How are volcanoes constructive forces?

Volcanoes are considered constructive forces primarily due to their ability to build up new land. When they erupt, the lava that flows from the volcano can solidify and harden into new rock, thereby creating new landforms. This volcanic activity can lead to the formation of various geological features such as islands, plateaus, and mountains.

While it is true that volcanic eruptions can throw ash and rock into the air, which can contribute to the formation of new layers of soil and landscapes, the primary constructive aspect is the solidification of lava into rock.

The idea that they "destroy themselves" is more a consideration of the cyclical nature of volcanic activity and erosion, but it does not negate their role in constructing new land. In summary, the main constructive force comes from the lava that hardens into new rock during eruptions.