Group in Shanxi Province, China, has 99 isolated volcanic cones within a radius of about 123 k㎡, of which the Langwo Mountain volcanic cone is nearly 1900 m high.
Dormant volcanoes have erupted in recorded human history but have remained inactive ever since. Such volcanoes are well preserved in pyramidal form and still have volcanic activity capacity, or can not be concluded that they have lost volcanic activity capacity. For example, Tianchi of Baitou mountain in China erupted twice in 1327 and 1658, and there were many activities before that. Although there is no eruption activity at present, the volcano is currently in a dormant state as high-temperature gases are continuously ejected from some deep and unfathomable vents on the hillside.