iFOCUS Science Colloquium Lecture Series


When Volcanoes Erupt: Understanding Why Some Explode and Others Fizzle

Streaming Media

Document Type

Video File


1 hour 0 minutes 55 seconds

Publication Date



Fluid Dynamics | Geophysics and Seismology | Volcanology


Volcanic eruptions vary in intensity due to a variety of physical and chemical variables. One of the most significant variables that determines if an eruption will be explosive or effusive is the amount of pressure build-up inside the volcano conduit at the time of the eruption. The source of this pressure is primarily due to exsolved gases (bubbles) in the magma. Under certain conditions, bubbles are able to grow and form extensive networks within the conduit. These bubble-networks are believed to be the primary method for gasses to escape from the magma during an eruption, reducing the pressure within the conduit. Therefore, if the gasses are able to escape from the volcano conduit, an eruption will be effusive, analogous to typical Hawaiian eruptions. However, if the gas is not able to escape, pressure will build up and the volcano will explode in a high-intensity eruption, such as with Mt. St. Helens in 1980. We can better understand why some volcanoes explode and others fizzle by understanding how bubbles behave in the volcano conduit during an eruption.


Sponsored by the Hearst Foundations and the Linfield College Physics Department.