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A Lot of Hot Air: Degassing and Volcanic Eruptions

Volcanism is one of Earth's most spectacular phenomena and it poses significant hazards to our society. Volcanic eruptions may take many forms, ranging from fluid lava flows to ash-rich explosive columns and pyroclastic flows.

As well as silicate melt, volcanoes erupt gas, and it is this volatile phase that is the engine of volcanic eruptions. The exsolution of gases lowers magma density during its ascent through the crust and influences buoyancy as well as its rheological properties. How fast the magma ascends, the formation of bubbles and how efficiently the melt and gas can segregrate from one another in the volcanic conduit largely determines the style of the volcanic eruption at the surface.

This lecture will examine the process of magma degassing and volcanic eruptions using observations from large scales using satellite-based instruments, down to the microscopic scale using observations of crystals and melt in the erupted rocks. A variety of eruption types and tectonic settings will be considered, which together illustrate some of the most dramatic aspects of volcanism. The implications of such emissions of gases for atmospheric chemistry and climate will be discussed, both in recent times and in the geological past.


Marie Edmonds, University of Cambridge


Marie Edmonds is a geologist, geochemist and igneous petrologist, and is currently a lecturer at the Earth Sciences Department at the University of Cambridge. She has worked extensively on magma degassing problems in many different volcanic settings, such as the Soufriere Hills Volcano, Montserrat, an eruption ongoing since 1995, and then as a Mendenhall postdoctoral Fellow with the United States Geological Survey based at the Hawaiian Volcano Observatory, before returning to Cambridge in 2006. She has a BA and PhD from the University of Cambridge.