09-10-2023-2037 - draft (the volatile compounds transform to gaseous phase as pressure is reduced with decreasing depth., etc., draft)

Formation

Volcanic pipes form as the result of violent eruptions of deep-origin volcanoes.^[1] These volcanoes originate at least three times as deep as most other volcanoes, and the resulting magma that is pushed toward the surface is high in magnesium and volatile compounds such as water and carbon dioxide. As the body of magma rises toward the surface, the volatile compounds transform to gaseous phase as pressure is reduced with decreasing depth. This sudden expansion propels the magma upward at rapid speeds, resulting in a supersonic Plinian eruption. 

https://en.wikipedia.org/wiki/Volcanic_pipe