Waves in volcanic and glacial conduits

Geological fluid mechanics is a strange brand of physics: research problems often involve spatial scales that we can see and interact with directly, but dynamics that are 'hidden' in the sense that they involve timescales outside the human experience or initial and boundary conditions that are challenging to constrain. In this talk I will discuss a particular outstanding problem in volcano and glacier science: inferring the geometry of and fluid motion within conduit and crack structures beneath the surface of the Earth. In particular, I will discuss the phenomenology of fluid resonance in elastic-walled tubes and cracks containing stratified and bubbly fluids. I will first discuss seismic observations at Kilauea volcano, Hawaii, that are well explained by resonance in a coupled conduit-crack system. By studying long period ground surface displacements collected by seismometers around the volcanic vent, we learn about the shallow volcanic plumbing system structure and the properties of the bubbly magma within it. I will then talk about a more recent application of these ideas to glaciers, where the fluid and solid are different (water and ice compared to magma and rock), but the physical processes and basic science questions are similar.